The seriousness of the problem is indicated by the following: • Within a 30-MHz RA band at 2.7 GHz, -255 dB(w/m Hz) implies total noise emission of 15 mW by an isotropic radiator at a distance of 35800 km. In any 3-kHz band 1.5 pW would exceed the standard. If a sub-array gain of 50 dB is assumed, numbers are decreased by 10 . 1- implies 156-dB reduction in signal level from 2.45 GHz to 2.67 GHz or 206-dB reduction if sub-array gain is considered. • For the case of 100 satellites, an additional 20 dB is required. Depending on transmitter amplifier and antenna design, this level of performance is at least conceivable. However, reliability of transmitter subsystems would be extremely critical. Each satellite has 10 x 70-KW klystrons. One of these devices developing some subtle error to radiate 1 pW in an RA band will exceed standards. It may prove to be extremely difficult to locate and turn off the offending unit. The potential overloading problems are severe. The projected power levels at 2.45 GHz for 1 Earth radius) from the SPS main beam are - 2 pW/m . This is equivalent to the power level from a 10-kw transmitter with gain of 20 located 100 km from observatory, 1ine-of-sight. A large telescope with % 40-dB side lobes would produce 1 pW from such a source. Parametric amplifiers give trouble at about 0.001 pW. System performance may be seriously degraded by one satellite at 2.45 GHz, but good filters might handle the problem. It is interesting to note that a 100-satel1ite system is equivalent to a 10-kW transmitter at 10 km from the observatory. A 440-km side lobe is equivalent to a transmitter at 1.4 km from the observatory. It does not appear to be possible for a radio observatory to operate within a few hundred kilometers of a rectenna. This problem needs much more study. Other effects of interference require investigation, including: • Ionospheric Modification: What of scattering at 2.45 GHz? What of reflection of terrestrial interference by modified ionosphere? What of ionospheric cross-modulation effects? What of large-scale ionospheric modification?
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