# FBS 1.4 release (January 2020 update - FBS 1.4 Runs)

**URL:** <https://www.rubin.community/t/fbs-1-4-release-january-2020-update-fbs-1-4-runs/4006>\
**Category:** Survey Strategy\
**Tags:** run-release\
**Created:** [January 24, 2020, 7:50pm UTC](https://www.rubin.community/t/fbs-1-4-release-january-2020-update-fbs-1-4-runs/4006 "2020-01-24T19:50:30Z")\
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**Author:** ![ljones](https://sea2.discourse-cdn.com/flex002/user_avatar/www.rubin.community/ljones/32/1804_2.png) [@ljones](https://www.rubin.community/u/ljones)\
**Post date:** [January 24, 2020, 7:50pm UTC](https://www.rubin.community/t/fbs-1-4-release-january-2020-update-fbs-1-4-runs/4006/1 "2020-01-24T19:50:31Z")

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**FBS 1.4 runs** - released in January 2020.

There are 75 simulations in this release (although we have recently added extra runs as part of a “1.4.1” set, upon requests from the community - so as of April 2020, closer to 120 runs). Most previous sets of simulations have been recreated with a consistent set of software (updates/bugfixes), however some runs have been dropped. Please be sure to note which _version_ of runs you are comparing (and generally try to compare runs in the same release). If a run that was useful to you was dropped, please let us know so that we can add it back in. The version information is generally included in the simulation name, it is also contained inside the simulation database file (in the `info` table).

**Release notes**

These runs are the first to use a more realistic distribution of seeing, which varies more strongly from season to season and year to year than our previous simulations. For more information on this new seeing distribution and why it was adopted, please see the discussion in [https://github.com/lsst/sims\_seeingModel/issues/2](https://github.com/lsst/sims_seeingModel/issues/2) along with the documentation linked there. In short, the new seeing distribution has a slightly worse median value, significantly worse tails toward ‘worse seeing’, and more variation from year to year and season to season … the new inputs are based on a much longer set of DIMM measurements than was previously available.

In response to evaluations of the _u_ band filter swap/mount simulations in FBS 1.3, we have implemented a filter swap at 15% lunar illumination, together with a strategy with attempts to take _u_ band visits in pairs – either _u_ paired with _u_, _u_ paired with _g_ or _u_ paired with _r_. This results in a more uniform _u_ band coverage across the sky and when paired with another filter, allows for the potential for _u_ band colors to be obtained within a night. To continue the pairing of visits within a night in all filters, we have also added _y_ band pairs (instead of singles, as was the previous strategy) – now _y_ band will be paired with _y_ or with _z_ in most simulations. This means all visits are now paired in the ‘blob’ surveys, which operate under stable (not near twilight) conditions.

As in FBS 1.2 and 1.3, 1x30s visits are used as the defaults for the standard simulations (although 2x15s visits must remain the official baseline and will be tested for all final runs).

Observations for the Deep Drilling fields continue to be refined here (and will be updated further in future simulations - we anticipate that less time will be spent in DDFs than is currently used in the standard simulations, once something closer to the AGN/DESC requirements is implemented). In these runs, DDF observations are now taken at lower airmasses than in previous simulations. The DDF dithering strategies in FBS 1.3 are continued, imprinting a 0.7 degree dithering pattern.

The rotation angles are slightly more restricted than previously, in order to maintain the camera within the rotator boundaries. The rotator angle dithering introduced in FBS 1.3 is continued.

The rolling cadence simulations have improved basis functions implemented, which result in a more uniform final survey. Feedback on the rolling cadences will be greatly appreciated.

In the code itself, some changes have been made to improve cross-platform repeatability, and the configuration scripts have been updated to help improve documentation and readability (and thus maintainability as well). This release was created with the [sims\_featureScheduler v1.4](https://github.com/lsst/sims_featureScheduler/releases/tag/v1.4) together with the configuration and slurm scripts in the directories available at [NCSA](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/).

**Availability**  
The simulation output databases are available at [https://lsst-web.ncsa.illinois.edu/sim-data/sims\_featureScheduler\_runs1.4/](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/): follow the directories in that location (mirrored in the descriptions below) to find specific runs. If you are familiar with the general python configuration scripts used to set up these surveys, you may find the configurations at [https://github.com/lsst-sims/sims\_featureScheduler\_runs1.4](https://github.com/lsst-sims/sims_featureScheduler_runs1.4) useful – the READMEs in the github repo can be useful for understanding the output contents as well.

A variety of MAF outputs (and additional links to the databases) for these runs are also available at [http://astro-lsst-01.astro.washington.edu:8082](http://astro-lsst-01.astro.washington.edu:8082/) – more outputs will come online here over the next few weeks. The MAF outputs are identified by the same run names as the DB links.  
You can also download (proposal labelled) versions of the databases at [https://epyc.astro.washington.edu/~lynnej/opsim\_downloads/fbs\_1.4/](https://epyc.astro.washington.edu/~lynnej/opsim_downloads/fbs_1.4/)

**FBS 1.4 runs**

- _[baseline](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/baseline/)_ This now contains a comparison of 1x30s visits vs. 2x15s visits (inter-night variation of survey strategy have gone to the ‘pair\_strat’ section). For other sets of simulations, we have taken the 1x30s + mixed pairs of filters configuration as the standard intranight cadence … however please take this as a working premise, but NOT an official constraint or choice. The final decision to choose 1x30s vs. 2x15s visits will not be made until on-sky observations with the survey camera are acquired, and 2x15s visits must be carried as the _official_ baseline until that point.

- _[Pair strategy](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/pair_strat/)_ These runs look at variations in the intra-night strategy. In FBS 1.3 runs, the visits were paired as _r-g_ , _i-r_ , _z-i_ , with some _z_ visits unpaired, and _u_ and _y_ visits always unpaired. One idea that came out of the `filter_load` simulations in FBS1.3 was that _u_ band visits would perhaps be better paired with another filter, at least some of the time, in order to obtain _u_ band colors for transients. Variations on the filter pairing are evaluated here.

- _[footprints](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/footprints/)_ Variations on the WFD footprint and overall survey footprint. For now, we’ve continued to take the ‘traditional WFD and minisurvey’ footprint to be the basis for most of the other experiments, but this may change in a future set of simulations.

- _[alt\_roll\_dust](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/alt_roll_dust/)_ These two (now three) simulations investigate some rolling cadence variations on an extended N/S dust-limit footprint.

- _[Rolling\_cadence](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/rolling_cadence/)_ A range of variations on the rolling cadence. There is more to do here, but we need better metrics to distinguish between the effects of these difference cadences. The rolling cadences tested so far are all declination band-based, using between 2-6 bands (`mod2`, `mod3`, or `mod6`). All of these rolling cadences feature a ‘delay’ or modification, so that the dec bands switch at an appropriate point in the season for each field. There are also variations on the weight for the ‘background’ (non-rolling / non-emphasized) portions of the WFD, from 10-20% (`_sdf_0.10` or `_sdf_0.20`). For now, we’ve taken a non-rolling cadence as the basis for other experiments, but this may change in a future set of simulations.

- _DDF_ These simulations experiment with the cadence and number of visits per filter (per night) requested by the DESC and AGN white papers, as well as adding a fifth DDF at the Euclid location. The filter swap time is the same as in the baseline (15% lunar illumination), and translational dithers are applied to the DD visits.

- _[bulge](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/bulge/)_ These experiments vary the number and strategy of observations within the galactic bulge region. The “background” survey footprint is the “big sky” footprint - i.e. an extended WFD region, but minimal coverage north or south of this region, or beyond a galactic latitude of +/-15 degrees unless otherwise modified in the simulation. The ‘low galactic latitude’ region in question as specified by the SAC is then |b| \< 10 degrees, with a further specification of galactic ‘bulge’ |l| \< 20 degrees and |b| \< 10 degrees.

- _[twilight\_neo](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/twilight_neo/)_ The previous twilight survey indicated that twilight time was not necessary to meet the SRD requirements; with the degraded weather added in FBS 1.2, this is no longer true. These experiments tested adding an NEO-specific survey during twilight. The NEO survey included fields with |ecliptic latitude| \< 40 degrees and Dec \< 30 degrees, then attempted to take 3 observations per pointing with about 3 minutes spacing, in one of _riz_ filters, up to airmass of 2 and with a preference for pointing as near as possible toward the Sun. This twilight survey was repeated on various intervals - either every night (`mod_1`) or every other night (`mod_2`), every third night (`mod_3`) or every fourth night (`mod\_4).

- _[twilight\_filters](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/twilight_filters/)_ These runs investigated if there was a benefit to restricting the filters available for use in twilight (i.e. forcing the simulator to use a particular filter or filters during twilight). The number (`_1` through `_5`) indicates how many filters were available for use during twilight, dropping filters from the blue end until `_1` is equivalent to allowing only _y_ band during twilight.

- _[DCR](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/DCR/)_ Add high airmass observations in _u_ and _g_ to enhance estimates of colors/spectra via DCR. The number of high airmass observations per filter per season was varied in the different simulations, from 1 (`nham1`) to 5 (`nham5`).

- _[Short exposures](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/short_exp/)_ These simulations add a mini-survey which takes short exposures – either 1 or 5 seconds long (`_1expt` or `_5exp`) – over the entire sky either 2 or 5 times per year (`_2ns` or `_5ns`). In FBS 1.2, we saw these had a minimal impact on the overall survey.

- _[Spiders](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/spiders/)_ This run investigated the effect of setting the rotator angle such that the expected diffraction spikes from stars would run along columns/rows (i.e. match the rotTelPos to the angle of the spiders, +/- 45 degrees, for each visit).

- _[Variable exposure times](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/var_expt/)_ This run allows the exposure time to vary between 20s to 100s to maintain a more uniform depth per image. This mode may not be supported by Data Management.

- _[WFD depth](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/wfd_depth/)_ This set of runs experiments with weighting the WFD portion of the footprint to different depths. The survey footprint is the standard traditional footprint. The WFD % in each case represents an estimate of the requested number of visits in WFD. The runs with `_noddf` in the name do not have DD fields and hold exactly to the requested scaling, the runs with DDF can have slight deviations due to small variations of the time spent on DDFs. The WFD fraction was varied from 65 - 99%, in steps of 5%.

- _[Weather](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/weather/)_ These runs attempt to shed light on over/under subscription effects, by varying the limit for stopping observing due to clouds. This should preferentially reduce the time available during bad weather periods of the year, increasing the effect of oversubscription in areas which are correlated with bad weather. We have noticed that the area around RA=0 (near most of the DD fields, nearby but not directly next to the galactic plane, and under the edge of the NES) appears oversubscribed with regard to the amount of time available at that time of year. These runs vary the cloud limit from 0.3 (`_0.3`) to 1.2 (`_1.2`), where 0.3 would indicate less time available (shutting down at a lower cloud limit) while 1.2 would indicate never closing due to clouds, and 0.7 (`_0.7`) is close to the earlier (OpsimV3/FBS1.1) values. The current standard value is 0.3, which results in about 32% downtime due to clouds (see [release notes](http://www.rubin.community/t/july-2019-update/3760) in the FBS 1.2 runs release announcement). The other runs in this simulation should be viewed as instructive about oversubscription, but not realistic.

**Added later in FBS 1.4 (April 2020)**

Due to requests for updates in _u_ band coverage, we did re-run the filter load sequence, but also extended these by evaluating the effect of ‘flexible’ DD sequences (i.e. dropping the separation between dark time in _u_ band and non-dark time in _grizy_, so that the sequences are continuous in whatever filters are available), and then evaluating the effect of varying the filter load time while also attempting to pair _u_ band visits with either _g_ or _r_ band (including varying the amount of _u_ band visits requested, so as to add more pairs).  
These sets of runs are available in

- [Filter\_load](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/filter_load/)
- [DDF\_experiment](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/DDF_experiment/)
- [u pairs](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/u_pairs/)
- We also ran an series of experiments where we added a priority on obtaining ‘good seeing’ images in _r_ and _i_ bands – [good\_seeing](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/good_seeing/)
- And a further series of runs where we attempted to add a third visit in at the end of some percent of nights, in the [third\_obs](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/third_obs/) series.
- We extended the WFD variation runs by varying the _area_ in the WFD, not just the fraction of time devoted to WFD, in the [wfd\_vary](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs1.4/wfd_vary/) series.

**Dropped in FBS 1.4**

If these sets of simulations are of interest to you, please get in touch and we can recreate them with the updated seeing inputs and code used for the FBS 1.4 runs. In the meantime, we’ve dropped these sets of runs to simplify analysis or because we think we learned what we need for the moment.

- _[Filter\_load](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs_1.3/filter_load/)_ The SAC recommended confining u band observations to within +/- 2 days of new moon, and understanding when to change the u band filter (for either z or y band) is useful. These sets of runs complete an (updated and extended) evaluation of the impact of changing the _u_ band filter loading time. The time of filter swap is varied from 3% lunar illumination - 60% lunar illumination. 10% is the default carried to other simulations. We evaluated this for FBS 1.2 and FBS 1.3, and came to the conclusion that below about 7-10% lunar illumination resulted in extremely uneven sky coverage in _u_ band, due to oversubscription at some points in the year (due to a combination of weather and sky footprint). Pairing the _u_ band filter resulted in more even coverage in general, and as was pointed out in the previous community [thread](http://www.rubin.community/t/u-band-filter-swap-time/3802/5) - obtaining _u_ band images in combination with visits in _g_ or _r_ allows color determination for very interesting transients such as TDEs. Based on an evaluation of this in FBS 1.3, we are carrying forward a strategy of swapping the filter at 15% lunar illumination and requesting _u_ band visits in pairs – most of the time the visits are paired with other _u_ band images, but some percent of the time they are instead paired with _g_ or _r_.

- _[alt\_sched](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs_1.3/alt_sched/)_  
The previous simulations were an attempt to come closer to recreating the alt scheduler outputs, without some of the drawbacks to the alt scheduler. A footprint that looks more like the ‘standard’ footprint is included in the ‘roll\_alt’ set. These simulations illustrate what a basic North-South daily interleaving of observations gives you, over some simple footprints. This is somewhat contained in the alt\_roll/alt\_roll\_mod2\_dust\_v1.4 simulation. The general alt\_sched footprint did not meet SRD (too much area, not enough depth) and the bluer filters were obtained at bad times (even with the FBS algorithms).

- _[roll\_alt](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs_1.3/roll_alt/)_ These previous simulations investigated imposing the alt\_scheduler daily N/S variation on top of a season N/S dec band rolling cadence. This has been replaced by a simulation in alt\_roll\_dust, removing the attempt to impose this on a standard footprint.

- _[Rolling\_cadence](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs_1.3/rolling_cadence/)_ Many of these runs are recreated here, but we dropped the “simple” runs, where the declination bands swapped based on time rather than at a given point in their (individual RA) seasons.

- _[templates](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs_1.3/templates/)_ Difference imaging will require a usable template image. This set of simulations experimented with adding weighting to parts of the sky which had not received at least 3 visits within the last ~300 days. The run parameters are similar, just with different weighting for this feature, the weight ranging from 0 to 10. The default, 6, has been carried out as a baseline for the other simulations. Note that we need better information from Data Management regarding what is required for a template! These simulations are dropped for now, until we have more information about the requirements; the default is continued through these simulations.

- _[WFD only](https://lsst-web.ncsa.illinois.edu/sim-data/sims_featureScheduler_runs_1.3/wfd_only/)_ These simulations contained only WFD visits, on a traditional WFD footprint. They are somewhat included in the `wfd_depth` series above, as there are now versions without DD fields.

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_[View the full topic](https://www.rubin.community/t/fbs-1-4-release-january-2020-update-fbs-1-4-runs/4006)._