We are pleased to announce the release of v1.7 of the survey strategy simulations. For general information on the survey simulations, see our PSTN-051 document. PSTN-051 will be updated shortly to include more in-depth analysis of these new runs.
The major change for this release, we have switched the default observing behavior to visits of 2x15s exposures rather than 1x30s exposures. The extra shutter motion and readout time is a significant increase in overhead compared to our previous default simulations. The run
baseline_nexp2_v1.7_10yrs.db is the simulation which other runs in this release should be compared to.
other updates in this release:
• Updated telescope kinematic model which fixes problems that previous releases included observations slightly below the altitude limit of the telescope and put the camera rotator in unphysical positions.
• Improved rolling cadence that maintains the proper weighting for regions outside the wide-fast-deep survey and has proper variable strength.
MAF outputs for these (and previous releases) can be found at: http://astro-lsst-01.astro.washington.edu:8081/
The sqlite files for these simulations are also at NCSA: https://lsst.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.7/
Descriptions of runs
We run 2 baseline simulations,
baseline_nexp2_v1.7_10yrs.db. Again, the rest of the runs in this release have 2x15s visits and should be compared to
We try a variety of different survey footprints based on increasing the low-extinction area of the wide-fast-deep footprint. We also test including coverage of the bulge and outer Milky Way disk as part of the WFD area.
We test rolling cadence by dividing the sky in half (nslice2) or thirds (nslice3). We also vary the weight of the rolling from 20% (scale0.2) to 100% (scale1.0). Because the scheduler tries to keep observations at low airamss, the rolling, especially for the nslice3 runs, is not as strong as it could be.
These runs also include a basis function which modulates the emphasis of the survey so the northern half of the sky is observed on even days and the southern half on odd days.
These are rolling simulations similar to the above, but do not include the daily north/south modulation.
These runs vary the size of the spatial dithering of the deep drilling fields from 0 to 2 degrees.
These runs test using a custom dither pattern for the Euclid deep drilling field to better match the Euclid field of view.
In the baseline, observations are typically taken in pairs separated by ~22 minutes. In these runs, we vary that pair time from 11 minutes to 55 minutes.
The baseline simulations to not attempt to pair twilight visits. In these runs twilight observations are paired in either the same filter, or a different filter (mixed). The twilight observations are also set to attempt to re-observe areas of the sky that have already been observed in the night (repeat).
An update of previous experiments that use twilight time to perform an NEO survey. These simulations include a large number of 1s observations. We still need to verify that the camera and network could handle taking so many short exposures.
Observations in the u filter are taken as single snaps, and we test increasing u-band exposure times. Note, DDF u-band observations are still the default 2x15s exposures.
An experiment where long gaps in g-band exposures are avoided, even if that means observing g in bright time. We test different limits on how many g-observations are taken and if the blob scheduler tries to maintain contiguous areas.