Graveyard orbit

Summary

Orbit size comparison of GPS, GLONASS, Galileo, BeiDou-2, and Iridium constellations, the International Space Station, the Hubble Space Telescope, and geostationary orbit (and its graveyard orbit), with the Van Allen radiation belts and the Earth to scale.[a]
The Moon's orbit is around 9 times as large as geostationary orbit.[b] (In the SVG file, hover over an orbit or its label to highlight it; click to load its article.)

A graveyard orbit, also called a junk orbit or disposal orbit, is an orbit that lies away from common operational orbits. One significant graveyard orbit is a supersynchronous orbit well above geosynchronous orbit. Some satellites are moved into such orbits at the end of their operational life to reduce the probability of colliding with operational spacecraft and generating space debris.

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 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 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.[2] However, as of 2011, most[clarification needed] recently decommissioned geosynchronous spacecraft were said to have been moved to a graveyard orbit.[3]

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

where is the solar radiation pressure coefficient 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 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, , of about 300 km.[6]

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[7] 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.[7]:3

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 necessitates 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, large satellite networks 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 orbit — a disposal orbit—where 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.[8]

See also

  • List of orbits
  • SNAP-10A – nuclear reactor satellite, remaining in a 700-nautical-mile (1,300 km; 810 mi) sub-synchronous Earth orbit for an expected 4,000 years
  • Spacecraft cemetery, in the Pacific Ocean

Notes

  1. ^ Orbital periods and speeds are calculated using the relations 4π2R3 = T2GM and V2R = GM, where R, radius of orbit in metres; T, orbital period in seconds; V, orbital speed in m/s; G, gravitational constant, approximately 6.673×10−11 Nm2/kg2; M, mass of Earth, approximately 5.98×1024 kg.
  2. ^ Approximately 8.6 times (in radius and length) when the moon is nearest (363104 km ÷ 42164 km) to 9.6 times when the moon is farthest (405696 km ÷ 42164 km).

References

  1. ^ "Method for re-orbiting a dual-mode propulsion geostationary spacecraft – Patent # 5651515 – PatentGenius". Archived from the original on 2013-11-10. Retrieved 2012-10-28.
  2. ^ "ESA - Space debris mitigation: the case for a code of conduct". www.esa.int.
  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. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2015-04-02. Retrieved 2015-03-07.CS1 maint: archived copy as title (link)
  5. ^ "FCC Enters Orbital Debris Debate". Archived from the original on March 8, 2005.
  6. ^ "US Government Orbital Debris Standard Practices" (PDF).
  7. ^ a b Anderson, Paul; et al. (2015). Operational Considerations of GEO Debris Synchronization Dynamics (PDF). 66th International Astronautical Congress. Jerusalem, Israel. IAC-15,A6,7,3,x27478.
  8. ^ Brodkin, Jon (4 October 2017). "SpaceX and OneWeb broadband satellites raise fears about space debris". Ars Technica. Retrieved 28 April 2019.