Week 10 of the Early Operations system performance optimization period.
High dew point temperatures prevented on-sky testing early in the week. The team used this time to gather calibration data for an upcoming LSST Camera sequencer CCD readout controller firmware update to use the natural frequency of the readout electronics, in particular, acquiring full-night photon transfer curve (PTC) measurements. The suite of calibration data products are being generated in advance so that they can be deployed together with the firmware update for use in regular nighttime operations.
Once the environmental conditions improved, the team completed the multi-night observing campaign for a refined elevation and physical rotator angle look-up table (LUT) that will incorporate both hexapod and mirror bending mode degrees of freedom by running the active optics system (AOS) closed loop to convergence at a grid of elevation and rotator angle coordinates.
The team also continued pre-LSST observations driven by the feature based scheduler (FBS) using multiple scheduler configurations. As a potential near-term mitigation for the time-varying filter focus offset that is under active investigation, the team began experiments inserting AOS closed-loop iterations at the location of the next scheduled visit immediately after a filter change during the pre-LSST observations. This approach could improve the delivered image quality consistency at the expense of some additional overhead time around filter changes.