CONSIDERATIONS REGARDING DEEP SPACE COMMUNICATIONS AND THE SPS N. de Groot Exploration of the solar system by means of spacecraft is totally dependent on radio communication, which is carried out in radio frequency bands allocated to space research. The region of space beyond the moon is called deep space. Deep-space communications depend on radio systems of exceptional sensitivity, rivaled only by those of radio astronomy. The proposed SPS is characterized by such unprecedented microwave power that it is essential to examine its relationship to the needs of successful deep-space research. This paper will consider the radio frequency interference that can be tolerated by deep-space communications and the effects of excessive interference. In attempting to assess the environment that would be created by SPS, missing or incomplete information will be identified, along with suggested studies and tests. DEEP-SPACE COMMUNICATION SYSTEMS United States deep-space missions are conducted from three earth station complexes, located at Goldstone, California, in Spain, and in Australia. The Goldstone complex would be most directly affected by SPS, and includes a 64-m antenna with a 100-kw transmitter and a receiver with 16 to 30 K system noise temperature, depending on band and operating mode. (The system noise temperature includes the clear atmosphere.) Signals from deep space are received in the bands 2290 to 2300 MHz and 8400 to 8500 MHz. There is a proposed band at 12.75 to 13.25 GHz. The microwave window in the vicinity of 32 GHz is a candidate for future use. Earth-to-space and space-to-Earth communication links utilize phase coherent reception for carrier tracking and data recovery. Phase shift keyed, biphase modulation is utilized, with additional coding of the baseband data stream for error reduction. Error rates no higher than 10 are tolerated for
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