Attendance: Julian, Lloyd, Raphael, Al, Amy, Kris Gorski (for his presentation only)
Notes by Amy
Kris Gorski on Survey strategy (no slides)
EPIC scan strategy has large bore angle / good polarization scan angles / quickly covers the sky. But it required large sun shields and reduced the power per area from the solar arrays. CORE survey is a compromise that addresses some of the engineering challenges associated with the EPIC strategy, has a 120deg opening angle ring - donut on the sky precessing elliptically. Some similarities to WMAP but somewhat better crossing angles on each pixel. A scan strategy similar to Planck but with more continuous precession (less discrete) would be notably better than Planck. Kris also considering a “fantasy idea” - spacecraft spins with spin angle along Sun axis (simple, maximal power, maximal shaded volume for optics) and does not precess - instead add a moving mirror to optics. BEAST an example. But don't know about emissivity as a function of angle (large angles), and polarization propagation through such a system. Amy to arrange a meeting with a JPL optics expert to discuss these things.
Comment: it would be good to explore the other limiting case - beams 90deg to Sun line - slow to cover entire sky, but good angles for Q and U, and may be good for spectrometer, Kris asked Julian about simulating many pixels - Julian says have emulated 1,000+ pixels. Some discussion about half wave plate - haven't closed the door on this, but Amy doesn't think its likely a good fit in cost and risk for the single imaging telescope design (perhaps for smaller telescopes). Kris also wants to know how effectively polarization angles can be aligned and varied for current technologies, and what we know about correlated noise on multi-wafer experiments. Comment: need to define metrics by which we want to evaluate scan strategy options. Al notes spectrometer and imager treat 1/f drifts in time domain very differently. In spectrometer they don’t effect large angle pixel to pixel comparison the way they would in an imager. Kris notes he's willing to call in again if invited.
Raphael has slides “Theory update and plan”
Slide 2 are people who expressed an interest - different people interested in different aspects of the topics described in the following slides. Different people volunteered for different topics. There is not currently a telecom planned, or a dedicated wiki space - Lloyd recommends setting this up, and Amy notes that this can be done as a subpage in the public part of this wiki (as has been done for the “Imager Group.” Raphael notes that its maybe not good to talk about models that could be ruled out, but rather classes of models. Regarding summary slide, Amy notes that activities of first bullet will feed in to Science Traceability Matrix development, and activities of second bullet should be informed by some discussions in the technology area about what frequency bands we can defensibly propose (e.g. 25-600GHz). Some confusion about who is leading optimization of frequency bands. Shaul should help sort this out.
Lloyd has slides “New Working Groups and Data Challenge Plan”
See slide 1 - no objections heard to formation of Working Group 1, but Amy suggests this decision not be finalized until Shaul returns. Shaul will also talk about the Galactic Science working group when he gets back.
Regarding the Data Challenge, Lloyd will be in Berkeley Friday and has 1.5hr scheduled with Julian to talk about this. Some discussion about the purpose and content of the data challenge (which I didn't understand well enough to notate). Amy notes that it could be nice to have data challenge results in time for mid-October Payload decision (Imager only vs Combined mission), and that the target for defining the nominal Imager-only architecture to be used as the example for that decision point (concept including an optical design, survey design, focal plane bands/sensitivities) is mid-August, or perhaps early September. So running the data challenge in September might make some sense. And if there is a second data challenge, Amy suggests an appropriate time for it might be roughly February 2018, when we will likely be reevaluating/refining the instrument design. Also, then it could be timed to be followed close after by the community workshop.
Possible topics for next week's agenda