ESA’s CryoSat satellite, dedicated to measuring the thickness of polar sea ice and monitoring changes in ice sheets, recently faced a fuel leak that threatened to end its mission in 2025. However, a successful swap to its back-up propulsion system has potentially extended the satellite’s lifespan by 5 to 10 years. CryoSat’s thirteen-year climate record of global ice and sea levels is unparalleled, providing critical data for climate reports and policymakers.

CryoSat’s primary propulsion system uses compressed nitrogen for manoeuvres in space. In 2016, operators at ESA’s European Space Operations Centre (ESOC) noticed that the spacecraft was consuming its compressed nitrogen faster than expected. As of November 2023, CryoSat has 13 kg less fuel than it should have, jeopardizing its ability to control direction and maintain orbit. The leak was traced to one of CryoSat’s smaller attitude thrusters, causing concern among operators.

To save the satellite, CryoSat’s back-up propulsion system was initiated on November 21, 2023. The team at ESOC closely monitored the pressure in the back-up system and instructed the satellite’s onboard computer to use the back-up thrusters instead of the primary ones. After a nerve-wracking 25 minutes, CryoSat emerged fully functional and capable of continuing scientific activities.

The decision to wait until now to address the leak was not taken lightly. CryoSat had gathered seven years of crucial ice mapping data from 2016 to 2023, and switching immediately could have resulted in data loss if problems had occurred during reconfiguration. November 21 was chosen as the balancing point between gaining additional years and minimizing fuel loss.

The success of the back-up thruster swap discovers possibilities for extending CryoSat’s mission. Monitoring the fuel reserves over the next few days and weeks will determine if there are any smaller leaks or issues in the back-up system. This operation could prove invaluable for humankind’s polar ice records and bridge the gap until the launch of CRISTAL, CryoSat’s successor.

Furthermore, a collaboration with NASA’s ice monitoring satellite ICESat-2 could improve the accuracy of satellite measurements of ice volume. By combining the orbits of ICESat-2 and CryoSat, scientists can map snow on ice, reducing uncertainty in estimates. These findings will also benefit future ice missions, including CRISTAL.

CryoSat’s mission continues to offer consistent improvements to its data products, covering sea ice, land ice, polar oceans, coastal oceans, and inland waters. With its extended lifespan, CryoSat remains a valuable asset in the study of global ice and its impact on climate change.