Three-channel intercomparison and direct comparison on-orbit stability analyses as applied to the CERES instruments on the Terra and Aqua satellites

Clouds and the Earth's Radiant Energy System (CERES) is an investigation into the role of clouds and radiation in the Earth's climate system. Four CERES scanning thermistor bolometer instruments are currently operational. Flight model 1 (FM1) and 2 (FM2) are aboard the Earth Observing System (EOS) Terra satellite and FM3 and FM4 are aboard the EOS Aqua satellite. Terra was launched in December 1999 and Aqua in May 2002. Each CERES instrument measures in three broadband radiometric regions: the shortwave (0.3 - 5.0 μm), total (0.3 ->100 μm), and window (8 - 12 μm). Several vicarious analyses have been developed to aid in monitoring the health and stability of the instruments' radiometric measurements. One analysis is a three-channel inter-comparison of the radiometric channel measurements for each instrument. A second analysis compares temporally synchronized nadir measurements for each sensor of two instruments on the same platform. These analyses along with onboard calibrations have been used to monitor the drifts in the shortwave measurements and have provided information used to remove the drift using ground software. Previously documented, these analyses will be reviewed and further results for the Terra CERES instruments will be presented along with initial findings for the CERES instruments on Aqua.