Arecibo. Looking at these orbits, and noting that for the ERS-1 example the altitude is 785 km, it seems clear that an ASAP launch is dictated. Figure 10.1.5 Number of Passages over Arecibo by a) ERS-1 b) Spot-2 and c) STS-46 Orbits During the Year 1992 10.1.3 Mission Objectives To choose a proper vehicle configuration within the limitations of such a small spacecraft we must decide exactly what we want the demonstration to achieve within the overall space solar power program. To do this, three major aspects of the demonstration's mission must be considered: collection of scientific data, demonstration of the reception of useful power levels, and publicity. One possibility is to orient the mission mainly around low cost and collection of scientific data. Here the main objective would be collection of data regarding beam scattering, sidelobe strength, frequency dispersion, atmospheric absorption under different weather conditions, and rectenna efficiency. Excellent information would be gained about rectenna performance over an extended period in the hostile conditions of the orbital environment. This type of mission could probably generate useful scientific data even if the power received was only on the order of milliwatts. However, the lower the power levels received, the more tenuous the connection with the high level power beaming which the experiment is supposed to model. Keeping that in mind, one should remember the objective of showing that beamed power can be received over long distances at power levels high enough to be useful. The problems with reception of milliwatt power levels have already been discussed. With a single watt of received power, a small transponder could be powered. If power on the order of 10-100 watts was received, a small light bulb could be operated for the time the satellite was in the beam. If the step was made to kilowatts of power received, almost any space system now in operation could be powered. The third mission objective that must be addressed is that of publicity. Engineering and science aside, people around the world love a good show. The more visible a demonstration is, the more likely it is to be funded. For instance, on the single watt level, a transponder could send out a “beep” or Morsecode signal saying something like “power received” strongly enough for amateur radio operators to
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