Accuracy and spatial resolution analysis of spaceborne pencil beam microwave scatterometers for ocean observation

Abstract

For ocean observation, the wind velocity over water is one major concern. Spaceborne microwave scatterometers can provide global, all-day, all-time, high-accuracy, high-resolution and short cycle wind velocity observations over the earth's bodies of water. For a microwave scatterometer system, backscattering coefficient accuracy and spatial resolution are two important parameters. And they are used to evaluate the performance of a scatterometer. High quality scatterometer data intends to have both high accuracy measurement of backscattering coefficient and high resolution. However, these two important parameters are restricted by each other, and cannot reach optimal level at the same time. Therefore, a compromise between the two variables is necessary for the system design of a scatterometer. In this paper, simulation results of conically scanned pencil beam scatterometers are presented. Analysis of backscattering coefficient measurement accuracy under different spatial resolution conditions is also presented. With the same instrument parameters, larger spatial resolution will increase the number of independent samples of backscattering measurement. It is well known that the backscattering coefficient accuracy of scatterometers is decided by the SNR of returned signal and number of independent samples. And simulation results show that the number of independent samples plays a more important role in backscattering coefficient accuracy than SNR of the returned signal. As a result, backscattering measurement accuracy and accuracy of retrieved wind velocity can be improved. The simulation results and analysis can be of benefit to the system design of next generation spaceborne pencil beam scatterometers.