LOS ANGELES — A cooling issue with a key instrument on a weather satellite launched less than three months ago could degrade its performance for at least part of each day, with potential but still undetermined effects on weather forecasts, said officials on May 23.
The National Oceanic and Atmospheric Administration said the GOES-17 weather satellite’s Advanced Baseline Imager (ABI) cooling system failed to start as expected during an on-orbit check a few weeks ago. The satellite, formerly known as GOES-S, was launched on an Atlas 5 on March 1.
The cooling system is required to maintain the ABI detectors at an operating temperature of 60 Kelvin. This system does not work sufficiently for 13 of the 16 bands of the instrument, at infrared and near infrared wavelengths, during part of each orbit. Three other bands, which operate at visible wavelengths, are not affected by the cooling problem. The other instruments of the spacecraft are also not altered.
“This is a serious problem. This is the first Earth-pointing instrument on the GOES platform,” said NOAA Satellite and Information Service Manager Stephen Volz, discussing the matter with 13 of ABI’s 16 channels in a media conference call, “If they’re not fully functioning, it’s a loss, a performance issue that we need to fix.”
The problem appears to be with a cryocooler and associated hardware on the instrument. “The heat pipes that carry heat from the cryocooler to the external radiator don’t appear to be working as expected at this time,” said Pam Sullivan, NASA flight project manager for the GOES-R program, which includes GOES-17.
This only causes problems when the spacecraft is on the nighttime part of Earth, where the instrument receives more heat from the sun. “There is a portion of the day centered around the satellite’s local midnight where the data is not usable, and that’s what we’re currently tackling,” said GOES-R system program manager Tim Walsh. directly to NASA.
“Visually, you can think of it as the sun over Earth’s shoulder, as you look down at Earth, and it shines directly into the camera aperture,” Volz said.
The ABI is the same as GOES-16, which works normally. It is also identical to the instruments of two Japanese weather satellites, Himawari 8 and 9, which also function correctly. The four ABI instruments, as well as two for future GOES satellites, were built by Harris Corporation.
The investigation into the problem is ongoing and could take several weeks. Volz and others, however, said that even if the problem cannot be fixed, the instrument will still be able to provide some data, albeit at lower quality for part of the orbit. “Worst-case scenario doesn’t mean we don’t have any infrared channels,” he said. “We get degraded performance on infrared and near-infrared channels, not zero performance.”
NOAA pointed out that the issue with the GOES-17 ABI does not currently affect weather forecasts, since the satellite is still being checked out and not used in weather models. If the problem cannot be resolved, the effect of the degraded data on the models will need to be determined. “We’re going to have to take some time to assess what the impact of that would be,” said Joe Pica, director of the observations office at the National Weather Service.
The next satellite in the series, GOES-T, is expected to be ready for launch in 2020. Volz and other NOAA officials said it was too early to discuss accelerating the launch of this satellite if the Efforts to fix the ABI on GOES-17 are failing, in part because they will have to see what fixes are needed for the planned ABI for GOES-T.
“The first thing we need to do is understand the anomaly and whether or not it affects the other elements, the GOES-T and -U spacecraft,” Volz said. “At this point, it is premature to say where and how we would change this launch date.”
Sullivan said the project team was working hard to determine the root cause of the failure and ways to fix it. “People have dug in. They’re not even close to running out of ideas,” she said. “People are being very creative in trying to recover the ABI completely or as much as possible.”
“That’s obviously not what you want to see,” Volz said, adding that spacecraft anomalies aren’t unusual. “It’s never as bad as it looks the first time you see it, and we’re certainly ready to maximize system performance, even given the trade-off we’re seeing right now.”