When a geostationary satellite reaches the end of its mission, it does not come back to Earth. Bringing it down from 35,786 km would require far too much propellant. Instead, operators raise it into a disposal orbit above the geostationary ring, commonly called a graveyard orbit. This article explains how that works and which rules apply.
Why GEO needs a graveyard orbit
The geostationary ring is a limited resource: every satellite there shares the same altitude above the equator. A dead satellite drifting in that region would threaten active spacecraft. The Inter-Agency Space Debris Coordination Committee (IADC) therefore defines a protected geosynchronous region: from 200 km below to 200 km above geostationary altitude, and between 15 degrees south and 15 degrees north latitude.
How high is a graveyard orbit?
According to the IADC Space Debris Mitigation Guidelines, a retired GEO satellite should be moved into an orbit that remains above the protected region. The guidelines give two conditions at the end of the disposal phase:
- A minimum increase in perigee altitude of 235 km plus a term that depends on the satellite's solar radiation pressure coefficient and its area to mass ratio.
- An eccentricity of 0.003 or less.
The 235 km consist of the 200 km upper limit of the protected region plus 35 km, the maximum descent of a reorbited spacecraft caused by the gravity of the Sun and Moon and by irregularities in the Earth's gravity field.
Passivation
Reaching the graveyard orbit is not enough. Satellites should be passivated, meaning remaining propellant is vented and batteries are discharged, so that no stored energy can cause an explosion. The IADC guidelines also say that GEO propulsion systems should be designed for passivation and should not be separated from the spacecraft.
What about satellites in low Earth orbit?
For low Earth orbit, the approach is different: satellites should be deorbited so that they reenter the atmosphere. In the United States, the FCC requires satellites in LEO to deorbit no later than five years after the end of their mission. See our article on space debris rules for details.
Frequently asked questions
What is a graveyard orbit?
A disposal orbit above the geostationary ring into which satellites are moved at the end of their mission, so they do not interfere with active satellites in GEO.
How far above GEO is the graveyard orbit?
According to the IADC guidelines, the perigee should be raised by at least 235 km plus a term depending on solar radiation pressure and the area to mass ratio, with an eccentricity of at most 0.003.
Why don’t GEO satellites reenter the atmosphere?
Lowering a satellite from 35,786 km all the way into the atmosphere would require far more propellant than raising it a few hundred kilometres into a disposal orbit.
Related reading
- Satellite End of Life: Deorbiting, Graveyard Orbits and Passivation
- Space Debris Rules: What Satellite Operators Need to Plan For
- LEO, MEO and GEO Satellites Compared
Sources
- IADC Space Debris Mitigation Guidelines (hosted by UNOOSA), PDF
- FCC: New 5-Year Rule for Deorbiting Satellites (2022)
Cover image: NOAA's geostationary weather satellite GOES-U during processing at the Astrotech Space Operations Facility, 24 January 2024. Credit: NASA/Ben Smegelsky (KSC-20240124-PH-JBS01_0071), public domain.