<title>NASA scatterometer (NSCAT) calibration philosophy and approach</title>

Abstract

The NASA Scatterometer (NSCAT) is scheduled for launch aboard the Japanese Advanced Earth Observing Satellite (ADEOS) in early 1996. The NSCAT instrument is a K(mu) -band radar which measures global ocean surface wind speeds and directions at 50 km resolution. The wind measurement is accomplished by first measuring the normalized backscatter cross section ((sigma) 0) of the ocean at three different azimuth angles and two different polarizations using eight fan-beam antennas. Wind vectors are then retrieved during ground data processing using an empirical geophysical model function which relates (sigma) 0 to wind speed and direction. The accuracy with which the ocean surface wind can be estimated is a sensitive function of the radiometric accuracy of the (sigma) 0 measurements. For this reason, NSCAT must be a highly calibrated and stable instrument. A considerable amount of effort has been invested by the NSCAT project in (1) analysis, to understand and quantify the effects of calibration errors on wind retrieval performance, and (2) the development of both a pre- and post-launch calibration approach to insure that (sigma) 0 measurement accuracy requirements are met. This paper summarizes these efforts and their resulting conclusions.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.