ESA's new Izaña-1 (IZN-1) Laser Ranging Station in Tenerife, Spain, tracking satellites and debris
ESA's Izaña-1 laser ranging station in Tenerife, Spain, has recently undergone months of testing and commissioning, passing its final tests with flying colours. As it reached ‘station acceptance’, it was handed over to ESA from the German company contracted to build it, DiGOS, a startup company in Potsdam. The station is a technology testbed and a vital first step in making debris mitigation widely accessible to all space actors with a say in the future of our space environment. 1)
Figure 1: ESA's IZN-1 laser ranging station on top of the Izaña mountain in Tenerife, Spain, has recently undergone months of testing and commissioning, passing its final tests with flying colours. As it reached ‘station acceptance’, it was handed over to ESA from the German company contracted to build it, DiGOS. The station is a technology test bed and a vital first step in making debris mitigation widely accessible to all space actors with a say in the future of our space environment (image credit: ESA)
IZN-1, developed and now operated by ESA is a test-bed for future technologies and was installed in mid-2021 at the Teide Observatory. The station, telescope and laser have undergone months of testing and commissioning and since July last year have aimed the laser beam of concentrated green light to the sky to actively detect, track and observe active satellites.
At present, the laser light operates at 150 mW but it will soon be upgraded to also track space debris on the basis of much more powerful infrared lasers with an average power of 50 Watts.
Hence, only satellites fitted with ‘retroreflectors’ can be tracked from ESA’s Izaña station, making up just a proportion of the total population,” explains Clemens Heese, Head of the Optical Technologies Section.
Figure 2: Perched on the slopes of Tenerife’s Mount Teide, ESA’s latest tracking station is focused on the challenge of space debris. Instead of radio waves, the IZN Laser Ranging Station relies on laser light. Its laser pulses probe hundreds of kilometres into space, making contact with items of debris as well as intact satellites, fixing their position down to a matter of centimetres. Operated for ESA by the company DiGOS GmbH Potsdam, this new station is operated as part of ESA’s Space Safety programme, protecting life and infrastructure on Earth and in orbit (video credit: ESA)
“The station will be upgraded in the next couple of years, enabling it to perform the same vital ‘ranging’ services with uncooperative targets – vitally, debris objects and older satellites fitted without retroreflecting patches.”
The first of many in Europe
While dozens of laser tracking stations are dotted around Europe, the Izaña station’s dual functionality makes it a first. Built by German company DiGOS, the remotely controlled Izaña station can also be used for optical communications and is intended to become a state-of-the-art, fully autonomous robotic system. It is hoped to be the first of many across the globe.
As ESA’s newest addition to the Space Safety family, Izaña-1 provides support for vital collision avoidance and provides a testbed for new sustainable technologies like laser momentum transfer or coordination of space traffic.
Such satellite and debris tracking capability in Europe could contribute to building and accessing a European catalogue of space objects.
Figure 3: The cost of avoiding collision. Space might seem an empty, vast expanse, but satellites in Earth's orbit face the constant risk of collision - with other satellites, dead or alive, or with fragments of debris. It is now routine for operators of spacecraft in busy highways to divert their mission out of harms way. In fact at ESA, each mission flown performs on average two 'collision avoidance manoeuvres' per year. These manoeuvres are costly. Hours are spent on the ground monitoring the skies, calculating the risk and planning manoeuvres, not to mention the extra fuel spent and missed science and data collected while instruments are turned off. (image credit: ESA / UNOOSA)
Lasers in space. Is that ... safe?
But hold on, there are birds, planes, astronauts above us! Doesn’t aiming lasers into the sky come with an unacceptable risk? Fortunately, lasers used for satellite and debris tracking would be a disappointment to any self-respecting Bond villain.
Ultimately, the IZN-1 station will use a power of under 100 Watts, giving the Izaña laser about 1/20th of the energy of an electric kettle.
Figure 4: ESA's IZN-1 laser ranging station on top of the Izaña mountain in Tenerife, Spain, has recently undergone months of testing and commissioning, passing its final tests with flying colours. As it reached ‘station acceptance’, it was handed over to ESA from the German company contracted to build it, DiGOS. The station is a technology test bed and a vital first step in making debris mitigation widely accessible to all space actors with a say in the future of our space environment (image credit: ESA)
These pinpoint light sources shine short pulses of light at their target, determining the distance, velocity and orbit of each one with millimetre precision, calculated from the time it takes to complete the return journey.
Although such lasers don’t come anywhere close to cutting through, or even nudging (yet) the objects they target, they can damage sensitive optical instruments on satellites and the paths of aircraft must be considered.
“If lasers strike planes they can be very dangerous, as pilots can become distracted and in worst-case scenarios, lose control,” explains Andrea di Mira, ESA Optoelectronics Engineer. “We are very, very careful that this does not happen, with a set of sensors scanning the sky for aircraft to ensure our lasers do not get remotely close to them”.
These lasers also have the potential to disrupt telescopes studying the night’s sky. To prevent this, the Laser Traffic Control System (LTCS) was introduced by the Instituto de Astrofísica de Canarias (IAC) – much like IZN-1 helps to prevent collisions between objects in orbit, the LTCS software prevents ‘collisions’ between laser light and areas of observation. Additionally, switching to an infrared laser frequency can minimize conflicts with astronomers.
A vital step towards space traffic control
As the era of New Space is now fully underway, large constellations are being launched to the skies consisting of thousands, sometimes tens of thousands of satellites.
Current, costly methods of collision avoidance will be futile as numbers increase and as such the international space community will need to establish a method of space traffic control.
For this, precise and rapid determination of the location, velocity and orbit of space objects will be vital, and ESA’s IZN-1 station will provide a much-needed testbed for this technology, far more accurate than current radar methods, to be developed.
Europe must develop operational, real-time systems to enable the detection, identification and avoidance of natural and human-made space hazards. The need to remove dead satellites from orbit means developing a new European commercial capacity to provide innovative in-orbit services, like deorbiting, repairing and refuelling active satellites, creating a circular economy in space.
Figure 5: Protection of space assets. There are a great many objects in orbit around Earth, mostly comprising functioning and dead satellites as well as fragments of past break-ups, explosions and collisions. Some 36,000 objects larger than a tennis ball are orbiting Earth – and only 13% of these are actively controlled. The rest is space junk that threatens all the satellites on which our economies and society depend. - On top of this growing hazard, space weather caused by unpredictable solar activity can damage and even destroy satellites and can cause power blackouts and cut communication networks on the ground. Developing an air traffic control system for space would protect civil infrastructure on Earth (image credit: ESA)
Laser focus on the future
In the near future, ESA’s IZN-1 station will be a fully autonomous, highly productive satellite and debris tracking station. It will also be used to test the concept of ‘networked space debris laser ranging’ to build a satellite catalogue.
When it comes to optical communication, it will also be upgraded to receive signals with a very high data rate of 10 gigabits and beyond (adhering to international standards) from satellites in low-Earth orbit 400 km away.
Izaña will then become part of a planned European Optical Nucleus Network, the first operational optical communication ground station service of its kind that will be made available to the wider commercial space community.
On top of all this, the station provides an opportunity to test and develop technologies underpinning ‘laser momentum transfer’, in which lasers would not merely shine a light on debris objects but very gently nudge them into new orbits, out of the way of potential collisions and out of the busiest orbital highways.
As IZN-1 is welcomed into to ESA’s Space Safety family, so is a bright future of sustainable technologies, vital for a responsible future in orbit and beyond.
Figure 6: The scales of the space debris problem. An impressive shot from ESA's latest space debris movie: Time to Act. The launch of Sputnik, humankind’s first satellite, in 1957 marked the dawn of a new era for the people of the 'Pale Blue Dot'. Decades later, our planet is now surrounded by spacecraft carrying out extraordinary work. But they are up against a huge problem, they share space with millions of fragments of fast-moving and dangerous space debris (image credit: ESA)
1) ”New laser station lights the way to debris reduction,” ESA Safety & Security, 15 February 2022, URL: https://www.esa.int/Safety_Security/Space_Debris/New_laser_station_lights_the_way_to_debris_reduction
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).