Correction of drifts in the measurements of the Clouds and the Earth's Radiant Energy System scanning thermistor bolometer instruments on the Terra and Aqua satellites

Abstract

The 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 in orbit. 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. Both satellites are in high inclination near-polar, sun synchronous orbits. Terra crosses the equator at 10:30 am local time in the descending portion of the orbit. Aqua ascends across the equator at 1:30 pm local time. Each CERES instrument on Terra and Aqua measures in three broadband radiometric regions: the shortwave (0.3 - 5.0 micrometers), total (0.3 - >100 micrometers), and window (8 - 12 micrometers). 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. This procedure can derive an estimate of the shortwave portion of the total channel radiance measurement. A second analysis compares temporally synchronized nadir measurements for each sensor of two instruments on the same platform. The three-channel inter-comparison along with the direct comparison and onboard internal calibrations have been used to identify and correct drifting in the measurements of the CERES instruments. Although these drifts and the correction of the measurements have been previously documented, this paper is a continuation of the efforts to quantify and correct drifting in the measurements using ground-processing software. Previous papers only reported drift correction to the CERES instruments on the Terra platform. In addition to the Terra instruments, this paper documents drift correction to the CERES instruments on the Aqua platform.