Abstract
In February 2021, a GOES-17 Advanced Baseline Imager (ABI) infrared (IR) image with a stripe near the Equator came to our attention. It was found later that this abnormal feature also occurs on some other days for several IR channels, and the location of the anomaly changes with the ABI scan modes. Further characterization revealed that this calibration anomaly can be observed when the Focal Plane Module (FPM) temperature is stable, the predictive calibration (pCal) algorithm is enabled, and before the satellite midnight. The pCal algorithm is the adopted ABI IR operational calibration algorithm to mitigate the GOES-17 Loop Heat Pipe (LHP) anomaly. We found that it can cause relatively large erroneous calibration coefficient values at certain swaths in a timeline when it is enabled in the stable FPM time before satellite midnight, resulting in the stripe near the Equator. A related but previous unnoticed anomaly was also found during this investigation. These calibration anomalies can be reduced in operation with a new operational pCal turn-on scheme. The operational mitigation effort is undergoing.
Calibration Anomaly for GOES-17 ABI Infrared Images before Local Midnight
In February 2021, a GOES-17 Advanced Baseline Imager (ABI) infrared (IR) image with a stripe near the Equator came to our attention. It was found later that this abnormal feature also occurs on some other days for several IR channels, and the location of the anomaly changes with the ABI scan modes. Further characterization revealed that this calibration anomaly can be observed when the Focal Plane Module (FPM) temperature is stable, the predictive calibration (pCal) algorithm is enabled, and before the satellite midnight. The pCal algorithm is the adopted ABI IR operational calibration algorithm to mitigate the GOES-17 Loop Heat Pipe (LHP) anomaly. We found that it can cause relatively large erroneous calibration coefficient values at certain swaths in a timeline when it is enabled in the stable FPM time before satellite midnight, resulting in the stripe near the Equator. A related but previous unnoticed anomaly was also found during this investigation. These calibration anomalies can be reduced in operation with a new operational pCal turn-on scheme. The operational mitigation effort is undergoing.