The Design of an Onboard Digital Doppler Processor for a Spaceborne Scatterometer

Abstract

The Seasat scatterometer (SASS) demonstrated the ability to infer near sea surface wind vectors from space [3]. The fixed-frequency analog filters employed in SASS did not compensate for the Doppler shift induced by the Earth's rotation and led to performance degradation and loss of swath. A digital Doppler processor, which will permit the Doppler center frequency of the measurement cell bandwidths to be adjusted to compensate for the effects of the Earth's rotation, will be used on the next NASA spaceborne scatterometer known as NSCAT. This paper describes the design and genesis of the NSCAT digital Doppler processor and discusses the performance tradeoff issues that were critically evaluated during the design phase. This discussion will be of value to the designers of other related radar remote-sensing instruments. © 1988 IEEE