IMAGING COMPARISON BETWEEN THE REAL APERTURE AND SYNTHETIC APERTURE MICROWAVE RADIOMETERS: A CASE STUDY FOR GEO SOUNDER

The dream of launching a microwave radiometer into geostationary orbit (GEO) for atmosphere sounding has lasted for over four decades. Several concepts have been proposed, but none of them has come into reality by now. All these concepts can be divided into two different ways, using real aperture microwave radiometer (RA-MWR) and using synthetic aperture microwave radiometer (SA-MWR). This paper is dedicated to make a preliminary comparison between the imaging performances of the RA-MWR and SA-MWR in GEO applications. In the comparison, a similar concept with the Geostationary Observatory for Microwave Atmospheric Sounding (GOMAS) with a Cassegrain antenna proposed by ESA is taken as the RA-MWR example, while the concept of Geostationary Interferometric Microwave Sounder (GIMS) with a circular antenna array pursued in China is taken as the example of SA-MWR. The numerical simulation results indicate that, with the benefits of using a predesigned Earch model, or even using a simple disc target, SA-MWR can greatly reduce the imaging error especially in the areas near to the Earth contour, and thus achieve a higher imaging accuracy than RA-MWR.