Weeks 20-21 of the on-sky commissioning campaign with LSSTCam. The summit crew spent much of Week 20 recovering from a late August winter storm that interrupted commercial power delivery to the summit. By Friday 5 September, full operational capabilities were restored, and on-sky testing resumed with a continued emphasis on engineering tests to improve the delivered image quality reliability. There is approximately one week remaining for the on-sky commissioning campaign with LSSTCam, and the team is focused on acquiring data to characterize the system before a planned engineering downtime in September-October.
New activities from the past two weeks:
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The Active Optics System (AOS) commissioning is progressing on two fronts. First, the team has acquired a more extensive set of in-dome laser tracker metrology measurements to refine the elevation and Camera physical rotator angle look-up tables (LUTs) for the open-loop control system. Refined LUTs are being iteratively tested with scans in both elevation and rotator angle to evaluate whether a two-dimensional non-separable elevation and rotation LUT is required to adequately correct the optics while surveying the sky. Second, the team has continued tests to improve the convergence of the closed-loop control system, including further stability tests to evaluate stochastic variations in the wavefront estimation, tests to isolate individual Zernike wavefront aberrations, and running the AOS closed loop in full-array mode to evaluate the wavefront across the full field of view. The team has also been expanding the suite of both realtime visualization and offline analysis tools.
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A first set of dome louvers are being integrated and the software control systems are now being commissioned to allow nighttime operation to improve the dome ventilation. Work continues to characterize the systems and optimize the thermal control loops.
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The primary-tertiary mirror (M1M3) thermal control system is now operating each night with the Environmental Awareness System automatically adjusting the thermal set point to match ambient temperature variations.
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The Science Validation (SV) surveys have continued in parallel, typically in the second half of the night following the completion of other on-sky engineering activities. The Wide component continues to concentrate remaining observations within the 750 deg^2 footprint. The strategy for the Deep component has been modified to prioritize observations of the ELAIS-S1 and the Extended Chandra Deep Field South (ECDFD) LSST Deep Drilling Fields (DDFs). These fields were selected because they present the best opportunities to test difference imaging and to acquire deep integrated exposure given the remaining time available for the on-sky commissioning campaign. The scheduler configuration was modified to increase the number of visits acquired during a given epoch while observing the DDFs. In recent weeks, the DDFs have been observed with larger dither patterns to inform optimization of the observing strategy for the LSST 10-year survey. Templates to enable testing of the Prompt Processing framework with difference image analysis have now been deployed for a subset of bands for both the Wide and Deep components of the SV surveys. Rubin Observatory will continue to post updates for the SV survey progress and provide Nightly observing reports.
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The team plans to use the griz filters for the remaining week of the LSSTCam on-sky commissioning campaign.
Rubin Observatory is now preparing for a final construction downtime and the first operations engineering downtime. The Simonyi Survey Telescope will not be operated at night, and instead, the summit will be busy with complex daytime engineering tasks that cannot be accommodated during the regular 24 hour cycle of summit operations. The planned duration of the downtime is approximately 4 weeks, starting on Monday 22 September, with on-sky observations resuming in late October.