Abstract
The MODerate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments for the NASA’s EOS program. Since launch, Terra and Aqua MODIS have successfully operated for more than 18 and 16 years, respectively. MODIS observations, which are made in the spectral range from visible (VIS) to long-wave infrared (LWIR), have enabled a broad range of science products to be generated. These data products have been openly distributed and widely used in support of various studies of the earth’s system of land, oceans, and atmosphere and numerous key environmental parameters. MODIS level 1B (L1B) data products include the TOA reflectance factors for the reflective solar bands (RSB), radiances for both the RSB and the thermal emissive bands (TEB), and the associated uncertainty indices. The RSB on-orbit calibration is performed primarily by a solar diffuser (SD), coupled with regularly scheduled lunar observations, and the TEB by an on-board blackbody (BB). Through entire missions of Terra and Aqua MODIS, several collections of the data products have been generated or reprocessed. Currently, both collections 6 and 6.1 (C6 and C6.1) are being produced and distributed. In general, the data reprocessing is made to address various calibration issues and to implement algorithm changes, and thus to produce consistent data records with improved quality. In this presentation, we describe the process of MODIS data reprocessing with a focus on the L1B calibration and data production, and illustrate the improvements made in various Collections. Also discussed are calibration challenges and lessons learned at different stages of each mission.
MODIS Level 1B Reprocessing: Progresses, Challenges, and Lessons
The MODerate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments for the NASA’s EOS program. Since launch, Terra and Aqua MODIS have successfully operated for more than 18 and 16 years, respectively. MODIS observations, which are made in the spectral range from visible (VIS) to long-wave infrared (LWIR), have enabled a broad range of science products to be generated. These data products have been openly distributed and widely used in support of various studies of the earth’s system of land, oceans, and atmosphere and numerous key environmental parameters. MODIS level 1B (L1B) data products include the TOA reflectance factors for the reflective solar bands (RSB), radiances for both the RSB and the thermal emissive bands (TEB), and the associated uncertainty indices. The RSB on-orbit calibration is performed primarily by a solar diffuser (SD), coupled with regularly scheduled lunar observations, and the TEB by an on-board blackbody (BB). Through entire missions of Terra and Aqua MODIS, several collections of the data products have been generated or reprocessed. Currently, both collections 6 and 6.1 (C6 and C6.1) are being produced and distributed. In general, the data reprocessing is made to address various calibration issues and to implement algorithm changes, and thus to produce consistent data records with improved quality. In this presentation, we describe the process of MODIS data reprocessing with a focus on the L1B calibration and data production, and illustrate the improvements made in various Collections. Also discussed are calibration challenges and lessons learned at different stages of each mission.