Radiometric stability monitoring of the MODIS reflective solar bands using the Moon

Because of its stable surface reflectance and its stable irradiance in the visible (VIS) and near-infrared (NIR) spectral regions, the Moon can be used as a reference source for monitoring the response stability of Earth-orbiting sensors. MODerate Resolution Imaging Spectroradiometer (MODIS) Protoflight Model (PFM), launched on-board the NASA Terra spacecraft on 18 December 1999, has been in operation for more than two years. Its reflective solar bands (RSB) are calibrated on-orbit by a solar diffuser (SD). In addition, MODIS on-orbit lunar views are used to characterize the stability of the RSB radiometric calibration and the response change at an angle of incidence (AOI) different from that of the SD. In this report, we describe an approach that properly selects the viewing conditions to minimize the effects that need to be corrected and its application to the MODIS lunar observations. Results, derived from MODIS lunar views. are reported and compared with the on-board SD observations.