Clouds and the Earth’s Radiant Energy System (CERES) instrument was designed to provide accurate measurements for the long-term monitoring of Earth’s radiation energy budget. Flight Model 5, the sixth of the CERES instrument was launched aboard the NPP spacecraft on October 2011 and it has started the Earth-viewing measurements on January 26, 2012. The CERES instrument with the three scanning sensors measure radiances in 0.3 to 5.0 micron region with Shortwave sensor, 0.3 to <100 microns with Total sensor and 8 to 12 micron region with Window sensor. The pre-launch accuracy goal for the CERES instrument measurements is to have the emitted longwave radiances within 0.5% and the shortwave radiances within 1.0%. An accurate determination of the radiometric gains and spectral responsivity of CERES FM5 sensors was accomplished through rigorous calibrations using the primary sources. Post-launch evaluation of the sensor performance consists of sensor calibrations with the on-board sources and the solar diffuser called Mirror Attenuator Mosaic (MAM). The calibration results using onboard sources are also compared to pre-launch values which serve as a traceability standard to carry the ground determined sensor radiometric gains to orbit. Several validation studies utilising targets such as tropical ocean and deep convective clouds are performed as part of the Cal/Val protocol. The scan elevation offset in the sensor measurement will be determined from the spacecraft pitch manuveur activity viewing the deep space. This paper covers the early-orbit checkout activities and the overall performance of the CERES-FM5 instrument. The postlaunch calibration and the validation results from the instrument are presented.

Date Published: 19 October 2012
PDF: 8 pages
Proc. SPIE 8510, Earth Observing Systems XVII, 851005 (19 October 2012); doi: 10.1117/12.930775

Published in SPIE Proceedings Vol. 8510:
Earth Observing Systems XVII
James J. Butler; Xiaoxiong Xiong; Xingfa Gu, Editor(s)