Accession Number : ADP003885

Title :   Ice Depolarization on Low-Angle 11 GHz Satellite Downlinks,

Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG

Personal Author(s) : Stutzman,W. L. ; Bostian,C. W. ; Tsolakis,A. ; Pratt,T.

Report Date : FEB 1984

Pagination or Media Count : 11

Abstract : Although many observations of ice depolarization have appeared in the literature, little has been reported on the impact of ice depolarization on the statistical performance of satellite downlinks. As part of an experiment with the SIRIO spacecraft's 11.6 GHz beacon, we have analyzed propagational data recorded during 1979 and 1980 to see what impact ice depolarization would have had on link performance. Our measurements were made with first one and then with two dual-circularly-polarized terminals spaced 7.2 km apart; the elevation angle was 10.7 degrees. While periods of intense ice depolarization occurred, the overall effects on the XPD statistics amounted to at most a 2 to 4 dB reduction in the XPD values that rain acting alone would have produced for a given percentage of time. Ice depolarization had no effect on the statistics of XPD values below the 0.01% level. Most of the severe ice depolarization events which occurred were associated with drops in barometric pressure and the passage of intense cold fronts through our area. To model the theoretical behavior of ice depolarization, we have defined ice contents as the product of three individually undetermined quantities: ice particle density (number of ice particles per cu m), ice cloud thickness (in m), and the average volume (in cu m) of the ice crystals. A comparison with our measurements indicates that populations of ice particles with ice contents on the order of 0.002 m to 4th power are probably responsible for the lower values of measured XPD. (Author)

Descriptors :   *Electromagnetic wave propagation, *Radio waves, *Satellite communications, Downlinks, Ice, Depolarization, Atmospheric attenuation, Cold fronts, Barometric pressure, Communication satellites

Distribution Statement : APPROVED FOR PUBLIC RELEASE