Time trend evaluations of absolute accuracies for ALOS optical instruments

The Advanced Land Observing Satellite (ALOS, nicknamed ¿Daichi¿) was successfully launched on January 24, 2006, and continues to work very well. In this paper, we introduce the updating calibration results and their time trends of the standard products for two optical instruments onboard ALOS, the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and the Advanced Visible and Near Infrared Radiometer type-2 (AVNIR-2). Geometric calibration is important in generating a precise digital surface model (DSM) by a stereo pair image of PRISM. Relative geometric calibration of both PRISM and AVNIR-2 are conducted by evaluating accuracies within one scene and evaluating sensor alignments as absolute calibration. For absolute geometric accuracies, we achieved 7.8 m for nadir-, 8.0 m for forward-, 18.7 m for backward-looking images of PRISM, and 114.2 m for AVNIR-2, respectively.