Assessment of the MODIS RSB detector differences using Earth-View targets

摘要

MODIS has 20 reflective solar bands (RSB) with a total of 330 individual detectors. Currently, there are two nearly identical MODIS instruments operating in space: one on the Terra spacecraft launched in December 1999 and another on the Aqua spacecraft launched in May 2002. MODIS reflective solar bands (RSB) are calibrated on-orbit by a system that consists of a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). Near-monthly lunar observations are also used to track the sensor response versus scan angle (RVS) change on-orbit. On-orbit observations show that the changes in the detector response are wavelength, scan-angle and mirror side dependent. This paper provides a comprehensive assessment of the detector-to-detector calibration differences in the MODIS VIS/NISR spectral bands using the on-board calibrators and earth-view (EV) level 1B (L1B) data products. Different EV targets are analyzed to accommodate the high-gain ocean bands which tend to saturate over land surfaces. The results from this study highlight the necessity of the constant monitoring of the detector-level gain and its change as a function of scan-angle, as implemented in the MODIS Collection 6 (C6) products.