CERES

The Cloud's and the Earth's Radiant Energy System (CERES) is a 3-channel radiometer measuring reflected solar radiation in the 0.3-5 µm wavelength band, emitted terrestrial radiation in the 8-12 µm band, and total radiation from 0.3 µm to beyond 100 µm. These data are being used to measure the Earth's total thermal radiation budget, and, in combination with MODIS data, detailed information about clouds. The first CERES instrument was launched on the Tropical Rainfall Measuring Mission (TRMM) satellite in November 1997; the second and third CERES instuments were launched on the Terra satellite in December 1999; and the fourth and fifth CERES instruments are on board the Aqua satellite.

Instrument Characteristics

• Selected for flight on TRMM, Terra, and Aqua.
• Two broadband, scanning radiometers: One cross-track mode, one rotating azimuth plane (bi-axial scanning).
• First instrument (cross-track scanning) is continuing ERBE, TRMM, and Terra measurements and the second (biaxially scanning) is providing angular radiance information to improve the accuracy of angular models used to derive the Earth's radiative balance.
• Single scanner on TRMM mission (launched Nov. 1997)
• Dual scanners on Terra (launched Dec. 1999) and Aqua, and single thereafter.

Instrument Facts
Responsible Center:	NASA Langley Research Center
Heritage:	Earth Radiation Budget Experiment (ERBE)
Three channels in each radiometer:	Total radiance (0.3 to 100 µm); Shortwave (0.3 to 5 µm); Window (8 to 12 µm)
Swath:	Limb to limb
Spatial Resolution:	20 km at nadir
Mass:	50 kg per scanner
Duty Cycle:	100%
Power:	47 W (average) per scanner, 104 W (peak: biaxial mode) both scanners
Data Rate:	10 kbps per scanner
Thermal Control By:	Heaters, radiators
Thermal Operating Range:	38±0.1°C (detectors)
Field of View (FOV):	±78° cross-track, 360° azimuth
Instrument Instantaneous FOV:	14 mrad
Pointing Requirements (platform+instrument, 3σ)
Control:	720 arcsec
Knowledge:	180 arcsec
Stability:	79 arcsec/6.6 sec
Physical Size:	60 x 60 x 57.6 cm/unit