Determining the Relationship between the Total and Window Channel Nighttime Radiances for the CERES Instrument

Observing Earth s radiant energy budget from space is critical to improving our understanding of Earth s climate system. The Earth Radiation Budget Experiment (ERBE) was the first initiative to provide simultaneous observations of Earth s radiant energy with identical instruments flying aboard separate satellites. The design of the ERBE instrument was based upon three complementary broadband radiometers which measured the shortwave (< 5 mm), longwave (> 5 mm), and total regions of the spectrum. Since any two of the ERBE radiometers could be used to simulate the third, a three channel intercomparison, based on redundancy, was available to uncover any changes in the relative sensitivities of the individual radiometers. Such a three channel intercomparison thus provided confidence in the application of the ERBE measurements over the lifetime of the instrument while mitigating the concern over instrument degradation.