An Enhanced Resolution Spaceborne Scatterometer

Abstract

Spaceborne wind scatterometers are designed principally to measure radar backscatter from the ocean's surface for the determination of the near-surface wind direction and speed. Although measurements of the radar backscatter are made over land, application of these measurements has been limited primarily to the calibration of the instrument due to their low resolution (typically 50 km). However, a recently developed resolution enhancement technique can be applied to the measurements to produced medium-scale radar backscatter images of the earth's surface. Such images have proven useful in the study of tropical vegetation3 as well as glacial5 and sea6 ice. The technique has been successfully applied2 to Seasat scatterometer (SASS) data to achieve image resolution as fine as 3-4 km. The method can also be applied to ERS-l scatterometer data. Unfortunately, the instrument processing method employed by SASS limits the ultimate resolution which can be obtained with the method. To achieve the desired measurement overlap, multiple satellite passes are required. However, with minor modifications to future Doppler scatterometer systems (such as the NASA scatterometer [NSCAT] and its follow-on EoS-era scatterometer NEXSCAT) imaging resolutions down to 1-2 km for land/ice and 5-10 km for wind measurement may be achieved on a single pass with a moderate increase in downlink bandwidth (from 3.1 kbps to 750 kbps). This paper describes these modifications and briefly describes some of the applications of this medium-scale Ku-band imagery for vegetation studies, hydrology, sea ice mapping, and the study of mesoscale winds.