Multi-year on-orbit performance of the Terra and Aqua MODIS Reflective Solar Bands

Since their launch in 1999 and 2002, the two MODIS instruments continue to operate nominally with all on-board calibrators (OBC) functioning properly. Twenty of the 36 MODIS spectral bands, covering wavelengths from 0.41 to 2.2 μm, are the reflective solar bands (RSB). The RSB are primarily calibrated using a solar diffuser (SD) and solar diffuser stability monitor (SDSM) system. The near-monthly lunar measurements, coupled with the SD measurements and long-term response trends from select ground reference sites are used to characterize the on-orbit response versus scan angle (RVS) for the MODIS RSB. The multi-year performance of the MODIS RSB, including detector gain degradation, noise performance, RVS, and long-term stability using ground sites, is presented. The SD on both MODIS instruments has experienced degradation at short wavelengths, with most degradation ( 50%) observed at 0.412 µm for Terra MODIS. Among the 330 RSB detectors, there are no inoperable detectors on Terra MODIS. With the exception of the inoperable detectors in the SWIR bands (most in band 6) that were identified prelaunch, there are no inoperable detectors in the remaining RSB of Aqua MODIS. While a majority of RSB continue to rely on the on-board calibrator measurements for RVS characterization, supplemental information from pseudo-invariant desert sites is used for some short wavelength bands. Overall, the performance of Aqua MODIS RSB is better than Terra MODIS in terms of gain degradation and mirror side differences. Also discussed in this paper are the future challenges, such as increased impacts due to polarization, electronic crosstalk in the SWIR bands and improved RVS characterization.