Table of Contents Page
Executive Summary 2
Table of Figures
Figure 1 GSV 5
Figure 2 Refueler and Depot 7
Figure 3 Refueling Scenario 8
Figure 4 RSV 14
Table 1 Distribution of active satellites 4
Table 2 GEO Servicing opportunities 4
Table 3 GSV mass breakdown 6
Table 4 Power Budget 9
Table 5 Cost of Refueler/Depot 11
Launching a satellite into space with a mission to service other satellites is a plausible idea. Servicing a satellite means to somehow make it so a satellite’s design life ...view middle of the document...
1 Add that to the 4–5% failure rate of launch vehicles and this calculates to almost one out of seven satellites failing before EOL.2
In an effort to limit these failures industry designers are obligated to use what is called legacy hardware on space systems. This means that the hardware has to be proven in the environment of space. NASA is one example how systems can become legacy. They use technology readiness levels (TRL) for measuring the maturity of a system.3 They use a scale of 1–9 with most spacecraft designs needing a TRL of at least 8 to insure “flight qualified” hardware.4 These techniques help to reduce risk, it also negatively effects satellite performance and stalls improvement.5
Another way to limit risk along with using legacy hardware is to utilize on-orbit servicing. There have been a number of on-orbit servicing starting in 1984 (the Solar Maximum Mission Satellite) 6. Probably the most famous on-orbit servicing was the Hubble Space Telescope. Many of the manned space operations have included satellite servicing. These missions have proved that it is possible to service satellites after launch. However, they were all made by human intervention. The benefits of on-orbit services have not been offered to satellites outside of human reach. The question arises as to whether or not it is possible to service satellites without human presence. Research has proven that it is technically possible and much cheaper if done in geostationary orbit (GEO).7
The mission of the On-orbit Servicing Satellite (OSS) will be to relocate and restore a failing satellite. An example of relocation would be taking a dead satellite into a disposal orbit or stationing a satellite into a mission orbit after launch vehicle failure. An example of restoring a satellite would be refueling or proximity operations to discover how a satellite failed. An example of this might have been a rescue of Milstar 3 which failed to reach its operational slot in GEO due to an upper stage failure. This on-orbit servicing might have saved $1.2 billion8.
Refueling operations could be done for the purpose of lifetime extension, performing extra maneuvering of a spacecraft, and station-keeping. In October 1984, the crew of Challenger on STS-41G performed on-orbit refueling by transferring 60 kg of hydrazine between two pallet-mounted tanks9.
Table 1 General distribution of active satellites10
LEO MEO GEO Elliptical Total
Astronomy 53 0 1 17 71
Communications 203 2 318 11 534
Earth observation 87 0 23 2 112
Navigation 9 44 3 0 56
Total 352 46 345 30
Table 1 shows the distribution of satellites in different orbits. The vast majority of active satellites are found in LEO and GEO. This would make the conclusion that the most likely place to put a servicing satellite would be either LEO or GEO. With the plethora of space junk in LEO it would be more reasonable to put the OSS in GEO.
Table 2 Annual number of GEO servicing...