Detector

There were two occasions in which the FIES dewar needed to be pumped. Based on feedback from an observer, the first of these pumping introduced a fixed high-frequency ripple pattern clearly seen in the summed flat field frames. The ripple pattern resembled additional but constant-in-time spacial pixel-to-pixel response variations, and could be fully removed as part of a standard reduction. After the second time the dewar was pumped the ripple pattern had disappeared again.

The CryoTiger compressor used for the FIES detector has an inbuilt filter, and the compressor will need to be send back to the supplier to allow for a regular filter change. A spare compressor is available to cover this period.