JWST Development

Development Status of the JWST Project

• December 24, 2021: The James Webb Space Telescope is safely stowed inside the fairing of ESA's Ariane 5 launch vehicle, which is now on the launch pad undergoing final checks and fuelling for a targeted liftoff at 12:20 GMT / 13:20 CET on 25 December from Europe's Spaceport in French Guiana. ¹⁾

- Webb will be the largest, most powerful telescope ever launched into space. As part of an international collaboration agreement, ESA is providing the telescope's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace.

• December 18, 2021: The James Webb Space Telescope is confirmed for the target launch date of 24 December, at 12:20 GMT / 13:20 CET. ²⁾

- Late yesterday, teams at the launch site successfully completed encapsulation of the observatory inside the Ariane 5 rocket that will launch it to space. Webb's launch final readiness review will be held on Tuesday 21 December and, if successful, roll-out is planned for Wednesday 22 December.

• December 14, 2021: Before the MIRI instrument – one of four scientific instruments aboard the observatory – can operate, it has to be cooled down to almost the coldest temperature matter can reach. ³⁾

- Set to launch on Dec. 22, NASA's James Webb Space Telescope is the largest space observatory in history, and it has an equally gargantuan task: to collect infrared light from the distant corners of the cosmos, enabling scientists to probe the structures and origins of our universe and our place in it.

- Many cosmic objects – including stars and planets, as well as the gas and dust from where they form – emit infrared light, sometimes called heat radiation. But so do most other warm objects, like toasters, humans, and electronics. That means Webb's four infrared instruments can detect their own infrared glow. To reduce those emissions, the instruments have to be really cold – about 40 kelvins, or minus 388 degrees Fahrenheit (minus 233 degrees Celsius). But to operate properly, the detectors inside the mid-infrared instrument, or MIRI, will have to get even colder: less than 7 kelvins (minus 448 degrees Fahrenheit, or minus 266 degrees Celsius).

- That's just a few degrees above absolute zero (0 kelvins) – the coldest temperature theoretically possible, though it's never physically attainable because it represents the total absence of any heat. (MIRI is not, however, the coldest imaging instrument ever to operate in space.)

- Temperature is essentially a measurement of how fast atoms are moving, and in addition to detecting their own infrared light, the Webb detectors can be trigged by their own thermal vibrations. MIRI detects light in a lower-energy range than the other three instruments. As a result, its detectors are even more sensitive to thermal vibrations. These unwanted signals are what astronomers refer to as "noise," and they can overwhelm the faint signals that Webb is trying to detect.

- After launch, Webb will unfold a tennis-court-size sunshield that will block MIRI and the other instruments from the Sun's heat, allowing them to cool passively. Beginning about 77 days after launch, MIRI's cryocooler will spend 19 days lowering the temperature of the instrument's detectors to less than 7 kelvins.

- "It's relatively easy to cool something down to that temperature on Earth, typically for scientific or industrial applications," said Konstantin Penanen, a cryocooler specialist at NASA's Jet Propulsion Laboratory in Southern California, which manages the MIRI instrument for NASA. "But those Earth-based systems are very bulky and energy inefficient. For a space observatory, we need a cooler that is physically compact, highly energy efficient, and it has to be highly reliable because we can't go out and repair it. So those are the challenges we faced, and in that respect, I would say the MIRI cryocooler is certainly at the cutting edge."

- One of Webb's big science goals will be to study the properties of the first generation of stars to form in the universe. Webb's Near-Infrared Camera, or NIRCam instrument, will be able to detect these extremely distant objects, and MIRI will help scientists confirm that these faint sources of light are clusters of first-generation stars, rather than second-generation stars that form later as a galaxy evolves.

- By peering through even thicker clouds of dust than the near-infrared instruments, MIRI will reveal the birthplaces of stars. It will also detect molecules that are common on Earth – like water, carbon dioxide, and methane, and those of rocky minerals like silicates – in cool environments around nearby stars, where planets may form. Near-infrared instruments are better at detecting these molecules as vapor in much hotter environments, while MIRI can see them as ices.

- "By combining expertise from both the United States and Europe, we have developed MIRI as a powerful capability for Webb that will enable astronomers from all over the world to answer big questions about how stars, planets, and galaxies form and evolve," said Gillian Wright, co-lead of the MIRI science team and the instrument's European principal investigator at the UK Astronomy Technology Centre (UK ATC).

The Big Chill

- The MIRI cryocooler uses helium gas – enough to fill about nine party balloons – to carry heat away from the instrument's detectors. Two electrically powered compressors pump the helium through a tube that extends to where the detectors are located. The tube runs through a block of metal that is also attached to the detectors; the cooled helium absorbs excess heat from the metal block, which in turn keeps the detectors at their operational temperature below 7 kelvins. The warmed (but still quite cold) gas then returns to the compressors, where it dumps the excess heat, and the cycle begins again. Fundamentally, the system is similar to those used in home refrigerators and air conditioners.

- The tubing that carries the helium is made of gold-coated stainless steel and measures less than one-tenth of an inch (2.5 mm) in diameter. It extends about 30 feet (10 meters) from the compressors, located in a region called the spacecraft bus, to MIRI's detectors, located in the Optical Telescope Element, behind the observatory's honeycomb-shaped primary mirror. Hardware called the DTA (Deployable Tower Assembly), connects these two regions. When packed for launch, the DTA is compressed, sort of like a piston, to help fit the stowed observatory into the protective faring that rides atop the rocket. Once in space, the tower will extend to separate the room-temperature spacecraft bus from the much colder Optical Telescope Instrument, and to allow the sunshield and telescope to fully deploy.

- But the elongation process requires the helium tubing to extend along with the Deployable Tower Assembly. So the tube is coiled like a spring, which is why MIRI engineers nicknamed this portion of the tube the "Slinky."

- "There were a couple of challenges working on a system that spans multiple regions of the observatory," said Analyn Schneider, MIRI's project manager at JPL. "Those different regions are led by different organizations or centers, including Northrop Grumman and NASA's Goddard Space Flight Center, and we had to interface with everybody. There's no other hardware on the telescope that requires that, so that was a challenge unique to MIRI. It's definitely been a long road for the MIRI cryocooler, and we're ready to see it perform in space."

• December 14, 2021: On Saturday 11 December, the James Webb Space Telescope was placed on top of the Ariane 5 rocket that will launch it to space from Europe's Spaceport in French Guiana. ⁴⁾

- After its arrival in the final assembly building, Webb was lifted slowly about 40 m high and then carefully manoeuvred on top of Ariane 5, after which technicians bolted Webb's launch vehicle adapter down to the rocket.

- This whole process was performed under strict safety and cleanliness regulations, as it was one of the most delicate operations during the entire launch campaign for Webb.

- A ‘shower curtain' about 12 m high and 8 m in diameter was installed in between two platforms, to create a closed-off space around Webb to avoid any contamination.

- The next step is to encapsulate Webb inside Ariane 5's specially adapted fairing.

• December 8, 2021: The Ariane 5 launch vehicle which will launch the James Webb Space Telescope was moved to the final assembly building at Europe's Spaceport in French Guiana on 29 November 2021. ⁵⁾

- Ariane 5 parts shipped from Europe to French Guiana, have been coming together inside the launch vehicle integration building.

- The lower part of the Ariane 5 comprises the cryogenic main core stage (with the Vulcain main engine, oxygen and hydrogen tanks), two solid rocket boosters and the upper composite, including the cryogenic upper stage (with the HM7B engine, oxygen and hydrogen tanks), the vehicle equipment bay – the 'brain' of the launcher, and all supporting structures that will interface with Webb on its adaptor.

- A launch table is used to transport the Ariane 5 vehicle between the launch vehicle integration building, the final assembly building and the launch pad.

- Webb, now fuelled, will soon be integrated on Ariane 5's upper stage and then encapsulated inside Ariane 5's specially adapted fairing.

- Webb will be the largest, most powerful telescope ever launched into space. As part of an international collaboration agreement, ESA is providing the telescope's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace.

• December 6, 2021: The James Webb Space Telescope was fuelled inside the payload preparation facility at Europe's Spaceport in French Guiana ahead of its launch on Ariane 5. ^{6) 7)}

• November 9, 2021: Ariane 5 parts are coming together in the launch vehicle integration building for the launch of Webb from Europe's Spaceport in French Guiana. ⁸⁾

- The Ariane 5 core stage is 5.4 m diameter and 30.5 m high. On 6 November it was taken out of its shipping container and raised vertical.

- At launch it will contain 175 t of liquid oxygen and liquid hydrogen propellants. With its Vulcain 2 engine it provides 140 t of thrust. It also provides roll control during the main propulsion phase. This rolling maneuver will ensure that all parts of the payload are equally exposed to the sun which will avoid overheating of any elements of Webb.

- Two boosters followed. They are 3 m in diameter and 31 m high. This week they will be positioned on the launch table and then anchored to the core stage. Engineers will then carry out mechanical and electrical checks. Each booster contains 240 t of solid propellant, together they will provide 1200 t of thrust which is 90 percent of the thrust at liftoff.

- On the countdown to launch, the Vulcain 2 engine is ignited first. A few seconds later, when it reaches its nominal operating level, the two boosters are fired to achieve a thrust of about 1364 t at liftoff.

- Webb will be the largest, most powerful telescope ever launched into space. As part of an international collaboration agreement, ESA is providing the telescope's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace.

- Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

- These activities mark the beginning of a five-week campaign to prepare the Ariane 5 launch vehicle which runs in parallel with teams preparing Webb, which started three weeks earlier. Soon Webb will meet Ariane 5 and teams will unite for the final integration for launch.

• November 5, 2021: After its arrival at Pariacabo harbor in French Guiana on 12 October 2021, the James Webb Space Telescope was transported to Europe's Spaceport and unboxed in the cleanroom. It is now being prepared for its launch on an Ariane 5 rocket in December. ⁹⁾

- Though the telescope weighs only six tons, it is more than 10.5 m high and almost 4.5 m wide when folded. It was shipped in its folded position in a 30 m long container which, with auxiliary equipment, weighed more than 70 tons.

- Webb's launch campaign involves more than 100 specialists. Teams will work separately to prepare the telescope and the launch vehicle until they become one combined team to join the telescope with its rocket for a momentous liftoff.

- Webb will be the largest, most powerful telescope ever launched into space. As part of an international collaboration agreement, ESA is providing the telescope's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace.

- Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

• November 2, 2021: Now that NASA's James Webb Space Telescope has safely arrived at its launch site in French Guiana, on the northeastern coast of South America, technical teams have begun making progress on the final checklist of preparations before liftoff later this year. ¹⁰⁾

- These preparations are expected to last 55 days from the observatory's arrival by ship to the day of launch.

- After Webb arrived at the Arianespace clean room facilities in French Guiana, contamination control technicians ensured the observatory is clean and contaminant free following its 5,800 mile journey. Then engineers ran a final set of electrical and functional tests and checked the stowed mechanical configuration to ensure delivery went smoothly. A trained crew in special hazmat suits will soon begin the two-week process of loading the spacecraft with the hydrazine fuel and nitrogen tetroxide oxidizer it will need to power its rocket thrusters to maintain its orbit. Next, Webb will move to the nearby vehicle integration building to be lifted and mounted on top of the Ariane 5 rocket "stack." The final few remove-before-flight "red-tag" items are taken off, and a few remaining add-before-flight "green tag" items are installed. Then the rocket fairing is lifted and lowered over top and locked into place, signifying the conclusion of a long journey. At this point, Webb will be very nearly ready to launch from Europe's Spaceport, also known as the Guiana Space Center (CSG).

- As a fully integrated launch vehicle with Webb as the payload, the Ariane rocket will roll out to the launch pad a few days before launch. Engineers monitor the rocket via electrical connections running from the payload control room to the pad through an umbilical attachment to the vehicle that separates at liftoff. A few hours before liftoff, the rocket is loaded with liquid hydrogen fuel and liquid oxygen oxidizer. About a half hour before launch, engineers in the payload control room switch the spacecraft from external electrical power to the spacecraft's on-board battery.

- Webb's launch will be a pivotal moment for NASA and its partners, ESA (European Space Agency) and the Canadian Space Agency (CSA), but it is only the beginning. The following 29 days will be an exciting but harrowing time. Thousands of parts must work correctly, in sequence, to unfold Webb and put it in its final configuration, all while it flies through the expanse of space alone, to a destination nearly one million miles away.

• October 18, 2021: The greatest origin story of all unfolds with the James Webb Space Telescope. Webb's launch is a pivotal moment that exemplifies the dedication, innovation, and ambition behind NASA and its partners, the European Space Agency (ESA) and Canadian Space Agency (CSA), but it is only the beginning. ¹¹⁾

• October 13, 2021: The James Webb Space Telescope arrived safely at Pariacabo harbor in French Guiana on 12 October 2021 ahead of its launch on an Ariane 5 rocket from Europe's Spaceport. ¹²⁾

• October 12, 2021: The James Webb Space Telescope, a once in a generation space mission, arrived safely at Pariacabo harbor in French Guiana on 12 October 2021, ahead of its launch on an Ariane 5 rocket from Europe's Spaceport. ¹³⁾

- Webb, packed in a 30 m long container with additional equipment, arrived from California on board the MN Colibri which sailed the Panama Canal to French Guiana. The shallow Kourou river was specially dredged to ensure a clear passage and the vessel followed high tide to safely reach port.

- The MN Colibri, like its sister vessel the MN Toucan, were built to ship Ariane 5 rocket parts from Europe to French Guiana. They were specifically designed to carry a complete set of Ariane 5 parts across the Atlantic, while having a low enough draft to enable them to follow a route along the shallow Kourou river to the Pariacabo harbor.

- Webb will be the largest, most powerful telescope ever launched into space. As part of an international collaboration agreement, ESA is providing the telescope's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace.

- Few space science missions have been as eagerly anticipated as the James Webb Space Telescope (Webb). As the next great space science observatory following Hubble, Webb is designed to resolve unanswered questions about the Universe and see farther into our origins: from the formation of stars and planets to the birth of the first galaxies in the early Universe.

- Every launch requires meticulous planning and preparation. For Webb, this process began about 15 years ago. Its arrival at Pariacabo harbor is a major milestone in the Ariane 5 launch campaign.

- Though the telescope weighs only six tons, it is more than 10.5 m high and almost 4.5 m wide when folded. It was shipped in its folded position in a 30 m long container which, with auxiliary equipment, weighs more than 70 tons. This is such an exceptional mission that a heavy articulated vehicle was brought on board MN Colibri to carefully transport Webb to the Spaceport.

- The Spaceport's preparation facilities are ready for Webb's arrival. As extra protection from contamination, the clean rooms are fitted with additional walls of air filters and a dedicated curtain will shroud Webb after it is mounted on the rocket.

- This launch campaign involves more than 100 specialists. Teams will work separately to prepare the telescope and the launch vehicle until they become one combined team to join the telescope with its rocket for a momentous liftoff.

- When Webb arrives at the Spaceport, it will be unpacked inside a dedicated spacecraft preparation facility where it will be examined to ensure that it is undamaged from its voyage and in good working order.

- In parallel to Webb preparations, Ariane 5 rocket parts from Europe will come together in the launch vehicle integration building.

- Europe's powerful and highly reliable heavy-lift workhorse has an excellent track record spanning more than 100 launches and three decades. Ariane 5's ample fairing, 5.4 m diameter and 17 m high, provides enough space for Webb's folded spacecraft components, sunshield and mirrors.

- Ariane 5 is well suited for science satellites with proven capability to send missions to the second Lagrange Point (L2). Ariane 5 will release Webb directly on a path towards L2 on which it will continue for four weeks, eventually arriving at L2 which is four times farther away than the Moon is from Earth.

- A few customized features make Ariane 5 a perfect fit for Webb. These include the adaptation of venting ports at the base of the fairing which will be forced fully open during the flight. The fairing – the rocket's nose cone – will protect Webb from the acoustics at liftoff and during its journey through Earth's atmosphere. Its venting ports will enable extremely smooth depressurization of the fairing from ground pressure to vacuum during the flight.

- Then, to avoid overheating of any elements of Webb, Ariane 5 will perform a specially developed rolling maneuver to ensure that all parts of the satellite will be equally exposed to the sun.

- An extra battery will provide power for a boost to the upper stage after release of the telescope, safely distancing it from Webb.

• October 12, 2021: NASA's James Webb Space Telescope successfully arrived in French Guiana Tuesday, after a 16-day journey at sea. The 5,800-mile voyage took Webb from California through the Panama Canal to Port de Pariacabo on the Kourou River in French Guiana, on the northeastern coast of South America. ¹⁴⁾

- The world's largest and most complex space science observatory will now be driven to its launch site, Europe's Spaceport in Kourou, where it will begin two months of operational preparations before its launch on an Ariane 5 rocket, scheduled for Dec. 18.

- Once operational, Webb will reveal insights about all phases of cosmic history – back to just after the big bang – and will help search for signs of potential habitability among the thousands of exoplanets scientists have discovered in recent years. The mission is an international collaboration led by NASA, in partnership with the European and Canadian space agencies.

- "The James Webb Space Telescope is a colossal achievement, built to transform our view of the universe and deliver amazing science," said NASA Administrator Bill Nelson. "Webb will look back over 13 billion years to the light created just after the big bang, with the power to show humanity the farthest reaches of space that we have ever seen. We are now very close to unlocking mysteries of the cosmos, thanks to the skills and expertise of our phenomenal team."

- After completing testing in August at Northrop Grumman's Space Park in Redondo Beach, California, the Webb team spent nearly a month folding, stowing, and preparing the massive observatory for shipment to South America. Webb was shipped in a custom-built, environmentally controlled container.

- Late in the evening of Friday, Sept. 24, Webb traveled with a police escort 26 miles through the streets of Los Angeles, from Northrop Grumman's facility in Redondo Beach to Naval Weapons Station Seal Beach. There, it was loaded onto the MN Colibri, a French-flagged cargo ship that has previously transported satellites and spaceflight hardware to Kourou. The MN Colibri departed Seal Beach Sunday, Sept. 26 and entered the Panama Canal Tuesday, Oct. 5 on its way to Kourou.

- The ocean journey represented the final leg of Webb's long, earthbound travels over the years. The telescope was assembled at NASA's Goddard Space Flight Center in Greenbelt, Maryland, starting in 2013. In 2017, it was shipped to NASA's Johnson Space Center in Houston for cryogenic testing at the historic "Chamber A" test facility, famous for its use during the Apollo missions. In 2018, Webb shipped to Space Park in California, where for three years it underwent rigorous testing to ensure its readiness for operations in the environment of space.

- "A talented team across America, Canada, and Europe worked together to build this highly complex observatory. It's an incredible challenge – and very much worthwhile. We are going to see things in the universe beyond what we can even imagine today," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate in Washington. "Now that Webb has arrived in Kourou, we're getting it ready for launch in December – and then we will watch in suspense over the next few weeks and months as we launch and ready the largest space telescope ever built."

- After Webb is removed from its shipping container, engineers will run final checks on the observatory's condition. Webb will then be configured for flight, which includes loading the spacecraft with propellants, before Webb is mounted on top of the rocket and enclosed in the fairing for launch.

- "Webb's arrival at the launch site is a momentous occasion," said Gregory Robinson, Webb's program director at NASA Headquarters. "We are very excited to finally send the world's next great observatory into deep space. Webb has crossed the country and traveled by sea. Now it will take its ultimate journey by rocket one million miles from Earth, to capture stunning images of the first galaxies in the early universe that are certain to transform our understanding of our place in the cosmos."

• September 8, 2021: ESA, NASA and Arianespace have jointly defined 18 December 2021 as the target launch date for Ariane 5 flight VA256. This third Ariane 5 launch of 2021 will fly the James Webb Space Telescope to space from Europe's Spaceport in French Guiana. ¹⁵⁾

- Important milestones of the launch program for Webb have already been passed or are approaching, such as the final mission analysis review for its launch, the shipment of the Ariane 5 launch vehicle elements from continental Europe to French Guiana, and the scheduled shipment of Webb to French Guiana by the end of September 2021.

- Webb is an international partnership between NASA, ESA, and the Canadian Space Agency (CSA). As part of the international collaboration agreement, ESA is providing the telescope's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service. Besides that, ESA is contributing the NIRSpec instrument and a 50% share of the MIRI instrument, as well as personnel to support mission operations.

- "ESA is proud that Webb will launch from Europe's Spaceport on an Ariane 5 rocket specially adapted for this mission. We are on track, the spaceport is busy preparing for the arrival of this extraordinary payload, and the Ariane 5 elements for this launch are coming together. We are fully committed, with all Webb partners, to the success of this once-in-a-generation mission," said Daniel Neuenschwander, ESA Director of Space Transportation.

- "We now know the day that thousands of people have been working towards for many years, and that millions around the world are looking forward to. Webb and its Ariane 5 launch vehicle are ready, thanks to the excellent work across all mission partners. We are looking forward to seeing the final preparations for launch at Europe's Spaceport," said Günther Hasinger, ESA Director of Science.

• September 7, 2021: Major elements of the Ariane 5 rocket to launch the James Webb Space Telescope arrived safely in Kourou, French Guiana from Europe on 3 September 2021. ¹⁶⁾

- Webb will be stowed folded inside the fairing built by RUAG Space in Emmen, Switzerland. This ogive-shaped fairing at the top of Ariane 5 is 5.4 m in diameter and over 17 m high. Made of carbon fibre-polymer composite, this structure will protect Webb from the thermal, acoustic, and aerodynamic stresses at liftoff on the ascent to space.

- Ariane 5's upper stage is built by ArianeGroup in Bremen, Germany. It gives Ariane 5 the flexibility to deploy scientific payloads to a highly precise second Lagrangian injection orbit. Its HM7B engine burns 14.7 t of liquid oxygen and liquid hydrogen propellant to deliver 6.6 t of thrust. It provides attitude control during the ascent and the separation of Webb. The Vehicle Equipment Bay, ‘the brain', autonomously controls the whole vehicle and transmits all key flight parameters to the ground station network.

- The cryogenic core stage, built by ArianeGroup in France, is 5.4 m diameter and 30.5 m long and unfuelled weighs more than 14 tons. At liftoff, its Vulcain 2 engine burns 175 t of liquid oxygen and liquid hydrogen propellants to provide 140 t of thrust. It also provides roll control during the main propulsion phase.

- At Europe's Spaceport these Ariane 5 parts will be checked and prepared for assembly and integration before the mating of Webb on its top.

- Webb will be the largest, most powerful telescope ever launched into space. As part of an international collaboration agreement, ESA is providing the telescope's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace.

- Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

• August 26, 2021: The NASA/ESA/CSA James Webb Space Telescope has successfully completed its final tests and is being prepared for shipment to its launch site at Europe's Spaceport in French Guiana. ¹⁷⁾

- Tests were carried out at Northrop Grumman's facilities in California, USA, to ensure that the complex space science observatory will operate as designed when in space. Shipment operations have now begun, including all the necessary steps to prepare Webb for a safe journey through the Panama Canal to its launch location in French Guiana, on the northeastern coast of South America.

- Once Webb arrives at Europe's Spaceport, launch processing teams will prepare and configure the observatory for flight. This involves post-shipment checkouts and carefully loading the spacecraft's propellant tanks with fuel. Then, engineering teams will mate the observatory to its launch vehicle, an Ariane 5 rocket provided by ESA and make a ‘dress rehearsal', before it rolls out to the launch pad two days before launch.

- The James Webb Space Telescope is an amazing feat of human ingenuity – a mission with contributions from thousands of scientists, engineers, and other professionals from more than 14 countries and 29 states, in nine different time zones. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service. Besides that, ESA is contributing the NIRSpec instrument and a 50% share of the MIRI instrument, as well as personnel to support mission operations.

- "We are glad about the completion of all tests for Webb and thank all the teams for their excellent work. We are really excited that all the items necessary for the launch are now coming together at Europe's Spaceport," said Günther Hasinger, ESA Director of Science.

- After launch, Webb will undergo an action-packed six-month commissioning period. Moments after completing a 26-minute ride aboard the Ariane 5 launch vehicle, the spacecraft will separate from the rocket and its solar array will deploy automatically.

- Webb will take one month to fly to its intended orbital location in space nearly one million miles away from Earth at L2, slowly unfolding as it goes. Sunshield deployments will begin a few days after launch, and each step can be controlled expertly from the ground, giving Webb's launch full control to circumnavigate any unforeseen issues with deployment.

- Once the sunshield starts to deploy, the telescope and instruments will enter shade and start to cool over time. Over the ensuing weeks, the mission team will closely monitor the observatory's cooldown, managing it with heaters to control stresses on instruments and structures. In the meantime, the secondary mirror tripod will unfold, the primary mirror will unfold, Webb's instruments will slowly power up, and thruster firings will insert the observatory into a prescribed orbit.

- Once the observatory has cooled down and stabilized at its frigid operating temperature, several months of alignments to its optics and calibrations of its scientific instruments will occur. Scientific operations are expected to commence approximately six months after launch.

- ‘Flagship' missions like Webb are generational projects. Webb was built on both the legacy and the lessons of missions before it, such as the NASA/ESA Hubble Space Telescope, and it will in turn provide the foundation upon which future large astronomical space observatories may one day be developed.

- Webb is the next great space science observatory, designed to answer outstanding questions about the Universe and to make breakthrough discoveries in all fields of astronomy. Webb will see farther into our origins – from the formation of stars and planets, to the birth of the first galaxies in the early Universe.

• August 18, 2021: The upper stage of the Ariane 5 rocket which will launch the James Webb Space Telescope later this year, is on its way to Europe's Spaceport in French Guiana. ¹⁸⁾

- Webb will be the largest, most powerful telescope ever launched into space. As part of an international collaboration agreement, ESA is providing the telescope's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace.

- Overnight on 17 August 2021, Ariane 5's upper stage was transported in its container from ArianeGroup in Bremen to Neustadt port in Germany. Here it will board the MN Toucan vessel alongside other Ariane 5 elements to continue its journey to Kourou, French Guiana.

- The upper stage of Ariane 5 is manufactured by ArianeGroup, the prime contractor for the development and construction of the European family of Ariane 5 and Ariane 6 launch vehicles.

- Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).

• May 11, 2021: For the last time while it is on Earth, the world's largest and most powerful space science telescope opened its iconic primary mirror. This event marked a key milestone in preparing the observatory for launch later this year. ¹⁹⁾

- As part of the NASA's James Webb Space Telescope's final tests, the 6.5 meter (21 feet 4 inch) mirror was commanded to fully expand and lock itself into place, just like it would in space. The conclusion of this test represents the team's final checkpoint in a long series of tests designed to ensure Webb's 18 hexagonal mirrors are prepared for a long journey in space, and a life of profound discovery. After this, all of Webb's many movable parts will have confirmed in testing that they can perform their intended operations after being exposed to the expected launch environment.

- "The primary mirror is a technological marvel. The lightweight mirrors, coatings, actuators and mechanisms, electronics and thermal blankets when fully deployed form a single precise mirror that is truly remarkable," said Lee Feinberg, optical telescope element manager for Webb at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "This is not just the final deployment test sequence that the team has pulled off to prepare Webb for a life in space, but it means when we finish, that the primary mirror will be locked in place for launch. It's humbling to think about the hundreds of dedicated people across the entire country who worked so hard to design and build the primary mirror, and now to know launch is so close."

- Making the testing conditions close to what Webb will experience in space helps to ensure the observatory is fully prepared for its science mission one million miles away from Earth.

- Commands to unlatch and deploy the side panels of the mirror were relayed from Webb's testing control room at Northrop Grumman, in Redondo Beach, California. The software instructions sent, and the mechanisms that operated are the same as those used in space. Special gravity offsetting equipment was attached to Webb to simulate the zero-gravity environment in which its complex mechanisms will operate. All of the final thermal blanketing and innovative shielding designed to protect its mirrors and instruments from interference were in place during testing.

- To observe objects in the distant cosmos, and to do science that's never been done before, Webb's mirror needs to be so large that it cannot fit inside any rocket available in its fully extended form. Like a piece of origami artwork, Webb contains many movable parts that have been specifically designed to fold themselves to a compact formation that is considerably smaller than when the observatory is fully deployed. This allows it to just barely fit inside a 16-foot (5-meter) rocket fairing, with little room to spare.

- To deploy, operate and bring its golden mirrors into focus requires 132 individual actuators and motors in addition to complex backend software to support it. A proper deployment in space is critically important to the process of fine-tuning Webb's individual mirrors into one functional and massive reflector. Once the wings are fully extended and in place, extremely precise actuators on the backside of the mirrors position and bend or flex each mirror into a specific prescription. Testing of each actuator and their expected movements was completed in a final functional test earlier this year.

- "Pioneering space observatories like Webb only come to fruition when dedicated individuals work together to surmount the challenge of building something that has never been done before. I am especially proud of our teams that built Webb's mirrors, and the complex back-end electronics and software that will empower it to see deep into space with extreme precision. It has been very interesting, and extremely rewarding to see it all come together. The completion of this last test on its mirrors is especially exciting because of how close we are to launch later this year," said Ritva Keski-Kuha, deputy optical telescope element manager for Webb at Goddard.

- Following this test engineers will immediately move on to tackle Webb's final few tests, which include extending and then restowing two radiator assemblies that help the observatory cool down, and one full extension and restowing of its deployable tower.

- The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

• As of 01 July 2021, the international James Webb Space Telescope has passed the final mission analysis review for its launch on an Ariane 5 rocket from Europe's Spaceport in French Guiana. ²⁰⁾

- This major milestone, carried out with Arianespace, the Webb launch service provider, confirms that Ariane 5, the Webb spacecraft and the flight plan are set for launch. It also specifically provides the final confirmation that all aspects of the launch vehicle and spacecraft are fully compatible.

- During launch, the spacecraft experiences a range of mechanical forces, vibrations, temperature changes, and electromagnetic radiation. All technical evaluations performed by Arianespace on the mission's key aspects, including the launch trajectory and payload separation, have shown positive results.

- "We are thrilled to have passed this important step towards the launch of Webb and to have received the green light from Arianespace and NASA," says Peter Rumler, ESA Webb project manager.

- Webb will be the largest, most powerful telescope ever launched into space. As part of an international collaboration agreement, ESA is providing the observatory's launch service using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service.

- Ariane 5 has been customized to accommodate all the specific requirements of the Webb mission. New hardware ensures that venting ports around the base of the fairing remain fully open. This will minimize the shock of depressurization when the fairing jettisons away from the launch vehicle.

- Some elements of Webb are sensitive to radiation from the Sun and heating by the atmosphere. To protect it after the fairing is jettisoned, Ariane 5 will perform a specially developed rolling maneuver to avoid any fixed position of the telescope relative to the Sun.

- Additionally, an extra battery is installed on Ariane 5 to allow a boost to the upper stage after release of the telescope, distancing it from Webb.

- Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service.

• June 2, 2021:The launch of the NASA/ESA/CSA James Webb Space Telescope (Webb) on an Ariane 5 rocket from Europe's Spaceport in French Guiana is now planned for November 2021. ²¹⁾

- American and European officials acknowledged June 1 that the launch of the James Webb Space Telescope will likely slip from the end of October to at least mid-November because of delays linked to the Ariane 5.

- At an ESA briefing about the space telescope, representatives of the agency and Arianespace said they were finalizing reviews to correct a payload fairing problem found on two Ariane 5 launches last year that had grounded the rocket since August. Arianespace described the issue last month as "a less than fully nominal separation of the fairing" on those two launches.

- "The origin of the problem has been found. Corrective actions have been taken," Daniel de Chambure, acting head of Ariane 5 adaptations and future missions at ESA, said. "The qualification review has started, so we should be able to confirm all that within a few days or weeks."

- He did not elaborate on the problem or those corrective actions, beyond stating that the problem took place during separation of the payload fairing. Industry sources said in May that, on the two launches, the separation system imparted vibrations on the payload above acceptable limits, but did not damage the payloads.

- The issue is not linked to a modification to the payload fairing required for JWST. Arianespace has been testing new vents on the fairing designed to reduce the pressure differential once the fairing is separated and thus reduce the loads on the spacecraft. "The issue of the modification of the venting system and the fairing anomaly are different," de Chambure said.

- The Ariane 5 is scheduled to make its next launch, the first since the August 2020 launch that had the payload fairing anomaly, in the second half of July, said Beatriz Romero, JWST project manager at Arianespace. That launch will be the first of two commercial Ariane 5 launches before the JWST launch.

- At a May 11 media event, Greg Robinson, program director for JWST at NASA Headquarters, said that the JWST launch would take place about four months after the first of the two commercial Ariane 5 launches ahead of it. That would push the launch, currently scheduled for no earlier than Oct. 31, to at least the middle of November.

- At the ESA briefing, Thomas Zurbuchen, NASA associate administrator for science, offered a similar schedule. Asked if a mid-November launch was likely, based on 10-week launch processing schedule that begins with JWST's shipment from California to the launch site in French Guiana in late August, he said that timeframe is "approximately correct."

- "We want to be sure that we launch exactly when we're ready, not a day earlier," he said. "That is, when the spacecraft is ready and when the rocket and the fairing and everything is ready."

• March 30, 2021: Mission officials for NASA's James Webb Space Telescope have announced the selection of the General Observer programs for the telescope's first year of science, known as Cycle 1. These specific programs will provide the worldwide astronomical community with one of the first extensive opportunities to investigate scientific targets with Webb. ^{22) 23)}

- The General Observer scientific observations for the NASA/ESA/CSA James Webb Space Telescope's first year of operation have been selected. Proposals from ESA member states comprise 33% of the total number of selected proposals and correspond to 30% of the available telescope time on Webb.

- The 286 selected proposals address a wide variety of science areas and will help fulfill NASA's overarching mission to further our understanding of the universe and our place in it. Webb will begin observing the universe in 2022 after the spacecraft unfolds, travels a million miles, and checks the functioning of all of its instruments.

- "The initial year of Webb's observations will provide the first opportunity for a diverse range of scientists around the world to observe particular targets with NASA's next great space observatory," said Dr. Thomas Zurbuchen, Associate Administrator for the Science Mission Directorate at NASA. "The amazing science that will be shared with the global community will be audacious and profound."

- Webb's large mirror, near- to mid-infrared sensitivity, and high-resolution imaging and spectroscopic capabilities will reveal parts of the universe that have been hidden so far. General Observer programs selected in this cycle seek to find the first galaxies, explore the formation of stars, and measure physical and chemical properties of planetary systems, including our own solar system.

- "We are opening the infrared treasure chest, and surprises are guaranteed," said Dr. John C. Mather, Senior Project Scientist for the Webb mission and Senior Astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "How did the universe make galaxies, stars, black holes, and planets, and our own very special little Earth? I don't know yet, but we are getting closer every day."

- General Observer time with Webb is extremely competitive. As a result, the proposal selection process conducted by the Telescope Allocation Committee is both rigorous and meticulous. The committee was comprised of nearly 200 members of the worldwide astronomical community who were assigned to 19 different panels covering broad scientific topics. The panels met virtually, due to the ongoing COVID-19 pandemic circumstances, over the course of several weeks. Members additionally spent countless hours outside of formal meetings to assess proposals.

- Using dual-anonymous review, where the identities of the proposing investigator and team were concealed, the scientific merit of each proposal was evaluated and ranked. The final, ranked list of selected proposals was presented to the Space Telescope Science Institute's Director, Dr. Kenneth Sembach, for review and approval.

- "The first observing cycle with a new observatory is always special, especially one as powerful and highly anticipated as Webb. We had an incredibly interesting couple of weeks of intense proposal reviews during which the reviewers did a great job of sorting through and ranking all the possible science cases proposed. I commend them for their hard work, especially under pandemic conditions," said Sembach. "I'm very pleased to be able to approve such a strong science program for the observatory. These observations are going to provide stunning views of the universe and lead us in new investigative directions that will set the stage for decades of research."

- More than 1,000 proposals were submitted by the November 24, 2020 deadline. Scientists hailing from 44 countries applied for a portion of the 6,000 observing hours available in Webb's first year, which represents about two-thirds of all Cycle 1 observing time.

- "We celebrate the very successful partnership between the European Space Agency and our colleagues at NASA and the Canadian Space Agency," said Prof. Günther Hasinger, Director of Science at the European Space Agency. "We look forward to the beautiful images and spectra and the amazing discoveries that Webb will make in this first year of observations."

- "The Canadian Space Agency is proud to join NASA and ESA on this fantastic exploration of the Universe and back in cosmic time. We're all really looking forward to seeing this next generation space telescope in action," said Dr. Sarah Gallagher, Science Advisor to the President of the Canadian Space Agency. "Excitement is building as we get closer to the launch of Webb. These new targets for Webb's first science are highly anticipated observations that promise to expand our view of the Universe and our place in it. Congratulations to the group of outstanding astronomers on their successes in this rigorous selection process."

- General Observer programs will take place alongside Director's Discretionary-Early Release Science (ERS) and Guaranteed Time Observation (GTO) programs. All of these observations begin after the telescope's commissioning period, which takes at least six months.

- The full list of General Observer programs is available at https://www.stsci.edu/jwst/science-execution/approved-programs/cycle-1-go.

- The Space Telescope Science Institute (STScI) in Baltimore will conduct Webb science operations and house Webb's mission operations center, which commands and controls the telescope. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

- The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

• March 18, 2021: NASA's James Webb Space Telescope is making continued progress for a launch in October as engineers close out a series of technical issues with the spacecraft but deal with one new problem. ²⁴⁾

- In a March 16 presentation during a meeting of NASA's Astrophysics Advisory Committee, Eric Smith, JWST program scientist, said engineers had either completed work on, or were in the process of wrapping up, several technical issues the program had been tracking in recent months, none of which posed a risk to the mission's schedule.

- Those issues included concerns about residual air pressure in the spacecraft's sunshield that could stress it when the Ariane 5 rocket that will launch JWST jettisons its payload fairing. Smith said that issue has been closed after adding a couple patches to the sunshield to ensure it could handle double the required pressure differential. Another issue, fasteners on the spacecraft that may not have been installed with sufficient torque, has also been resolved by retorquing those fasteners.

- The project has 48 days of schedule margin remaining, which Smith said was in line with projections at this phase of development. "We're burning it down at the pace expected," he said of that schedule margin.

- JWST is currently going through a final series of deployment tests, including of its primary mirror. The spacecraft will then be prepared for shipment later this summer to Kourou, French Guiana, for final launch preparations.

- Smith said the program is dealing with one new technical issue. Two communications transponders suffered separate problems during testing in January. Engineers have tracked down the problems with the two units and started repairs this week. "Those boxes will be back in time for us to make our planned shipping date," he said.

- That issue, he acknowledged, will use some of the remaining schedule margin. "The plan right now is that we'll get them back in time so that we don't have to use all of it," he said. "That's the main thing that we're watching regarding the margin."

- One other issue is the name of the spacecraft itself. The telescope is named after James Webb, the NASA administrator for much of the 1960s known for his leadership of the agency during the race to the moon. Earlier in his career, Webb worked at the State Department and reportedly oversaw policies there to purge the department of LGBT employees. Some object to the name for that reason and have called on NASA to rename the telescope.

- Smith said both NASA's chief historian, Brian Odom, and other historians outside the agency have been studying Webb's activities at the State Department. "They haven't completed their research in the archives yet, but when they do, that's when the agency would come out with a position on that," he said.

Roman Delays

- While JWST is sticking to its October launch date, the next flagship astrophysics mission, the Nancy Grace Roman Space Telescope, is likely to be delayed because of a slowdown in activity during the pandemic.

- "We do have COVID impacts," said Julie McEnery, senior project scientist for the mission, previously known as the WFIRST (Wide Field Infrared Survey Telescope). In a presentation at the same meeting March 16, she said the program has been running at "70% efficiency" since the start of the pandemic a year ago, and would likely remain there for several more months as the pandemic slowly ebbs.

- "The delay is on the order of months, not years," she said, adding that the pandemic was the only issue the telescope was facing. "Fundamentally, Roman is on track. Except for the COVID-related impacts, everything is coming together and is where it needs to be."

- Speaking to the committee March 15, Paul Hertz, director of NASA's astrophysics division, said Roman's launch date would likely move from late 2025 to the middle of 2026 because of the pandemic. "It will need additional funding to pay for that schedule slip," he said, but didn't give an estimate of that increased cost since the agency is still reviewing estimates of the delay and related costs.

• March 8, 2021: On the occasion of International Women's Day 2021, and as excitement builds for the launch of the James Webb Space Telescope (Webb) in October, ESA is highlighting women that play an important role in Europe's contribution to Webb. ²⁵⁾

- Webb, which is scheduled for launch on 31 October 2021, will be the next great space science observatory expected to make breakthrough discoveries in all fields of astronomy. It will look farther and deeper into the Universe than ever before: from our own Solar System, to exoplanets around other stars, and the birth of the first stars and galaxies.

- ESA is one of the partners in the international Webb mission alongside NASA and the Canadian Space Agency (CSA). Europe plays a crucial role by contributing to two instruments (NIRSpec and MIRI), and by launching the telescope on an Ariane 5 rocket from Europe's Spaceport in Kourou. ESA scientists are also supporting Webb mission operations at the Space Telescope Science Institute (STScI) in Baltimore, USA.

- On International Women's Day, which was first celebrated in four European countries in 1911, ESA joins in to honor women's achievements in making our upcoming space observatory a reality. We have asked women working on the Webb telescope about their challenges, their career highlights, what they're looking forward to about the Webb mission, and their advice to young people who might be considering careers in the space industry.

• March 1, 2021: February marked significant progress for NASA's James Webb Space Telescope, which completed its final functional performance tests at Northrop Grumman in Redondo Beach, California. Testing teams successfully completed two important milestones that confirmed the observatory's internal electronics are all functioning as intended, and that the spacecraft and its four scientific instruments can send and receive data properly through the same network they will use in space. These milestones move Webb closer to being ready to launch in October. ²⁶⁾

- These tests are known as the comprehensive systems test, which took place at Northrop Grumman, and the ground segment test, which took place in collaboration with the STScI (Space Telescope Science Institute) in Baltimore.

- Before the launch environment test, technicians ran a full scan known as a comprehensive systems test. This assessment established a baseline of electrical functional performance for the entire observatory, and all of the many components that work together to comprise the world's premiere space science telescope. Once environmental testing concluded, technicians and engineers moved forward to run another comprehensive systems test and compared the data between the two. After thoroughly examining the data, the team confirmed that the observatory will both mechanically and electronically survive the rigors of launch.

- Through the course of 17 consecutive days of systems testing, technicians powered on all of Webb's various electrical components and cycled through their planned operations to ensure each was functioning and communicating with each other. All electrical boxes inside the telescope have an "A" and "B" side, which allows redundancy in flight and added flexibility. During the test all commands were input correctly, all telemetry received was correct and all electrical boxes, and each backup side functioned as designed.

- "It's been amazing to witness the level of expertise, commitment and collaboration across the team during this important milestone," said Jennifer Love-Pruitt, Northrop Grumman's electrical vehicle engineering lead on the Webb observatory. "It's definitely a proud moment because we demonstrated Webb's electrical readiness. The successful completion of this test also means we are ready to move forward toward launch and on-orbit operations."

Webb's Recent Systems Scan Confirms the Observatory Will Withstand the Launch Environment

- Following the completion of Webb's final comprehensive systems evaluation, technicians immediately began preparations for its next big milestone, known as a ground segment test. This test was designed to simulate the complete process from planning science observations to posting the scientific data to the community archive.

- Webb's final ground segment test began by first creating a simulated plan that each of its scientific instruments would follow. Commands to sequentially turn on, move, and operate each of four scientific instruments were then relayed from Webb's Mission Operations Center (MOC) at the Space Telescope Science Institute (STScI) in Baltimore. During the test, the observatory is treated as if it were a million miles away in orbit. To do this, the Flight Operations Team connected the spacecraft to the Deep Space Network, an international array of giant radio antennas that NASA uses to communicate with many spacecraft. However, since Webb isn't in space yet, special equipment was used to emulate the real radio link that will exist between Webb and the Deep Space Network when Webb is in orbit. Commands were then relayed through the Deep Space Network emulator to the observatory at Northrop Grumman.

- One of the unique aspects of Webb's final ground segment test occurred during a simulated flight environment when the team successfully practiced seamlessly switching over control from its primary MOC at STScI in Baltimore to the backup MOC at NASA's Goddard Space Flight Center in Greenbelt, Maryland. This demonstrated a backup plan that isn't anticipated to be needed but is necessary to practice and perfect prior to launch. Additionally, team members successfully sent multiple software patches to the observatory while it was performing its commanded operations.

- "Working in a pandemic environment, of course, is a challenge, and our team has been doing an excellent job working through its nuances. That's a real positive to highlight, and it's not just for this test but all of the tests we've safely completed leading up to this one," said Bonnie Seaton, deputy ground segment & operations manager at Goddard. "This recent success is attributable to many months of preparation, the maturity of our systems, procedures, and products and the proficiency of our team."

- When Webb is in space, commands will flow from STScI to one of the three Deep Space Network locations: Goldstone, California; Madrid, Spain; or Canberra, Australia. Signals will then be sent to the orbiting observatory nearly one million miles away. Additionally, NASA's Tracking and Data Relay Satellite network – the Space Network in New Mexico, the European Space Agency's Malindi station in Kenya, and ESOC (European Space Operations Centre) in Germany – will help keep a constant line of communication open with Webb.

- Engineers and technicians continue to follow personal safety procedures in accordance with current CDC and Occupational Safety and Health Administration guidance related to COVID-19, including mask wearing and social distancing. The team is now preparing for the next series of technical milestones, which will include the final folding of the sunshield and deployment of the mirror, prior to shipment to the launch site.

- The next series of milestones for Webb include a final sunshield fold and a final mirror deployment.

- The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

• December 18, 2020: Lengthened to the size of a tennis court, the five-layer sunshield of NASA's fully assembled James Webb Space Telescope successfully completed a final series of large-scale deployment and tensioning tests. This milestone puts the observatory one step closer to its launch in 2021. ²⁷⁾

- "This is one of Webb's biggest accomplishments in 2020," said Alphonso Stewart, Webb deployment systems lead for NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We were able to precisely synchronize the unfolding motion in a very slow and controlled fashion and maintain its critical kite-like shape, signifying it is ready to perform these actions in space."

- The sunshield protects the telescope and reflects light and background heat from the Sun, Earth and Moon into space. The observatory must be kept cold to accomplish groundbreaking science in infrared light, which is invisible to human eyes and felt as heat.

- In the sunshield's shadow, Webb's innovative technologies and sensitive infrared sensors will allow scientists to observe distant galaxies and study many other intriguing objects in the universe.

- Maintaining the sunshield's shape involves a delicate, complicated process.

- "Congratulations to the entire team. Due to Webb's large size and stringent performance requirements, the deployments are incredibly complex. In addition to the required technical expertise, this set of tests required detailed planning, determination, patience and open communication. The team proved that it has all these attributes. It's amazing to think that next time Webb's sunshield is deployed it will be many thousands of miles away, hurtling through space," said James Cooper, Webb's sunshield manager at Goddard.

- The Kapton® polymer-coated membranes of Webb's sunshield were fully deployed and tensioned in December at Northrop Grumman in Redondo Beach, California. Northrop Grumman designed the observatory's sunshield for NASA.

- During testing, engineers sent a series of commands to spacecraft hardware that activated 139 actuators, eight motors, and thousands of other components to unfold and stretch the five membranes of the sunshield into its final taut shape. A challenging part of the test is to unfold the sunshield in Earth's gravity environment, which causes friction, unlike unfolding material in space without the effects of gravity.

- For launch the sunshield will be folded up around two sides of the observatory and placed in an Ariane 5 launch vehicle, which is provided by the European Space Agency.

- In this test, two pallet structures that hold the sunshield upright folded down, then two huge "arms" (known as the Mid-Boom Assembly) of the sunshield slowly telescoped outward, pulling the folded membranes along with them to resemble the synchronized movements of a very slowly choreographed dance. Once the arms locked in their horizontal position, the membranes of the sunshield were successfully tensioned individually starting with the bottom layer, separating each into their fully deployed shape.

- The large sunshield divides the observatory into a warm, Sun-facing side (about 185 degrees Fahrenheit) and a cold-space-facing side (minus 388 degrees Fahrenheit) comprised of the optics and scientific instruments. The sunshield will protect the observatory's optics and sensors, so they remain at extremely cold temperatures to conduct science.

- "This milestone signals that Webb is well on its way to being ready for launch. Our engineers and technicians achieved incredible testing progress this month, reducing significant risk to the project by completing these milestones for launch next year," said Bill Ochs, project manager for Webb at Goddard. "The team is now preparing for final post-environmental deployment testing on the observatory these next couple of months prior to shipping to the launch site next summer."

- Webb has passed other rigorous deployment tests during its development, which successfully uncovered and resolved technical issues with the spacecraft. These tests validate that once in orbit, the observatory and its many redundant systems will function flawlessly.

- The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

• August 24, 2020: Testing teams have successfully completed a critical milestone focused on demonstrating that NASA's James Webb Space Telescope will respond to commands once in space. - Known as a "Ground Segment Test," this is the first time commands to power on and test Webb's scientific instruments have been sent to the fully-assembled observatory from its Mission Operations Center at the Space Telescope Science Institute (STScI) in Baltimore, Maryland. ²⁸⁾

- Since reliably communicating with Webb when in space is a mission-critical priority for NASA, tests like these are part of a comprehensive regimen designed to validate and ensure all components of the observatory will function in space with the complex communications networks involved in both sending commands, and downlinking scientific data. This test successfully demonstrated the complete end-to-end flow from planning the science Webb will perform to posting the scientific data to the community archive.

- "This was the first time we have done this with both the actual Webb flight hardware and the ground system. We've performed pieces of this test as the observatory was being assembled, but this is the first ever, and fully successful, end-to-end operation of the observatory and ground segment. This is a big milestone for the project, and very rewarding to see Webb working as expected," said Amanda Arvai, Deputy Division Head of Mission Operations at STScI in Maryland.

- In this test, commands to sequentially turn on, move, and operate each of Webb's four scientific instruments were relayed from the Mission Operations Center. During the test, the observatory is treated as if it were a million miles away in orbit. To do this, the Flight Operations Team connected the spacecraft to the Deep Space Network, an international array of giant radio antennas that NASA uses to communicate with many spacecraft. However, since Webb isn't in space yet, special equipment was used to emulate the real radio link that will exist between Webb and the Deep Space Network when Webb is in orbit. Commands were then relayed through the Deep Space Network emulator to the observatory, which is currently inside a Northrop Grumman clean room in Redondo Beach, California.

- "This was also the first time we've demonstrated the complete cycle for conducting observations with the observatory's science instruments. This cycle starts with the creation of an observation plan by the ground system which is uplinked to the observatory by the Flight Operations Team. Webb's science instruments then performed the observations and the data was transmitted back to the Mission Operations Center in Baltimore, where the science was processed and distributed to scientists," said Arvai.

- When Webb is in space, commands will flow from STScI in Baltimore to one of the three Deep Space Network locations —California, Spain, or Australia. Signals will then be sent to the orbiting observatory nearly one million miles away. Additionally the NASA's Tracking and Data Relay Satellite network, the Space Network in New Mexico, the European Space Agency's Malindi station in Kenya, and European Space Operations Centre in Germany will also aid in keeping a constant line of communication open with Webb at all times.

- To complete the ground segment test a team of nearly 100 people worked together through the course of four consecutive days. Due to staffing restrictions in place due to the coronavirus (COVID-19) pandemic, only seven individuals were present inside the Mission Operations Center, with the rest working remotely to routinely monitor progress. Next up for Webb: observatory level acoustic and sine-vibration testing that will demonstrate that the assembled telescope is capable of surviving the rigors of launch by exposing it to similar conditions.

- Webb is NASA's next great space science observatory, which will help in solving the mysteries of our solar system, looking beyond to distant worlds around other stars, and probing the mystifying structures and origins of our universe. Webb is an international program led by NASA, along with its partners ESA (European Space Agency) and the Canadian Space Agency.

• July 16, 2020: NASA is targeting Oct. 31, 2021, for the launch of the agency's James Webb Space Telescope from French Guiana, due to impacts from the ongoing coronavirus (COVID-19) pandemic, as well as technical challenges. ²⁹⁾

This decision is based on a recently completed schedule risk assessment of the remaining integration and test activities prior to launch. Previously, Webb was targeted to launch in March 2021.

NASA statement of Release 18-019 of 27 March 2018 regarding the new launch target of May 2020 for JWST

• NASA's James Webb Space Telescope currently is undergoing final integration and test phases that will require more time to ensure a successful mission. After an independent assessment of remaining tasks for the highly complex space observatory, Webb's previously revised 2019 launch window now is targeted for approximately May 2020.

- "Webb is the highest priority project for the agency's Science Mission Directorate, and the largest international space science project in U.S. history. All the observatory's flight hardware is now complete, however, the issues brought to light with the spacecraft element are prompting us to take the necessary steps to refocus our efforts on the completion of this ambitious and complex observatory," said acting NASA Administrator Robert Lightfoot.

- Testing the hardware on the observatory's telescope element and spacecraft element demonstrate that these systems individually meet their requirements. However, recent findings from the project's Standing Review Board (SRB) indicate more time is needed to test and integrate these components together and then perform environmental testing at Northrop Grumman Aerospace Systems in Redondo Beach, California, the project's observatory contractor.

- NASA is establishing an external Independent Review Board (IRB), chaired by Thomas Young, a highly respected NASA and industry veteran who is often called on to chair advisory committees and analyze organizational and technical issues. The IRB findings, which will complement the SRB data, are expected to bolster confidence in NASA's approach to completing the final integration and test phase of the mission, the launch campaign, commissioning, as well as the entire deployment sequence. Both boards' findings and recommendations, as well as the project's input, will be considered by NASA as it defines a more specific launch time frame. NASA will then provide its assessment in a report to Congress this summer.

- NASA will work with its partner, ESA (European Space Agency), on a new launch readiness date for the Ariane 5 vehicle that will launch Webb into space. Once a new launch readiness date is determined, NASA will provide a cost estimate that may exceed the projected $8 billion development cost to complete the final phase of testing and prepare for launch. Additional steps to address project challenges include increasing NASA engineering oversight, personnel changes, and new management reporting structures.

- This is a pivotal year for Webb when the 6.5-meter telescope and science payload element will be joined with the spacecraft element to form the complete observatory. The spacecraft element consists of the tennis-court-sized sunshield, designed by Northrop Grumman, and the spacecraft bus, which houses the flight avionics, power system, and solar panels. Because of Webb's large size, engineers had to design components that fold origami-style into the Ariane 5 rocket's fairing configuration.

- Webb has already completed an extensive range of tests to ensure it will safely reach its orbit at nearly one million miles from Earth and perform its science mission. As with all NASA projects, rigorous testing takes time, increasing the likelihood of mission success.

- "Considering the investment NASA and our international partners have made, we want to proceed systematically through these last tests, with the additional time necessary, to be ready for a May 2020 launch," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate.

- After the successful test performance of Webb's telescope and science payload in 2017 at NASA's Johnson Space Flight Center in Houston, the telescope element was delivered to Northrop Grumman earlier this year. Both halves of the 13,500-pound observatory now are together in the same facility for the first time.

- The spacecraft element will next undergo environmental testing, subjecting it to the vibrational, acoustic and thermal environments it will experience during its launch and operations. These tests will take a few months to complete. Engineers then will integrate and test the fully assembled observatory and verify all components work together properly.

- Webb is an international project led by NASA with its partners, ESA and the Canadian Space Agency. ESA is providing the Ariane 5 as part of its scientific collaboration with NASA.

- The James Webb Space Telescope will be the world's premier infrared space observatory and the biggest astronomical space science telescope ever built, complementing the scientific discoveries of NASA's Hubble Space Telescope and other science missions. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.

• June 9, 2020: To test the James Webb Space Telescope's readiness for its journey in space, technicians successfully commanded it to deploy and extend a critical part of the observatory known as the Deployable Tower Assembly. ³¹⁾

- The primary purpose of the deployable tower is to create a large gap between the upper part of the observatory that houses its iconic gold mirrors and scientific instruments, and the lower section known as the spacecraft bus which holds its comparatively warm electronics and propulsion systems. By creating a space between the two, it allows for Webb's active and passive cooling systems to bring its mirrors and sensors down to staggeringly cold temperatures required to perform optimal science.

- Webb was designed to look for faint traces of infrared light, which is essentially heat energy. To detect the extremely faint heat signals of astronomical objects that are incredibly far away, the telescope itself has to be very cold and stable.

- During the test, the tower was slowly extended 48 inches (1.2 meters) upward over the course of several hours, in the same maneuver it will perform once in space. Simulating the zero-gravity environment Webb will operate in, engineers employed an innovative series of pulleys, counterbalances and a special crane called a gravity-negation system that perfectly offloaded all of the effects of Earth's gravity on the observatory. Now that Webb is fully assembled, the difficulty of testing and properly simulating a zero-gravity environment has increased significantly.

- "The Deployable Tower Assembly worked beautifully during the test," said Alphonso Stewart the Webb deployment systems lead for NASA's Goddard Space Flight Center in Greenbelt, Maryland. "It performed exactly as predicted, and from our expectations from previous tests before the full observatory was assembled. This was the first time that this part of Webb was tested in its flight-like configuration to the highest level of fidelity we possibly could. This test provides the opportunity to assess all interfaces and interactions between the instrument and bus sections of the observatory."

- In addition to helping the observatory cool down, the Deployable Tower Assembly is also a big part of how Webb is able to pack into a much smaller size to fit inside an Ariane 5 rocket for launch. Webb is the largest space science observatory ever built, but to fit a telescope that big into a rocket, engineers had to design it to fold down into a much smaller configuration. Webb's Deployable Tower Assembly helps Webb to just barely fit inside a 17.8-foot (5.4-meter) payload fairing. Once in space, the tower will extend to give the rest of Webb's deployable parts, such as the sunshield and mirrors, the necessary amount of room needed to unpack and unfold into a fully functional infrared space observatory.

- "We need to know that Webb will work the way we expect it to before we send it to space," said Stewart. "This is why we test, and when we do, we test as flight-like as possible. The way we send the commands to the spacecraft, the sequence, the individual sitting at the console, the communication that we use. We replicate all of these things to see if we are missing something, to see if there is something that needs to be changed, and to make sure that all of our planning to date has been correct."

- Following augmented personal safety procedures due to COVID-19, the James Webb Space Telescope's Northrop Grumman team in California continued integration and testing work with significantly reduced on-site personnel and shifts. The NASA/Northrop Grumman team recently resumed near-full operations. NASA is evaluating potential impacts on the March 2021 launch date, and will continually assess the schedule and adjust decisions as the situation unfolds.

• May 14, 2020: NASA's James Webb Space Telescope has been successfully folded and stowed into the same configuration it will have when loaded onto an Ariane 5 rocket for launch next year. ³²⁾

- Webb is NASA's largest and most complex space science telescope ever built. Too big for any rocket available in its fully expanded form, the entire observatory was designed to fold in on itself to achieve a much smaller configuration. Once in space, the observatory will unfold and stretch itself out in a carefully practiced series of steps before beginning to make groundbreaking observations of the cosmos.

- "The James Webb Space Telescope achieved another significant milestone with the entire observatory in its launch configuration for the first time, in preparation for environmental testing," said Bill Ochs, Webb project manager for NASA Goddard Space Flight Center in Greenbelt, Maryland. "I am very proud of the entire Northrop Grumman and NASA integration and test team. This accomplishment demonstrates the outstanding dedication and diligence of the team in such trying times due to COVID-19."

- The testing team's charter is to make sure every piece of hardware and every piece of software that comprise Webb will work not only individually, but as a full observatory. Now that Webb is completely assembled, technicians and engineers have seized the unique opportunity to command the entire spacecraft and carry out the various stages of movement and deployment it will perform when in space. By folding and stowing the spacecraft into the same configuration when it launches from French Guiana, the engineering team can confidently move forward with final environmental testing (acoustics and vibration). After completing the series of tests, Webb will be deployed one last time on Earth for testing prior to preparing for launch.

- "While operating under augmented personal safety measures because of the novel coronavirus (COVID-19), the project continues to make good progress and achieve significant milestones in preparation for upcoming environmental testing," said Gregory L. Robinson, the Webb program director at NASA Headquarters in Washington, D.C. "Team member safety continues to be our highest priority as the project takes precautions to protect Webb's hardware and continue with integration and testing. NASA will continually assess the project's schedule and adjust decisions as the situation evolves."

- The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

• March 31, 2020: In a recent test, NASA's James Webb Space Telescope fully deployed its primary mirror into the same configuration it will have when in space. ³³⁾

- As Webb progresses towards liftoff in 2021, technicians and engineers have been diligently checking off a long list of final tests the observatory will undergo before being packaged for delivery to French Guiana for launch. Performed in early March, this procedure involved commanding the spacecraft's internal systems to fully extend and latch Webb's iconic 21 feet 4-inch (6.5 meter) primary mirror, appearing just like it would after it has been launched to orbit. The observatory is currently in a cleanroom at Northrop Grumman Space Systems in Redondo Beach, California.

- The difficulty and complexity of performing tests for Webb has increased significantly, now that the observatory has been fully assembled. Special gravity offsetting equipment was attached to Webb's mirror to simulate the zero-gravity environment its mechanisms will have to operate in. Tests like these help safeguard mission success by physically demonstrating that the spacecraft is able to move and unfold as intended. The Webb team will deploy the observatory's primary mirror only once more on the ground, just before preparing it for delivery to the launch site.

- A telescope's sensitivity, or how much detail it can see, is directly related to the size of the mirror that collects light from the objects being observed. A larger surface area collects more light, just like a larger bucket collects more water in a rain shower than a small one. Webb's mirror is the biggest of its kind that NASA has ever built.

- In order to perform groundbreaking science, Webb's primary mirror needs to be so large that it cannot fit inside any rocket available in its fully extended form. Like the art of origami, Webb is a collection of movable parts employing applied material science that have been specifically designed to fold themselves to a compact formation that is considerably smaller than when the observatory is fully deployed. This allows it to just barely fit within a 5-meter payload fairing, with little room to spare.

- "Deploying both wings of the telescope while part of the fully assembled observatory is another significant milestone showing Webb will deploy properly in space. This is a great achievement and an inspiring image for the entire team," said Lee Feinberg, optical telescope element manager for Webb at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

- The evolving novel coronavirus COVID-19 situation is causing significant impact and disruption globally. Given these circumstances, Webb's Northrop Grumman team in California has resumed integration and testing work with reduced personnel and shifts until the Deployable Tower Assembly set up in April. The project will then shut down integration and testing operations due to the lack of required NASA onsite personnel related to the COVID-19 situation. The project will reassess over the next couple of weeks and adjust decisions as the situation continues to unfold.

- The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

• January 6, 2020: Researchers may have found a way that NASA's James Webb Space Telescope can quickly identify nearby planets that could be promising for our search for life, as well as worlds that are uninhabitable because their oceans have vaporized. ³⁴⁾

- Since planets around other stars (exoplanets) are so far away, scientists cannot look for signs of life by visiting these distant worlds. Instead, they must use a cutting-edge telescope like Webb to see what's inside the atmospheres of exoplanets. One possible indication of life, or biosignature, is the presence of oxygen in an exoplanet's atmosphere. Oxygen is generated by life on Earth when organisms such as plants, algae and cyanobacteria use photosynthesis to convert sunlight into chemical energy.

- But what should Webb look for to determine if a planet has a lot of oxygen? In a new study, researchers identified a strong signal that oxygen molecules produce when they collide. Scientists say Webb has the potential to detect this signal in the atmospheres of exoplanets.

- "Before our work, oxygen at similar levels as on Earth was thought to be undetectable with Webb, but we identify a promising way to detect it in nearby planetary systems," said Thomas Fauchez of the Universities Space Research Association at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "This oxygen signal is known since the early 80's from Earth's atmospheric studies, but has never been studied for exoplanet research." Fauchez is the lead author of the study, appearing in the journal Nature Astronomy January 6.

- The researchers used a computer model to simulate this oxygen signature by modeling the atmospheric conditions of an exoplanet around an M dwarf, the most common type of star in the universe. M dwarf stars are much smaller, cooler, and fainter than our Sun, yet much more active, with explosive activity that generates intense ultraviolet light. The team modelled the impact of this enhanced radiation on atmospheric chemistry, and used this to simulate how the component colors of the star's light would change when the planet would pass in front of it.

- As starlight passes through the exoplanet's atmosphere, the oxygen absorbs certain colors (wavelengths) of light— in this case, infrared light with a wavelength of 6.4 µm. When oxygen molecules collide with each other or with other molecules in the exoplanet's atmosphere, energy from the collision puts the oxygen molecule in a special state that temporarily allows it to absorb the infrared light. Infrared light is invisible to the human eye, but detectable using instruments attached to telescopes.

- "Similar oxygen signals exist at 1.06 and 1.27 m and have been discussed in previous studies but these are less strong and much more mitigated by the presence of clouds than the 6.4 µm signal," said Geronimo Villanueva, a co-author of the paper at Goddard.

- Intriguingly, oxygen can also make an exoplanet appear to host life when it does not, because it can accumulate in a planet's atmosphere without any life activity at all. For example, if the exoplanet is too close to its host star or receives too much star light, the atmosphere becomes very warm and saturated with water vapor from evaporating oceans. This water could be then broken down by the strong ultraviolet radiation into atomic hydrogen and oxygen. Hydrogen, which is a light atom, escapes to space very easily, leaving the oxygen behind.

- Over time, this process can cause entire oceans to be lost while building up a thick oxygen atmosphere. So, abundant oxygen in an exoplanet's atmosphere does not necessarily mean abundant life, but may instead indicate a rich water history.

- "Depending upon how easily Webb detects this 6.4 µm signal, we can get an idea about how likely it is that the planet is habitable," said Ravi Kopparapu, a co-author of the paper at Goddard. "If Webb points to a planet and detects this 6.4 µm signal with relative ease, this would mean that the planet has a very dense oxygen atmosphere and may be uninhabitable."

- The oxygen signal is so strong that it also can tell astronomers whether M dwarf planets have atmospheres at all, using just a few Webb transit observations.

- "This is important because M dwarf stars are highly active, and it has been postulated that stellar activity might ‘blow away' entire planetary atmospheres," said Fauchez. "Knowing simply whether a planet orbiting an M dwarf can have an atmosphere at all is important for understanding star-planet interactions around these abundant but active stars."

- Although the oxygen signal is strong, cosmic distances are vast and M dwarfs are dim, so these stars will have to be relatively nearby for Webb to detect the signal in exoplanet atmospheres within a reasonable amount of time. An exoplanet with a modern Earth-like atmosphere will have to be orbiting an M dwarf that is within approximately 16 light-years of Earth. For a desiccated exoplanet with an oxygen atmosphere 22 times the pressure of Earth's, the signal could be detected up to about 82 light-years away. One light-year, the distance light travels in a year, is almost six trillion miles. For comparison, the closest stars to our Sun are found in the Alpha Centauri system a little over 4 light-years away, and our galaxy is about 100,000 light-years across.

- The research was funded in part by Goddard's Sellers Exoplanet Environments Collaboration (SEEC), which is funded in part by the NASA Planetary Science Division's Internal Scientist Funding Model. This project has also received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant, the NASA Astrobiology Institute Alternative Earths team, and the NExSS Virtual Planetary Laboratory.

- Webb will be the world's premier space science observatory, when it launches in 2021. It will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

• August 28, 2019: Reaching a major milestone, engineers have successfully connected the two halves of NASA's James Webb Space Telescope for the first time at Northrop Grumman's facilities in Redondo Beach, California. Once it reaches space, NASA's most powerful and complex space telescope will explore the cosmos using infrared light, from planets and moons within our solar system to the most ancient and distant galaxies. ³⁵⁾

- To combine both halves of Webb, engineers carefully lifted the telescope (which includes the mirrors and science instruments) above the already-combined sunshield and spacecraft using a crane. Team members slowly guided the telescope into place, ensuring that all primary points of contact were perfectly aligned and seated properly. The observatory has been mechanically connected; next steps will be to electrically connect the halves, and then test the electrical connections.

- "The assembly of the telescope and its scientific instruments, sunshield and the spacecraft into one observatory represents an incredible achievement by the entire Webb team," said Bill Ochs, Webb project manager for NASA Goddard Space Flight Center in Greenbelt, Maryland. "This milestone symbolizes the efforts of thousands of dedicated individuals for over more than 20 years across NASA, the European Space Agency, the Canadian Space Agency, Northrop Grumman, and the rest of our industrial and academic partners."

- Next up for Webb testing, engineers will fully deploy the intricate five-layer sunshield, which is designed to keep Webb's mirrors and scientific instruments cold by blocking infrared light from the Earth, Moon and Sun. The ability of the sunshield to deploy to its correct shape is critical to mission success.

- "This is an exciting time to now see all Webb's parts finally joined together into a single observatory for the very first time," said Gregory Robinson, the Webb program director at NASA Headquarters in Washington, D.C. "The engineering team has accomplished a huge step forward and soon we will be able to see incredible new views of our amazing universe."

- Both of the telescope's major components have been tested individually through all of the environments they would encounter during a rocket ride and orbiting mission a million miles away from Earth. Now that Webb is a fully assembled observatory, it will go through additional environmental and deployment testing to ensure mission success. The spacecraft is scheduled to launch in 2021.

- Webb will be the world's premier space science observatory. It will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, ESA (European Space Agency), and the Canadian Space Agency.

• August 6, 2019: In order to do groundbreaking science, NASA's James Webb Space Telescope must first perform an extremely choreographed series of deployments, extensions, and movements that bring the observatory to life shortly after launch. Too big to fit in any rocket available in its fully deployed form, Webb was engineered to intricately fold in on itself to achieve a much smaller size during transport. ³⁶⁾

- Technicians and engineers recently tested a key part of this choreography by successfully commanding Webb to deploy the support structure that holds its secondary mirror in place. This is a critical milestone in preparing the observatory for its journey to orbit. The next time this will occur will be when Webb is in space, and on its way to gaze into the cosmos from a million miles away.

- The secondary mirror is one of the most important pieces of equipment on the telescope, and is essential to the success of the mission. When deployed, this mirror will sit out in front of Webb's hexagonal primary mirrors, which form an iconic honeycomb-like shape. This smaller circular mirror serves an important role in collecting light from Webb's 18 primary mirrors into a focused beam. That beam is then sent down into the tertiary and fine steering mirrors, and finally to Webb's four powerful scientific instruments.

- "The proper deployment and positioning of its secondary mirror is what makes this a telescope – without it, Webb would not be able to perform the revolutionary science we expect it to achieve. This successful deployment test is another significant step towards completing the final observatory," said Lee Feinberg, optical telescope element manager for Webb at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

- Though there are many preparations still underway for the full assembly of the James Webb Space Telescope's two halves, the secondary mirror test represents the last large milestone before the integration of Webb into its final form as a complete observatory. This operation was also another demonstration that the electronic connection between the spacecraft and the telescope is working properly, and is capable of delivering commands throughout the observatory as designed.

- Webb will be the world's premier space science observatory. It will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

• February 8, 2019: NASA's James Webb Space Telescope has successfully passed another series of critical testing milestones on its march to the launch pad. In recent acoustic and sine vibration tests, technicians and engineers exposed Webb's spacecraft element to brutal dynamic mechanical environmental conditions to ensure it will endure the rigors of a rocket launch to space. ³⁷⁾

- During liftoff, rockets generate extremely powerful vibrations and energetic sound waves that bounce off the ground and nearby buildings and impact the rocket as it makes its way skyward. Technicians and engineers aim to protect Webb from these intense sound waves and vibrations.

- To simulate these conditions, flight components are intentionally punished with a long litany of tests throughout different facilities to identify potential issues on the ground. Webb was bombarded by powerful sound waves from massive speakers and then placed on an electrodynamic vibration table and strongly but precisely shaken. Together, these tests mimic the range of extreme shaking that spacecraft experience while riding a rocket to space.

- "Webb's launch vibration environment is similar to a pretty bumpy commercial airplane flight during turbulence," said Paul Geithner, deputy project manager – technical, James Webb Space Telescope at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "And, its launch acoustic environment is about 10 times more sound pressure, 100 times more intense and four times louder than a rock concert."

- One half of the Webb observatory, known as the "spacecraft element," was the subject of this latest testing. The spacecraft element consists of the "bus," which is the equipment that actually flies the observatory in space, plus the tennis-court-size sunshield that will keep Webb's sensitive optics and instruments at their required super-cold operating temperature. Northrop Grumman in Redondo Beach, California, NASA's lead industrial teammate on Webb, designed and built the spacecraft element, and conducted the testing in their facilities with NASA support and guidance. Northrop Grumman and NASA engineers and technicians worked tirelessly together as a team over the last few months to complete these complex dynamic mechanical environmental tests.

- The initial attempt at acoustic testing last spring uncovered a problem with a specific portion of sunshield hardware, which required some modifications taking several months. Subsequently, the acoustic test was redone, and this time everything went successfully. With acoustic testing complete, the spacecraft element was transported in a mobile clean room to a separate vibration facility, where its spacecraft hardware was exposed to the bumps and shakes that occur when riding a rocket soaring through the atmosphere at high Mach speeds. Northrop Grumman, NASA and its partner, ESA (European Space Agency), are familiar with the flight profile and performance of the Ariane 5 rocket that will carry Webb into space in early 2021, so technicians tuned the tests to mimic the conditions it's expected to face during launch.

- With the successful completion of its mechanical environmental testing, the spacecraft element is being prepared for thermal vacuum testing. This other major environmental test will ensure it functions electrically in the harsh temperatures and vacuum of space. The other half of Webb, which consists of the telescope and science instruments, had completed its own vibration and acoustic testing at Goddard and cryogenic-temperature thermal vacuum testing at NASA's Johnson Space Center in Houston prior to delivery at Northrop Grumman last year. Once finished with thermal vacuum testing, the spacecraft element will return to the giant clean room where it was assembled, to be deployed from its folded-up launch configuration and into its operational configuration, which will be the final proof that it has passed all of its environmental tests. Then, the two halves of Webb — the spacecraft and the telescope elements — will be integrated into one complete observatory for a final round of testing and evaluation prior to launch.

- Webb will be the world's premier space science observatory. It will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, ESA and the Canadian Space Agency.

• September 26, 2018: For the first time, the two halves of NASA's James Webb Space Telescope — the spacecraft and the telescope—were connected together using temporary ground wiring that enabled them to "speak" to each other like they will in flight. ³⁸⁾

- Although it was a significant step forward for the program, this test was an optional "risk reduction" test that took advantage of an opportunity to connect the two halves of the observatory together electrically months earlier than planned. If any issues had been found, it would have given engineers more time to fix them and without causing further delays. As a bonus, it also provided a jumpstart for the separate spacecraft and telescope test teams to begin working jointly as they will when the whole observatory is put together in one piece next year.

- The James Webb telescope is both an exceedingly complex and rewarding undertaking for NASA and its international partners. Scientists anticipate its findings to rewrite textbooks on astronomy by providing revolutionary observations of the cosmos, while engineers and involved technicians forecast that its challenging design will enable and influence future spacecraft architecture for years to come.

- Each piece of Webb has undergone rigorous testing throughout various historic and state of the art facilities across the United States. This ensures the entire observatory is prepared to survive the inherent harshness of a rocket launch to space, and years of continuous exposure to the extremes encountered on a mission nearly a million miles away from Earth.

- In February, Webb made an important, and symbolic step forward in its path to completion when all primary flight components of the observatory came to reside under the same roof at Northrop Grumman in Los Angeles, California. This is where all flight hardware is undergoing final assembly and testing until cleared to launch from the Guiana Space Centre near Kourou in French Guiana.

- "What we did now was make electrical connections between the flight telescope and flight spacecraft to understand all the nuances of the electrical interface. Specifically in this test, the spacecraft commanded mirror motion on the telescope, and the telescope replied back with telemetry confirming it. Even though we have tested each half with a simulator of the other half during their parallel construction, there is nothing exactly like connecting the real thing to the real thing. While the sunshield was being reassembled to get back into its environmental testing, we took advantage of the time and did a flight-to-flight electrical dry run right now to reduce schedule risk later," said Mike Menzel, Webb's Mission System Engineer. "The full complement of electrical and software tests will be run next year when the observatory is finally fully assembled for flight."

- The James Webb Space Telescope will be the world's premier space science observatory. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

• September 5, 2018: Success in JWST critical communications tests: When NASA's James Webb Space Telescope launches in 2021, it will write a new chapter in cosmic history. This premier space science observatory will seek the first stars and galaxies, explore distant planets around other stars, and solve mysteries of own solar system. Webb will be controlled from the MOC (Mission Operations Center) at the STScI (Space Telescope Science Institute) in Baltimore, Maryland. ³⁹⁾

- To prepare for launch, the flight operations team recently conducted two successful communications tests. The first simulated the complex communications among numerous entities in the critical period of launch through the first six hours of flight. The second demonstrated that the MOC could successfully communicate with the telescope.

- A complicated dance: From the moment Webb launches, and through the first six hours of flight, five different telecommunications service providers located around the world will alternately convey command and telemetry data to the mission operations team in the MOC. The first exercise demonstrated the complex exchange among these facilities.

- These different providers are needed because of the geometry of Earth in relation to Webb's orbit and altitude. "Whereas most low-Earth missions can use TDRS (Tracking and Data Relay Satellite) or some other kind of communications satellite in orbit around Earth to relay data, we are so far away that we have to use other facilities," explained NASA's Carl Starr, the Mission Operations Manager for Webb at NASA's Goddard Space Flight Center, Greenbelt, Maryland.

- By six hours after liftoff, Webb will be about halfway to the Moon and six times higher in altitude than the geosynchronous Earth orbit (GEO) where TDRS and many communications satellites dwell. When the telescope reaches its destination, it will be 1.5 million km from Earth—about 45 times farther away than GEO.

- "It's a lot of going back and forth," said Starr. "You have to change configurations, you need a stable connection with Webb at each change, you have to establish the network connections, you have to process the data—and you have to do it multiple times with different stations and make it seamless."

- "And to make things even more complicated," Starr continued, "everyone we are talking about is in different places. You have the Space Network out in New Mexico, the DSN (Deep Space Network) in California, and the European Space Agency's Malindi station in Kenya and ESOC (European Space Operations Center) in Germany. It becomes a very complicated test to do, because no one is in the same time zone—and all of that data comes in and out of this building."

- This test was a major step in demonstrating the flight operations capabilities and processes to support launch-day communications. After the first day, the team moves to a normal setup with just the three DSN terminals around the world.

- "The teams were able to talk with the external entities, and prove the concept that we can manipulate the communications on the day of launch here in the building for the mission," Starr said. "We'll have other proficiency exercises later, but this was the first time that we did it, and it was very successful."

- Talking to the Telescope: No mission would be possible without communicating with the telescope. The flight operations team in Baltimore recently did that for the first time, talking to the actual Webb spacecraft on the ground while it's being integrated and tested across the country at the Northrop Grumman facility in Los Angeles, California.

- "We treated Webb as if it were a million miles away," said Starr. To do this, the flight operations team connected the spacecraft to the Deep Space Network. However, since Webb isn't really in space yet, special equipment was used to emulate the real radio link that will exist between Webb and the Deep Space Network when Webb flies. "We can command and control the vehicle now, and run tests with it from here, without having to travel to Northrop Grumman," Starr explained. "It really is making use of technology to stay on schedule."

- It didn't really matter where Webb was during the test. "As far as we're concerned, it could be in the basement of this building, and we wouldn't know any different," Starr added. "You're just at your console, you've got a data line, your screen ...it's all very much remote. I could imagine it must be how drone pilots feel. They're not anywhere near where their vehicle is."

- During the exercise, the team executed non-operational commands and initiated a recorder playback. This important test demonstrated the flight operations team's ability to command Webb from the MOC in Baltimore.

- Throughout most of commissioning, the MOC will be in constant communication with Webb. After commissioning, approximately 180 days after launch, the team will communicate for 8 hours a day with the telescope. During that time, operators will send up packages of commands for the telescope to run autonomously and downlink the science data.

- More to come: More tests will follow, but these were the first to show the MOC's successful communication with Webb and with the many command and telemetry service providers. The fact that these exercises were carried out flawlessly is a testament to the hard work of the flight operations team, as well as teams across the country and around the world.

- The JWST will be the world's premier space science observatory. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, the European Space Agency (ESA) and the Canadian Space Agency (CSA).

• July 18, 2018: The sound associated with a rocket launch creates extreme vibrations that can adversely affect any satellite or observatory, so engineers put spacecraft through simulations to ensure they will remain operational. ⁴⁰⁾

- The sunshield separates the observatory into a hot, sun-facing side (reaching temperatures close to 110º C), and a cold side (approximately -240ºC) where the sunlight is blocked from interfering with the sensitive telescope instruments.

- The James Webb Space Telescope will be the world's premier space science observatory. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, the European Space Agency (ESA) and the Canadian Space Agency (CSA).

• June 5, 2018: How will NASA's James Webb Space Telescope shed the heat generated by its science instruments and their supporting electronics? To anyone who is not an engineer or scientist, the answer might be complex and "baffling," and it turns out the process is exactly that. ⁴¹⁾

- Webb's four science instruments are held within a support structure called the integrated science instrument module (ISIM), located behind the telescope's primary mirror. The ISIM and Webb's optics form the science payload of the observatory. To keep heat away from the sensitive instruments, a majority of the electronics used to power and operate the instruments are housed in a compartment below ISIM, where specially designed baffles direct the heat safely into space and away from any cold surfaces of the observatory.

- The baffles essentially act as mirrors to reflect the heat (infrared radiation) outward in a specific direction. If that sounds familiar, it is because Webb's mirrors will do very much the same thing — but instead of reflecting the infrared light into space, they will guide it with pinpoint accuracy to the telescope's science instruments.

- "Gold has a very high reflectivity in the infrared spectrum range, so it is ideal for directing heat," explained Matthew Stephens, a mechanical systems engineer for Webb at NASA's Goddard Space Flight Center in Greenbelt, MD. "This is the same reason all of the primary, secondary, and tertiary mirrors are gold-coated."

- The engineers in this photo of Figure 44 are reinstalling the baffles, which had been previously removed and safely stored in a clean environment to protect them from any contamination during integration and testing of the science payload. The clear plastic sheets placed over the baffles will protect them from any contamination during the remaining integration and testing phases for the observatory.

- The engineers had to reinstall the baffles before Webb's science payload and its spacecraft element (the combined spacecraft bus and sunshield) are integrated at Northrop Grumman Aerospace Systems in Redondo Beach, California, where both halves of the observatory currently reside. If the engineers wait until after integration, Webb's tennis-court-sized sunshield will obstruct the ISIM electronics compartment and make reinstalling the baffles much more difficult.

• June 4, 2018: In the last year, the James Webb Space Telescope (JWST) and in particular the telescope and the instruments have passed some key milestones on their road towards launch, now planned for 2020. ⁴²⁾

- The first landmark was the completion of four-month long cryogenic tests in the giant thermal vacuum chamber, known as Chamber A, at NASA's Johnson Space Center in Houston, Texas. There, JWST's optical telescope and integrated science instrument module (OTIS) underwent a series of tests designed to check that the telescope and its four scientific instruments functioned as expected in an extremely cold, airless environment, similar to the conditions they will experience in space.

- On 27 September 2017, after confirming that OTIS can survive and operate flawlessly in temperatures of approximately 40 Kelvin (-233º C), engineers began to gradually warm the chamber. This was a very precise operation that required extreme caution in order to avoid contaminating the optical equipment or generating mechanical stresses that could damage the instruments or other JWST hardware.

- Once the thermal conditions inside the chamber returned to near room temperature, a final set of functional tests was performed under vacuum conditions. These tests confirmed that the warm-up procedure and OTIS cold testing had not caused any issue with respect to the functionality of the instruments and telescope. After this, the vacuum was slowly counteracted by pumping extra-clean air back into the chamber.

- The 40-ton chamber door was unsealed on 18 November 2017, marking the successful completion of the cryogenic testing, and OTIS finally emerged from Chamber A on 1 December, after some 100 days shut inside the cavernous vault.

A Closer Look at NIRSpec Microshutters and Detectors

- After analysis of the data collected during the OTIS cryogenic test campaign, the team responsible for the European NIRSpec (Near InfraRed Spectrograph) confirmed that the instrument had operated very well and that its performance had not been impacted negatively, despite the intensive OTIS test campaign.

- The NIRSpec team was particularly pleased that the instrument's MSA (Micro Shutter Assembly), which comprises approximately 250,000 minuscule 'doors' that enable its Multi-Object Spectrograph capabilities, was in good health, having survived the earlier severe vibration and acoustic testing of OTIS. The performance of the microshutters, which are extremely delicate and can be susceptible to the strong acoustic stresses, could only be verified fully in cryogenic conditions.

- During testing, ESA scientists also commanded the instrument to mimic scientific operations in space and acquired samples of data to verify the spectrograph performance. The testing of OTIS demonstrated that the NIRSpec optics are very stable and ready to withstand the harsh conditions of launch.

- As for the detectors, their performance was confirmed to be "exquisite". Calibration images were acquired during OTIS testing while operating in NIRSpec MOS (Multi-Object Spectrographic) mode, which will allow astronomers to obtain spectra of more than 100 sources simultaneously. A typical calibration image shows many spectra recorded by the NIRSpec detectors and obtained by commanding selected microshutters open, with illumination provided using one of the instrument's internal calibration lamps.

- The calibration image of Figure 48 was acquired during testing of the NIRSpec instrument. NIRSpec will be used to study astronomical objects focussing on very distant galaxies. It will do so by splitting their light into spectra – separating the light into components allows scientists to investigate what these objects are made of.

- Created using one of the instrument's internal calibration lamps as the light source, the image shows many spectra as horizontal bands that were recorded by two detectors,. The wavelengths are spread from left to right; the pattern of dark stripes, called absorption lines, is characteristic of the light source, much like a fingerprint.

- The image was produced by sending commands to open over 100 of the instrument's micro-shutters – minuscule windows the width of a human hair – that will be used to study hundreds of celestial objects simultaneously. The thin strips in the upper and lower parts of the image are spectra created by light that passed through the micro-shutters, while the thicker bands at the center of the images were produced by light that enters the instrument through five slits at the center.

- Once in space, the micro-shutters will be opened or closed depending on the distribution of stars and galaxies in the sky.

- This calibration image was obtained in 2017 during testing in the giant thermal vacuum chamber at NASA's Johnson Space Center in Houston, Texas. The tests demonstrated that the combined structure, comprising the Webb telescope and its four science instruments, operated flawlessly at temperatures of around –233°C, similar to those they will experience in space.

- The telescope and instruments are now at Northrop Grumman Aerospace Systems in Redondo Beach, California, where they will be integrated with the spacecraft and sunshield for further tests and launch preparations.

OTIS in the Spotlight

- During the OTIS test campaign, the telescope and the instrument module were tested together at their operating temperature for the first time. To take advantage of that, a long suite of tests was performed using dedicated light sources that were temporarily mounted on OTIS.

- These sources, called ASPA (Aft Optical System Plate Assembly) optical stimuli, are used to send a variety of light beams onto the telescope and instrument optics in order to perform true end-to-end testing of the full JWST optical system, something that had not been done before.

- The resulting images and spectra obtained using all four of the Webb's instruments matched remarkably well with the expectations from computer simulations that had been performed several years prior to the actual OTIS test campaign.

- Another set of entirely different measurements also took place in the chamber to assess the stability of the OTIS hardware. Three very high-resolution camera systems, equipped with specially designed flash lamps and mounted on gigantic 3.4 meter-long rotating booms, were used to take multiple photographs of OTIS, tracking the position of hundreds of little reflective targets installed on the OTIS hardware.

- The photogrammetry technique was instrumental to measure the miniscule movements and shrinkage of the hardware during the cool down. By doing so, engineers were able to measure positions with an accuracy of only a few tens of µm across the full extent of OTIS, which spans several meters.

- Finally a set of tests was conducted to check that a particular optical path, known as the "rogue path", was blocked. Unlike the NASA/ESA Hubble Space Telescope, which is equipped with a tube, JWST has an open, tubeless telescope design, so extra effort has to be spent to make sure that stray light cannot reach its detectors.

- This check was conducted using a third set of special light sources, consisting of arrays of LEDs arranged around the perimeter of the primary mirror. The procedure confirmed that this stray light path is properly blocked.

- After the warm-up inside Chamber A was completed, the actuators for the telescope's primary mirror segment were functionally tested before all 18 of the mirror segments were stowed. This cleared the way for the transportation of OTIS from Houston to Northrop Grumman Aerospace Systems in Redondo Beach, California, at the beginning of 2018 ⁴²⁾.

Independent Review Board of JWST ⁴³⁾

• April 6, 2018: NASA has assembled members of an external Independent Review Board for the agency's James Webb Space Telescope. The board will evaluate a wide range of factors influencing Webb's mission success and reinforce the agency's approach to completing the final integration and testing phase, launch campaign, and commissioning for NASA's next flagship space science observatory.

- "We are exploring every aspect of Webb's final testing and integration to ensure a successful mission, delivering on its scientific promise," said Thomas Zurbuchen, Associate Administrator for NASA's Science Mission Directorate. "This board's input will provide a higher level of confidence in the estimated time needed to successfully complete the highly complex tasks ahead before NASA defines a specific launch time frame."

- The board, convened by NASA's Science Mission Directorate, includes individuals with extensive experience in program and project management, schedule and cost management, systems engineering, and the integration and testing of large and complex space systems, including systems with science instrumentation, unique flight hardware, and science objectives similar to Webb.

- The Independent Review Board review process will take approximately eight weeks. Once the review concludes, the board members will deliver a presentation and final report to NASA outlining their findings and recommendations, which are expected to complement recent data input from Webb's Standing Review Board. NASA will review those findings and then provide its assessment in a report to Congress at the end of June. Northrop Grumman Aerospace Systems, the project's observatory contractor, will proceed with the remaining integration and testing phase prior to launch.

The board consists of the following notable leaders in the space science community:

Mr. Thomas Young, NASA/Lockheed Martin in Bethesda, Maryland – Retired (Chair)

Dr. William Ballhaus, Aerospace Corporation in El Segundo, California- Retired

Mr. Steve Battel, Battel Engineering, Inc. in Scottsdale, Arizona

Mr. Orlando Figueroa, NASA Headquarters and Goddard Space Flight Center in Greenbelt, Maryland – Retired

Dr. Fiona Harrison, Caltech University in Pasadena, California

Ms. Michele King, NASA Office of Chief Financial Officer/Strategic Investments Division in Washington, DC

Mr. Paul McConnaughey, NASA/Marshall Space Flight Center/Webb Standing Review Board (Chair) in Huntsville, Alabama

Ms. Dorothy Perkins, NASA Goddard Space Flight Center in Greenbelt, Maryland - Retired

Mr. Pete Theisinger, Jet Propulsion Laboratory in Pasadena, California

Dr. Maria Zuber, Massachusetts Institute of Technology in Cambridge, Massachusetts

• February 05, 2018: The two halves of NASA's James Webb Space Telescope now reside at Northrop Grumman Aerospace Systems in Redondo Beach, California, where they will come together to form the complete observatory. ⁴⁴⁾

- Webb's OTIS (Optical Telescope and Integrated Science) instrument module arrived at Northrop Grumman Feb. 2, from NASA's Johnson Space Center in Houston, where it successfully completed cryogenic testing.

- "This is a major milestone," said Eric Smith, director of the James Webb Space Telescope Program at NASA. "The Webb observatory, which is the work of thousands of scientists and engineers across the globe, will be carefully tested to ensure it is ready to launch and enable scientists to seek the first luminous objects in the universe and search for signs of habitable planets."

- In preparation for leaving Johnson, OTIS was placed inside a specially designed shipping container called the Space Telescope Transporter for Air, Road and Sea (STTARS). The container then was loaded onto a U.S. military C-5 Charlie aircraft at Ellington Field Joint Reserve Base, just outside of Johnson. From there, OTIS took a flight to Los Angeles International Airport. After arrival, OTIS was driven from the airport to Northrop Grumman's Space Park facility (Figure 50).

- "It's exciting to have both halves of the Webb observatory – OTIS and the integrated spacecraft element – here at our campus," said Scott Willoughby, vice president and program manager for Webb at Northrop Grumman. "The team will begin the final stages of integration of the world's largest space telescope."

- During this summer, OTIS will combined with the spacecraft element to form the complete Webb observatory. Once the telescope is fully integrated, the entire observatory will undergo more tests during what is called observatory-level testing. Webb is scheduled to launch from Kourou, French Guiana, in 2019.

Legend to Figure 50: STTARS is a massive container, measuring 4.6 m wide, 5.2 m toll, and 33.5 m long with a mass of 75,000 kg. It's much larger than the James Webb itself, but even then, the primary mirror wings and the secondary mirror tripod must be folded into flight configuration in order to fit.

• November 13, 2017: Following the recommendation of the Time Allocation Committee and a thorough technical review, the STScI (Space Telescope Science Institute) Director Ken Sembach has selected 13 science programs for the JWST Director's DD-ERS (Discretionary Early Release Science Program). It is anticipated that the DD-ERS observations will take place during the first 5 months of JWST science operations, following the 6-month commissioning period. ^{45) 46)}

- With a total award of 460 hours of JWST observing time, the selected programs span a wide range of science areas as well as instrument modes, such as surveys of galaxies and their nuclei, stellar clusters and star formation near and far, the chemistry of interstellar and circumstellar matter, and the characterization of exoplanets. The successful programs include 16 Principal investigators (PIs) and co-PIs from North America and 6 from Europe, with broad world-wide participation.

1) The selected programs represent participation by 253 investigators from 18 countries, 22 U.S. states, and 106 unique institutions.

2) Of the 253 investigators, 157 are based in the U.S., 84 are from ESA countries, 7 are from Canada, and 5 are from other countries (Australia and Chile), with 248 unique investigators.

3) There are an additional 456 science collaborators involved in the programs.

4) The three largest teams have combined totals of 138, 105, and 80 investigators and collaborators.

The successful DD-ERS teams are now tasked with developing "science-enabling products," such as documentation for their programs, scientific software, and data products — all designed to help the full astronomical community maximize the science output of the JWST mission.

• October 19, 2017: What appears to be a unique selfie opportunity was actually a critical photo for the cryogenic testing of NASA's James Webb Space Telescope in Chamber A at NASA/JSC (Johnson Space Center) in Houston. The photo (Figure 52) was used to verify the line of sight (the path light will travel) for the testing configuration. ⁴⁷⁾

- During Webb's extensive cryogenic testing, engineers checked the alignment of all the telescope optics and demonstrated the individual primary mirror segments can be properly aligned to each other and to the rest of the system. This all occurred in test conditions that simulated the space environment where Webb will operate, and where it will collect data of never-before-observed portions of the universe. Verifying the optics as a system is a very important step that will ensure the telescope will work correctly in space.

- The actual test of the optics involved a piece of support equipment called the ASPA (AOS Source Plate Assembly). The ASPA is a piece of hardware that sits atop Webb's AOS (Aft Optics Subsystem), which is recognizable as a black "nose cone" that protrudes from the center of Webb's primary mirror. The AOS contains the telescope's tertiary and fine-steering mirrors. The ASPA is ground test hardware, and it will be removed from the telescope before it is launched into space.

- During testing, the ASPA fed laser light of various infrared wavelengths into and out of the telescope, thus acting like a source of artificial stars. In the first part of the optical test, called the "half-pass" test, the ASPA fed laser light straight into the AOS, where it was directed by the tertiary and fine-steering mirrors to Webb's science instruments, which sit in a compartment directly behind the giant primary mirror. This test let engineers make measurements of the optics inside the AOS, and how the optics interacted with the science instruments. Critically, the test verified the tertiary mirror, which is immovable, was correctly aligned to the instruments.

- In another part of the test, called the "pass-and-a-half" test, light traveled in a reverse path through the telescope optics. The light was again fed into the system from the ASPA, but upwards, to the secondary mirror. The secondary mirror then reflected the light down to the primary mirror, which sent it back up to the top of Chamber A. Mirrors at the top of the chamber sent the light back down again, where it followed its normal path through the telescope to the instruments. This verified not only the alignment of the primary mirror itself but also the alignment of the whole telescope — the primary mirror, secondary mirror, and the tertiary and fine-steering mirrors inside the AOS.

- Taken together, the half-pass and pass-and-a-half tests demonstrated all the telescope optics are properly aligned and that they can be aligned again after being deployed in space.

- The photo, snapped by Ball Aerospace optical engineer Larkin Carey after the final fiber optic connections between ASPA and the laser source outside the chamber were made, verified the line of sight for the pass-and-a-half part of the test. The image was compared with one collected once the telescope was cold inside the chamber, to ensure any observed obscurations were due to the ASPA hardware and would not be present during science data collection on orbit.

- In the photo, Carey is harnessed to a "diving board" over the primary mirror. All tools (including the camera) were tethered, and all safety protocol for working over the mirror were closely followed. Carey faced upwards and took the photo of the secondary mirror to verify the ASPA line of sight. The secondary mirror is reflecting him as well as the AOS, the ASPA, and the primary mirror below.

- "Intricate equipment is required to test an instrument as complex as the Webb telescope. The ASPA allowed us to directly test key alignments to ensure the telescope is working as we expect, but its location meant we had to have a person install over 100 fiber optic cables by hand over the primary mirror," said Allison Barto, Webb telescope program manager at Ball Aerospace. "This challenging task, which Larkin rehearsed many times to ensure it could be performed safely, also offered the opportunity to check the alignments by taking this ‘selfie' prior to entering the test."

- After cryogenic testing at Johnson is complete, Webb's combined science instruments and optics journey to Northrop Grumman in Redondo Beach, California, where they will be integrated with the spacecraft element, which is the combined sunshield and spacecraft bus. Together, the pieces form the complete James Webb Space Telescope observatory. Once fully integrated, the entire observatory will undergo more tests during what is called "observatory-level testing." This testing is the last exposure to a simulated launch environment before flight and deployment testing on the whole observatory.

- Webb is expected to launch from Kourou, French Guiana, in the spring of 2019.

• August 24, 2017: NASA's James Webb Space Telescope will use its infrared capabilities to study the "ocean worlds" of Jupiter's moon Europa and Saturn's moon Enceladus, adding to observations previously made by NASA's Galileo and Cassini orbiters. The Webb telescope's observations could also help guide future missions to the icy moons. ⁴⁸⁾

- Europa (Galilean moon of Jupiter) and Enceladus (moon of Saturn)are on the Webb telescope's list of targets chosen by guaranteed time observers, scientists who helped develop the telescope and thus get to be among the first to use it to observe the universe. One of the telescope's science goals is to study planets that could help shed light on the origins of life, but this does not just mean exoplanets; Webb will also help unravel the mysteries still held by objects in our own solar system (from Mars outward).

- Geronimo Villanueva, a planetary scientist at NASA/GSFC in Greenbelt, Maryland, is the lead scientist on the Webb telescope's observation of Europa and Enceladus. His team is part of a larger effort to study our solar system with the telescope, spearheaded by astronomer Heidi Hammel, the executive vice president of the Association of AURA (Universities for Research in Astronomy). NASA selected Hammel as an interdisciplinary scientist for Webb in 2002.

- Of particular interest to the scientists are the plumes of water that breach the surface of Enceladus and Europa, and that contain a mixture of water vapor and simple organic chemicals. NASA's Cassini-Huygens and Galileo missions, and NASA's Hubble Space Telescope, previously gathered evidence that these jets are the result of geologic processes heating large subsurface oceans. "We chose these two moons because of their potential to exhibit chemical signatures of astrobiological interest," said Hammel.

- Villanueva and his team plan to use Webb's near-infrared camera (NIRCam) to take high-resolution imagery of Europa, which they will use to study its surface and to search for hot surface regions indicative of plume activity and active geologic processes. Once they locate a plume, they will use Webb's NIRSpec (Near-Infrared Spectrograph) and MIRI (Mid-Infrared Instrument) to spectroscopically analyze the plume's composition.

- Webb telescope's observations might be particularly telling for the plumes on Europa, the composition of which largely remains a mystery. "Are they made of water ice? Is hot water vapor being released? What is the temperature of the active regions and the emitted water?" questioned Villanueva. "Webb telescope's measurements will allow us to address these questions with unprecedented accuracy and precision."

- For Enceladus, Villanueva explained that because that moon is nearly 10 times smaller than Europa as seen from the Webb telescope, high-resolution imagery of its surface will not be possible. However, the telescope can still analyze the molecular composition of Enceladus' plumes and perform a broad analysis of its surface features. Much of the moon's terrain has already been mapped by NASA's Cassini orbiter, which has spent about 13 years studying Saturn and its satellites.

- Villanueva cautioned that while he and his team plan to use NIRSpec to search for organic signatures (such as methane, methanol, and ethane) in the plumes of both moons, there is no guarantee the team will be able to time the Webb telescope's observations to catch one of the intermittent emissions, nor that the emissions will have a significant organic composition. "We only expect detections if the plumes are particularly active and if they are organic-rich," said Villanueva.

- Evidence of life in the plumes could prove even more elusive. Villanueva explained that while chemical disequilibrium in the plumes (an unexpected abundance or scarcity of certain chemicals) could be a sign of the natural processes of microbial life, it could also be caused by natural geologic processes.

- While the Webb telescope may be unable to concretely answer whether the subsurface oceans of the moons contain life, Villanueva said it will be able to pinpoint and better characterize active regions of the moons that could merit further study. Future missions, such as NASA's Europa Clipper, the primary objective of which is to determine if Europa is habitable, could use Webb's data to hone in on prime locations for observation.

• August 9, 2017: NASA's James Webb Space Telescope began a nearly 100-day cryogenic test in a giant chamber in Texas in mid-July. Components of the Webb have previously endured similar tests to ensure they would function in the cold environment of space. Now all of those components are being tested together in the giant thermal vacuum known as Chamber A at NASA's Johnson Space Center in Houston. ⁴⁹⁾

- "A combination of liquid nitrogen and cold gaseous helium will be used to cool the telescope and science instruments to their operational temperature during high-vacuum operations," said Mark Voyton, manager of testing effort, who works at the NASA Goddard Space Flight Center in Greenbelt, Maryland.

- Next year, the tennis-court sized sunshield and spacecraft bus will be added to make up the entire observatory.

• May 1, 2017: The JWST has successfully passed the center of curvature test, an important optical measurement of Webb's fully assembled primary mirror prior to cryogenic testing, and the last test held at NASA's Goddard Space Flight Center in Greenbelt, Maryland, before the spacecraft is shipped to NASA's Johnson Space Center in Houston for more testing. ^{50) 51)}

- After undergoing rigorous environmental tests simulating the stresses of its rocket launch, the Webb telescope team at Goddard analyzed the results from this critical optical test and compared it to the pre-test measurements. The team concluded that the mirrors passed the test with the optical system unscathed.

- "The Webb telescope is about to embark on its next step in reaching the stars as it has successfully completed its integration and testing at Goddard. It has taken a tremendous team of talented individuals to get to this point from all across NASA, our industry and international partners, and academia," said Bill Ochs, NASA's Webb telescope project manager. "It is also a sad time as we say goodbye to the Webb Telescope at Goddard, but are excited to begin cryogenic testing at Johnson."

- The Webb telescope will be shipped to Johnson for end-to-end optical testing in a vacuum at its extremely cold operating temperatures. Then it will continue on its journey to Northrop Grumman Aerospace Systems in Redondo Beach, California, for final assembly and testing prior to launch in 2018.

• March 28, 2017: The JWST team completed the acoustic and vibration portions of environmental testing on the telescope at NASA/GSFC. These tests are merely two of the many that spacecraft and instruments endure to ensure they are fit for spaceflight. ⁵²⁾

- For the acoustic test, the telescope was wrapped in a clean tent, and engineers and technicians pushed it through a large pair of insulated steel doors, nearly 30 cm thick, into the Acoustic Test Chamber. In the chamber the telescope was exposed to the earsplitting noise and resulting vibration of launch.

- A new vibration test system also known as a shaker table, was built specifically for testing the Webb. The Webb was mounted on the shaker table and experienced the simulated forces the telescope will feel during the launch by vibrating it from 5 to 100 times per second. The test ensures a spacecraft like Webb can withstand the vibrations that occur as a result of the ride into space on a rocket.

- This spring, after other environmental tests are completed, the Webb telescope will be shipped to NASA's Johnson Space Center in Houston, Texas, for end-to-end optical testing in a vacuum at its extremely cold operating temperatures, before it goes to Northrop Grumman Aerospace Systems in Redondo Beach, California, for final assembly and testing prior to launch.

- By performing these tests, scientists and engineers can ensure that the spacecraft and all of its instruments will endure the launch and maintain functionality when it is launched from French Guiana in 2018.

• January 25, 2017: Engineers have resumed a series of critical and rigorous vibration qualification tests on JWST at NASA/GSFC. On December 3, 2016, vibration testing automatically shut down early due to some sensor readings that exceeded predicted levels. After a thorough investigation, the JWST team at NASA Goddard determined that the cause was extremely small motions of the numerous tie-downs or "launch restraint mechanisms" that keep one of the telescope's mirror wings folded-up for launch. ⁵³⁾

- "In-depth analysis of the test sensor data and detailed computer simulations confirmed that the input vibration was strong enough and the resonance of the telescope high enough at specific vibration frequencies to generate these tiny motions. Now that we understand how it happened, we have implemented changes to the test profile to prevent it from happening again," said Lee Feinberg, an engineer and James Webb Space Telescope Optical Telescope Element Manager at Goddard. "We have learned valuable lessons that will be applied to the final pre-launch tests of Webb at the observatory level once it is fully assembled in 2018. Fortunately, by learning these lessons early, we've been able to add diagnostic tests that let us show how the ground vibration test itself is more severe than the launch vibration environment in a way that can give us confidence that the launch itself will be fully successful."

- The team resumed testing last week picking up where they left off in December. The test was successfully completed. Now that vibration testing along this one direction or "axis" is finished, the team is now moving forward with shaking the telescope in the other two directions to show that it can withstand vibrations in all three dimensions. "This was a great team effort between the NASA Goddard team, Northrop Grumman, Orbital ATK, Ball Aerospace, the European Space Agency, and Arianespace," Feinberg said. "We can now proceed with the rest of the planned tests of the telescope and instruments."

• January 3, 2017: Vibration tests are one of the many tests that spacecraft and instruments endure to ensure they are fit for spaceflight. During routine testing of NASA's James Webb Space Telescope, an unexpected response occurred from several of the more than 100 devices designed to detect small changes in the motion of the structure. This prompted the engineers put the vibration tests on hold to determine the cause. ⁵⁴⁾

- Since then, the team of engineers and scientists have analyzed many potential scenarios for the measured responses. They are closer to pinning down the cause, and have successfully conducted three low-level vibrations of the telescope.

- All visual and ultrasonic examinations of the structure continue to show it to be sound. "Currently, the team is continuing their analyses with the goal of having a review of their findings, conclusions and plans for resuming vibration testing in January," said Eric Smith, program director for NASA's James Webb Space Telescope, NASA Headquarters in Washington.

- "This is why we test—to know how things really are, as opposed to how we think they are," said Paul Geithner, deputy project manager-technical for the Webb telescope at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

- During the vibration tests on December 3, 2016 at NASA/GSFC, accelerometers attached to the telescope detected unexpected responses and consequently the test shut itself down to protect the hardware.

- The test shut itself down in a fraction of a second after a higher-than-expected response was detected at a particular frequency of vibration, about one note lower than the lowest note on a piano.

- At NASA, vibration and acoustics test facilities provide vibration and shock testing of spaceflight hardware to ensure that functionality is not impaired by severe launch and landing environments. Launches create high levels of vibration in spacecraft and equipment and ground testing is done to simulate that launch induced vibration. Vibration testing is done on components as small as a few ounces to as large as complete structures or systems.

- By performing the vibration tests on NASA's James Webb Space Telescope, scientists and engineers can ensure that the spacecraft and all of its instruments will endure the launch and maintain functionality when it is launched from French Guiana in 2018.

• November 2, 2016: Engineers and technicians working on the James Webb Space Telescope successfully completed the first important optical measurement of Webb's fully assembled primary mirror, called a Center of Curvature test. ⁵⁵⁾

- Taking a "before" optical measurement of the telescope's deployed mirror is crucial before the telescope goes into several stages of rigorous mechanical testing. These tests will simulate the violent sound and vibration environments the telescope will experience inside its rocket on its way out into space. This environment is one of the most stressful structurally and could alter the shape and alignment of Webb's primary mirror, which could degrade or, in the worst case, ruin its performance.

- The JWST has been designed and constructed to withstand its launch environment, but it must be tested to verify that it will indeed survive and not change in any unexpected way. Making the same optical measurements both before and after simulated launch environment testing and comparing the results is fundamental to Webb's development, assuring that it will work in space.

- "This is the only test of the entire mirror where we can use the same equipment during a before and after test," said Ritva Keski-Kuha, the test lead and NASA's Deputy Telescope Manager for Webb at NASA/GSFC in Greenbelt, Maryland. "This test will show if there are any changes or damages to the optical system."

- In order to conduct the test, optical engineers set up an interferometer, the main device used to measure the shape of Webb's mirror. Waves of visible light are less than a thousandth of a millimeter long, and optics like Webb's need to be shaped and aligned even more accurately than this to work correctly. Making measurements of the mirror shape and position by lasers prevents physical contact and damage (scratches to the mirror). So scientists use wavelengths of light to make tiny measurements. By measuring light reflected off the optics using an interferometer, they are able to measure extremely small changes in shape or position. An interferometer gets its name from the process of recording and measuring the ripple patterns that result when different beams of light mix and their waves combine or 'interfere.'

- During the test conducted by a team from NASA Goddard, Ball Aerospace of Boulder, Colorado, and the Space Telescope Science Institute in Baltimore Maryland, temperature and humidity conditions in the cleanroom were kept incredibly stable to minimize drift in the sensitive optical measurements over time. Even so, tiny vibrations are ever-present in the cleanroom that cause jitter during measurements, so the interferometer is a 'high-speed' one, taking 5,000 'frames' every second, which is a faster rate than the background vibrations themselves. This allows engineers to subtract out jitter and get good, clean results.

- The Center of Curvature test measures the shape of Webb's main mirror by comparing light reflected off of it with light from a computer-generated hologram that represents what Webb's mirror ideally should be. By interfering the beam of light from Webb with the beam from the hologram reference, the interferometer accurately compares the two by measuring the difference to incredible precision. "Interferometry using a computer-generated hologram is a classic modern optical test used to measure mirrors," said Keski-Kuha.

- With the largest mirror of any space telescope, taking this measurement is a challenge. "We have spent the last four years preparing for this test," said David Chaney, Webb's primary mirror metrology lead at Goddard. "The challenges of this test include the large size of the primary mirror, the long radius of curvature, and the background noise. Our test is so sensitive we can measure the vibrations of the mirrors due to people talking in the room."

- After the measurements come back from the interferometer the team will analyze the data to make sure the mirrors are aligned perfectly before the launch environment tests. The Center of Curvature test will be repeated after the launch environment testing and the results compared to confirm that Webb's optics will work after their launch into space.

- The most powerful space telescope ever built, the Webb telescope will provide images of the first galaxies ever formed, and explore planets around distant stars. It is a joint project of NASA, the European Space Agency and the Canadian Space Agency.

• October 31, 2016: The last of the five sunshield layers responsible for protecting the optics and instruments of NASA's James Webb Space Telescope is now complete. Designed by Northrop Grumman in Redondo Beach, California, the Webb telescope's sunshield will prevent the background heat from the sun from interfering with the telescope's infrared sensors. The five sunshield membrane layers, designed and manufactured by the NeXolve Corporation in Huntsville, Alabama, are each as thin as a human hair. The layers work together to reduce the temperatures between the hot and cold sides of the observatory by approximately 300ºC. Each successive layer of the sunshield, made of Kapton, is cooler than the one below. The fifth and final layer was delivered on Sept. 29, 2016 to Northrop Grumman Corporation's Space Park facility in Redondo Beach. ⁵⁶⁾

- "The completed sunshield membranes are the culmination of years of collaborative effort by the NeXolve, Northrop Grumman and NASA team," said James Cooper, Webb telescope Sunshield manager at NASA Goddard Space Flight Center in Greenbelt, Maryland. "All five layers are beautifully executed and exceed their requirements. This is another big milestone for the Webb telescope project."

- Northrop Grumman, who also designed the Webb telescope's optics and spacecraft bus for NASA Goddard will integrate the final flight layers into the sunshield subsystem to conduct folding and deployment testing as part of the final system validation process. The sunshield is the size of a tennis court, helping solidify the Webb telescope as the largest ever built for space. The sunshield, along with the rest of the spacecraft, will fold origami-style into an Ariane 5 rocket.

- "The five tennis court-sized sunshield membranes took more than three years to complete and represents a decade of design, development and manufacturing," said Greg Laue, sunshield program manager at NeXolve.

• May 24, 2016: With surgical precision, two dozen engineers and technicians successfully installed the package of science instruments of the James Webb Space Telescope into the telescope structure (Figure 58). The package is the collection of cameras and spectrographs that will record the light collected by Webb's giant golden mirror. ⁵⁷⁾

- Inside the world's largest clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland, the team crane-lifted the heavy science instrument package, lowered it into an enclosure on the back of the telescope, and secured it to the telescope.

- Now that the instruments, mirrors, and telescope structure have been assembled, the combination will go through vibration and acoustic tests in order to ensure the whole science payload will withstand the conditions of launch.

• April 27, 2016: NASA engineers recently unveiled the giant golden mirror of NASA's JWST (James Webb Space Telescope) as part of the integration and testing of the infrared telescope. The 18 mirrors that make up the primary mirror were individually protected with a black covers when they were assembled on the telescope structure. Now, for the first time since the primary mirror was completed, the covers have been lifted. ⁵⁸⁾

- Scientists from around the world will use this unique observatory to capture images and spectra of not only the first galaxies to appear in the early universe over 13.5 billion years ago, but also the full range of astronomical sources such as star forming nebulae, exoplanets, and even moons and planets within our own Solar System. To ensure the mirror is both strong and light, the team made the mirrors out of beryllium. Each mirror segment is about the size of a coffee table and weighs approximately 20 kg. A very fine film of vaporized gold coats each segment to improve the mirror's reflection of infrared light. The fully assembled mirror is larger than any rocket so the two sides of it fold up. Behind each mirror are several motors so that the team can focus the telescope out in space.

• March 21, 2016: After over a year of planning, nearly four months of final cryo testing and monitoring, the testing on the science instruments module of the observatory was completed. They were removed from a giant thermal vacuum chamber at NASA/GSFC in Greenbelt, Maryland called the SES (Space Environment Simulator) that duplicates the vacuum and extreme temperatures of space. The SES is a 12 m tall, 8.3 m diameter cylindrical chamber that eliminates almost all of the air with vacuum pumps and uses liquid nitrogen and even colder gaseous helium to drop the temperature. ⁵⁹⁾

- The testing is critical because at these instrument's final destination in space at L2, 1.5 million km away from Earth, it will operate at incredibly cold temperatures of 40 K. The science instrument modules tested consist of MIRI (Mid Infrared Instrument), jointly developed by a nationally funded European Consortium under the auspices of ESA (European Space Agency) and the JPL (Jet Propulsion Laboratory); NIRSpec (Near Infrared Spectrometer), jointly developed by Airbus for ESA and the U.S.; FGS/NIRISS (Fine Guidance Sensor/ Near-InfraRed Imager and Slitless Spectrograph), provided by CSA (Canadian Space Agency) and developed by COM DEV International, Cambridge, Ontario, Canada; and NIRCam (Near Infrared Camera), built by a team at the University of Arizona and Lockheed Martin's Advanced Technology Center.

• March 7, 2016: The sole secondary mirror that will fly aboard NASA's James Webb Space Telescope was installed onto the telescope at NASA's Goddard Space Flight Center in Greenbelt, Maryland, on March 3, 2016. ⁶⁰⁾

• Feb. 24, 2016: The year 2015 marked big progress on NASA's James Webb Space Telescope and there are still a number of large milestones before the next generation telescope is launched in 2018. Recently, all of the 18 segments of the Webb telescope primary mirror segments were installed on the observatory's backplane at NASA's Goddard Space Flight Center in Greenbelt, Maryland. But that's just one component of the Webb. ⁶¹⁾

- Over the next two years, more components of the Webb will be integrated onto the spacecraft and it will visit three more locations before launch. "From 2016 to 2018, there are installations and tests for the telescope and the telescope plus the instruments, followed by shipping to NASA's Johnson Space Center in Houston, Texas where end-to-end optical testing in a simulated cryo-temperature and vacuum space environment will occur," said Paul Geithner, Webb telescope manager - Technical, at NASA Goddard. "Then all the parts will be shipped to Northrop Grumman for final assembly and testing, then to French Guiana for launch."

- The two largest parts of the observatory are the primary mirror and the tennis-court-sized sunshield. Additionally, there are four scientific instruments—cameras and spectrographs with detectors able to record extremely faint signals—that will fly aboard Webb. All four flight science instruments were integrated into the ISIM (Integrated Science Instrument Module) in March 2014 and since have been undergoing multiple tests. However, the ISIM has not yet been added to the observatory.

- Over the next year, teams at Goddard will work to complete the telescope by installing the other optics in addition to the primary mirror segments. The other optics include installing the aft-optics subsystem or AOS, secondary mirror and both fixed and deployed radiators. Once complete, engineers will connect the Telescope and instruments together when the ISIM is attached to the observatory.

- Testing is a continuous part of the assembly process. "After the mating of the ISIM, to the Telescope there will be a room-temperature optical check before a simulated launch environment exposure," Geithner said. That means the observatory will undergo vibration and acoustic testing to ensure it can endure the sound and shaking that occurs during launch. After those tests, there is yet another room-temperature optical check.

- Once all of those milestones are accomplished, the observatory will then be prepared and flown to NASA's Johnson Space Center, Houston, Texas. At Johnson, the observatory will endure end-to-end optical testing in a simulated cryo-temperature and vacuum space environment in Chamber-A. Chamber-A is NASA's giant thermal vacuum chamber where the Webb telescope pathfinder or non-flight replica was tested in April 2015.

- After NASA/JSC, the Webb telescope will be then transported to Northrop Grumman in Redondo Beach, California where engineers will connect the telescope and instruments together with the spacecraft and sunshield to form the complete Observatory. Once every component is together, more testing is done. That testing is called "Observatory-level testing." It's the last exposure to a simulated launch environment before flight and deployment testing on the whole observatory.

- What follows the flight and deployment testing is the shipping of the complete observatory to the launch site in South America where the Webb telescope is slated to launch in 2018.

A general list of milestones before launch ⁶¹⁾

• At NASA/GSFC (Goddard Space Flight Center):

- Aft-Optics System installation

- Secondary mirror installation

- ISIM (Integrated Science Instrument Module) installation into Telescope Structure

- Metrology test of Telescope and Instruments

- Vibration test of Telescope and Instruments

- Acoustic test of Telescope and Instruments

• At NASA/JSC (Johnson Space Center):

- Optical test of Telescope and Instruments in Chamber A

• At Northrop Grumman:

- Assemble Spacecraft Element

- Finish Sunshield and Integrate into Spacecraft

- Assembling entire Observatory (Telescope and Instruments and Spacecraft)

- Observatory-level tests

- Transport to French Guiana

• February 4, 2016: The 18^th and final primary mirror segment is installed on what will be the biggest and most powerful space telescope ever launched. The final mirror installati at NASA's Goddard Space Flight Center in Greenbelt, Maryland marks an important milestone in the assembly of the agency's James Webb Space Telescope. ⁶²⁾

- Using a robotic arm reminiscent of a claw machine, the team meticulously installed all of Webb's primary mirror segments onto the telescope structure. Each of the hexagonal-shaped mirror segments measures just 1.3 m across with a mass of ~40 kg. Once in space and fully deployed, the 18 primary mirror segments will work together as one large 6.5 m diameter mirror.

- The mirrors were built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. Ball is the principal subcontractor to Northrop Grumman for the optical technology and optical system design. The installation of the mirrors onto the telescope structure is performed by Harris Corporation, a subcontractor to Northrop Grumman. Harris Corporation leads integration and testing for the telescope.

• Dec. 28, 2015: As the year 2015 comes to an end, the assembly of the JWST reached the halfway point in the installation of the primary mirrors onto the telescope structure. Technicians have just installed the ninth of 18 primary flight mirrors onto the mirror holding backplane structure at the NASA/GSFC in Greenbelt, MD. ⁶³⁾

• Dec. 17, 2015: The next great space observatory took a step closer this week when ESA signed the contract with Arianespace that will see the James Webb Space Telescope launched on an Ariane 5 rocket from Europe's Spaceport in Kourou in October 2018. The contract includes a cleaner fairing and integration facility to avoid contaminating the sensitive telescope optics. ⁶⁴⁾

- With a 6.5 m diameter telescope, the observatory must be launched folded up inside Ariane's fairing. The 6.6 ton craft will begin unfolding shortly after launch, once en route to its operating position some 1.5 million km from Earth on the anti-sunward side.

• Nov. 25, 2015: NASA has successfully installed the first of 18 flight mirrors onto the James Webb Space Telescope, beginning a critical piece of the observatory's construction. In the clean room at NASA/GSFC this week, the engineering team used a robot arm to lift and lower the hexagonal-shaped segment that measures just over 1.3 m with a mass of ~40 kg. After being pieced together, the 18 primary mirror segments will work together as one large 6.5 m mirror. The full installation is expected to be complete early next year. ⁶⁵⁾

• Nov. 16, 2015: Inside the clean room at NASA/GSFC, engineers successfully completed two deployments for the James Webb Space Telescope's "wings" or side portions of the backplane structure that fold up. The wings and telescope structure are essential because they make up the telescope's carbon fiber framework which will hold all 18 of the telescope's mirrors and the tower for the primary mirror.⁶⁶⁾

- "We deploy the wings one at a time. Each individual deployment can take up to 16 hours or more to complete," said Adam Carpenter, Mechanical Integration Engineer at Goddard, as he and other engineers prepared for the move. "It is a delicate operation requiring multiple groups to perform specific tasks." Leading up to this test, engineers lined the telescope structure with cables. In space, these cables will enable the telescope to open up and will provide electrical signals to the active the mirror segments. During the wing test, however, the engineers needed to make sure the cables did not block the deployment, and so the team arranged the cables carefully.

- "The two wings of the telescope structure will eventually hold 6 of Webb's 18 primary mirror segment assemblies," said Carpenter said. "They are necessary so that the observatory can fold up in order to fit into the launch vehicle." The James Webb Space telescope, once fully assembled, will be bigger than any rocket that can launch the telescope into space. So the engineering team designed the telescope to fold like origami to fit inside its Ariane 5 rocket.

• October 8, 2015: Northrop Grumman is reporting that the manufacturing and assembly of the JWST spacecraft structure was successfully completed July 1 at NGC's (Northrop Grumman Corporation's) Redondo Beach facility (Figure 64). ⁶⁷⁾

- The bus must withstand a force equivalent to 45 tons while supporting the observatory during launch. The spacecraft structure integrates the system's optical telescope, sunshield, and instrument electronics and mounts the whole observatory to the Ariane 5 rocket — tasked with launching the Webb Telescope to its destination in space. To launch such a large observatory out to the L2 orbit 1.5 km away, the structure must also be of very low mass so its mass efficiency allows it to carry 64 times its own mass.

• Sept. 16, 2015: The flight structure of NASA's JWST was standing tall on a platform in the cleanroom at NASA's Goddard Space Flight Center in Greenbelt, Maryland on August 30 (Figure 65). The telescope structure includes the primary mirror backplane assembly; the main backplane support fixture; and the deployable tower structure that lifts the telescope off of the spacecraft. The three arms at the top come together into a ring where the secondary mirror will reside. ⁶⁸⁾

- Standing tall and standing up in the stowed-for-launch configuration as it appears in this photo, the complete telescope structure stretches about 8 m from its base on the roll-over fixture to the secondary mirror support at the top. There is a yellow fixture at the bottom of the telescope structure that is designed to secure the bottom of the tower until the telescope structure is mounted on the spacecraft.

- In late fall, Webb's hexagonal flight mirrors will be placed by a robotic arm onto the backplane, which will hold the hexagonal mirrors and instruments steady while the telescope is looking into deep space. Together, those 18 mirrors make up Webb's 6.5 m diameter "primary mirror." Along with the secondary, tertiary, and fine steering mirrors, this primary mirror comprises a telescope that will help scientists observe the formation of the first stars and galaxies over 13.5 billion years ago.

- In addition to the primary mirror, the backplane will also be carrying 2400 kg of telescope optics and instruments. The backplane must keep the mirrors motionless in order to get clear images far in deep space. It was engineered to remain stationary down to about 1/10,000 the diameter of a human hair (32 nm) at temperatures colder than -240°C, such as those experienced in space.

- The flight backplane arrived at Goddard after undergoing integration and testing at Northrop Grumman Aerospace Systems in Redondo Beach, California. ATK designed, engineered and constructed the backplane at its facilities in Magna, Utah. Once the backplane arrived, it was inspected by engineers and then set upright using a giant crane in the clean room.

• August 12, 2015: The sunshield on NASA's James Webb Space Telescope is the largest part of the observatory—five layers of thin, silvery membrane that must unfurl reliably in space. The precision in which the tennis-court sized sunshield has to open must be no more than a few centimeters different from its planned position (Figure 66). ⁶⁹⁾

- The sunshield separates the observatory into a warm sun-facing side and a cold side where the sunshine is blocked from interfering with the sensitive infrared instruments. The infrared instruments need to be kept very cold (under 50 K to operate. The sunshield protects these sensitive instruments with an effective SPF (Sun Protection Factor) of 1,000,000. A sunscreen generally has an SPF of 8 to 50.

• Summer 2015: The JWST team has just successfully completed the first of three planned, large-scale pathfinder tests at the Chamber A facility at Johnson Space Center in Houston, Texas. These tests are designed to verify the operation of the support and test equipment as well as check critical alignment and test procedures, train personnel, and improve test efficiency in preparation for the final, full scale flight testing of JWST scheduled for Winter, 2016-2017. ⁷⁰⁾

- This first pathfinder test, denoted OGSE1 (Optical Ground Support Equipment test 1), incorporated an engineering version of the JWST composite backplane (the mounting and support system for the telescope), two spares of the eighteen primary mirror segments and a flight spare secondary mirror and support structure.

- The next pathfinder test (OGSE2 - currently scheduled for Fall, 2015) will add the flight AOS (Aft-Optics-System) incorporating the flight tertiary and fine steering mirrors as well as a set of precisely located sources ASPA (AOS Source Plate Assembly) which will be imaged through the telescope system.

- A third, primarily thermal model validation pathfinder, is scheduled for testing in spring 2016.

• April 20, 2015: Inside NASA's giant thermal vacuum chamber, called Chamber A, at NASA's Johnson Space Center in Houston, the James Webb Space Telescope's Pathfinder backplane test model, is being prepared for its cryogenic test. Previously used for manned spaceflight missions, this historic chamber is now filled with engineers and technicians preparing for a crucial test. Exelis developed and installed the optical test equipment in the chamber. ⁷¹⁾

- "This will be the first time on the program that we will be aligning two primary mirror segments together," said Lee Feinberg, NASA Optical Telescope Element Manager. "In the past, we have always tested one mirror at a time, but this time we will use a single test system and align both mirrors to it as though they are a single monolithic mirror."

• March 17-18, 2015: John Durning, JWST Deputy Program Manager, presented a current general status of the JWST project at the Astrophysics Subcommittee Meeting . He remarked that the schedule is healthy, with 10 months of critical path slack. The milestones are such that a lot of hardware will be delivered in FY16. Almost all hardware has passed critical design review (CDR). There was a late thermal challenge with the radiator, but that is catching up. The mission is deep into building and testing at this point. ^{72) 73)}

- OTE (Optical Telescope Element): The flight telescope build begins in August 2015. All flight backplane components are built and are at Northrop Grumman for integration.

- The sunshield is making good progress and the team has done a practice deployment, including integration onto a practice spacecraft. There is a lot of testing and verification going on, as this is a key risk reduction activity. The flight membranes are in varying levels of completion.

- Four instruments make up the ISIM payload: the Fine Guidance Sensor (FGS) from Canada, the MIRI from Europe, the Near Infra-Red Camera (NIRCam), and the Near Infra-Red Spectrometer (NIRSpec). The spacecraft is not as far along in integration and testing, but the components are coming together.

- There will be three risk reductions tests this year for the Optical Telescope and ISIM (OTIS). Each test establishes the procedures and processes for higher- level assembly, giving confidence that the procedures work.

- Two of the three MIRI cryocooler components have been delivered, but the compressor assembly is taking longer than expected. Still, it should be delivered to JPL this summer. On the NIRSpec microshutter control electronics, there was a shorted wire during testing. The team is therefore rebuilding the affected board and the adjacent board; these will be delivered next month. The NIRCam detector system tests found that two of the four detector chips on one of the instrument channels had anomalous readings. Replacement of those units will be completed by the end of the month.

• The Figure 69 is a photo of the ISIM (Integrated Science Instrument Module), released by ESA on March 2, 2015. ISIM is a structure containing the four science infrared instruments of JWST. The JWST team hit a milestone in the summer of 2014 as all four science instruments passed their cryogenic testing in this chamber, the SES (Space Environment Simulator). The three near-infrared units were cooled to around –233°C, while the MIRI (Mid-Infrared Instrument) reached an even lower –266°C, for a total of 116 days. ⁷⁴⁾

Legend to Figure 69: The photographer, wielding a torch at the bottom of the SES, took his picture of ISM prior to the cooling test in 2014.

• Oct. 21, 2014: After 116 days of being subjected to extremely frigid temperatures like that in space, the heart of the James Webb Space Telescope, the ISIM (Integrated Science Instrument Module) and its sensitive instruments, emerged unscathed from the thermal vacuum chamber at NASA/GSFC (Goddard Space Flight Center) in Greenbelt, Maryland. ⁷⁵⁾

- SES (Space Environment Simulator) is the name of the massive thermal vacuum chamber, that duplicates the vacuum and extreme temperatures of space. SES is a cylindrical chamber of 12 m in height and 8.3 m in diameter which was kept at a temperature of 40 K during the ISIM test. SES eliminates the tiniest trace of air with vacuum pumps and uses liquid nitrogen and even colder liquid helium to drop the temperature simulating the space environment.

- These tests were conducted to make sure that when JWST cools down in space, the four instruments of ISIM are still positioned meticulously so that when light enters the telescope, it is captured in the right way. Paul Geithner, the JWST deputy project manger, commented: "The biggest stress for this telescope will be when it cools down. When the telescope structure goes from room temperature to its super cold operating temperature (of ~ 35 K), it will see more stress from shrinkage than it will from violent vibration during launch."

- Once the test was completed, the team warmed up the chamber, and completed the final functional test and a series of data analyses before they opened up the chamber.

• In July 2014, the sunshield of JWST was fully and successfully tested for the first time, at a cleanroom in the Northrop Grumman facility in Redondo Beach, CA, USA. ^{76) 77)}

The Sunshield is the largest part of the Webb telescope (about the size of a tennis court). The five layers of thin membrane called Kapton, that feels like a Mylar balloon, must unfurl reliably in space like a parasol. The sunshield provides a cold-side stable environment of < 50 K to permit in particular top quality measurements of the instruments in the far infrared region of the spectrum. - The Sunshield will be folded up like an umbrella around the Webb telescope's mirrors and instruments during launch. Once it reaches its orbit, the Webb telescope will receive a command from Earth to unfold, and separate the sunshield's five layers into their precisely stacked arrangement with its kite-like shape.

Thanks to the sunshield, these low temperatures are reached passively, without the help of any active cooling system, by re-radiating the sun's heat into deep space. Just one of JWST's instruments, MIRI (Mid-Infrared Instrument), will be cooled even further by a dedicated cryogenic cooler, reaching around 7 K (–266 ºC ). Although parts of JWST will reach such low temperatures, the shield will create a thermal barrier so that on JWST's ‘hot' side, the spacecraft electronics can work at room temperature.

• During the summer of 2014, a milestone event in the JWST test program is underway: the first of two cryo-verification tests of the complete ISIM (Integrated Science Instrument Module). Pumpdown for this critical test began a few weeks ago in Goddard's largest thermal-vacuum chamber, the SES (Space Environment Simulator). The team expects the test will continue for about 110 days. ⁷⁸⁾

• In August 2014, the central piece of the "pathfinder" backplane that will hold all the mirrors for JWST, has arrived at the agency's Goddard Space Flight Center in Maryland for critical assembly testing on vital parts of the mammoth telescope. ⁷⁹⁾

• In July 2014, the JWST has reached another development milestone with the completion of static load testing of its primary mirror backplane support structure (PMBSS) moving the telescope one step closer to its 2018 launch. The PMBSS is the stable platform that holds the telescope's science instruments and the 18 beryllium mirror-segments that form the 6.5 m diameter primary mirror nearly motionless while the telescope peers into deep space. The primary mirror is the largest mirror in the telescope — the one starlight will hit first. ⁸⁰⁾

• In January 2014, JWST has passed its first significant mission milestone for 2014, the SCDR (Spacecraft Critical Design Review) that examined the telescope's power, communications and pointing control systems. ^{81) 82) 83)}

During the SCDR, the details, designs, construction and testing plans, and the spacecraft's operating procedures were subjected to rigorous review by an independent panel of experts. The week-long review involved extensive discussions on all aspects of the spacecraft to ensure the plans to finish construction would result in a vehicle that enables the powerful telescope and science instruments to deliver their unique and invaluable views of the universe.

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39) Ann Jenkins, "Success in Critical Communications Tests for NASA's James Webb Space Telescope," NASA, 5 September 2018, URL: https://www.nasa.gov/feature/goddard/2018/success-in-critical-communications-tests-for-nasas-james-webb-space-telescope

40) "Technicians Ensure James Webb Space Telescope's Sunshield Survives Stresses Experienced During Liftoff," NASA, 18 July 2018, URL: https://www.nasa.gov/image-feature/goddard/2018/technicians-ensure-james-webb-space-telescope-s-sunshield-survives-stresses

41) Eric Villard, Rob Gutro, "Engineers Solve Excessive Heat Removal from NASA's Webb Telescope," NASA, 5 June 2018, URL: https://www.nasa.gov/feature/goddard/2018/engineers-solve-excessive-heat-removal-from-nasa-s-webb-telescope

42) "#14: Tests, moving to a new home, and more tests," ESA, 4 June 2018, URL: http://sci.esa.int/jwst/60351-14-tests-moving-to-a-new-home-and-more-tests/

43) "NASA Announces Independent Review Board Members for James Webb Space Telescope," NASA, 6 April 2018, URL: https://www.nasa.gov/feature/nasa-announces-independent-review-board-members-for-james-webb-space-telescope

44) "Combined Optics, Science Instruments of NASA's James Webb Space Telescope Arrive in California," NASA, 5 Feb. 2018, Release 18-007, URL: https://www.nasa.gov/press-release/combined-optics-science-instruments-of-nasa-s-james-webb-space-telescope-arrive-in

45) "Selections Made for the JWST Director's Discretionary Early Release Science Program," STScI, 13 Nov. 2017, URL: https://jwst.stsci.edu/news-events/news/News%20items/selections-made-for-the-jwst-directors-discretionary-early-release-science-program

46) "Webb's first space targets chosen," ESA Science and Technology, 13 Nov. 2017, URL: http://sci.esa.int/jwst/59765-webb-s-first-space-targets-chosen/

47) "Self-Portrait of NASA's James Webb Space Telescope Marks Critical Test," NASA, 19 Oct. 2017, URL: https://www.nasa.gov/feature/goddard/2017/self-portrait-of-nasa-s-james-webb-space-telescope-marks-critical-test

48) Eric Villard, "NASA's Webb Telescope Will Study Our Solar System's "Ocean Worlds"," NASA, Aug. 24, 2017, URL: https://www.nasa.gov/feature/goddard/2017/nasa-s-webb-telescope-will-study-our-solar-system-s-ocean-worlds

49) Rob Gutro, Lynn Jenner, "NASA's Webb Telescope Summertime Deep-Freeze Continues," NASA, Aug. 9, 2017, URL: https://www.nasa.gov/feature/goddard/2017/nasas-webb-telescope-summertime-deep-freeze-continues

50) Laura Betz, "NASA's Webb Telescope Completes Goddard Testing, Heading to Texas for More," NASA, May 1, 2017, URL: https://www.nasa.gov/feature/goddard/2017/nasa-s-webb-telescope-completes-goddard-testing-heading-to-texas-for-more

51) "#12: Testing times for JWST," ESA, 16, June 2017, URL: http://sci.esa.int/jwst/59233-12-testing-times-for-jwst/

52) Rob Gutro, "NASA's James Webb Space Telescope Completes Acoustic and Vibration Tests," NASA, March 28, 2017, URL: https://www.nasa.gov/feature/goddard/2017/nasas-james-webb-space-telescope-completes-acoustic-and-vibration-tests

53) Laura Betz, Lynn Jenner, "NASA Restarts Rigorous Vibration Testing on the James Webb Space Telescope," NASA, Jan. 25, 2017, URL: https://www.nasa.gov/feature/goddard/2017/nasa-restarts-rigorous-vibration-testing-on-the-james-webb-space-telescope

54) "NASA's Webb... Seeking Good Vibrations," Satnews Daily, Jan. 3, 2017, URL: http://www.satnews.com/story.php?number=286107654

55) Laura Betz, "NASA completes Webb Telescope Center of Curvature pre-test," NASA, Nov. 2, 2016, URL: http://www.nasa.gov/feature/goddard/2016/nasa-completes-webb-telescope-center-of-curvature-pre-test

56) Connie Reese, Rob Gutro, "Final Sunshield Layer Completed for NASA's James Webb Space Telescope," NASA, Oct. 31, 2016: URL: http://www.nasa.gov/feature/goddard/2016/final-sunshield-layer-completed-for-nasa-s-james-webb-space-telescope

57) Laura Betz, "Science Instruments of NASA's James Webb Space Telescope Successfully Installed," NASA, May 24, 2016, URL: http://www.nasa.gov/feature/goddard/2016/science-instruments-of-nasa-s-james-webb-space-telescope-successfully-installed

58) Laura Betz, "James Webb Space Telescope's Golden Mirror Unveiled," NASA, April 27, 2016, URL: http://www.nasa.gov/feature/goddard/2016/james-webb-space-telescopes-golden-mirror-unveiled

59) Laura Betz, "NASA Marks Major Milestones for the James Webb Space Telescope," NASA, March 21, 2016, URL: http://www.nasa.gov/feature/goddard/2016/james-webb-space-telescopes-instruments-removed-from-super-cold-chamber

60) Rob Gutro, "NASA's James Webb Space Telescope Secondary Mirror Installed," NASA, March 7, 2016, URL: http://www.nasa.gov/feature/goddard/2016/nasas-james-webb-space-telescope-secondary-mirror-installed

61) Rob Gutro, "NASA's James Webb Space Telescope Coming Together Over Next Two Years," NASA, Feb. 24, 2016, URL: http://www.nasa.gov/feature/goddard/2016/nasas-james-webb-space-telescope-coming-together-over-next-two-years

62) Felicia Chou, Rob Gutro, "NASA's James Webb Space Telescope Primary Mirror Fully Assembled," NASA, Press Release, 16-013, Feb. 4, 2016, URL: https://www.nasa.gov/press-release/nasas-james-webb-space-telescope-primary-mirror-fully-assembled

63) Laura Betz, "James Webb Space Telescope Mirror Halfway Complete," NASA/GSFC, Dec. 28, 2015, URL: http://www.nasa.gov/feature/goddard/james-webb-space-telescope-mirror-halfway-complete

64) "ESA confirms James Webb Telescope Ariane Launch," December 17, 2015, URL: http://www.esa.int/Our_Activities/Space_Science/ESA_confirms_James_Webb_telescope_Ariane_launch

65) Dwayne Brown, Lynn Chandler, "NASA's Webb Space Telescope Receives First Mirror Installation," NASA Release 15-226, Nov. 25, 2015, URL: http://www.nasa.gov/press-release/nasa-s-webb-space-telescope-receives-first-mirror-installation

66) Laura Betz, "James Webb Space Telescope 'Wings' Successfully Deployed," NASA, Nov. 16, 2015, URL: https://www.nasa.gov/feature/goddard/james-webb-space-telescope-wings-successfully-deployed

67) "Northrop Grumman Team Successfully Completes Manufacturing of Optical Class Spacecraft Structure for NASA's James Webb Space Telescope," Northrop Grumman, Oct. 8, 2015, URL: http://investor.northropgrumman.com/phoenix.zhtml?c=112386&p=irol-newsArticle_Print&ID=2095587

68) Rob Gutro, "NASA's James Webb Space Telescope Structure Stands Tall," NASA, Sept. 16, 2015. URL: http://www.nasa.gov/feature/goddard/nasas-james-webb-space-telescope-structure-stands-tall

69) Rob Gutro, "NASA's Webb Sunshield Gives an 'Open Wide' for Inspection," NASA, Aug. 12, 2015, URL: http://www.nasa.gov/image-feature/goddard/nasas-webb-sunshield-gives-an-open-wide-for-inspection

70) Chuck Bowers, "Pathfinder Tests Completed at Johnson Space Center," NASA,Webb Update, Issue No 18, Summer 2015, URL: http://jwst.nasa.gov/resources/WebbUpdate_Summer2015.pdf

71) Laura Betz, "Building Hubble's Successor: Crucial Pathfinder Test Set Up Inside Chamber A," NASA, April 20, 2015, URL: http://www.nasa.gov/image-feature/goddard/building-hubbles-successor-crucial-pathfinder-test-set-up-inside-chamber-a

72) Hashima Hasan, "NAC (NASA Advisory Council) Astrophysics Subcommittee Meeting Minutes," NASA HQ, Washington DC, March 17-18, 2015, URL: http://science.nasa.gov/media/medialibrary/2015/04/29/APS_March_Minutes_Final.pdf

73) John Durning, "James Webb Space Telescope Mission Status," Astrophysics Subcommittee Meeting, NASA HQ, Washington DC, March 17-18, 2015, URL: http://science.nasa.gov/media/medialibrary/2015/04/07/Durning_JWST
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74) "Simulating space for JWST's four infrared instruments," ESA, March 2, 2015, URL: http://www.esa.int/spaceinimages/Images/2015/03/Simulating_space_for_JWST_s_four_infrared_instruments

75) Laura Betz, "NASA Webb's Heart Survives Deep Freeze Test," NASA, Oct. 21, 2014, URL: http://www.nasa.gov/content/goddard/nasa-webbs-heart-survives-deep-freeze-test/#.VO3gBy7-Y_c

76) Rob Gutro, "NASA's Webb Sunshield Stacks Up to Test!," NASA, July 25, 2014, URL: http://www.nasa.gov/content/goddard/nasas-webb-sunshield-stacks-up-to-test/#.U_sBGqNmP5o

77) "Shelter from the Sun," ESA, Aug. 25, 214, URL: http://www.esa.int/spaceinimages/Images/2014/08/Shelter_from_the_Sun

78) Randy Kimble, "Cryo-Verification Test of the Complete ISIM Begins!," NASA, JWST Update, Issue No 17, Summer 2014, URL: http://jwst.nasa.gov/resources/WebbUpdate_Summer2014.pdf

79) Ken Kremer, "James Webb Space Telescope's Pathfinder Mirror Backplane Arrives at NASA Goddard for Critical Assembly Testing," Universe Today, August 13, 2014, URL: http://www.universetoday.com/113890/james-webb-space-telescopes-pathfinder-mirror-backplane-arrives-at-nasa-goddard-for-critical-assembly-testing/

80) J. D. Harrington, Christina Thompson, Hillary Searle, "Testing Completed on NASA's James Webb Space Telescope Backplane," NASA, Release 14-178, July 8, 2014, URL: http://www.nasa.gov/press/2014/july/testing-completed-on-nasas-james-webb-space-telescope-backplane/

81) J. D. Harrington, Lynn Chandler, "James Webb Space Telescope Passes a Mission Milestone," NASA News Release 14-026, Jan. 24, 2014, URL: http://www.nasa.gov/press/2014/january/james-webb-space-telescope-passes-a-mission-milestone/#.UuNDv_swdR4

82) "NGC Completes Critical Design Review For James Webb Space Telescope," Space Daily, Jan. 30, 2014, URL: http://www.spacedaily.com/reports/Northrop_Grumman_Completes_Critical
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83) "JWST Recent Accomplishment," NASA, March 12, 2014, URL: http://jwst.nasa.gov/recentaccomplish.html

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (eoportal@symbios.space).