Improvement of AVNIR-2 Radiometric Calibration by TOA Directional-Reflectance Cross-Calibration and On-Board Calibration Data

A cross-calibration scheme which uses top-of-atmosphere (TOA) reflectance functions of satellite zenith angle at temporally and spatially stable ground sites is proposed. Each function is made from MODIS 500m-channel observations over 16 days which includes AVNIR-2 observation dates. The results showed that radiances of AVNIR-2 channels 1 (463 nm), 2 (560 nm), and 3 (652 nm) agreed to the radiances of Aqua and Terra MODIS channels 3 (466 nm), 4 (554 nm) and 1 (646 nm) respectively within 5% accuracy. AVNIR-2 channel-4 (821 nm) decreased more than 5% by water-vapor absorption in some cases. Using many samples from this scheme, we found possible gain dependencies on Field Of View (FOV) and gain-modes. Lamp calibration system onboard AVNIR-2 showed dependencies on FOV, time change of the FOV error, and gain-mode consistent with the cross-calibration results. After correction of the identified errors, inter-channel consistency of FOV in the polar-snow scenes was improved.