Release of V3.4 Simulations

This announcement summarizes a set of simulations available in a “v3.4” release, which includes minor code updates. Baseline_v3.4 should be used as the current reference run for these simulations.

With our last baseline release (baseline_v3.3), we announced the update of the Rubin throughput curves to as-measured versions as well as moving to 3xAg (“triple silver”) mirror coatings.
(and if you haven’t seen the mirror after coating, it looks beautiful - Rubin Observatory Achieves Another Major Milestone: Reflective Coating of the 8.4-Meter Primary/Tertiary Mirror | Rubin Observatory)
The SCOC are currently evaluating the effect of extending the time spent on u-band to rebalance the final coadded depths in each bandpass, accommodating the changes due to this change in throughputs. These simulations include extending u-band exposure time to 38 or 45 seconds, as well as potentially increasing the number of u-band visits by 0, 10, or 20%. Simulations including these changes are available here:
u band 30 seconds x 1.1 visits
u band 30 seconds x 1.2 visits
u band 38 seconds x 1.0 visits
u band 38 seconds x 1.1 visits
u band 38 seconds x 1.2 visits
u band 45 seconds x 1.0 visits
u band 45 seconds x 1.1 visits
Additional analysis of these effects on our standard metrics are available in a jupyter notebook and a more in-depth analysis of the effects on photo-z is summarized in these slides.

Next up will be evaluating the effects of varying rolling cadence to improve uniformity at specific data releases. Simulations implementing these effects are available here - Index of /sim-data/sims_featureScheduler_runs3.4/roll_uniform_early_half/
with roll_uniform_early_half_mjdp0_v3.4_10yrs being the primary run (with the same start date as the baseline).
Additional simulations that aid in evaluating the impact of these rolling cadence variations include:
noroll_mjdp0_v3.4_10yrs (and other non-rolling variations at Index of /sim-data/sims_featureScheduler_runs3.4/noroll/) as well as a 3-cycle rolling cadence roll_3_v3.4_10yrs.

Simulations adding a weather variances (the “weather_*” runs) are available here: Index of /sim-data/sims_featureScheduler_runs3.4/weather/
And simulations which add start-date variances throughout the year (evaluating impacts of starting the survey at different times during the year - the “start_date_*” runs) are available here:
Index of /sim-data/sims_featureScheduler_runs3.4/start_date/

In addition, task forces to evaluate the Milky Way / Galactic Plane coverage and the Deep Drilling Field coverage are continuing their work, comparing various survey strategy choices and simulations. Please contact the task force leaders (via the LSSTC slack – #scoc-community-ddf-discuss and #scoc-community-milkyway-discuss is preferred, or email if necessary) if you would like more information or to become involved.
Galactic Plane Coverage - Jay Strader and Rachel Street
DDF - Saurabh Jha

As always, more detailed individual simulation metric results are available online at

I’d also like to take this opportunity to note the release of a new (and growing) survey strategy website,, which includes a brief summary of the changes in the baseline survey strategy over time (Updates to the baseline — Observing Strategy).

Al always, the SCOC welcomes input on these simulations from the community and is accessible in a number of ways: if you are in a Science Collaboration, the most effective way to share input is via your SC liaison (see The Survey Cadence Optimization Information | Rubin Observatory to find out who liaisons with your science collaboration). Additionally, and if you are not in a Science Collaboration, feedback can be shared as replies to this post, by contacting the SCOC by email (see The Survey Cadence Optimization Information | Rubin Observatory for details) or by coming to the monthly SCOC office hour no the last Monday of the month at 7AM Pacific (see SCOC office hour - #8 by fed). The SCOC will continue to deliberate through August 2024 to deliver its Phase 3 recommendation in September 2024, the last recommendation on survey strategy before the beginning of LSST. Therefore, prompt feedback is preferred. Feedback received leading up to and at the Rubin Community Workshop, where the SCOC will discuss its recommendations, and through July 2024 will be incorporated, later feedback may be incorporated in our deliberations on a best-effort basis. The SCOC plans to review the surevey strategy annually, so additional feedback, even it it may not be incorporated in the Phase 3 recommendation, will be incorporated throughout the 10-year survey

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To clear up some confusion - there are also additional simulations with “rolling_uniform” in the name, but these are early experiments and not considered ‘release’ runs. When looking at the impact of rolling cadence variations (uniform (aka, with pauses), no rolling, 3 cycles of rolling cadence or 4 (the standard baseline) cycles of rolling cadence) please do not consider these additional sets of simulations.

We are also working on some “accordion WFD” versions that are the “roll_uniform_accordian_” sets of simulations, but these are also considered early experiments and not formally released.

Within the boundaries of “rolling cadence variations” this means:

  • roll_uniform_early_half: - four simulations, with start dates scattered throughout the year (the “pXXX” means how many days after the standard start time the simulation was started … this moves the start date from May to August, to November, and to February (of the next year).
    What changes in these simulations? There are three cycles of rolling cadence, with occasional pauses throughout the simulation so that intermediate data releases at year 4 and 7 are uniform.
  • no_roll : - consider the four simulations with “pXXX” in the names, which describes offsets to the start of the survey simulation, as above.
  • start_date: the baseline (with 4 cycles of rolling cadence), with offsets throughout the year.
  • roll_3 : the baseline (no pauses) but with 3 cycles of rolling cadence. There is only one of these.
  • baseline: the baseline, with 4 cycles of rolling cadence. There is only one of these.

You may also find some of the slides within [RollingCadences_2024 - Google Slides] to be helpful to illustrate the uniform rolling strategy.

fix grammar

At LINCC Frameworks we work on a new catalog-level light-curve simulation tool for LSST community. OpSim files are extremely useful for that purpose, but they miss a significant bit of information: zero point value for the given observation. Could I ask to add a new OpSim column with zero point provided?

I’m not sure if it was the right place to ask, please redirect me to the right place.