A graveyard orbit, also called a supersynchronous orbit, junk orbit or disposal orbit, is an orbit significantly above synchronous orbit, where spacecraft are intentionally placed at the end of their operational life. It is a measure performed in order to lower the probability of collisions with operational spacecraft and of the generation of additional space debris.
A graveyard orbit is used when the delta-v required to perform a de-orbit maneuver is too high. De-orbiting a geostationary satellite requires a delta-v of about 1,500 m/s, while 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 above the operational orbit. The transfer to a graveyard orbit above geostationary orbit requires the same amount of fuel that a satellite needs for approximately three months of stationkeeping. It also requires a reliable attitude control during the transfer maneuver. While most satellite operators try to perform such a maneuver at the end of the operational life, only one-third succeed in doing so.
According to the Inter-Agency Space Debris Coordination Committee (IADC) the minimum perigee altitude above the geostationary orbit is:
where is the solar radiation pressure coefficient (typically between 1.2 and 1.5) and is the aspect area to mass ratio of the satellite. This formula includes about 200 km for the GEO protected zone to also permit orbit maneuvers in GEO without interference with the graveyard orbit. Another 35 kilometers 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 life. U.S. government regulations require a boost, of ~300 km.
Famous quotes containing the words graveyard and/or orbit:
“We thought it would be worth the while to read the epitaphs where so many were lost at sea; however, as not only their lives, but commonly their bodies also, were lost or not identified, there were fewer epitaphs of this sort than we expected, though there were not a few. Their graveyard is the ocean.”
—Henry David Thoreau (1817–1862)
“The Fitchburg Railroad touches the pond about a hundred rods south of where I dwell. I usually go to the village along its causeway, and am, as it were, related to society by this link. The men on the freight trains, who go over the whole length of the road, bow to me as to an old acquaintance, they pass me so often, and apparently they take me for an employee; and so I am. I too would fain be a track-repairer somewhere in the orbit of the earth.”
—Henry David Thoreau (1817–1862)