The European Space Agency (ESA) successfully performed a first-of-its-kind assisted reentry of an Earth observation satellite over Antarctica on July 28, 2023. The satellite, named Aeolus, was not designed for a controlled reentry when it was launched by ESA in 2018. To avoid the risk of space debris falling onto inhabited areas, ESA lowered the satellite’s orbit from 320 km to 120 km and positioned it over a planned Atlantic ground track. LeoLabs, the leading commercial provider of Space Traffic Management (STM) and Space Situational Awareness (SSA) services, supported this mission as a tracking partner, receiving ephemeris data from ESA Mission Control and tasking its global radar network to track the satellite.
Aeolus: A Pioneer in Wind Measurement
Aeolus was a groundbreaking mission that aimed to improve the understanding of global wind patterns and their impact on weather, climate, and air quality. The satellite carried a unique instrument called ALADIN (Atmospheric Laser Doppler Instrument), which used a powerful laser to measure wind speeds from space. Aeolus provided the first global map of wind profiles, filling a critical gap in the observation of Earth’s atmosphere. The mission also contributed to improving weather forecasts and climate models.
Aeolus was launched on August 22, 2018 from Kourou, French Guiana, on board a Vega rocket. It had an initial planned lifetime of three years, but it exceeded its expectations and operated for nearly five years. During its mission, Aeolus faced several challenges, such as avoiding collisions with space debris, coping with high solar activity, and maintaining its laser performance. Despite these difficulties, Aeolus delivered valuable data to the scientific community and demonstrated the feasibility of wind lidar technology in space.
Assisted Reentry: A Novel Way to Reduce Space Debris
As Aeolus approached the end of its operational life, ESA decided to perform an assisted reentry of the satellite, rather than letting it decay naturally. This was because Aeolus was not equipped with a propulsion system that could ensure a controlled reentry over a specific location. Without any intervention, Aeolus would have experienced an uncontrolled reentry, which could pose a threat to people and property on the ground.
To avoid this scenario, ESA performed a series of maneuvers between July 24 and July 28, 2023, using the satellite’s reaction wheels and magnetic torquers to lower its orbit from 320 km to 120 km. This increased the aerodynamic drag on the satellite and accelerated its descent. ESA also adjusted the satellite’s orientation to minimize its cross-sectional area and reduce its orbital lifetime. The final maneuver placed Aeolus over a planned Atlantic ground track, where it reentered the atmosphere and burned up over Antarctica.
ESA described this assisted reentry as a “first-of-its-kind” because it was the first time that such a technique was used for a satellite that was not designed for a controlled reentry. The agency said that this experiment contributed to a novel ending for the mission that successfully reduced space debris and enabled a safe reentry. ESA also said that by testing space tracking capabilities for assisted and controlled reentries, it was one step closer to achieving sustainable space.
LeoLabs: A Reliable Tracking Partner for Space Missions
LeoLabs supported this mission as a tracking partner, receiving ephemeris data prior to and after each maneuver from ESA Mission Control. This data was used by LeoLabs to task its global radar network to track the satellite, helping ESA verify and monitor orbital changes after each de-orbit maneuver. LeoLabs also provided ESA with real-time tracking data during the final reentry phase.
LeoLabs is the leading commercial provider of STM and SSA services, offering high-resolution mapping and monitoring of objects in low Earth orbit (LEO). The company operates a network of phased-array radars around the world that can track objects as small as 2 cm in size. LeoLabs provides accurate and timely information on the location, motion, and status of objects in LEO, enabling satellite operators, commercial enterprises, and government agencies to launch and operate missions safely and sustainably.
LeoLabs said that it was proud to support this groundbreaking effort by ESA, which represented a milestone towards making space safer and more sustainable. The company said that it illustrated how responsible behavior by owner/operators could normalize space safety measures and contribute to growing expertise in active debris removal. LeoLabs also said that this partnership served as a successful test of its object tracking capabilities in very low Earth orbit (VLEO), which includes altitudes below 400 km. LeoLabs said that it was able to demonstrate its ability to reliably track objects in VLEO, which is difficult due to higher aerodynamic drag and stronger gravitational pull on the object while on orbit. By illustrating these capabilities, LeoLabs built confidence in the ability for satellite owner/operators to safely deorbit objects, the final critical stage of future active-debris removal missions.