Graveyard orbit

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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. However, recent findings have shown that satellites left in a graveyard orbit will slowly break apart as micrometeorites hit them, and the smaller fragments will filter back down to lower altitudes.^{[citation needed]} Thus satellites boosted to higher disposal orbits will eventually endanger operational satellites.

It is used when the delta-v required to perform a de-orbit maneuver would be too high. De-orbiting a geostationary satellite would require a delta-v of about 1,500 m/s while re-orbiting it to a graveyard orbit would require about 11 m/s.

For satellites in a geostationary orbit and geosynchronous orbits, the graveyard orbit would be few hundred kilometers above the operational orbit. The transfer to graveyard orbit above geostationary orbit however 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.^{[citation needed]}

According to the Inter-Agency Space Debris Coordination Committee (IADC) [1] the minimum perigee altitude above the geostationary orbit should be:

where is the solar radiation pressure coefficient (typically between 1.2 and 1.5) and is the aspect area [m²] to mass [kg] 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 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.^[1] U.S. government regulations require a boost, ΔH, of ~300 km.^[2]

References

1. ^ "FCC Enters Orbital Debris Debate". http://www.space.com/spacenews/businessmonday_040628.html. 
2. ^ "US Government Orbital Debris Standard Practices". http://www.orbitaldebris.jsc.nasa.gov/library/USG_OD_Standard_Practices.pdf. 

See also

• List of orbits
• Spacecraft cemetery

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