MODIS geolocation algorithm and error analysis tools

The Moderate Resolution Imaging Spectroradiometer (MODIS) contains 36 bands from the visible to the thermal infrared with the nominal ground field of views of 250 m, 500 m and 1 km. This paper summarizes the MODIS Earth location algorithm from the focal plane/detector system through the telescope system, rotating scan mirror system, spacecraft ephemeris/attitude processing system, and digital elevation model. It also describes how the geolocation of other bands can be derived from the ideal band ground coordinates. Some tools have been developed to check the model accuracy and validity of the geolocation. This paper describes these tools including a ground control point matching program, a trend and bias error analysis program, and a MODIS image simulation program using Landsat TM (Thematic Mapper) images. Some post launch findings on the model accuracy and necessary changes to the model are also described