Lynne Jones (UW/DIRAC/LSST) – OpSim Simulations & Small Body Metrics (with MAF = Metrics Analysis Framework)
OpSim generates simulated pointing histories under realistic conditions; it will eventually be the actual LSST scheduler. Pointing history includes 5-sigma depth, seeing, filter, etc. Generating one OpSim output is ~50 CPU-hours.
sims_movingObjects takes a set of orbits/objects and an output from OpSim to generate observations LSST would acquire (passes along OpSim results). Reports SNR (including trailing losses) for a given H. Current status: it is there and it works, but it may not be efficient. Generating 2000 objects (single thread) is ~4 CPU-hours.
Metrics Analysis Framework (MAF) analyses these observations and applies a “metric” to all observations of the same object. Can separate size and orbit properties, as if cloning same orbit over a range of H magnitudes; can also keep H-orbit correlations if you want. For a discovery metric, for example, ~0.1 CPU-hours.
Current metrics (see Cahpter 3 of Community Observing Strategy Evaluation Paper (COSEP) include: discovery (time of first discovery, number of opportunities for discovery – summarized as completeness as a function of H over population); number of observations or total arc length; light curve inversion; color determination.; likelihood of detecting activity for a given object assuming random distribution of activity times. All of these can be summarized as fraction of population as a function of H.
Potential metrics: number of objects lost; accuracy of orbital parameters as a function of time; does an object receive enough observations to determine rotation period / spin pole / phase curve? Will an object need followup on any given night? Improvements on exiting metrics.
You can calculate metrics over H or over orbital properties, etc. These metrics define performance of a given survey strategy in a quantitative way, allowing for quantitative decision making in cadence and other calculations. [Need also a metric to sceince conversion, e.g., metric X going above level Y enables science Z.] Survey Strategy White Papers are going to explore this in detail; many questions for solar system. Snaps (2x15s vs. 1x30s), Wide-Fast-Deep survey cadence? North Ecliptic Spur (NES) footprint and cadence? Pairs in same or different filters? Filter selection criteria? Other mini surveys for solar system? [For reference, a single visit gets several thousand asteroids in a single visit and pointing at the ecliptic.]
The Survey Strategy Committee is going to review all these and provide a recommendation for the initial survey strategy. As the survey progresses, things could be re-evaluated. COSEP is living document, but White Papers are for our best guesses now.
For us to do: be familiar with all these things and contribute. Contribute metrics to sims_maf_contrib. Add sections to COSEP to include supporting text. Defend your science!
So great to have Lynne’s expertise!