of the satellite is reduced because it will provide a positive net salvage value. The present value of SPS revenue requirements, reflected in the SPS charge rates, may accordingly be reduced by this amount. For example, if it is found that the salvage value of an SPS satellite is equal to ten percent of the capital cost of the satellite, then the annual capital carrying charge for the satellite, for purposes of comparison to alternative systems, may be reduced by ten percent. Any SPS satellites or portions thereof which are not salvaged will, in all likelihood, have to be removed from geosynchronous orbit. An objective of this study is to estimate SPS satellite disposal costs. To do this a number of disposal alternatives were identified, the velocity requirements for each were estimated and then the costs of each were determined. SPS disposal costs include four major cost categories: cost of propellant, cost of transporting the propellant to GEO, cost of modifying the SPS satellite as necessary (mainly installation of thrusters, tankage and controls) and the cost of mission operations. Cost estimates provided are based on the assumption that the satellite is disposed of intact. Wherever possible cost estimates used in this study were derived from the * SPS Concept Definition Study performed by Rockwell International, and are in 1977 dollars, consistent with this report. Thus while these cost estimates contain considerable uncertainty, the variation in estimates of salvage value and disposal costs are likely to approximate the variations in satellite captial costs. Hence the estimates provided can be taken to be relatively firm when viewed in comparison to the capital cost estimates. Satellite Power Systems (SPS) Concept Definition Study, System Engineering, Part 2 (Cost and Programmatics, Rockwell International Report No. SSD 79- 0010-2-2, March 1979.
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