Graveyard orbit

A graveyard orbit, also called a junk orbit or disposal orbit, is an orbit that lies significantly away from common operational orbits, where spacecraft are intentionally placed at the end of their operational life. Most commonly, it refers to a supersynchronous orbit that lies significantly above synchronous orbit. It is a measure performed in order to reduce the probability of collisions with operational spacecraft and of the generation of additional space debris (known as Kessler syndrome). After moving a spacecraft to a graveyard orbit, it will typically be passivated.

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 1,500 metres per second (4,900 ft/s), whereas re-orbiting it to a graveyard orbit only requires about 11 metres per second (36 ft/s).[1]

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 succeeded in doing so as of 2005.[2] However, as of 2011, the majority of recently decommissioned geosynchronous spacecraft were said to have been relocated to a graveyard orbit.[3]

According to the Inter-Agency Space Debris Coordination Committee (IADC)[4] the minimum perigee altitude \Delta{H} \, above the geostationary orbit is:

\Delta{H} = 235\mbox{ km} + \left ( 1000 C_R \frac{A}{m} \right )\mbox{ km}

where C_R \, is the solar radiation pressure coefficient (typically between 1.2 and 1.5) and \frac{A}{m} \, 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 kilometres (22 mi) 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 life.[5] U.S. government regulations require a boost, \Delta{H}, of ~300 km.[6]

See also

References

  1. ↑ Method for re-orbiting a dual-mode propulsion geostationary spacecraft - Patent # 5651515 - PatentGenius
  2. ↑ Space debris mitigation: the case for a code of conduct / Operations / Our Activities / ESA
  3. ↑ Johnson, Nicholas (2011-12-05). Livingston, David, ed. "Broadcast 1666 (Special Edition) - Topic: Space debris issues" (podcast). The Space Show. 1:03:05-1:06:20. Retrieved 2015-01-05.
  4. ↑ http://www.iadc-online.org/Documents/IADC-UNCOPUOS-final.pdf
  5. ↑ "FCC Enters Orbital Debris Debate". Archived from the original on March 8, 2005.
  6. ↑ "US Government Orbital Debris Standard Practices" (PDF).
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