Potential Applications of LRR-STAR Technology for GPM Mission

The Earth Science Division of NASA (Code Y) supports the development of advanced technology, including new aircraft and satellite instrumentation, under the Instrument Incubator Program (IIP). The IIP is administrated through the Earth Science Technology Office (ESTO) whose mandate includes helping guide new technology ideas up the development path for possible space flight opportunities. The Lightweight Rainfall Radiometer (LRR) project has been funded by ESTO to develop a prototype synthetic thinned array radiometer (STAR) for measuring precipitation in the cm-mm spectrum. This paper describes the potential applications of a LRR-STAR instrument for the recently approved Global Precipitation Measurement (GPM) mission. [Another paper in this volume, provided by Professor Christopher Ruf and various of his colleague, describes the instrument design, engineering, calibration, and test program aspects of the LRR-STAR instrument.] The GPM mission will involve a constellation of 8-10 satellites, all of which will require some type of passive microwave radiometer taking measurements in various or all of the standard rain frequencies from 10.7 to 90 GHz. There are two possible entry points for LRR-STAR technology into the mission in the near term (given that certain strategic and/or fiscal conditions arise), and a strong possibility that this type of technology will displace the more conventional radiometer design which involves real-aperture scanning antennas, feedhorn arrays, and somewhat cumbersome calibration apparatus.