Public SCOC meeting minutes


The SCOC designed a set of simulations relating to the ToO program that reflect the community recommendation in, as well as down and upscoped versions of the recommendation. These simulations, together with the scientific motivation for the ToO described in the report, will enable the incorporation of the ToO program in the Phase 3 survey strategy recommendation due September 2024.

The SCOC identified a parameter in the implementation of a rolling strategy that was previously not explicitly discussed, namely, the number of rolling cycles. A rolling cycle is defined as (roughly) 2-year period over which each rolling region receives alternate high- and low-intensity coverage. While the SCOC has made explicit recommendations on the sky rolling regions (recommending a 2 sky region split, see PSTN-055 Section 2.5.2) and on the strength of the rolling (0.9, see PSTN-055 Section 2.5.2), the number of rolling cycle was never explicitly discussed and deliberated on. Since, like the parameters discussed earlier, the number of cycle rolling strategies impacts uniformity and time-domain science, the SCOC is preparing to deliberate on it in its Phase 3 recommendation.

The SCOC has voted affirmatively on extending the u-band exposure to 38 seconds per visit and boosting the number of u-band observations by 10% compared to Baseline v3.2. This compensates for the relative throughput loss associated with the Triple-Silver mirror coating (discussed here) while preserving the increased survey depth at bands redder than g.

The survey strategy team has recently released a new set of simulations (v3.4) that include variations on the exposure time and number of u-band visits and modified rolling strategies for the community to review and share feedback on.

The next meeting of the SCOC, scheduled for May 27th, would fill on a US holiday and will be postponed to ensure sufficient attendance.


The SCOC met to review simulations that represent the community recommendation of the Target of Opportunity program formulated during the ToO workshop The simulations of the program showed little to no impact on the science to be conducted with the Wide Fast Deep survey, but took a smaller fraction of the survey time than expected. The Survey Strategy team is investigating this issue and the SCOC will reconvene to reevaluate the impact of the ToO program as more information becomes available.

The SCOC reviewed updated ToO simulations. The impact of the addition of a ToO program implemented as per the recommendation of the Rubin ToO24 participants ( as well as with down and upscoped implementation was reviewed. A statistically significant impact in the metrics tracking SN Ia number at low redshift and parallax is observed with the introduction of the ToO program. For other metrics (e.g. Brown Dwarfs) the observed impact is within the 1-sigma uncertainty determined by weather predictions. The SCOC will vote on ballots regarding the implementation of the ToO program within the first week of July. The observing strategy team prepared supporting material for this decision including notebooks reviewing the ToO program simulations can be found at sims_featureScheduler_runs3.4/maf/ql_too_com.ipynb at main · lsst-sims/sims_featureScheduler_runs3.4 · GitHub and survey_strategy/fbs_3.4/v3_4_too.ipynb at main · lsst-pst/survey_strategy · GitHub
The SCOC agreed to meet every monday in July leading to the Rubin CW to advance discussions on the recommendations for Galaxy survey strategy, DDFs, and rolling strategies.

The SCOC discussed the report of the Galaxy Survey Strategy task force including recommendations on footprint details, rolling, coordination with Roman and filter balance. While some details of the filter balance in special regions remain to be defined, the SCOC has prepared ballots to vote on the recommendations of the Task Force. The outcome of the vote is expected by 7/15.
The SCOC heard a preliminary report from the Deep Drilling Field Task Force. The TF has ready recommendations for a variety of aspects of the DDF strategy including observation properties, dithering, and field prioritization over the 10 year survey. More work remains to be done on the nightly cadence and on balancing season length with cadence requirements.