Cemetery orbit

Known objects in orbits (2005), 95% of which was space debris

As a graveyard orbit ( English graveyard orbit ), graveyard orbit or short graveyard orbit refers to an Earth orbit ( "Orbit") for your old apogee satellites . While spacecraft in low orbits ( LEO ) are disposed of by lowering their trajectory in the atmosphere, launching them into higher orbits is the only option for earth synchronous satellites ( GEO ).

The final disposal of these objects is necessary because the orbits of interest for satellites are in great demand and because they could become a danger for other satellites, space shuttles and (through crashes) also for the earth through drifting (in lower orbits also through braking in the residual atmosphere ), see space debris .

The limited lifespan of a satellite is mainly due to the fact that, in addition to various possible defects, the on-board fuel, which is necessary to stabilize the orbit position, is used up or is only sufficient for a few maneuvers in another orbit.

The cemetery orbit is usually above the regular orbit of the satellite, in the case of geostationary satellites by around 300 km (supersynchronous orbit) . If a geostationary satellite enters a cemetery orbit below geosynchronous orbit (GEO), there is always the risk that it will collide with a new satellite on the GTO orbit leading to the GEO . The Inter-Agency Space Debris Coordination Committee (IADC) defines the area to be kept clear of the geosynchronous orbits at ± 200 km and ± 15 ° from the geostationary orbit. The minimum orbit height of the cemetery orbit above the geostationary orbit should be increased by a further 35 km due to possible orbit disturbances caused by gravity and by a further amount depending on the properties of the satellite due to solar radiation pressure-related orbital disturbances: ${\displaystyle \Delta {H}\,}$

${\displaystyle \Delta {H}=235{\mbox{ km}}+1000\,c_{\mathrm {R} }\,{\frac {A}{m}}\ \mathrm {\frac {kg\,km}{m^{2}}} }$

Here is the reflectivity coefficient of the satellite, its maximum shadow area and its mass. The reflectivity coefficient is 1 with complete absorption, 2 with complete reflection, i.e. for an ideally black or mirrored satellite. In practice it is usually between 1.2 and 1.5. ${\displaystyle c_{\mathrm {R} }}$ ${\displaystyle A}$ ${\displaystyle m}$

Some failed geostationary satellites could not be relocated and pose a risk to other geostationary satellites. Others failed while being brought back to their position in the GEO after a disturbance. For example, the cemetery orbit of the communication satellite DFS-Kopernikus 3 is about 100 km below the earth-synchronous orbit. There it was stabilized after drifting due to a defect during the decision-making on how to proceed; moreover, the orbit was no longer geostationary and the satellite drifted along the equator towards its previous position as planned. However, he no longer had enough fuel to return to the GEO, so he remained in this unfavorable cemetery orbit.

Specially planned fuel is used to change the path. Once the satellites have reached the cemetery orbit, any remaining fuel is drained and the batteries are discharged in order to prevent the satellite from being dismantled through uncontrolled release of energy.

Individual evidence

1. ^ Esa.int: Mitigating space debris generation
2. ↑ Report of the IADC Activities on Space Debris Mitigation Measures ( Memento of March 18, 2009 in the Internet Archive ) (PDF, English; 129 kB)

See also

• Spaceship graveyard

Web links

• Explanation of the cemetery orbit using the example of DFS Copernicus 3 ( Memento from December 20, 2007 in the Internet Archive )