CERES Instruments
The first CERES instrument (PFM) was launched aboard the NASA Tropical Rainfall Measuring Mission (TRMM) in November 1997 from Japan. An additional four CERES instruments were launched on the EOS Terra satellite in December 1999 (FM1 and FM2) and on EOS Aqua satellite in May 2002 (FM3 and FM4). Currently operational are all CERES instruments on Terra and Aqua satellites. Each CERES instrument is a radiometer which has three channels - a shortwave channel to measure reflected sunlight in 0.3 - 5 µm region, a channel to measure Earth-emitted thermal radiation in the 8-12 µm "window" region, and a total channel to measure entire spectrum of outgoing Earth's radiation. CERES spatial resolution at nadir view (equivalent diameter of the footprint) is 10 km for CERES on TRMM, and 20 km for CERES on Terra and Aqua satellites. Onboard calibration sources include a solar diffuser, a tungsten lamp system with a stability monitor, and a pair of blackbody cavities that can be controlled at different temperatures. Cold space observations and internal calibration are performed during normal Earth scans. During its operation CERES has shown remarkable stability. There has been no discernible change in instrument gain for any channel at the 0.2% level with 95% confidence. Ground and in-space calibrations agree to within 0.25%.
Read more about this topic: Clouds And The Earth's Radiant Energy System
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