Numerical simulation of the Russian scatterometer: Choice of width swath

Abstract

Sea Winds scatterometer with an orbit altitude of 800 km was chosen as a prototype of the first Russian orbital scatterometer. A reduction of the orbit altitude to 650 km has brought about two competing approaches to the choice of swath width: either to remain the original 1800 km swath or the incidence angles by reducing the swath to 1500 km. The advantage of a wider swath is the best covering of the ocean surface. However, this leads to an increase of local incidence angles and thus to a decrease of the backscattered signal power. The selection criterion is the minimal error in wind speed and wind direction retrieval. Numerical simulation was carried out for both swath widths. The data were processed and the accuracy of wind speed and wind direction retrieval was estimated. The results showed that the accuracy of wind speed retrieval is rather high for both swaths, while the accuracy of wind direction retrieval for a wider swath is lower than that required by the scatterometer technical specifications. Thus, the swath of the new scatterometer should be 1500 km.