Development and flight qualification of a small satellite X-band spherical membrane antenna

Abstract

This paper describes the design, development and flight testing of a half-meter spherical membrane reflector antenna built out of reflective and clear Mylar segments. A custom-built line feed optimized for operation at 10.5 GHz is used for spherical correction. The antenna system has been jointly developed by the University of Arizona and FreeFall Aerospace, Inc as primary payload to be demonstrated on-orbit on the University of Arizona's 6U LEO mission CATSAT, nominally scheduled to launch in December 2021. The launch is a part of NASA's CSLI program. The mission has been designed for a low earth sun-synchronous orbit. With the primary objective being the demonstration of high data rate transmission from the inflatable antenna system. A multi-disciplinary design approach towards the development of the system which includes thermo-structural design, RF design and operational testing of the membrane antenna and feed system. Structural design of the spherical membrane and antenna system have been optimized to restrict dynamic modes of the deployed system to within the operational envelope of the on-board 3-axis attitude control system in the expected thermal environment. RF design has been focused on compensating for the expected cyclic variation of inflated shape. A shape photogrammetric shape measurement system has been developed for real-time inflated surface verification. Our design activities lead to a parameterized model of the antenna system to facilitate redesign for varying frequencies and orbits. The model has been used to construct scaling laws to understand performance variation with increasingly large spheres identify sensitive design parameters for more complex feed geometries optimized for higher frequencies.