The MODIS reflective solar band short-term stability assessment using the Spectro-Radiometric Calibration Assembly

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on-board the Aqua and Terra spacecraft have provided valuable Earth data to the science community for the last 20 and 22 years, respectively. The Spectro-Radiometric Calibration Assembly (SRCA) is an on-board calibrator (OBC) that can characterize the radiometric, spatial, and spectral properties of the MODIS reflective solar bands (RSBs). In radiometric mode, the SRCA is able to monitor the gain trends of the RSBs on a detector level. Nominal radiometric mode measurements are collected during a 10-minute period during spacecraft night using a combination of SRCA halogen lamps. These measurements are intended for deriving on-orbit gains, however due to several 10-watt lamp failures on-orbit, the frequency of SRCA calibrations has been reduced and no longer used in the official L1B LUT algorithm. Once per calendar year the SRCA is operated in radiometric mode over several consecutive orbits using a backup lamp, monitoring the gain changes of the RSBs under unique conditions. This paper will provide insight into the 1W short-term stability of the MODIS RSBs using these calibrations over both the Aqua and Terra missions, along with the long-term trends of these multi-orbit gain observations.