GOES-17 instrument problem blamed on blocked heat pipe

WASHINGTON — A report released Aug. 1 concluded that a problem with an instrument on the GOES-17 weather satellite is likely caused by some kind of blockage in a system used to cool the instrument.

NASA and the National Oceanic and Atmospheric Administration released a summary of the final report by a mishap investigation board convened last year to examine a problem with the Advanced Baseline Imager (ABI) instrument on GOES-17, launched in March 2018 as GOES-S. NOAA announced two and a half months after launch that a cooling problem with the instrument degraded performance of infrared channels on ABI, the spacecraft’s primary instrument for monitoring weather conditions.

The report confirmed that the ABI problems were caused by the failure of the instrument’s radiator and loop heat pipe (LHP) system to remove heat from the instrument in all phases of the orbit. The LHP system was required to handle a heat load of 390 watts, but initially carried 60 watts, later dropping to 10 to 20 watts. “This indicates that there was either a design issue or failure on-orbit,” the report concluded.

Limited data from the instrument, though, prevented investigators from determining a single root cause for that diminished performance of the loop heat pipes. However, the board concluded that, from the data that was available, “the most likely technical explanation for the failure of the GOES-17 LHPs to transport and reject their expected heat load is physical blockage of the LHP assembly by particulates contained in the working fluid.”

The report didn’t indicate if the particulates were contamination of the fluid itself when the instrument was built, or if they came from elsewhere in the instrument. The report’s recommendations included both those associated with ensuring proper cleanliness of the working fluid as well as those to study components of the instrument “that are capable of shedding particles.”

Spacecraft operators, meanwhile, have been working to maximize the performance of the ABI while working around the cooling issues. NOAA said that with operational changes to the instrument and spacecraft it has been able to get 97 percent of the data expected from ABI. That still falls short of the mission requirement that ABI suffer outages of no more than six hours per year.

Despite the problem, NOAA emphasized in an Aug. 1 statement that GOES-17 “is providing faster, more accurate, and more detailed observations” than previous generations of geostationary orbit weather satellites. The spacecraft is currently serving as the operational GOES-West weather satellite, covering the western United States and the eastern Pacific Ocean.

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