Galileo satellite GSAT0104 retires after 12 years of navigation service
On 12 March 2013, Galileo satellite GSAT0104, alongside its fellow In-Orbit Validation (IOV) satellites, made history by enabling the first position fix by Europe's independent satellite navigation system Galileo. Now, after 12 years of service mostly in the area of Search and Rescue, GSAT0104 makes history again by becoming the first satellite in the Galileo constellation to be decommissioned.
For a large and long-lasting constellation like Galileo, which serves as a critical public infrastructure and aims to deliver uninterrupted services over decades, decommissioning activities are as essential as launches. To run smoothly, the fleet needs continuous replenishment, and therefore disposing of satellites is not only about making space safer, but about making space for new satellites.
In October 2023, a board chaired by the EU Agency for the Space Program (EUSPA) with the European Space Agency (ESA) and the European Commission (EC) concluded for the first time to retire a Galileo satellite. Decommissioning activities for GSAT0104 began in March 2024 and were completed in April 2025.
Sustainability in Space
Sustainability in and from space is a core priority for ESA, which promotes a responsible use of space to benefit both society and the environment. Central to this commitment is reducing space debris, a serious global hazard threatening current and future missions, and the essential services they provide.
To address the growing space debris issue, ESA has set an ambitious goal of net zero space pollution for new missions by 2030. This target is backed by sustainable design practices, rigorous debris mitigation policies, and end-of-life satellite disposal protocols.
Decommissioning Activities
When a Galileo satellite reaches the end of its service, it is moved to a higher and safe orbit and passivated by depleting all its sources of energy. Galileo's graveyard orbits are located at least 300 km above the active constellation and are designed to remain stable for a very long time. This is a vast region that does not interfere with Galileo, geostationary satellites or any other constellation for hundreds of years.
| Operation | Description |
|---|---|
| Galileo Satellite Decommissioning | Moving satellites to graveyard orbits 700 km above the operational constellation. |
| Passivation | Depleting satellites’ sources of energy to ensure they do not interfere with operational missions. |
| Space Debris Mitigation | Following strict policies to manage and prevent space debris generation. |
Performance of the Galileo Constellation
GSAT0104 is one of the 38 Galileo First Generation satellites designed, developed, and tested by ESA, together with manufacturers EADS Astrium (4 In-Orbit Validation satellites) and OHB (34 Full Operational Capability satellites). After this decommissioning, the constellation provides the same level performance services with active satellites in all its prime slots, plus three active spare satellites.
Additionally, new satellites will continue to join the fleet, with six First Generation satellites ready to launch and 12 Second Generation ones in development.
Tidying up the Constellation
Protecting the space environment is only one of the reasons to properly dispose of satellites that no longer serve the constellation or are at risk of failure. "In Galileo we need to keep our orbits clear and safe to support the continuous renewal of the fleet. A healthy constellation is required to ensure optimal performance and reliable service provision for billions of users worldwide," explains Riccardo Di Corato, Head of the Galileo Constellation Analysis Unit.
All satellites have a design lifetime after which their systems are expected to be less reliable or effective (12 years in the case of Galileo First Generation and 15 years for Second Generation satellites). Galileo partners assess the condition and contribution of older satellites annually and determine either to extend service by one year or to decommission.
Future Directions
In light of the recent decommissioning, ESA is taking measures to improve future operational strategies, including:
- Increasing the frequency of satellite condition assessments.
- Refining disposal protocols to optimize satelitte end-of-life procedures.
- Investing in research for advanced technologies that enhance satellite durability and longevity.
Thanks to the propellant reserves in GSAT0104, it was possible to place it 700 km above the Galileo operational constellation on a very stable disposal orbit. Then, the satellite tank was depleted and the satellite passivated by removing all internal energy, such as battery charge. Future decommissioned Galileo satellites will be disposed at slightly different altitudes to maintain a safe distance between them.
Graveyard orbits are the standard disposal strategy for satellites in medium Earth and geostationary orbits, where Earth re-entry is generally not feasible.
Final Note
GSAT0104 was launched from Europe's Spaceport in French Guiana on 12 October 2012. It was the fourth and last Galileo In-Orbit Validation satellite, enabling the first determination of a ground location using only Galileo satellites. This satellite provided navigation services for years before shifting to serve Search and Rescue after a malfunction in the L-band antenna. In 2021, it was relocated from prime to spare slot to make room for one of the new satellites launched in April 2024. It continued providing service from this position until decommissioning activities started.
GSAT0104 is again involved in a Galileo "first." Its decommissioning has served as a model of responsibility in space activities for constellations to follow. Moreover, it has provided program partners essential experience that will prove crucial as decommissioning efforts become more frequent in the years to come.
The service performance of Galileo satellites is independently monitored by the Galileo Reference Center (GRC) and can be consulted at the GNSS Service Center.
