Comparison of the Geolocation Accuracy between ATMS on board JPSS-1 and SNPP

The JPSS-1 satellite was successfully launched in November 2017. It leads its predecessor SNPP satellite by a half orbit. Both satellites have Advanced Technology Microwave Sounder (ATMS) onboard. For the calibration and validation purpose, it is very necessary to compare the performance of the ATMS onboard both satellites. In this study, the on-orbit geolocation error of ATMS onboard JPSS-1 and SNPP is evaluated and further corrected by an algorithm developed in our previous study. In this algorithm, the geolocation accuracy is assessed by a refined coastline inflection point method, which significantly mitigates the underestimation issues in the traditional method. Furthermore, the geolocation error is converted to the beam pointing Euler angles, which can be used to construct the correction matrix in the on-orbit geolocation process. The result shows that, the boresight pointing error of ATMS on both satellites have scan-angle dependent feature. This feature is more obvious for ATMS onboard SNPP than JPSS-1. This indicates that the antenna beam misalignment is the dominant part in the total error budget. By using the correction matrix built by the algorithm, the geolocation error of ATMS on both satellites is obviously reduced. For ATMS on JPSS-1, the total geolocation error at nadir before/after correction is 3.7/1.1 km at K band, 4.8/1.2 at Ka band, 4.0/0.6 at W band, and 0.6/0.3 at G band. While for ATMS on SNPP, the numbers are 3.9/0.9 at K band, 6.2/1.6 at Ka band, 3.4/0.1 at W band, and 1.9/0.5 at G band.