CERES instrument assembly (TRW)
The CERES instrument pictured on the right is based on the successful ERBE scanning radiometer design with several improvements to accommodate upgraded performance requirements and hardware developments. CERES has twice the spatial resolution and improved instrument calibration. The two EOS spacecrafts will each carry two identical instruments: one will operate in a cross-track scan mode and the other in a biaxial scan mode. The cross-track scan will essentially continue the measurements of the ERBE, while the biaxial scan mode will provide new angular flux information that will improve the accuracy of angular models used to derive the Earth's radiation balance.
Each CERES instrument has three channels -- a shortwave channel to measure reflected sunlight, a longwave channel to measure Earth-emitted thermal radiation in the 8-12 μm "window" region, and a total channel to measure all wavelengths of radiation. Onboard calibration sources include a solar diffuser, a tungsten lamp system with a stability monitor, and a pair of blackbodies that can be controlled at different temperatures. Cold space looks and internal calibration are performed during normal Earth scans. During the first year of operation on TRMM, CERES has shown remarkable stability. There has been no discernable 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%.
|Orbits||705 km altitude, 10:30 a.m. descending node (Terra) or
1:30 p.m. ascending node (PM-1), sun-synchronous, near-polar;
350 km altitude, 35o inclination (TRMM)
|Spectral Channels||Solar Reflected Radiation (Shortwave): 0.3 - 5.0 μm
Window: 8 - 12 μm
Total: 0.3 to > 100 μm
|Swath Dimensions||Limb to limb|
|Angular Sampling||Cross-track scan and 360o azimuth biaxial scan|
|Spatial Resolution||20 km at nadir (10 km for TRMM)|
|Data Rate||10 kbps|
|Size||60 x 60 x 70 cm (deployed)|
|Design Life||6 years|
The CERES instrument is managed by the NASA Langley Research Center in Hampton, Virginia, and built by TRW's Space and Technology Group in Redondo Beach, California.