Monitoring MODIS thermal emissive band stability through brightness temperature trending of a ground target

Abstract

The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites have been operating since 2000 and 2002, respectively. To date both instruments have demonstrated good calibration stability for the Thermal Emissive Bands (TEB). Maintaining calibration accuracy is an important issue, as the instrument age, for continued production of high quality science data. In this paper a strategy to track the stability of MODIS TEB measurements from launch to present using a cold ground target is discussed. The land surface in the area surrounding Dome Concordia, Antarctica (75.1 S, 123.4 E) is well characterized and stable in terms of surface temperature and emissivity. A research station at Dome Concordia provides a record of climate variables and the opportunities for satellite validation field campaigns. Both MODIS instruments overpass the site 7-10 times per day, including a near-nadir overpass once every 2-3 days. The long-term data record of near-nadir Dome Concordia MODIS TEB measurements is analyzed relative to the measurements of ground-based (Automated Weather Station) and other satellite (e.g. Atmospheric Infrared Sounder (AIRS)) sensors. This approach allows for the detection of any long-term calibration drift and the calibration consistency between Aqua and Terra MODIS. Additionally, a method to correct the observed cold scene bias for Aqua MODIS versus AIRS is discussed.