Characterization of Terra MODIS blackbody uniformity and stability

Abstract

MODIS thermal emissive bands (TEB) are calibrated on-orbit via its on-board blackbody (BB) and observations through its space view (SV) port. For Terra MODIS, the BB temperature is nominally controlled at 290K. Periodically, a BB warm-up and cool-down (WUCD) process is scheduled and executed, during which the BB temperatures vary from approximately 272K, the instrument ambient temperature, to 315K. The on-board BB temperatures are monitored, on a scan-by-scan basis, using a set of 12 thermistors uniformly embedded in the BB panel. These thermistors were characterized pre-launch and are traceable to the NIST temperature standards. Using more than 10 years of on-orbit measurements, this paper reports Terra MODIS BB performance in terms of its temperature uniformity and stability. On-orbit characterization is made when the BB is operated under the same or different configurations and conditions. In this study, the variations of BB temperatures from its 12 individual thermistors are analyzed scan-by-scan in order to assess its short-term stability and uniformity. To illustrate the long-term stability over the entire mission, only the granule averaged BB temperatures are used. Results from this study will provide useful information for future missions and sensors, such as NPP VIIRS and LDCM TIRS, in support of their on-board BB design, operation, and performance assessments.