Laser power demand To show a measurable effect on the target satellite, 10% of its solar array power should be generated by laser beaming. Therefore the flux power density on the target satellite due to the laser beam should be about 130 W/m2 (1/10 sun solar power). To cover the full solar array of the satellite the diameter of the laser SPOT should be about 5 m which is equivalent to about 20 m2. Thus the total laser output power would have to be 2.6 kW. Figure 1 Beaming principle Spacecraft subsystem dimensioning Solar arrays; Current laser technology has an input power to beamed power efficiency of less than 15% (in infrared). So the spacecraft would have to provide at least 17 kW to the laser payload. The generation of this power requires a solar array area of 126 m2 for the laser payload only (assuming 10% overall conversion efficiency for the solar arrays). Assuming that the mass to power ratio of the solar panels is 30 W/kg (TDRS satellite), the mass of the solar arrays becomes about 570 kg. Laser: The total required laser output power was found to be at least 2.6 kW. Unfortunately there are no commercially available high power lasers in the visible wavelength range. The development of a dedicated high power laser system for short term demonstration seems unlikely. Since gas lasers operating in the visible light range can not be scaled up to the required power level, potential lasers will have to be of the solid state type. A solid state visible light laser system for high power output will lead to significant cooling problems and therefore be quite large and heavy (some hundreds of kilograms). Launch cost analysis Due to cost constraints it was suggested to use ASAP (ARIANE Structure for Auxiliary Payloads) to carry the laser experiment. The laser equipment is considered to be the payload of a satellite. As a general rule of thumb, the payload mass is usually about 20% of the overall spacecraft mass. Assuming a laser system weighing 400 kg the resulting overall spacecraft mass totals 2 tons. ASAP is a structure to carry micro satellites with a maximum weight of 50 kg each. Therefore the proposed launch scenario with ASAP is not feasible. Considering a conventional prime passenger launch with 70000/kg to GEO the total launch cost is $140M! Pointing accuracy and beam locking To keep the laser beam pointed on the satellite over a distance of 500 km would require a pointing accuracy of better than 1 arc second. No previous experience exists on accurate beam pointing. The first problem is to precisely locate the target satellite in a graveyard orbit without a pilot beam. The use of the target satellite's RF signals does not provide the necessary accuracy of better than 1 arc second. It is not clear whether optical systems could perform this task.
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