An Earth-Space Propagation Measurement at Crawford Hill Using the 12-GHz CTS Satellite Beacon

The launch of the CTS satellite has provided a useful signal source for earth-space propagation experiments. The interest is in measuring long-term (approximately one year) atmospheric attenuation and depolarization, primarily due to rain. The satellite carries a cw beacon at a frequency of 11.7 GHz with a nominal output power of 200 mW. The satellite beacon antenna is a right-hand sense, circularly polarized, earth-coverage horn with an axial ratio of 1.5 dB within an enclosed beam 1431 angle of 17 degrees. The satellite is in geosynchronous orbit and is located nominally at 116°W longitude with an inclination of less than 1 degree. A disadvantage in using the CTS satellite beacon for these measurements is that the beacon is turned off during the spring and fall eclipse periods when the solar cell panels are shadowed by the earth. In the fall 1976 eclipse, the beacon was turned off completely for seven weeks. Fortunately, few significant rain events occurred during this time. In the spring 1977 eclipse, the beacon was turned off for only short periods, approximately one hour each day over a six-week period. The rain attenuation data for these eclipse periods were bridged by statistically scaling data from a colocated 19-GHz COMSTAR A beacon measurement. This scaling technique is described in the appendix to this paper. The Crawford Hill receiving system is located in Holmdel, New Jersey at approximately 74° W longitude and 40° N latitude. For this location, the receiving antenna point is nominally at an azimuth angle of 234 degrees with an elevation of 27 degrees.