GOES ABI infrared calibration around midnight: GEO-GEO assessment (Conference Presentation)

We analyzed the radiance differences between GOES-East and GOES-West at ten-minute interval for a year and found some subtle fluctuation patterns around satellite midnight, which also varies seasonally. One occurs annually around the winter solstice, when the Internal Calibration Target (ICT) can be heated rapidly and unevenly after midnight. This fluctuation has the longest duration in late February and late October, lasting about two hours. The other occurs semiannually during eclipse seasons, when the Sun is close to the Earth before and after being occluded. This fluctuation is most pronounced near the times of occlusion and disappears as the Sun moves behind the Earth. The magnitudes of these two fluctuations are instrument-dependent and within only a few tenth of a degree at 300 K. Detecting and characterizing these fluctuations, while compliant with the calibration requirement, demonstrates the utility of comparing two nearby geostationary sensors (“GEO-GEO”) on a fine temporal scale. This complements the comparison of GEO with well-calibrated hyperspectral sensors on Low Earth Orbit (GEO-LEO).