A ground-based station should include the laser and the optical array together at the same rotating platform, capable of moving as a whole for pointing to the satellite. Optical ways and paths between elements in this case would be stable. The particular version of this scheme would design the system as an array, which consists of identical, parallel, laser-optical modules with one small telescope and one channel of laser amplifier being in each module. Such a laser system could have internal optical coordination by special optics between laser channels and the general PCM. For 100 laser channels and equivalent diameter of the optical system of 35 m (to provide power up to GEO) it is necessary to have a separate telescope with diameter about 4 m. Rough estimates of the telescope quality gives the acceptable deviation from the diffraction limit about 10-12 for a wavelength of 1 micron. This would be complex optics, but less difficult than for an astronomical telescope. The optical system for GEO is a large one, but it should be emphasized that the angular accuracy of the system could be very modest. For the steady-state regime, at least, it is enough to have the angular pointing which provides the simple transportation of the reference beam from input of the station to PCM without interruption by intermediate apertures. For telescope magnification 100 and the aspect ratio of the amplifier of 0.0001 an accuracy of about 1 arc minute (at the output of the laser channel) is sufficient. This is a simple technical task. The problems discussed above are significantly easier for lower orbits. The most difficult version has been chosen to show that even for this case problems are easily soluble, and that the principal technologies are available. The on-board part of power supply system includes a power converter, a source of reference beam, an optical system for pointing to the laser station, a cooling system, a reserve power supply system (including a buffer storage), diagnostics and control, cable and bus, etc. The principal on-board system is the energy converter. Its parameters define the efficiency of all the power supply system. The best converter now is the photovoltaic cell. The possibility of generating the reference beam by a passive on board system (more exactly by the ground based laser station with the assistance of a passive on board system) is really very interesting. The concept in brief is the following. The laser station irradiates the satellite, which has an on board PCM. Laser radiation, which is reflected exactly to the laser station by this PCM, serves as reference beam for the self-guiding of the two pass ground based laser amplifier to the on board receiving system, diffraction beam quality and diffraction pointing accuracy being provided. For such “three-pass” scheme the on board system could be simplified drastically: large high-quality main on-board mirror is not necessary, nor a precise on-board pointing system (it is sufficient to have the accuracy, which is equal to the
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