Round Tables

Round Table Guidance

The Round Table is named after King Arthur’s fabled congregation of Knights;  given the shape of the table, it has no head — everyone has an equal voice.  Each Round Table will have a moderator and a scribe/reporter.

The role of the moderator is to ensure each participant is invited to voice their opinion or ask probing questions about the topic at hand. We have suggested questions for each Round Table, but the moderator should feel free to adapt or expand the questions as the discussion unfolds.

The role of the scribe is to take notes on the discussion (as well as participate) and then synthesize the main points and give an informal ~five-minute summary to the Workshop later in the schedule. The scribe and moderator may want to work together preparing the synthesis.

Each physical round table (which is actually rectangular...) will have 12 participants, including the moderator and scribe. There will be a mix of experts and non-experts discussing the topic of each Round Table. We are hoping the 'non-experts' will challenge the 'experts' on some of their underlying assumptions. Sometimes it is the 'non-expert' questions that are the most probing... or the 'non-expert' scribe who gives the most refreshing summary.

Round Table Questions

Round Table Session #1: Milky Way dust and atmosphere

Additional question for all five tables to consider: Are atmospheric transmission effects, atmospheric PSF effects, and the impact of Milky Way dust factorizable at the level needed for LSST science?


Table A1, Moderator - Michael Schneider, Scribe - Andrew Bradshaw

Question: How do variations in observing parameters (e.g., exposure time, airmass, atmospheric transmission -- especially in y band) provide an advantage for understanding and quantifying photometry, photo-zs, chromatic PSFs, other? What are the trade-offs between decreasing the range or deliberately increasing the “lever arm” for some parameters?


Table B1, Moderator - David Burke, Scribe - Patrick Ingraham (TBC)

Question: Same as Table A.


Table C1, Moderator - Jeff Newman, Scribe - Alex Abate

Question: How can we use observations -- e.g., stars, galaxies, quasars, far infrared data, other? -- to constrain variations in Milky Way reddening (both amplitude and wavelength dependence) on small and large angular scales?


Table D1, Moderator - Sam Schmidt, Scribe - Eddie Schlafly

Question: Same as Table C.


Table E1, Moderator - David Kirkby, Scribe - Gregory Green

Question: Same as Table C.

Round Table Session #2:  CCDs; PSF corrections for physical effects

Table A2, Moderator - Andrei Nomerotski, Scribe - Chris Davis

Question:  How can we use differences in temporal and spatial variability to discriminate between shape perturbations introduced by 1) the sensors, 2) the optics, and 3) the atmosphere? Are there other differences we can exploit?


Table B2, Moderator - Chris Walter, Scribe - Andres Plazas

Question:  How can we use external data, such as HST images or laboratory measurements, to constrain shape systematics? What specific images or measurements are needed?


Table C2, Moderator - Mario Juric, Scribe - Daniel Gruen

Question:  What are the trade-offs in correcting sensor effects -- such as brighter-fatter, edge effects, or tree rings -- at the pixel level or the catalog level?


Table D2, Moderator - Eric Gawiser, Scribe - Rachel Bean

Question:  Which aspects of the survey strategy can be used to minimize and discriminate between different sources of systematics  -- e.g., dithering? exposure time? other?


Table E2, Moderator - Debbie Bard, Scribe - Steve Kent

Question: Same as Table D.

Round Table Session #3:  Tackling the unknowns

Table A3, Moderator - Tony Tyson, Scribe - Satoshi Miyazaki

Question:  Which system and observing parameters should we vary during commissioning (beyond the ranges anticipated during normal survey operations) to characterize known foreground physical effects and discover new systematics?  


Table B3, Moderator - Chuck Claver, Scribe - Michael Wood-Vasey

Question: Same as Table A.


Table C3, Moderator - Mike Jarvis, Scribe - Rachel Mandelbaum

Question:  Applying “null tests” in cosmic shear analyses is one way to identify residual systematic uncertainties. Which existing or new null tests will be most relevant for the full LSST data sample? Will these null tests have the required statistical sensitivity for cosmic shear measurements with LSST? (How do they scale?) What do we do when we see a 3-sigma effect, say, in a null test?


Table D3, Moderator - Steve Ritz, Scribe - Srikar Srinath

Question:  Due to the planned short exposure times, atmospheric turbulence dominates the spatial variability of the LSST PSF, especially at small angular scales.  How do we determine an appropriate model for the atmosphere (how many layers?, what parameters?), and what information is or should be made available to constrain this model (MASS/DIMM, scintillation of guider images, wavefront sensors, ...)?  What measurements are useful to obtain “statistically” for producing realistic simulations, and which are useful to obtain simultaneously with the survey to constrain PSF spatial variability in specific images?


Table E3, Moderator - Jim Bosch, Scribe - Will Dawson

Question:  How can the variable seeing in the large number of LSST epochs be used to learn about the impacts of the atmosphere - e.g., for blended objects, inferring the PSF from galaxy images?  Others?