Radiometric Calibration of the Advanced Wind Scatterometers Carried On-Board the METOP Satellites

摘要

The Advanced Wind Scatterometer (ASCAT) instrument [1,2 & 3] is one of the instruments carried by the ESA / EUMETSAT METOP satellites (METOP A, B & C) [4]. The ASCAT is a six-beam radar instrument designed to measure wind fields over the oceans [5 & 6]. The instrument also provides useful data for ice and land applications. For the ASCAT, calibration is vitally important; the scientific value of the data is directly related to the quality of the radiometric calibration. Therefore achieving. maintaining and demonstrating excellent radiometric calibration is of the utmost importance. ASCAT calibration is performed using three active calibration point targets, the ASCAT Transponders, which have very accurately known point target cross-sections. The calibration strategy is described below and a detailed explanation is given of how the transponder measurements are used to accurately estimate the in-flight antenna gain patterns and their orientations.