The MODIS operational geolocation error analysis and reduction methodology

The operational methodology used to analyze and reduce errors caused by biases and trends in the Moderate Resolution Imaging Spectroradiometer (MODIS) geolocation data is described. MODIS is scheduled for launch in 1999 on the polar orbiting EOS-AM1 satellite and will acquire daily global data in 36 spectral bands at three spatial resolutions. The satellite has onboard exterior orientation measurement systems designed to enable unaided geolocation of MODIS data to approximately 450 m (3σ). A global network of ground control points will be used to improve the navigation to approximately 150 m (3σ). The ground control points will be used to determine static biases in the interior orientation every MODIS repeat cycle (16 days). Over longer periods analyses will be performed to determine if there are any trends or cyclical variations. This approach will allow an operational characterization of the MODIS geolocation errors and will enable individual observations to be geolocated to the sub-pixel accuracies required for terrestrial global change applications