Main Engine Cut Off

As one team works to improve the performance of the ABI on GOES-17, another team is tracking down the root cause of the instrument. Sullivan said the issue appears to be with loop heat pipes that contain propylene coolant. “It doesn’t seem to be flowing appropriately through the loops,” she said.

She said that team has identified a “small handful” of likely causes for the lack of coolant flow. They include “excess non-condensable gas” or foreign object debris in the pipes. “Either one of those might prevent the fluid from traveling though the loop heat pipe as intended,” she said. There could also be mechanical damage to the pipes.

When NOAA first announced the problem with the ABI on GOES-17 in May, the agency said they did not see a similar problem with an identical instrument on GOES-16, the first of the GOES-R series of next-generation weather satellites launched in 2016. However, Sullivan said that, since then, engineers have seen “some evidence of reduced functionality” in the loop heat pipes in that spacecraft’s ABI, but one that has not affected the performance of the instrument.