B4K Pattern Noise
Monday, June 7, 2021 5:08 AM
After collecting calibration images, we noticed an odd noise source on the detector. It is a striped diamond pattern that is symmetric across the detector mosaic for all four amplifiers (will send image in email). It is present in bias images. The signal is lower (maybe 5 counts in amplitude) so it only became apparent in lower surface brightness images.
We saw in the trouble reports that some (similar?) issues were resolved by restarting the Head Electronics box. But it was late in the night and we are unfamiliar with the exact shutdown procedure so we did not attempt.
Pattern was faint enough that I could not reproduce it under daytime conditions with CHaS. Not sure what may have caused the issue, or what may have made it better. This particular night, the IC PC failed so I had swapped in the machine from tjhe 1.3m. On the next day, I was able to get the 2.4m IC back in service. I also cycled power to the HE and reseated the cable between the HE and the detector. Observers commented that the pattern is mostly improved and currently is not an issue.