Geolocation of AMSR-E data

The process of determining the geographic latitude and longitude (short:lat/lon) of the center point of the footprint is called geolocation, which is currently suboptimal for AMSR-E (Advanced Microwave Scanning Radiometer for Earth Observing System) Level 1 data provided by the Japan Aerospace Exploration Agency (JAXA). Here we present a study for improving the geolocation. The viewing angles (off-nadir angle and initial scan angle) that define the boresight direction of the instrument are optimized and new lat/lon coordinates are calculated. The optimization method is based on minimizing differences between ascending and descending swathes. The results of the here calculated viewing angles have an overall standard deviation of 0.005 degrees, which is 170 m on ground for the off-nadir angle and 70 m for the initial scan angle. The averaged repositioning between JAXA and our geolocation is 6.3 +/- 1.5 km. A comparison with a similar study, performed by Frank Wentz from RSS (Remote Sensing Systems), shows good agreement in the viewing angles, the RMS of the differences is 0.0083 degrees (approximate to 283 m) for the off-nadir angle and 0.0132 degrees (approximate to 191 m) for the initial scan angle.