should be considered. This station would not enjoy 191 dB of space loss from SPS. At a range of 300 km from the nearest power satellite, the smaller free space loss of 149 dB will aggravate interference by 42 dB. Goldstone is located in a desert area northeast of Los Angeles, a location that may be attractive for a rectenna. Reflection and radiation from the rectenna's fundamental or harmonic signals can be coupled into the Goldstone receiver via clear weather inhomogeneities and from diffraction over terrain features. Rain cells also provide coupling paths. Separation distances of many tens to several hundreds of kilometers may be required between Goldstone and the rectenna to provide needed transmission loss for rectenna-generated signals that fall within deep-space bands. Unlike radio astronomy observations, deep-space links cannot overcome added noise interference through increased integration time. The detection bandwidth is dictated by data rate. Furthermore, some mission phases are time- critical and cannot be repeated at a later time. Continuous tracking through the direction of the geostationary orbit is often required for navigation and scientific data recovery. With SPS satellites located at one-degree intervals over a substantial part of the geostationary arc over Goldstone, there is a significant probability of intersection by the earth station antenna, main beam, or near-main beam. Assuming 0 dBi SPS gain in the direction of the earth station, a -31 dB W input to the maser would result. This is 60 dB above the gain compression point and thus can be expected to cause performance degradation. An aspect of interference to space communications not treated in this article is that of the effects on signals received by spacecraft. While earth stations are relatively more sensitive, harm to Earth-to-space communication links must nevertheless be evaluated in connection with SPS feasibility. CONCLUSION The extreme sensitivity of deep-space communication systems makes them exceptionally vulnerable to radio frequency interference, particularly from very high power sources such as SPS. A definitive calculation of potential
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