TRADEOFFS IN THE DESIGN OF A SPACEBORNE SCANNING PENCIL BEAM SCATTEROMETER - APPLICATION TO SEAWINDS

SeaWinds is a spaceborne wind scatterometer to be flown on the second Japanese Advanced Earth Observing Satellite (ADEOS-II) in 1999, An imp ortant international element of NASA's earth observing system (EOS), S eaWinds is an advanced follow-on to the NASA scatterometer (NSCAT) on the first ADEOS platform, Unlike previous operational spaceborne scatt erometer systems, SeaWinds employs a scanning ''pencil-beam'' antenna rather than a ''fan-beam'' antenna, making the instrument more compact and yielding greater ocean coverage, The goals of this paper are twof old, First, the overall SeaWinds functional design and backscatter mea surement approach are described, and the relative advantages of the pe ncil-beam technique are outlined. Second, the unique aspects of measur ement accuracy optimization and signal processing for the SeaWinds ins trument are discussed, Applying the results of a separate companion pa per [11], a technique to significantly improve measurement accuracy by modulating the transmit pulse is described, Trade-offs to optimize th e transmit modulation bandwidth are presented.