Foreground workshop dates are set to be Nov 29 to Dec 1. Location is UCSD.
Science and complementarity workshop: JC proposed to keep S4 separate from an April/May Probe and decadal panel meeting. And have S4 in week of March 5 to 9. SH says that could work if we have a day or day and a half for complementarity. JC and S4 are going ahead looking at a 2-day or 2.5 day workshop, really focused on governance. JC still prefers a two separate workshop solution. Julian points out benefits to having these two workshops right next to each other, with some overlap. Chair selected by end of 2018. Julian and Lloyd to discuss at CMB-S4 ICCC meeting next week and report back.
Spectrometer decision steps forward: Al needs to transfer to Amy an entire set of engineering specifications and cost estimates. Then Amy can provide downscope impacts for Imager. Then we figure out how Imager science is impacted. Then we can make our decision.
Al has given engineering specifications to Amy, but is awaiting authority from GSFC to provide cost estimates. He and Amy are in communication. Amy is asking about the orientation of the spectrometer. She has looked at the technical information that they have (mass, power, data rate, thermal env. requirements, radiation tolerance, dimensions, moving parts, deployables, …) and they have not identified any immediate showstoppers or problems. what will take some time to investigate: the thermal needs and how do we accommodate them, and cost.
SH: when we talk about descoping the imager, it's not so much the volume but the cost impact on what's left for the imager. What are the major cost-drivers of the spectrometer? Amy: we don't have a cost yet. It's not a small amount of money to pay for the spectrometer. We're not going to be able to pull that out of a single element of the imager. We have to imagine a much smaller imager if we have a spectrometer too. SH: when do you need the cost? now? within 2 weeks? I want to know what to convey to Al. AT: we're late at really getting into this. we've been talking about it for months. I'd like to get it as quickly as possible. We're not sitting on our hands yet. But it's important context for us. SH: if you get it today or tomorrow, when do you think you can come back to us and say 'here are the impacts' AT: Providing rough guidance could come pretty quickly. Some weeks before one can turn that into mirror sizes and number of detectors on the focal plane. About a month. We're driving to have the derivatives of cost wrt technical capability in place. SH: if we want to do this by around mid October. If you get the cost, is it realistic for us to say, within a week, e.g. spectrometer is $50M, and we can do it if imager is modified in this, roughly speaking, way. AT: yes, we can do a rough analysis like that in a week or two, and then continue to develop it.
SH: we need the information probably by Monday. Then a few days afterwards we'll get together with Amy and Brian, and the next week give a rough sketch to the EC. Then in one more week get guidance from the EC. AT: sounds good.
SH: if the tradeoffs still look reasonably compelling then we go to the instrument teams.
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Includes risk factors, relevant papers, mitigation strategies, and simulation capabilities.
Coming up: what kinds of questions do we want to get answered for the report?
Julian: we do a lot of that in TOAST.
Brendan and Julian will talk.
SH: has anything came up that will impact design of the mission? BC: far sidelobes may be at the top of that list. PUshes for more baffling, fewer reflections, … but tend to make the spacecraft bigger.
SH: we talked a bit today about 1/f. HWP? Of, if 1/f is driven by systematics then baseline a… [I missed it.] We're looking for big coarse decisions. BC: I don't think at this point we've hit anything that points to requiring HWP. BC: not so scared by bandpass mismatch as much as optical things like far sidelobes.
BC: the thing about sidelobes is I feel like no one's quite got it right yet, with space missions. Everything with a risk factor greater than 2 will have to be dealt with somehow.
SH: next step is what of those items that are the highest risk can we do anything about, and that will impact the probe design and what are the things that are important but will take longer to work on, that are beyond the scope of this probe study.
BC: repeating back. WE want to identify the most likely to be the limits to this mission. Pick out some to go into over the next few months based on where progress can be made.
SH: yes. Let's take side lobes. Is it a fundamental limitation for us? I dont' know. But we do want in the end to say “1/f, beam mismatch that can be potentially be dealt with with wave plate or scan strategy, we have checked and we can deal with them.” But SH is worried side lobes are too hard to deal with. BC: maybe we can think of clever ways to place constraints. AT: There are already several things listed in this table that should be impacting our design, adn the way we are prioritizing effort on the design.
SH: when table is complete, come back to the EC with suggestions of what to work on more. BC: I hope that will happen in two weeks. We report to EC.
Data challenge: Shaul, Lloyd, Julian to touch base off line about how DC and FG workshop, and all ties together.