Millimeter wave propagation measurements from the applications technology satellite (ATS-V)

Abstract

A millimeter wave propagation experiment was launched on-board the Applications Technology Satellite (ATSV) in August, 1969, and is providing the first information on the propagation characteristics of the earth's atmosphere for earth-space links in the K_{u} (12.5 to 18 GHz) and K_{a} (26.5 to 40 GHz) frequency bands. Seven participating stations commenced data acquisition operations early in October, 1969. Amplitude and phase measurements on two independent test links at 15.3 GHz (downlink) and 31.65 GHz (uplink) are providing propagation characteristics during defined weather conditions. These measurements will provide the systems designer with a data base to support performance predictions for projected millimeter wave links and will aid in determining the utility of these frequency bands for communications and data-link applications. The satellite did not achieve the 3-axis earth-oriented stabilization condition that was originally planned and is presently spinning at 76 r/min at 105\deg west longitude, in geosynchronous orbit. Modifications have been made to the existing data analysis program which permit the conduct of meaningful propagation measurements, even with spin modulated data. Spacecraft and ground hardware systems are described, including modifications required by the satellite spin. Preliminary measurements acquired at the NASA Rosman, N. C. station during the early months of satellite operation are presented, including comparisons of attenuation with rainfall rate, sky temperature, and weather classification observations. The data available to date (March, 1970) are not yet sufficient to fully describe the long-term propagation statistics over all expected weather conditions, but they are presented here in response to requests for information on the initial characteristics of the first experimental data available from an operational earth-space millimeter wave link.