MODIS Reflective Solar Bands Unscheduled Lunar Observations

摘要

The MODIS Protoflight Model (PFM) on-board the Terra spacecraft and the MODIS Flight Model 1 (FM1) on-board the Aqua spacecraft were launched on December 18, 1999 and May 4, 2002, respectively. They are scheduled to view the Moon at a fixed Sun-Moon-MODIS phase angle (-55° for Aqua and 55° for Terra) through the space view (SV) port approximately once a month via a spacecraft roll maneuver to monitor the long-term radiometric stability of their reflective solar bands (RSB). MODIS can also automatically view the Moon in about four months each year without roll maneuvers. The lunar phase angles of the unscheduled lunar views are distributed in a wide range from -75° to -53° for Aqua and 53° to 75° for Terra. Similar to the scheduled lunar observations, the unscheduled lunar observations can be used to monitor the long-term radiometric stability of the RSB. In this report, the coefficients defined to trend degradation of the MODIS system response are derived from the unscheduled lunar observations and compared to those derived from the scheduled lunar views. It is shown that the unscheduled lunar observations can be used to track the radiometric stability of the MODIS RSB with about the same accuracy as the scheduled lunar views.