An inflatable parabolic torus antenna design for the soil moisture radiation mission

The Inflatable Radiometer Imaging System (IRIS) is a space-borne passive microwave system complementary to the existing Earth Observing System. It is designed to provide global measurements of land-surface soil moisture, surface temperature, vegetation water content and ocean salinity. Global measurement in a two day cycle, recorded with a high spatial resolution of 30 km at low frequencies (1.4 GHz and 2.56 GHz), demands an innovative multi-beam reflector antenna design. The multi-beam reflector antenna tailored to meet these requirements is an offset-fed parabolic torus reflector antenna (PTRA) with a torus tilt angle of 35/spl deg/, providing 47 beams in a multichannel, conical push-broom shape. PTRAs have been used in the past as earth stations for wide-scan angle applications. Limitations in weight, size and cost have hindered their application in large-scale space-borne systems. Recent developments in inflated antenna technology by L´Garde have provided the opportunity for proposing space-borne wide-scan angle applications, such as the IRIS. This paper describes a novel reflector antenna design using inflatable antenna technology for a multi-beam, wide-scan angle application. It is shown that the inflatable PTRA offers acceptable radiation characteristics and wide scan angle capabilities for space-borne applications.