Every satellite mission ends, and the way it ends is increasingly regulated. A satellite that simply stops working stays in orbit as debris, sometimes for decades or centuries. Planning the end of life is therefore part of mission design from the first day, and it affects the choice of orbit, propulsion and launch.
Option 1: Controlled reentry
The satellite uses its engines to lower its orbit steeply so that it reenters the atmosphere over a defined area, usually a remote part of the South Pacific. This is the preferred option for large spacecraft whose components could survive reentry. Europe's Automated Transfer Vehicles, which supplied the International Space Station, ended their missions this way, as the cover image shows.
Option 2: Uncontrolled reentry through natural decay
In low orbits, the thin upper atmosphere slowly brakes satellites until they reenter. Small satellites designed to burn up completely can rely on this, provided the decay happens fast enough. Satellites at higher altitudes can lower their orbit with their thrusters to speed up the process, or use drag devices such as sails.
Option 3: Graveyard orbits
For geostationary satellites, returning to Earth would require too much propellant. Instead, they are raised at the end of their life into a disposal orbit a few hundred kilometres above the geostationary ring, where they do not endanger active satellites.
Passivation
Regardless of the disposal method, satellites and upper stages should be passivated. Remaining propellant is vented and batteries are discharged, so that no stored energy can cause an explosion that would create new fragments.
Rules are getting stricter
International guidelines have long recommended limiting the time a satellite stays in low Earth orbit after its mission. Regulators and agencies are now tightening these expectations. The US Federal Communications Commission adopted a five year rule for satellites it licenses in low Earth orbit, and ESA has introduced its Zero Debris approach for its own missions. Operators should check the rules of every jurisdiction that licenses their satellite.
Related reading
- Space Debris Rules: What Satellite Operators Need to Plan For
- Space Situational Awareness: How Satellites Avoid Collisions
- Electric vs Chemical Propulsion: How Satellites Move in Orbit
Sources
- ESA: Mitigating space debris generation
- ESA: Space Debris
- FCC: FCC Adopts New '5-Year Rule' for Deorbiting Satellites
- ESA: ESA's Zero Debris approach
Cover image: Reentry of an ESA Automated Transfer Vehicle, photographed from the International Space Station in 2012. Credit: NASA (iss033e009232), public domain.