Week 31 of the Early Operations system optimization period
Rubin Observatory ran full nights of pre-LSST observations on each night of the past week, except for 27 May when the team took in-dome calibrations due to cloud cover at Cerro Pachón. A total of more than 4300 pre-LSST visits were acquired across six nights, including a new single-night record of 890 visits on 25 May. The delivered image quality largely traced estimates of the atmosphere seeing, which exhibited larger variations during the week, with per-night median PSF FWHM ranging between 0.9 and 1.4 arcseconds. The estimated instrumental contributions to the delivered image quality remained stable.
The team began a multi-night test for the primary-tertiary (M1M3) mirror thermal control that reduces the maximum rate of change for the temperature set point. The intent is that more gradual cooling of the M1M3 bulk temperature to follow changes of the nighttime ambient temperature will help to reduce distortions of the mirror figure attributed to temperature gradients across the mirror that are induced by more rapid cooling. The team will evaluate both the mirror figure and potential changes in the mirror seeing contribution over the next week.
The in-dome calibrations included additional monochromatic flats and filter scans with the collimated beam projector.
Next week is expected to continue with primarily pre-LSST observations.
A filter swap to remove u and install y occurred on 26 May such that the currently installed filter set in grizy.