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Following the launch of G17, an issue was discovered with its ABI loop heat pipe (LHP) that should maintain the ABI electronics (and in particular, Focal Plane Module, FPM) at their intended temperatures. There are two main implications. During normal operations, the G17 FPM temperature is elevated compared to the specifications (and compared to the ABI twin sensor onboard G16, which has been the NOAA operational GOES-East satellite since Dec’2017), leading to overall noisier BTs. During nighttime, especially in some seasons, when more sunlight impinges directly on the G17 ABI, its FPM temperature is elevated even further and becomes very unstable, resulting in increased noise and degraded ABI calibration (due to increased and band-specific emission from the focal plane itself), rendering measured BTs completely unusable for SST retrievals. The increased noise of the G17 ABI instrument necessitates changes in the ACSPO clear-sky mask (in particular, its spatial uniformity test), and in the collation-in-time algorithm introduced in ACSPO v2.60 for G16. When the ABI temperature is further elevated, its BTs in the longwave IR bands remain biased (although the calibration algorithm is expected to account for changes in the instrument temperature). When the temperature is near its maximum values, they saturate. The collation-in-time algorithm can partially fill in the periods of saturation, while the remaining biases may potentially be addressed empirically. We discuss the challenges imposed by the G17 ABI LHP and resulting BT anomalies, and our progress with mitigating those in the ACSPO SST products at NOAA. Future plans include tweaking ACSPO algorithms, to generate the best possible SST out of G17 BT data, reprocessing of G17 SST data, archival of data with the NASA/JPL Physical Oceanography Distributed Active Archive Center (PO.DAAC) and NOAA NCEI, and work with users to iteratively improve the processing algorithms and derived SST products. |
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