Validate and improve ATMS geolocation accuracy by using lunar observations

Recently, the advanced coastline inflection point method (CIPSD) was developed to retrieve the instrument boresight pointing error of Suomi National Polar-orbiting Partnership (SNPP) Advanced Technology Microwave Sounder (ATMS). Because of the use of mathematical model and separate-domain technique, this algorithm can retrieve the boresight pointing error in terms of Euler angles efficiently. But the retrieval uncertainty of yaw is larger than that of the other two angles due to the limitation in this method. This paper thoroughly investigates the phenomenon of asynchrony between the serial of space view counts and that of the simulated antenna response in lunar intrusion (LI) events. Sensitivity study shows that this asynchrony is mainly caused by the boresight pointing Euler angle yaw. A new retrieval algorithm for yaw is developed based on this relation. The yaw derived from the Lunar observations of space view 4 (SPV4) from 2011 to 2016 is 0.028° at K band, -0.012° at Ka band, -0.168° at V band, -0.005° at W band, and -0.054 at G band. This algorithm can serve as a supplement to CIPSD. The combined retrieval results, the roll and pitch from CIPSD and the yaw from lunar observations, are used to correct the ATMS SPV vectors when simulating the antenna response. The comparison between the corrected antenna response and the observed cold counts of ATMS channel 7 SPV4 at the LI event occurring on Jan 6-8, 2017 shows that, after correction, the simulated antenna response synchronizes very well with the actual observations.