Results and Lessons from MODIS Reflective Solar Bands Calibration: Pre-launch to On-orbit

摘要

MODIS is a major instrument for NASA's EOS missions, currently operating aboard the EOS Terra and Aqua spacecraft launched in December 1999 and May 2002, respectively. It was designed to extend heritage sensor measurements and data records and to enable new research studies of the Earth's land, oceans, and atmosphere. MODIS has 36 spectral bands (0.41 - 14.4μm) located on four focal plane assemblies (FPA). It makes measurements at three nadir spatial resolutions: 0.25km, 0.5km, and 1km. Because of instrument design complexity and more stringent calibration requirements, extensive calibration and characterization activities were conducted pre-launch by the sensor vendor for both Terra and Aqua MODIS. For the 20 reflective solar bands (RSB) with wavelengths below 2.2μm, these activities include detector noise characterization, radiometric response at different instrument temperatures and at different scan angles, and relative spectral response. On-orbit RSB calibration is performed using a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). In addition, regular lunar observations are made to track RSB radiometric stability. This paper provides a summary of Terra and Aqua MODIS RSB pre-launch and on-orbit calibration and characterization activities, methodologies, data analysis results, and lessons learned. It focuses on major issues that could impact MODIS RSB calibration and data product quality. Results presented in this paper include RSB detector noise characterization, response versus scan angle and instrument temperature, SD bi-directional reflectance factors characterization, and on-orbit calibration stability. Similar discussions on MODIS thermal emissive bands (TEB) are presented in a separate paper in these proceedings (Xiong et. al).