Moon: 50 year Journey
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50 Years Ago: The Journey to the Moon Begins (July 1969) NASA History
An estimated one million people gathered on the beaches of central Florida to witness first-hand the launch of Apollo 11, while more than 500 million people around the world watched the event live on television. Officially named as a crew just six months earlier, Commander Neil A. Armstrong, Lunar Module Pilot (LMP) Edwin E. "Buzz" Aldrin, and Command Module Pilot (CMP) Michael Collins were prepared to undertake the historic mission. Previous Apollo crews had tested the spacecraft in Earth orbit and around the Moon, and only two months earlier, Apollo 10 had completed a dress rehearsal to sort out all the unknowns for the lunar landing. Now it was time to attempt the landing itself. 1)
The astronauts' day on July 16, 1969, began with a 4 AM wake-up call from Chief of the Astronaut Office Donald K. "Deke" Slayton. After the traditional prelaunch breakfast with Slayton and backup CMP William A. Anders, the crewmembers donned their spacesuits and took the Astrovan to Kennedy Space Center's (KSC) Launch Pad 39A. Workers in the White Room assisted them into their seats in the Command Module (CM) Columbia, Armstrong into the left hand couch, Collins into the right, and finally Aldrin into the middle. After the pad workers closed the hatch to the capsule, the astronauts settled in for the final two hours of the trouble-free countdown. As Armstrong noted just before liftoff, "It's been a real smooth countdown."
At precisely 9:32 AM EDT, Apollo 11 lifted off from Launch Pad 39A to begin humanity's first attempt at a lunar landing. Engineers in KSC's Firing Room 1 who had managed the countdown handed over control of the flight to the MCC (Mission Control Center) at the MSC (Manned Spacecraft Center), now the JSC ( Johnson Space Center) in Houston, as soon as the rocket cleared the launch tower. In MCC, the Green Team led by Flight Director Clifford E. Charlesworth took over control of the mission. The Capcom, or capsule communicator, the astronaut in MCC who spoke directly with the crew, during launch was Bruce McCandless. The three stages of the Saturn V performed flawlessly and successfully placed Apollo 11 into low Earth orbit. For the next two and a half hours, as the Apollo spacecraft still attached to its S-IVB third stage orbited the Earth, the astronauts and MCC verified that all systems were functioning properly. McCandless then called up to the crew, "Apollo 11, you're go for TLI," the Trans Lunar Injection, the second burn of the third stage engine to send them on their way to the Moon.
Two hours and 44 minutes after liftoff, the third stage engine ignited for the six-minute TLI (Trans Lunar Injection) burn, increasing the spacecraft's velocity to more than 24,000 miles per hour, enough to escape Earth's gravity. Armstrong called down to the ground after the burn, "That Saturn gave us a magnificent ride. It was beautiful." A little over three hours after launch, and already more than 3,000 miles from Earth, the CSM (Command and Service Module) separated from the spent third stage to begin the transposition and docking maneuver. Collins flew the CSM Columbia out to a distance of about 100 feet and turned it around to face the now exposed LM Eagle still tucked into the top of the third stage. He slowly guided Columbia to a docking with Eagle, then extracted it from the third stage which was sent on a path past the Moon and into orbit around the Sun. During the maneuver, the spacecraft had traveled another three thousand miles away from Earth.
During the rest of their first day in space, MCC informed the crew that because the launch and TLI had been so precise, the planned first midcourse correction would not be needed. The astronauts were finally able to remove the spacesuits they'd been wearing since before launch. Armstrong called down with birthday wishes for the state of California (200 years old) and for Dr. George E. Mueller, NASA Associate Administrator for Manned Space Flight (stated as "not that old"). In MCC, Flight Director Eugene F. Kranz's White Team of controllers took over, with astronaut Charles M. Duke as the new Capcom. The astronauts provided a pleasant surprise with an unscheduled 16-minute color television broadcast, treating viewers on Earth with spectacular scenes of their home planet. They then placed their spacecraft in the PTC (Passive Thermal Control) or barbecue mode, rotating at three revolutions per hour, to evenly distribute temperature extremes. Finally, about 13 hours after launch and a very long day, the crew began its first sleep period, with Apollo 11 about 63,000 miles from Earth.
Overnight, Flight Director Glynn S. Lunney's Black Team of controllers, with astronaut Ronald E. Evans as Capcom, watched over the spacecraft's systems. By the time the astronauts awoke, now almost 110,000 miles from Earth, Charlesworth's Green Team was back on console. Capcom McCandless provided a morning news update to the crew, including a status of the Soviet Luna 15 robotic spacecraft that had launched three days before Apollo 11 and was still on its way to the Moon. About the time Apollo 11 reached the halfway mark in distance between Earth and Moon, the following light-hearted exchange took place between backup Apollo 11 Commander James A. Lovell in MCC and Armstrong aboard Columbia:
- Lovell: Is the Commander aboard? This is Jim Lovell calling Apollo 11.
- Armstrong: This is the Commander.
- Lovell: I was a little worried. This is the backup Commander still standing by. You haven't given me the word yet. Are you Go?
- Armstrong: You've lost your chance to take this one, Jim.
- Lovell: Okay. I concede.
The crew conducted the only midcourse correction needed during the coast to the Moon, a three-second burn of the SPS (Service Propulsion System) engine to lower the closest point to the Moon from 200 miles to 69 miles. McCandless informed the astronauts that Luna 15 had entered an elliptical orbit around the Moon, but that its objectives were still not clear.
The crew conducted a scheduled TV broadcast from about 150,000 miles, showing views of a much smaller Earth with Armstrong providing a detailed description of the planet. He then turned the camera inside the cabin for views of the astronauts and showing viewers their food pantry, concluding with filming the Apollo 11 mission patch on their flight suits. The broadcast lasted 35 minutes. The crew soon after settled down for its second night's sleep in space, which MCC extended since another midcourse correction the next morning was not needed as their trajectory remained very precise.
In Houston, astronaut Frank Borman and Christopher C. Kraft, Director of Flight Crew Operations, held a press conference about Luna 15. NASA managers were concerned that with Luna 15 now in orbit around the Moon and its objectives still not clear, it might interfere in some way with Apollo 11. Borman had visited Moscow earlier in July and met with Academician Mstislav V. Keldysh, President of the Soviet Academy of Sciences. Taking advantage of this new acquaintance, Borman telephoned Keldysh and expressed NASA's concerns. Keldysh assured Borman that Luna 15 would not interfere with Apollo 11 and in an unprecedented action in American-Soviet space relations he telegraphed Luna 15's precise orbital parameters to Borman. The Soviets didn't divulge Luna 15's true intentions, stating only that it would stay in lunar orbit for two days.
The major activity for Apollo 11's third day in space was the first activation and inspection of the LM Eagle, which the crew televised to the ground from about 201,000 miles away. Armstrong described the status of the docking mechanism, "Mike must have done a smooth job in that docking. There isn't a dent or a mark on the probe" – a compliment of Collins' excellent piloting skills. When they opened the hatch to Eagle, the lights came on automatically, prompting Capcom Duke to say, "How about that. Just like the refrigerator." Aldrin floated into the LM, taking the TV camera with him, and provided viewers with an excellent tour of all of its systems, as well as the astronauts' spacesuit helmet visors and backpacks. The broadcast lasted one hour and 36 minutes, after which Aldrin and Armstrong returned to Columbia and closed the hatches. Soon after, Apollo 11 passed into the Moon's gravitational sphere of influence, 214,086 miles from Earth and 38,929 miles from the Moon. The crew settled down for its third sleep period of the flight.
While the crew slept, MCC decided that a planned midcourse correction that day would also not be required and they extended the crew's rest. Shortly after they woke for their fourth day in space, Apollo 11 crossed into the Moon's shadow and they could observe the solar corona. They could see the Moon's surface lit by Earthshine, and for the first time they could see stars and constellations clearly. Capcom astronaut and backup Apollo 11 LMP Fred W. Haise read up the morning news to the crew. An item of interest was that in its reporting of the mission, the Soviet newspaper Pravda called Armstrong the "Czar of The Ship." The Soviet press was indicating that Luna 15 would accomplish everything that all previous Luna spacecraft had done, the first public hint that it might be trying to return samples from the Moon. Armstrong provided the following description of the Moon, which the astronauts were seeing for the first time:
The view of the Moon that we've been having recently is really spectacular. It fills about three-quarters of the hatch window, and of course, we can see the entire circumference, even though part of it is in complete shadow and part of it's in Earthshine. It's a view worth the price of the trip.
Shortly after, as Apollo 8 and 10 had done before, Apollo 11 sailed behind the Moon and all contact with Earth was cut off. Eight minutes later, they fired the SPS engine for the six-minute Lunar Orbit Insertion-1 (LOI-1) burn, and Apollo 11 entered into an elliptical lunar orbit. As Apollo 11 came around from the backside of the Moon, the crewmembers saw their first Earthrise and Aldrin reported their status to MCC, "The LOI-1 burn just nominal as all getout, and everything's looking good." A few minutes later, the astronauts got their first view of the approach to their landing site in the Sea of Tranquility, which was still in darkness. By the time of the landing the next day, the Sun will have risen at the landing site, the low angle illumination providing optimal lighting for the landing. Of the approach Armstrong commented, "It looks very much like the pictures, but like the difference between watching a real football game and one on TV. There's no substitute for actually being here."
During their second lunar orbit, the crew televised views of the Moon across much of the near side (clip 1, clip 2, clip 3). At the end of that revolution, and once again behind the Moon, they fired the SPS engine for the 17-second LOI-2 burn to circularize their orbit. Armstrong and Aldrin entered the LM Eagle for the second time to begin activation and transfer of equipment such as cameras. Aldrin reported that he could see the entire landing area as they flew over it. They returned to Columbia and the entire crew settled down for its first sleep period in lunar orbit. It was also their final night before attempting the first Moon landing the next day.
50 Years Ago: One Small Step, One Giant Leap
Men land on the Moon !! Words such as these were emblazoned in dozens of languages on the front page of newspapers around the world, echoing the first part of President John F. Kennedy's bold challenge to the nation, made more than eight years earlier – to land a man on the Moon. That part was successfully accomplished on July 20, 1969. The second part of the challenge, the safe return to Earth, would have to wait four more days. 2)
Apollo 11 astronauts Neil A. Armstrong, Edwin E. "Buzz" Aldrin, and Michael Collins awoke to start their fifth day in space at the end of their ninth revolution around the Moon. In Mission Control at the Manned Spacecraft Center, now the Johnson Space Center in Houston, Eugene F. Kranz's White Team of controllers arrived on console, with astronaut Charles M. Duke serving as Capcom. After a quick breakfast, Aldrin and Armstrong began re-activating the LM (Lunar Module) Eagle, including deploying its landing gear, and donned their pressure suits. Near the end of the 12th orbit around the Moon, Duke radioed up to Apollo 11 that they were GO to undock. The event took place behind the Moon during the start of their 13th revolution, the astronauts filming each other's spacecraft as they began their independent flights (clip 1, clip 2). After they reappeared from behind the Moon, Armstrong radioed their status to MCC saying, "The Eagle has wings." Collins in the CM (Command Module) Columbia observed, "I think you've got a fine looking flying machine there, Eagle, despite the fact you're upside down," prompting Armstrong to reply, "Somebody's upside down."
From this point on, it was time to get down to business as events happened rather quickly. As the Moon landing attempt was less than an hour away, the viewing gallery in Mission Control was filling with NASA managers from across the agency, and many astronauts were present in the control room itself to witness the historic event. Later during the 13th orbit, about 10 minutes before Apollo 11 disappeared again behind the Moon, Duke radioed up the GO for DOI (Descent Orbit Insertion). The DOI burn, a 30-second firing of the LM's DPS (Descent Propulsion System) engine took place behind the Moon, lowering the low point of Eagle's orbit to about 50,000 feet, as close as Apollo 10 got to the Moon's surface. The two craft now flying separately reappeared from behind the Moon on their 14th orbit. Duke radioed up the GO for PDI (Powered Descent Initiation), the beginning of the landing maneuver. Eagle's antenna repeatedly lost lock on the Earth so Mission Control had to communicate with Eagle through Collins in Columbia until reliable radio links were re-established.
At the beginning of PDI, the LM's DPS engine ran at 10% thrust for 26 seconds for a smooth initial deceleration before increasing to full thrust. Eagle was flying engine first and windows facing down toward the Moon's surface and was about 300 miles east of the landing site in the Sea of Tranquility. Eagle's attitude allowed Armstrong to track landmarks as they passed over them against the predicted times. Based on Eagle passing landmarks about two to three seconds early, Armstrong predicted that they would land about three miles further downrange than planned – and he was proved correct. At an altitude of 40,000 feet (~ 12 km), Armstrong maneuvered Eagle to a windows up orientation. This was in preparation for the pitch-over maneuver, which placed the windows facing forward in the direction of flight, and also positioned the landing radar so it could see the lunar surface.
At about 33,000-foot (10 km) altitude, Armstrong and Aldrin were surprised by the first 1202 program alarm, which they had not seen in simulations. After a few seconds of analysis in MCC, Duke gave them a GO to proceed. The alarm simply meant the computer was overloaded with too much data and couldn't process it all, but controllers felt confident they could proceed with the landing. When a second 1202 alarm sounded less than a minute later Duke once again gave the GO to proceed. Eagle maneuvered to a more vertical orientation for the final phase of the descent. At about 5,000 feet and descending about 100 feet per second, Armstrong took over manual control of Eagle's attitude. As they passed through 3,000 feet with their descent rate slowed to 70 feet/second, Duke gave them the GO for landing, and they received the 1201 program alarm. Once again, Duke gave them the GO to proceed. Another 1202 flashed at about 1,000 feet altitude. At about 600 feet, noticing Eagle's computer was taking them down into a boulder-strewn area near West Crater, Armstrong took over manual control of the descent. He pitched Eagle to a more vertical orientation, which slowed the descent, and decided to overfly the rough area and look for smoother terrain to land on. Armstrong found and flew to a clearer spot for landing, and Aldrin called out that he saw the LM's shadow on the Moon.
Armstrong picked his final spot, about 60 meters east of Little West Crater. At about 100 feet, the fuel quantity warning light came on, indicating only 5% fuel remaining, giving Armstrong about 90 seconds of hover time left. With 60 seconds of fuel remaining, they were down to about 40 feet and the descent engine was kicking up dust from the surface, increasingly obscuring Armstrong's visibility. At precisely 3:17:40 PM Houston time on July 20, 1969, Aldrin called out "Contact light," indicating that at least one of the three 67-inch probes hanging from the bottom of three of the LM's footpads had made contact with the Moon. Eagle drifted to the left when three seconds later, Armstrong called out, "Shutdown," followed by Aldrin's, "Okay. Engine stop," indicating the DPS engine was shut off. They were on the Moon. In Houston, Duke noted via telemetry that the engine had shut down, and called to Armstrong and Aldrin, "We copy you down, Eagle." Armstrong responded with the historic words, "Houston, Tranquility Base here. The Eagle has landed."
It should be noted that for everyone on Earth, the first Moon landing was purely an audio experience. Controllers in MCC had the added benefit of telemetry from the spacecraft, but there was no live television of the landing. A 16-mm silent film camera mounted in the right hand (Aldrin's) window recorded the event, but was not available for viewing until it was returned to Earth and developed. An annotated video of the landing was prepared from this film (courtesy of Apollo Flight Journal), and synchronized with space-to-ground communications, several loops in Mission Control, and video clips from MCC.
After a few minutes, Aldrin provided the first verbal description of their surroundings, including the types and sizes of rocks and the general color of the surface. Duke radioed to them, "Be advised there're lots of smiling faces in this room and all over the world," prompting Armstrong's response, "Well, there are two of them up here." Armstrong reported that neither he nor Aldrin had any trouble adjusting to the one-sixth gravity on the lunar surface. He continued with a more detailed description of their view out the forward windows. As they continued their postlanding activities, Armstrong called MCC to advise that he and Aldrin would like to forego the planned rest period before their Extra-Vehicular Activity (EVA), or spacewalk, and MCC concurred with their proposal.
Aldrin made the following request to anyone who might be listening, "I'd like to take this opportunity to ask every person listening in, whoever and wherever they may be, to pause for a moment and contemplate the events of the past few hours and to give thanks in his or her own way." He then proceeded to take communion with a chalice and consecrated wine he brought along for the occasion. He and Armstrong then began preparations for their historic spacewalk, including donning their Portable Life Support Systems (PLSS), the backpacks that provided oxygen, removed carbon dioxide, and enabled communications. The Green Team of flight controllers led by Clifford E. Charlesworth, with Bruce McCandless serving as Capcom, took their positions in Mission Control to help Armstrong and Aldrin prepare for and execute their EVA. They reconfigured Eagle's cabin for depressurization, donned their helmets, visors, and gloves, and then opened the valve that vented the cabin.
Aldrin opened Eagle's forward hatch, which swung inward toward him, giving Armstrong access to the outside front porch. Aldrin added, "About ready to go down and get some Moon rock?" He helped Armstrong navigate through the narrow confines of Eagle's hatch and onto the front porch. Once on the ladder, Armstrong pulled a lanyard that released the MESA (Modularized Equipment Stowage Assembly) on the side of Eagle's Descent Stage, on which was mounted a black and white TV camera, allowing hundreds of millions of viewers on Earth to see him descend the ladder down to the landing leg's footpad. As a precaution, he practiced the three-foot jump back up to the ladder's first rung, made easier in the one-sixth lunar gravity. Once back down on the footpad, Armstrong described that the footpads had only sunk one or two inches into the lunar dust which he noted was fine-grained, almost powdery. Armstrong announced, "I'm going to step off the LM now." And at 9:56 PM Houston time he did just that, firmly planting his left foot onto the lunar surface, proclaiming, "That's one small step for a man, one giant leap for mankind."
After taking his first tentative steps on the lunar surface, Armstrong began his first tasks of the spacewalk, including receiving the Hasselblad still camera from Aldrin via a lanyard and pulley system, using it to take the first photographs of Eagle to document how it fared during the landing as well as of their surroundings, and collecting the contingency sample of lunar material in case they had to make an emergency departure. A few minutes later, Aldrin began his descent to the surface, commenting on the way out of the cabin, "Now I want to .... partially close the hatch. Making sure not to lock it on my way out." This prompted a laugh from Armstrong who commented, "A particularly good thought."
Once Aldrin was on the surface, he and Armstrong unveiled the commemorative plaque that was mounted on the landing leg and read the words that were inscribed on it, "Here men from the planet Earth first set foot upon the Moon, July 1969 A.D. We came in peace for all mankind." The plaque bore the signatures of the Apollo 11 astronauts as well as of President Richard M. Nixon. Armstrong then removed the TV camera from the MESA, carried it about 60 feet from the LM, and mounted on a tripod so the world audience could watch their subsequent activities. Closer to the LM, Aldrin was setting up the Solar Wind Collector (SWC) experiment, a sheet of aluminum that was exposed to the Sun for 77 minutes to collect ions in the solar wind. Near the end of the EVA, Aldrin rolled up the foil and stowed it for return to Earth for analysis by scientists.
Their next task was to remove the Lunar Flag Assembly attached to Eagle's ladder and set up the American flag about 20 feet (6 m) from the LM. Because in the vacuum on the Moon there is no way for the flag to stay unfurled, a telescoping horizontal metal rod was inserted along the top of the 3-by-5-foot nylon flag. During the deployment, this metal rod did not extend all the way and left the edge of the flag somewhat wrinkled, giving it the appearance of waving in a non-existent lunar breeze. Aldrin began to experiment with different types of locomotion in the one-sixth gravity when Capcom McCandless requested that both astronauts position themselves in front of the TV camera. For the next two minutes, Armstrong and Aldrin talked to President Nixon in the White House's Oval Office, who offered the nation's congratulations on their historic accomplishment.
The phone call concluded, Armstrong and Aldrin resumed their tasks, which included Aldrin performing soil cohesion tests by kicking the lunar surface with his boot and observing the resulting sprays of dust which in the vacuum and one-sixth gravity on the Moon behaved differently from how they would on Earth. Armstrong returned to the MESA to retrieve the equipment for the bulk sample collection of lunar material. Aldrin picked up the Hasselblad to take photographs for the Bootprint Penetration Experiment, and took panoramic photos of the landing site, incidentally taking one of the few photographs of Armstrong on the surface as he packs the bulk sample at the MESA.
After more photography, Aldrin handed the camera back to Armstrong and walked to the back of the LM where the SEQ (Scientific Equipment) bay, containing the EASEP (Early Apollo Surface Experiment Package) was located. The EASEP consisted of two experiments, the PSEP (Passive Seismic Experiment Package) to measure Moon quakes and the LRRR (Laser Ranging Retro-Reflector) that contained an array of mirrors to reflect a laser beam sent from Earth for precise measurements of the Earth-Moon distance. Aldrin removed the two experiments from the SEQ bay and carried them about 40 feet from the LM where he deployed the PSEP and Armstrong the LRRR. At this point, they were running about 30 minutes behind the timeline, but their consumables were within limits so McCandless called to tell them that Mission Control had given them a 15-minute extension on the EVA. He also mentioned that scientists had activated the seismometer and it was picking up the vibrations from their footsteps.
Aldrin returned to the MESA to begin getting two core samples as part of the documented samples. Armstrong jogged 180 feet to Little West Crater that they had overflown during the descent and took a series of panoramic shots before jogging back to the LM to assist Aldrin with the core samples. Finishing the core samples, Aldrin rolled up the solar wind experiment. Armstrong collected about 20 rock samples weighing about 13 pounds (almost 6 kg).
And with that, it was time to finish the EVA. Armstrong and Aldrin gathered the film magazines and closed up the rock boxes. Armstrong scooped up about 13 pounds of lunar dirt as packing material for the rocks in the boxes as Aldrin climbed up the ladder and back into the LM. From there he helped Armstrong transfer the rock boxes up to the cabin using the lanyard system. A film cassette attached to the first rock box fell off and into the lunar dirt, but Armstrong retrieved and reattached it. The dirt attached to the cassette would later cause an accidental exposure to one of the employees once in the Lunar Receiving Laboratory in Houston. They hauled the second rock box up to the cabin without incident.
Just before Armstrong headed up the ladder, he reminded Aldrin about a small package of commemorative items that they wanted to leave on the surface. Aldrin tossed it down through the hatch from inside the cabin. The items included a silicon disc etched with goodwill greetings from 73 world leaders, an Apollo 1 patch commemorating astronauts Virgil I. Grissom, Edward H. White, and Roger B. Chaffee lost in the 1967 fire, two Soviet medals honoring cosmonauts Vladimir M. Komarov killed in the Soyuz 1 accident and Yuri A. Gagarin, the first man in space killed in an airplane crash in 1968, and a small gold olive branch, identical to ones the astronauts carried to the Moon and back for their wives. Armstrong then jumped up to the third rung of the ladder and climbed the rest of the way into the cabin. Within a minute they had the hatch closed and began repressurizing the LM. They removed their PLSS backpacks, took photographs out the windows to use up their remaining film, and ate a well-earned meal. Aldrin realized that probably while he was removing his PLSS, he broke the circuit breaker that armed the ascent stage engine, critical for their departure the next day. Fortunately, they were able to use a felt tip pen to depress the breaker button.
Director of Flight Crew Operations Donald K. "Deke" Slayton called to the crew, "That's a real great day, guys. I really enjoyed it." Armstrong replied, "Thank you. You couldn't have enjoyed it as much as we did," and Aldrin, "It was great." They then depressurized the LM cabin and threw their PLSS backpacks out the hatch along with a jettison bag containing their lunar boots and other items no longer necessary. This freed up space in the cramped cabin and reduced the weight of the LM at liftoff. Since the TV camera on the surface was still transmitting, MCC was able to observe the jettisons, and the PSEP recorded the items hitting the surface, prompting Armstrong to comment, "You can't get away with anything anymore, can you?" They then repressurized the cabin for the final time. Their last duty before they turned in for a well-deserved albeit restless night's sleep, having been awake for 21 hours, was to turn off the TV camera. Aldrin curled up on the floor of the LM while Armstrong devised a hammock and slept on the ascent stage engine cover. All was quiet on the Moon, but while the astronauts slept the American flag they planted shifted position as it settled in the loose lunar soil.
50 Years Ago: Apollo 11 – The Journey Home
"Tranquility Base, Tranquility Base, Houston," called Capcom Ronald E. Evans on July 21, 1969, to awaken Apollo 11 astronauts Neil A. Armstrong and Edwin E. "Buzz" Aldrin after their night's sleep on the Moon. Armstrong responded with a crisp, "Good morning Houston. Tranquility Base," and Aldrin went on to describe how he had slept on the floor of the Lunar Module (LM) Eagle while Armstrong slept on the ascent engine cover with a make-shift sling to hold his legs up. Both slept with their suits, helmets, and gloves on since the temperature in the cabin was a chilly 61o F. Neither man had slept too soundly, partly from the excitement of the previous day's activities, and partly from the unusual sleeping arrangements. Moreover, the Earth was shining through a navigation telescope right into Armstrong's eyes. Evans had earlier awakened Michael Collins orbiting aboard the more spacious Command Module (CM) Columbia, who had a more restful night. All three men prepared for Eagle's liftoff from the lunar surface and rendezvous and docking with Columbia. Before departure, Armstrong and Aldrin used the 16-mm film camera to once more document their landing site through the LM's windows, showing that overnight the American flag had shifted position, apparently settling in the loose lunar soil. 3)
As an historical side note, as Armstrong and Aldrin were preparing for their departure from the Moon, the Soviet Luna 15 robotic spacecraft, launched three days before Apollo 11, fired its retrorocket after completing 52 lunar orbits. Signals with the craft were lost four minutes later and it is believed to have crashed in the Mare Crisium approximately 500 miles from Tranquility Base, traveling at an estimated 300 miles per hour.
After ensuring that all switches and circuit breakers were properly configured, including the one that arms the ascent stage engine that was accidentally broken by Aldrin's Portable Life Support System backpack and that had to be activated using a felt tip pen, Evans called up, "You're cleared for takeoff." Aldrin responded, "Understand. We're number one on the runway." After a 21-hour stay, the LM's Ascent Propulsion System (APS) engine fired precisely on time, lifting Eagle's ascent stage off the surface of the Moon, using the descent stage as a launch pad. Aldrin reported, "We're off. Look at that stuff [insulation from the decent stage] go all over the place. Look at that shadow. Beautiful." Armstrong, for the second time during the mission, radioed, "The Eagle has wings." Aldrin had installed the 16-mm film camera in his window but didn't activate it until six seconds after liftoff. They reported that the ascent stage was giving them a very smooth and quiet ride. The seven-minute APS burn placed them in a 54-by-11-mile orbit. Armstrong proclaimed, "The Eagle is back in orbit, having left Tranquility Base."
An hour later, with both Eagle and Columbia behind the Moon, the LM's Reaction Control System (RCS) thrusters fired for two minutes to circularize the LM's orbit to be 58 by 53 miles. Another hour later, a one-minute RCS burn changed Eagle's orbit so it was a constant 17 miles below Columbia's. At this point, the two spacecraft were 100 miles apart with Eagle in the lower orbit catching up to Columbia. A final burn 30 minutes later put Eagle on an intercept course with Columbia. Armstrong then made a short braking burn followed by several smaller midcourse maneuvers to complete the rendezvous. The astronauts in the two vehicles could now see each others' spacecraft and Collins filmed Eagle's final approach. As the two spacecraft neared each other, they came around from the Moon's far side and Collins was treated to a view of Eagle back-dropped by the Earth rising over the lunar horizon. Less than four hours after lifting off from the lunar surface, and with Armstrong holding Eagle in position, Collins guided Columbia in for the docking. The two craft were reunited after spending nearly 28 hours apart. Eagle rendezvoused with Columbia at 21:24 UTC on July 21, and the two docked at 21:35. Eagle's ascent stage was jettisoned into lunar orbit at 23:41.
With the hatches open between the two spacecraft, Armstrong and Aldrin began to clean up as much of the lunar dust as they could, part of the back-contamination prevention procedures, and transferred the lunar rock boxes, film cassettes, the solar wind experiment, and other items from Eagle into Columbia. Within two hours they completed all the transfers, closed the hatches for the final time and jettisoned Eagle which remained in lunar orbit until crashing on the Moon's surface several months later.
Apollo 11 orbited the Moon for another five hours, then while behind the Moon fired the Service Propulsion System (SPS) engine for the two-and-one-half-minute Trans Earth Injection (TEI) burn at the end of Columbia's 30th lunar orbit to send the astronauts homeward. At the time of the burn, Columbia was 20 miles in front of and 1 mile below Eagle. As they rounded from behind the Moon, Armstrong called down to Capcom Charles M. Duke in Mission Control, "Time to open up the LRL doors, Charlie." He was referring to the Lunar Receiving Laboratory at the Manned Spacecraft Center, now the Johnson Space Center in Houston, where the astronauts were quarantined after their mission and the Moon rocks were first examined. Duke responded, "We got you coming home. It's well stocked." After TEI, the astronauts took their last photographs of the lunar far side and of an Earthrise.
The astronauts took a series of photographs of the receding Moon and placed their spacecraft into the Passive Thermal Control (PTC) or barbecue mode, rotating along the spacecraft's longitudinal axis three times each hour to evenly distribute temperature extremes. Director of Flight Crew Operations Donald K. "Deke" Slayton radioed up to the crew,
"This is the original CapCom. Congratulations on an outstanding job. You guys have really put on a great show up there. I think it's about time you powered down and got a little rest, however. You've had a mighty long day here. Hope you're all going to get a good sleep on the way back. I look forward to seeing you when you get back here. Don't fraternize with any of those bugs en route, except for the Hornet."
Slayton was making a humorous reference to any possible Moon germs the astronauts may be carrying back with them which necessitated the postflight quarantine to prevent back contamination, which began as soon as they arrived aboard the prime recovery ship the USS Hornet (CVS-12) after splashdown in the Pacific Ocean. As the Apollo 11 astronauts prepared for their first sleep period of the Earthbound journey, Mission Control finally lost contact with Eagle, still in lunar orbit, as its batteries could no longer power its navigation system to point its antenna toward Earth.
Shortly after the astronauts awoke from a 10-hour rest period, they passed out of the Moon's sphere of influence and into the Earth's, and began accelerating toward their home planet. At a distance of 194,500 miles from Earth, they conducted an 11-second midcourse maneuver using the Service Module's RCS thrusters to refine their trajectory for entry into Earth's atmosphere. The astronauts treated Earth-bound viewers with a 15-minute television broadcast, beginning with a view of the receding Moon. They turned the camera into the cabin and Armstrong displayed the two boxes that contained the precious samples of lunar rocks and soil. They demonstrated food preparation in their spacecraft and advancements that had been made in the types of food available to them. In brief physics lessons, Aldrin demonstrated how gyroscopes work and Collins displayed the behavior of fluids in zero-gravity. They ended the broadcast by showing viewers the Earth. The rest of their day was spent leisurely before they settled in for another 10-hour rest period, about 163,000 miles from home.
When they awoke for their final full day in space, they had closed the distance to Earth to 131,000 miles as they continued to accelerate. Capcom Owen K. Garriott informed them that Mission Control decided that since their trajectory was so precise, a planned midcourse maneuver that day was not necessary. They soon passed the halfway point between Earth and Moon, 118,424 miles from each. During a 12-minute TV broadcast, the astronauts provided their reflections on the mission. Collins stressed the complexity of the flight and the hard work done by the thousands of workers to make Apollo 11 possible. Aldrin opined that the flight represented not just the work that went into it but also humanity's innate curiosity to explore. Armstrong concluded by recognizing everyone who was responsible for making Apollo 11 possible and expressed special thanks to the workers who built their spacecraft. As a closing scene, the astronauts zoomed in on the Earth, now 105,000 miles away. Armstrong's wife Jan and their two children, Collins' wife Pat and their children, and Aldrin's son Andy visited the Mission Control Viewing Room during the broadcast.
Shortly before they retired for their last night in space, Capcom Duke informed the astronauts that due to a weather system approaching their nominal end-of-mission splashdown point, a new area 250 miles to the northeast would be targeted. No midcourse maneuvers were necessary, the CM used its lift capability to extend the entry trajectory. Hornet was already speeding toward the new location. President of the United States Richard M. Nixon departed on his journey to meet the Apollo 11 astronauts aboard Hornet.
50 Years Ago: The Recovery of Apollo 11
On July 24, 1969, Apollo 11 was 47,000 miles from Earth and rapidly accelerating toward its home planet when astronauts Neil A. Armstrong, Edwin E. "Buzz" Aldrin, and Michael Collins awoke for their last day in space, preparing for their splashdown in the Pacific Ocean 950 miles southwest of Hawaii. The previous day, managers were forced to move the splashdown point by 250 miles to the northeast due to inclement weather at the original recovery site. The aircraft carrier USS Hornet (CVS-12), the prime recovery ship for Apollo 11, was speeding for the new splashdown target area. Overcast skies made stellar navigation impossible, so Hornet used the ancient mariner's technique of dead reckoning to arrive on time and at the proper position to recover crew and spacecraft. Hornet's commanding officer Capt. Carl J. Seiberlich chose the slogan Hornet Plus 3 for the operation, signifying the safe recovery of the three Apollo 11 astronauts. 4)
President Richard M. Nixon was en route to Hornet to greet the astronauts upon their return. He had flown aboard Air Force One from San Francisco via Hawaii to Johnston Island, an atoll 825 miles west-southwest of Honolulu, accompanied by NASA Administrator Thomas O. Paine, Apollo 8 astronaut Frank Borman, and other dignitaries. From Johnston Island, they flew aboard Marine helicopters to the communications relay ship USS Arlington (AGMR-2), where they spent the night before helicoptering to Hornet early on splashdown day. Admiral John S. McCain, Commander in Chief of Pacific naval forces, greeted the President on Johnston Island and flew separately to Hornet to be present for the splashdown and recovery.
As they approached their home planet the astronauts aboard Columbia photographed the rapidly growing Earth. The Apollo 11 backup crew of James A. Lovell, Fred W. Haise, and William A. Anders, as well as the Chief of Flight Crew Operations Donald K. "Deke" Slayton, joined Capcom Ronald E. Evans in Mission Control. Haise radioed to the crew onboard Apollo 11, "Have a good trip, and make sure you remember to come in BEF," meaning blunt end forward, a humorous reminder to the crew to ensure that Columbia's heat shield faced in the direction of travel for reentry. Collins replied with, "You better believe. Thank you kindly." At an altitude of about 4,500 miles, Apollo 11 passed into the Earth's shadow and 12 minutes later, the Command Module (CM) separated from the Service Module that performed an evasive maneuver to avoid interfering with the reentry process. Hornet was still steaming toward the splashdown point but it had launched recovery helicopters already approaching their operational stations.
The CM turned around to point its heat shield in the direction of flight as its velocity increased to more than 24,700 miles per hour. At an altitude of 400,000 feet, the point called Entry Interface, Apollo 11 encountered the first tendrils of the Earth's atmosphere. About four minutes of radio blackout followed as ionized gases created by the heat of reentry surrounded the spacecraft. Aldrin filmed the entry through Columbia's right hand window with a 16-mm camera. The CM's computer used the spacecraft's lift capability to execute a small skip maneuver to lengthen the reentry trajectory and overfly the area of inclement weather. The astronauts experienced a peak deceleration of about 6.5 times the force of gravity. At this point, one of the deployed aircraft made visual contact with the descending capsule, still at about 65,000 feet altitude. Three minutes later Hornet made a transient visual contact through the mostly overcast skies.
At an altitude of about 24,000 feet, the spacecraft's apex cover was jettisoned, followed less than two seconds later by the two drogue parachutes to slow and stabilize the capsule. At 10,000 feet, the three main 83-foot diameter orange and white parachutes deployed, and Hornet established radio contact with Apollo 11 as it descended through the predawn sky. At precisely 195 hours and 18 minutes after lifting off from Florida, Apollo 11 splashed down in the Pacific Ocean, successfully completing the first human Moon landing mission. Hornet was still 13 miles away but rapidly closing the distance. Recovery helicopters were either on station or rapidly approaching.
Initially, Columbia assumed the Stable 2 position in the water, with the spacecraft's apex pointing downward. Within a few minutes, three flotation bags inflated to right the spacecraft. Then began a carefully choreographed and intensively rehearsed process to recover the astronauts and the capsule from the ocean and transport them to Hornet. Unlike previous recoveries, Apollo 11's was more complicated due to the back-contamination prevention measures that had to be strictly adhered to. Frogmen of the US Navy's UDT (Underwater Demolition Team) had trained aboard Hornet for weeks to precisely carry out the recovery operations. All the swimmers wore scuba gear to minimize any exposure to possible lunar microorganisms. A film of the recovery operations narrated by one of the swimmers provides an excellent perspective.
Once the capsule righted itself, the first swimmer in the water, John M. Wolfram, attached a sea anchor to the spacecraft to stabilize it in the rough seas. He was the first person on Earth to see the astronauts inside the capsule and reported on their condition as being excellent. Two other swimmers, Wesley T. Chesser and Michael G. Mallory, jumped into the water and the three of them attached a flotation collar around the capsule. A helicopter dropped the first raft into the water, which the three inflated and attached to the flotation collar. A second raft was inflated upwind from the capsule to protect the frogmen from any Moon germs. Clarence J. "Clancy" Hatleberg, the decontamination officer, was next in the water and climbed into the second raft. A helicopter lowered the Biological Isolation Garments (BIGs) for Hatleberg and the astronauts as well as the canisters containing decontamination solutions for the crew and the capsule. Hatleberg donned his BIG and was towed to and entered the raft attached to the capsule. His first task was to close vents on the spacecraft to prevent any air that might be contaminated from escaping into the atmosphere. The astronauts briefly opened the hatch to the capsule and Hatleberg handed them their BIGs, which they donned inside the spacecraft. The astronauts then emerged from the capsule and climbed aboard the raft, first Armstrong, then Collins and finally Aldrin. Hatleberg had some difficulty closing the capsule's hatch, and first Armstrong then Collins helped to finally secure it. Hatleberg sprayed the capsule with Betadine and wiped the astronauts down with a sodium hypochlorite solution for decontamination purposes.
The recovery helicopter one by one retrieved the three astronauts from the raft using a Billy Pugh net, first Armstrong, then Collins and finally Aldrin. NASA flight surgeon Dr. William R. Carpentier was aboard the helicopter and gave them a brief medical evaluation. The helicopter flew to the Hornet, landing on its deck 63 minutes after splashdown. From there, sailors placed it on an elevator, took it below decks, and towed it toward the reception area near the prime Mobile Quarantine Facility (MQF) – a second MQF was held in reserve in case problems arose with the first, or in case any of the ship's crew was inadvertently exposed to the astronauts or spacecraft. The three astronauts, Collins first, followed by Armstrong, Aldrin, and Dr. Carpentier, walked the ten steps from the helicopter to the MQF, amid the cheers of Hornet's crew and assembled media. NASA engineer John K. Hirasaki was waiting inside the MQF and filmed the astronauts entering. The five of them remained inside the MQF until their arrival at the Lunar Receiving Laboratory (LRL) at the Manned Spacecraft Center (MSC), now the Johnson Space Center in Houston, two days later.
Mission Control in Houston was closely monitoring the splashdown and recovery activities, with most communications with the spacecraft being handled by Hornet's recovery team. The room was rapidly filling to capacity as managers and engineers prepared for the celebration of a mission successfully accomplished. Once the recovery team safely delivered the astronauts aboard Hornet, everyone lit cigars and waved American flags amid a cacophony of cheers. One screen displayed the words of President John F. Kennedy from his May 1961 message to Congress that committed the nation to the goal "before this decade is out, of landing a man on the Moon and returning him safely to Earth," while another showed the Apollo 11 patch with the words "Task Accomplished – July 1969."
Once inside the MQF, the astronauts removed their BIGs, took showers, changed into comfortable flight suits, and prepared to be welcomed by the President Nixon. In a short speech, Nixon recognized the tremendous accomplishment of the Moon landing and invited the astronauts and their wives to a state dinner in Los Angeles on August 13, once they were out of quarantine. Hornet's chaplain provided a prayer and the service ended with the playing of the National Anthem. The ceremonies over, Nixon boarded Marine One and departed Hornet. He had been onboard for three hours.
The UDT (Underwater Demolition Team) swimmers and sailors aboard Hornet hauled Columbia out of the water and towed it below to the hangar deck next to the MQF. Once Columbia was aboard, Hornet set sail for Pearl Harbor, Hawaii. Workers erected a flexible plastic tunnel between the MQF and the capsule, allowing Hirasaki to leave the MQF, open the hatch to Columbia. He retrieved the two Apollo Lunar Sample Return Containers (ALSRC) containing the Moon rocks and soil, film cassettes, and spacesuits from the capsule and returned with them to the MQF without breaking the biological barrier. Hirasaki sealed the ALSRCs, film cassettes, and medical samples taken inside the MQF in plastic bags and transferred them outside through a transfer lock that included a decontamination wash. Outside the MQF, NASA engineers placed these items into transport containers and loaded them aboard two separate aircraft. The first aircraft carrying one ALSRC and a second package containing film departed Hornet within a few hours of the recovery, flying to Johnston Island 180 miles away. From there the two containers were placed aboard a C-141 cargo aircraft and flown directly to Ellington Air Force Base (AFB) near MSC in Houston, arriving there the afternoon of July 25. The second aircraft departed Hornet six and a half hours after the first and included the second ALSRC, additional film as well as the astronaut medical samples. It flew directly to Hickam AFB in Hawaii where workers transferred the containers to another cargo plane that flew it to Houston. Within 48 hours of splashdown, scientists in the LRL in Houston were examining the first lunar samples and processing the film.
50 Years Ago: Apollo 11 Returns to Houston
Apollo 11 splashed down 950 miles southwest of Hawaii on July 24, 1969. The Command Module (CM) Columbia and the crew of Neil A. Armstrong, Edwin E. "Buzz" Aldrin, and Michael Collins were successfully recovered and delivered aboard the prime recovery ship the aircraft carrier USS Hornet (CVS-12). Requirements to prevent back contamination of the Earth with any possible lunar microorganisms made the Apollo 11 recovery the most complicated in spaceflight history. Once aboard the carrier, the astronauts entered the Mobile Quarantine Facility (MQF) along with NASA flight surgeon Dr. William R. Carpentier and NASA recovery engineer John K. Hirasaki. The goal was to return the astronauts, Columbia, and the lunar samples and film magazines to the Lunar Receiving Laboratory (LRL) at the Manned Spacecraft Center (MSC), now the Johnson Space Center in Houston, as expeditiously as possible while maintaining the strict biological isolation protocols. 5)
Within hours after splashdown, Hirasaki retrieved the Moon rocks contained in two Apollo Lunar Sample Return Containers (ALSRC), film magazines, and other items from Columbia, which was connected to the MQF via a flexible tunnel to maintain biological isolation. He sealed the ALSRCs, film cassettes, and crew medical samples taken inside the MQF in plastic bags and transferred them to the outside through a transfer lock that included a sodium hypochlorite decontamination wash. Outside the MQF, NASA engineers retrieved the items from the transfer lock, placed them into transport containers, and loaded them aboard two separate aircraft. The first aircraft carrying the ALSRC containing Moon rocks, the core samples, and the Solar Wind Collection experiment, and a second package containing film magazines, departed Hornet within a few hours of the recovery, flying to Johnston Island 180 miles away. Workers there placed the two containers aboard a C-141 Starlifter cargo aircraft that flew directly to Ellington Air Force Base (AFB) near MSC in Houston, arriving the afternoon of July 25. The second aircraft departed Hornet six and a half hours after the first and included the second ALSRC, additional film as well as the astronaut medical samples. It flew directly to Hickam AFB in Hawaii where workers transferred the containers to an Apollo Range Instrumentation Aircraft (ARIA) that flew them directly to Houston.
Top NASA managers including NASA Administrator Thomas O. Paine, Samuel C. Phillips, Apollo Program Director at NASA Headquarters, Robert L. Gilruth, MSC Director, and George M. Low, MSC Apollo Spacecraft Program Manager, were on hand when the first delivery of Moon rocks arrived at Ellington. Howard J. Schneider and Gary W. McCollum, Quarantine Control Officers in the LRL, carried the containers from the C-141 to a NASA vehicle to make the 15-minute drive to the LRL to place them in quarantine.
Workers in the LRL unpacked the first ALSRC from its shipping container, weighed it with reporters eagerly watching from across a glass partition, and installed it in a glovebox in the Vacuum Laboratory. Armstrong and Aldrin had sealed the box in the vacuum of the lunar environment and the glovebox also provided a vacuum to prevent Earth's atmosphere from contaminating the pristine samples. Scientists opened the box at 3:55 PM on July 26, about 48 hours after splashdown, and got their first look at rocks returned by humans from another celestial body. One of the samples was sent off to the radiation counting lab for gamma radiation sampling and then to the biology lab to be assessed for any microorganisms. Scientists opened the second box on 5 August.
Elsewhere in the LRL, workers opened the boxes containing the film magazines and the crew medical samples. All items returned by Apollo 11 were decontaminated by being placed in an autoclave and sterilized with ethylene gas. The only incident of note occurred when NASA photographer Terry Slezak was unwrapping the film canisters, and he failed to heed a handwritten note by Aldrin attached to one of the magazines. The note indicated that it was the one magazine that Armstrong had accidentally dropped onto the lunar surface and then retrieved before climbing up the ladder to the LM at the end of their spacewalk. When Slezak picked up the magazine, he noticed a black dust adhering to his fingers. Besides the three Apollo 11 astronauts, he became the first human to touch lunar soil, albeit accidentally, and protocol dictated that he undergo a rigorous decontamination protocol.
Meanwhile, in the Pacific Ocean, the Hornet was sailing toward Pearl Harbor, Hawaii, with the astronauts inside the MQF to maintain the strict back-contamination protocols. The day after splashdown, Hornet's commanding officer Capt. Carl J. Seiberlich officiated at a formal welcoming ceremony for the Apollo astronauts. During the voyage, the astronauts rested and began to organize their thoughts for the postflight debriefings that began once they arrived in Houston. Dr. Carpentier conducted regular medical examinations of the astronauts, who showed no ill effects from their eight-day spaceflight or any signs of infection by any lunar microorganisms. The crewmembers availed themselves of one amenity aboard the MQF that was a novelty at the time – a microwave oven for meal preparation.
On the morning of July 26, Hornet arrived at Pearl Harbor, 52 hours after Columbia was safely hoisted aboard – a journey only 6 hours shorter than Apollo 11's trip back from the Moon! Sailors brought Columbia onto the flight deck so the assembled crowd of about 2,500 well-wishers could see it as the ship docked. Using a crane, workers lifted the MQF with the astronauts aboard onto a flat-bed trailer. Capt. Seiberlich joined Admiral John S. McCain, Commander-in-Chief of Pacific Command, Hawaii Governor John A. Burns, and Honolulu Mayor Frank F. Fasi for a brief welcoming ceremony including traditional Hawaiian flower leis, ukulele music and hula dancers. Workers drove the MQF to nearby Hickam AFB, where Air Force personnel loaded it onto a C-141 Starlifter. After an eight-hour flight, the C-141 arrived at Ellington on July 27, where the MQF was offloaded in front of a waiting crowd of well-wishers undeterred by the crew's 2 AM arrival. The astronauts' wives and children were on hand to welcome them home to Houston. Although still inside the MQF, the astronauts could talk with their families via a telephone connection and see each other through the windows. Workers placed the MQF on a flat-bed truck and drove it to the LRL, where once inside the Crew Reception Area (CRA), the crew said a few words of thanks to the personnel who welcomed and promptly went to sleep.
After a restful night, the astronauts began their regular routine in the LRL by holding their first debriefing session about their mission to the Moon. The sessions were held with the astronauts in the glass-enclosed crew debriefing room, communicating via telephone with Chief of Flight Crew Operations Donald K. "Deke" Slayton and Lloyd Reeder, crew training coordinator. They remained in quarantine for another two weeks.
After the astronauts departed Hornet in Pearl Harbor, workers used a crane to lift Columbia from the carrier's flight deck to the dock and towed it to an aircraft hangar on Ford Island, the remote location chosen because the spacecraft still contained some toxic propellants that workers drained to safe the vehicle. To preserve back-contamination protocols, Columbia's hatch remained sealed since the flexible tunnel connecting it to the MQF was removed. On July 29, workers loaded Columbia and the backup MQF onto a C-133 Cargomaster aircraft at Hickam AFB. After a refueling stop on the West Coast, Columbia arrived at Ellington on July 31 and workers trucked it to the LRL, where it was towed inside the spacecraft room. The Apollo 11 astronauts retrieved personal items from the spacecraft and Hirasaki removed the spacesuits for postflight inspections.
Special thanks go to John J. Uri of the NASA/JSC (Johnson Space Center) History Office who provided the various information installments of the Apollo 11 mission.
In retrospect: The Apollo Experiment That Keeps on Giving
July 24, 2019: Neil Armstrong, Buzz Aldrin and Michael Collins departed from the Moon 50 years ago, but one of the experiments they left behind continues to return fresh data to this day: arrays of prisms that reflect light back toward its source, providing plentiful insights. Along with the Apollo 11 astronauts, those of Apollo 14 and 15 left arrays behind as well: The Apollo 11 and 14 arrays have 100 quartz glass prisms (called corner cubes) each, while the array of Apollo 15 has 300. 6)
The longevity of the experiment can be attributed at least in part to its simplicity: The arrays themselves require no power. Four telescopes at observatories in New Mexico, France, Italy and Germany fire lasers at them, measuring the time that it takes for a laser pulse to bounce off the reflectors and return to Earth. This allows the distance to be measured to within a fraction of an inch (a few millimeters), and scientists at the Jet Propulsion Laboratory analyze the results.
The orbit, rotation and orientation of the Moon are accurately determined by lunar laser ranging. The lunar orbit and the orientation of the rotating Moon are needed by spacecraft that orbit and land on the Moon. For instance, cameras on spacecraft in lunar orbit can see the reflecting arrays, relying on them as locations accurate to less than a foot (about 0.2 m).
Laser ranging measurements have deepened our understanding of the dance between the Moon and Earth as well. The Moon orbits Earth at an average distance of 239,000 miles (385,000 km), but lunar laser ranging has accurately shown that the distance between the two increases by 1.5 inches (3.8 cm) a year.
Tides in Earth's oceans are highest not when the Moon is overhead, but hours later. The highest tide is east of the Moon. There are two tidal bulges, the second one half a day later. The gravitational force between the tidal bulges and the Moon pull against and slow Earth's rotation while also pulling the Moon forward along the direction it moves in its orbit about Earth. The forward force causes the Moon to spiral away from Earth by 0.1 inches (3 mm) each month.
In a similar way, Earth's gravity tugs on the Moon, causing two tidal bulges of the lunar rock. In fact, the positions of the reflecting arrays vary as much as six inches (15 cm) up and down each month as the Moon flexes. Measuring how much the arrays move has enabled scientists to better understand the elastic properties of the Moon (a measurement of this, called the Love number, is named after scientist A. E. H. Love).
Analysis of lunar laser data shows that the Moon has a fluid core. This was a surprise when discovered two decades ago because many scientists thought that the core would be cool and solid. The fluid core affects the directions in space of the Moon's north and south poles, which lunar laser detects.
Einstein's theory of gravity assumes that the gravitational attraction between two bodies does not depend on their composition. The Sun's gravity attracts the Moon and Earth. If this attraction depended on the composition of the two objects, it would affect the lunar orbit. Earth contains more iron than the Moon. Analysis of data from the lunar laser ranging experiment finds no difference in how gravity attracts the Moon and Earth due to their makeup.
The north star is nearly overhead at Earth's north pole. That pole changes direction compared to the stars due to the gravitational pull of the Moon and Sun on Earth's shape (the diameter at the equator is larger than the diameter at the poles). The pole will trace out a circle in the sky returning to the north star in 26,000 years. This motion of the pole is sensed and measured by lunar laser ranging.
With renewed interest in the exploration of the Moon, NASA has approved a new generation of reflectors to be placed on the lunar surface within the next decade. The improved performance of new reflectors and their wider geographical distribution on the Moon would allow improved tests of Einstein's relativity, study the deep lunar interior, investigation of the history of our celestial neighbor, and support of future exploration. The legacy of the first human visit to the Moon half a century ago will be continued.
Vice President Unveils NASA Spacecraft for Artemis 1 Lunar Mission on the 50th Moon Landing Anniversary
"Thanks to the hard work of the men and women of NASA, and of American industry, the Orion crew vehicle for the Artemis 1 mission is complete and ready to begin preparations for its historic first flight," said Vice President Pence.
He was joined on stage by Florida Governor Ron DeSantis, NASA Administrator Jim Bridenstine, Apollo 11 Lunar Module Pilot Buzz Aldrin, Kennedy Center Director Robert Cabana, Lockheed Martin Chairman, President and Chief Executive Officer Marillyn Hewson, and Rick Armstrong, son of Apollo 11 Commander Neil Armstrong. Before going to the Operations and Checkout Building, the Vice President, Aldrin and Armstrong visited Kennedy's historic launch pad, 39A, where the Apollo 11 mission lifted off.
NASA's goal 50 years ago was to prove the agency could land humans on the Moon and return them safely to Earth. The goal now is to return to the Moon in a sustainable way to prepare for the next giant leap – sending astronauts to Mars for the first time ever.
Artemis 1 will launch NASA's Orion spacecraft and Space Launch System (SLS) rocket around the Moon to test the system and pave the way for landing the first woman and the next man on the Moon in five years, as well as future missions to Mars.
"Similar to the 1960s, we too have an opportunity to take a giant leap forward for all of humanity," said Bridenstine. "President Trump and Vice President Pence have given us a bold direction to return to the Moon by 2024 and then go forward to Mars. Their direction is not empty rhetoric. They have backed up their vision with the budget requests need to accomplish this objective. NASA is calling this the Artemis program in honor of Apollo's twin sister in Greek mythology, the goddess of the Moon. And we are well on our way to getting this done."
Engineers recently completed building and outfitting the Orion crew module at Kennedy. The underlying structure of the crew module, known as the pressure vessel, was manufactured at NASA's Michoud Assembly Facility in New Orleans and shipped to Kennedy, where teams have integrated thousands of parts into the crew module and conducted tests to certify all of its systems for flight.
Orion's European Service Module, which will provide the power and propulsion for Orion during the mission, also is complete. Contributed by ESA (European Space Agency), the service module was manufactured by Airbus in Bremen, Germany, and shipped to Kennedy in November 2018 for final assembly and integration. Engineers have begun operations to join the crew module to the service module, and teams are connecting power and fluid lines to complete hardware attachment.
Once the two modules are joined, engineers will install a heatshield backshell panel on the spacecraft and prepare it for a September flight inside the agency's Super Guppy aircraft to NASA's Plum Brook Station in Sandusky, Ohio. Testing at Plum Brook will ensure the joined modules can withstand the deep space environment.
When testing in Ohio is complete, the spacecraft will return to Kennedy for final processing and inspections. Teams then will fuel the spacecraft and transport it to Kennedy's iconic Vehicle Assembly Building for integration with the SLS rocket before it is rolled out to Launch Pad 39B for the launch of Artemis 1.
Orion is part of NASA's backbone for deep space exploration, along with SLS and the lunar Gateway. During Artemis 1, SLS will send the uncrewed spacecraft – consisting of the crew and service modules – thousands of miles past the Moon for the first in a series of increasingly complex missions. Artemis 2 will be the first of these new missions to the Moon with astronauts on board, followed by Artemis 3, which will launch the next American moonwalkers into a new era of exploration.
Figure 56: Vice President Mike Pence visited NASA's Kennedy Space Center in Florida on July 20, 2019, to commemorate the 50th anniversary of the agency's Apollo 11 Moon landing. He joined Administrator Jim Bridenstine and other dignitaries to announce the completion of NASA's Orion crew capsule for the first Artemis lunar mission (video credit: NASA)
Working with U.S. companies and international partners, NASA will push the boundaries of human exploration forward to the Moon. Through Artemis, the agency will establish a sustainable human presence at the Moon by 2028 to continue scientific research and discovery, demonstrate new technologies, and lay the foundation for future missions to Mars.
1) John Uri, "50 Years Ago: The Journey to the Moon Begins," NASA Feature, 16 July 2019, URL: https://www.nasa.gov/feature/50-years-ago-the-journey-to-the-moon-begins
2) John Uri, "50 Years Ago: One Small Step, One Giant Leap," NASA Feature, 19 July 2019, URL: https://www.nasa.gov/feature/50-years-ago-one-small-step-one-giant-leap
3) John Uri, "50 Years Ago: Apollo 11 – The Journey Home," NASA Feature, 22 July 2019, URL: https://www.nasa.gov/feature/50-years-ago-apollo-11-the-journey-home
4) John Uri, "50 Years Ago: Hornet + 3 – The Recovery of Apollo 11," NASA Feature, 24 July 2019, URL: https://www.nasa.gov/feature/50-years-ago-hornet-3-the-recovery-of-apollo-11
5) John Uri, "50 Years Ago: Apollo 11 Returns to Houston," NASA Feature, 25 July 2019, URL: https://www.nasa.gov/feature/50-years-ago-apollo-11-returns-to-houston
6) DC Agle, "The Apollo Experiment That Keeps on Giving," NASA/JPL News, 24 July 2019, URL: https://www.jpl.nasa.gov/news/news.php?feature=7463&utm_source=iContact&utm
7) Bettina Inclán, Vice President Unveils NASA Spacecraft for Artemis 1 Lunar Mission on Moon Landing Anniversary," NASA Press Release 19-060, 20 July 2019, URL: https://www.nasa.gov/press-release/vice-president-unveils-nasa-spacecraft-for-artemis-1-lunar-mission-on-moon-landing
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 (email@example.com).