Graveyard orbit

Overview

A graveyard orbit is used when the change in velocity required to perform a de-orbit maneuver is too large. De-orbiting a geostationary satellite requires a delta-v of about 1500 m/s, whereas re-orbiting it to a graveyard orbit only requires about 11 m/s.

For satellites in geostationary orbit and geosynchronous orbits, the graveyard orbit is a few hundred kilometers beyond the operational orbit. The transfer to a graveyard orbit beyond geostationary orbit requires the same amount of fuel as a satellite needs for about three months of stationkeeping. It also requires a reliable attitude control during the transfer maneuver. While most satellite operators plan to perform such a maneuver at the end of their satellites' operational lives, through 2005 only about one-third succeeded. Given the economic value of the positions at geosynchronous altitude, unless premature spacecraft failure precludes it, satellites are moved to a graveyard orbit prior to decommissioning.

According to the Inter-Agency Space Debris Coordination Committee (IADC) the minimum recommended perigee altitude \Delta{H} beyond the geostationary orbit is

:\Delta{H} = 235\mbox{ km} + C_\mathrm{R} \frac{A \left[ \mathrm{m}^2 \right]}{m \left[ \mathrm{kg} \right]} \cdot 1000\mbox{ km} where :C_\mathrm{R} is the satellite's solar radiation pressure coefficient, whose value is between 1 (for absorption) and 2 (for specular reflection), :A is its aspect area, :m is its mass.

This formula includes 200 km for the GEO-protected zone to also permit orbit maneuvers in GEO without interference with the graveyard orbit. Another 35 km of tolerance must be allowed for the effects of gravitational perturbations (primarily solar and lunar). The remaining part of the equation considers the effects of the solar radiation pressure, which depends on the physical parameters of the satellite.

In order to obtain a license to provide telecommunications services in the United States, the Federal Communications Commission (FCC) requires all geostationary satellites launched after March 18, 2002, to commit to moving to a graveyard orbit at the end of their operational lives. U.S. government regulations require a boost, \Delta{H}, of about 300 km. In 2023 DISH received the first-ever fine by the FCC for failing to de-orbit its EchoStar VII satellite according to the terms of its license.

A spacecraft moved to a graveyard orbit will typically be passivated.

Uncontrolled objects in a near geostationary [Earth] orbit (GEO) exhibit a 53-year cycle of orbital inclination due to the interaction of the Earth's tilt with the lunar orbit. The orbital inclination varies ± 7.4°, at up to 0.8°pa.

Disposal orbit

While the standard geosynchronous satellite graveyard orbit results in an expected orbital lifetime of millions of years, the increasing number of satellites, the launch of microsatellites, and the FCC approval of large megaconstellations of thousands of satellites for launch by 2022 necessitated new approaches for deorbiting to assure earlier removal of the objects once they have reached end-of-life. Contrary to GEO graveyard orbits requiring three months' worth of fuel (delta-V of 11 m/s) to reach, large satellite networks in LEO require orbits that passively decay into the Earth's atmosphere. For example, both OneWeb and SpaceX have committed to the FCC regulatory authorities that decommissioned satellites will decay to a lower orbita disposal orbitwhere the satellite orbital altitude would decay due to atmospheric drag and then naturally reenter the atmosphere and burn up within one year of end-of-life.

Notes

References

References

1. "Method for re-orbiting a dual-mode propulsion geostationary spacecraft – Patent # 5651515 – PatentGenius".
2. "ESA – Space debris mitigation: the case for a code of conduct".
3. (20 April 2005). "End-of-Life Disposal of Geostationary Satellites". ESA/ESOC.
4. Johnson, Nicholas. (2011-12-05). "Broadcast 1666 (Special Edition) – Topic: Space debris issues". [[The Space Show]].
5. "Report of the IADC Activities on Space Debris Mitigation Measures".
6. "FCC Enters Orbital Debris Debate".
7. "US Government Orbital Debris Standard Practices".
8. (2 October 2023). "DISH gets first-ever space debris fine over EchoStar-7". Reuters.
9. (2015). "Operational Considerations of GEO Debris Synchronization Dynamics".