Evaluation of an inflatable antenna concept for microwave sensing of soil moisture and ocean salinity

A spaceborne inflatable antenna concept is evaluated for passive microwave sensinlkg of soil moisture and ocean salinity. The concept makes use of a l arge-diameter, offset-fed, parabolic-torus antenna with multiple feeds in a conical pushbroom configuration. An inflatable structure provides the mean s for deploying the large-aperture, low-mass, and low-cost antenna system i n space, suitable for operation in the 1-3-GHz frequency range needed for s oil moisture and salinity sensing. The concept is designed to provide multi channel, constant-incidence-angle, wide-swath, and high-radiometric-precisi on observations of the earth's surface. These capabilities facilitate estim ation of soil moisture and salinity, with global coverage every two to thre e days, Simulations show that a 25-m diameter, 1.41- and 2.69-GHz, dual-pol arized system should be capable of providing surface soil moisture estimate s with an accuracy of similar to 0.04 g-cm(-3) (where vegetation water cont ent is less than similar to 5 kg-m(-2)) at a spatial resolution of similar to 30 km, Although inflatable systems represent a new and untested technolo gy for remote-sensing applications, the advantages of low packaged volume, low manufacturing cost, and low mass provide an incentive for their study. This paper evaluates one possible concept for incorporating the capabilitie s of inflatable systems into a scientific mission and for demonstrating the se capabilities for remote-sensing applications.