Lightweight linear broadband antennas enabling small UAV wing systems and space flight nanosat concept

Abstract

The RadSTAR initiative merges an interferometric radiometer with a digital beam forming scatterometer, providing Earth surface backscatter and emission measurements. Heretofore these instrument developments have been designed for low flying brown platforms such as the NASA P-3. Commercial-off-the-shelf design materials can be used to inexpensively build antennas that approximate free-space permittivity, enabling remote sensing of soil moisture levels locally using small Unmanned Aerial Vehicles (UAVs). A foam/free-space sandwich can be used to minimize the weight of the dielectric backing structure. This technique enables rapid prototyping with space-grade materials. A low-mass 3-element antenna array of this design is already baselined for a University nano-satellite mission. A light-weighted version of the L-band Imaging Scatterometer (US) radar electronics is being developed for a Small Business Innovative Research (SBIR) program. This lightweight wing antenna has a large potential payoff to NASA. For example, it may enable an active/passive hydrology mission using a fleet of low cost small UAVs. A mesh ground plane can further reduce the overall mass and stowability of the very large antennas required for spaceborne observations at L-Band. The cross track scan success criterion was met at L-Band frequencies for radar and radiometry. That is, we designed and prototyped a wideband antenna patch tunable in this range and additional work is being earned out to improve the cross polarization isolation. Making the present broadband design into arrays will be limited to one dimension due to array spacing and the aspect ratio of the patch elements. A fore and aft Doppler beam synthesis and the US cross-track beam forming concept will be considered for potential application to surface hydrology measurements using these arrays