A New Antenna Pattern Correction Method for a Cross-Track Scanning Microwave Sounder with Full-Circular Sampling

The measured antenna temperature of microwave radiometers differs from the true brightness temperature due to antenna pattern effects. Corrections for the antenna pattern effects constitutes an essential component of microwave radiometer calibration. The Compact Atmospheric Microwave Sounder (CAMS) is a cross-track scanning microwave designed for small satellites. It adopts full-circle sampling on the scan plane. Leveraging its special scan geometry, a new method of antenna pattern correction (APC) is developed. This method utilizes adjacent samplings from consecutive scans to obtain APC coefficients, and correct antenna temperature to the pixel level brightness temperature. For the first time, real samplings from beyond the Earth swath are introduced to assist APC near the swath edges. The performance of the method are analyzed through scenarios of coastlines and Earth swath edges. Analysis in the coastline scenarios demonstrates that the proposed method is more effective in correcting antenna pattern effects and detecting brightness temperature variations than traditional APC approaches in heterogeneous Earth scenarios. Comparative analysis of the method at Earth swath edges demonstrates that the introduction of samplings outside the swath effectively enhances the precision of corrected brightness temperature at swath edges. This method provides a reference for antenna pattern correction and sampling strategy in other microwave radiometers.