Origins Space Telescope (OST)
Interim Report Review with STDT
|Purpose: ||To review and evaluate the OST interim report with STDT.||Facilitator/Host:|
Margaret Mexiner/ Spitzer Science Center
Telecon: WebEx Online
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|Review Team Comment||STDT Feedback |
|Science is oversold.|
- Should be careful with buying into predictions for spectrometer and detectors. Would help if we identify interesting spectroscopy (at 15 microns). Would show that we are superior (Johannes). Jonathan agrees that this is a good point.
- Student at Harvard may be able to provide some input.
- Reorganize bio-signature section for interim report and say that we are expanding on exoplanet case.
- May need to be softer about exoplanet case.
- Discuss other types of exoplanet science.
- Expand on exoplanet science outside of bio-signatures (Kevin).
- We can do a nice job on exoplanets (Jonathan and Tiffany).
|Is 4K needed and is 6K acceptable to science? Would this give us margin in the design.|
- Heard from Mike Dippirro and cryocooler expert. There is a sweet spot at cryocoolers at 4K. It is more complex to get to 6K then to get to 4-4.5K. 6K is the Miri temperature. Going above 6 is not good because of Julie Thompson effect. 8 K would not be in the sweet spot. The sweet spot is 4-6K.
- Less input power with 4-4.5K.
- 6K will be easier for massive cryocooler. Being up above version of temperature, it becomes harder to do.
- Possibly identifying this as a trade for Concept 2.
- 6K may make us background limited at 150 microns.
- Suggest looking at science cases that involve measurements such as these, and consider how much we will loose.
- Looking at constraining costs for Concept 2, this may be beneficial for constraining cost. The cost difference is unknown. Mexiner is taking this comment as good trade space in optimizing.
- Do we drift into regime of much higher technical risk if we baseline 4K for 6K. To go to 4K (has been demonstrated by Northrop) is not a big technical step. TRL5 to TRL 6. Main thing is input power needed- There are some more losses. Input power could be decreased by factor of two which would limit the cost solar arrays. Need about 24 standards
- Mechanical coolers are a shared resource in the observatory. 4K-6K was thinking to be a shared resource.
|Mission Concept 2 - Mentioned 5 meter but would a 6.5 meter be okay, and being smaller than JWST.|
- Think its a bad idea to be smaller. Being the same size as JWST with colder and longer wavelengths seems like a good solution. Asked about John Arenberg's action to check on this with Northrop.
- Should we modify the meter question for Concept 2.
- Field aperture for JWST would be 5.6 meters, its 25% bigger. Going to JWST would force OST to have a deployed primary or a bigger rocket (SLS). If we are just looking at copying the size of JWST we are only about 25% bigger.
- Does doing the same size but shaping it differently solve the psychological question (Mexiner).
- Discussion on having the same area as JWST solves the psychological playing field (Melnick/Leisawitz). Psychological factor of going bigger and concerns about cost (Leisawitz).
- Should justify that bigger since we've already discussed this, gain in sensitivity (Stephanie).
- In favor of cost cap, but if it is seen in community as bad , then that's something to think about.
- Finding that we can package a 5 m collecting area in 5 m fairing, but we may have to go to a larger launch vehicle. Proposed the question, whats more important staying on this side of the knee or considering the psychology factor. Have to design something now with notional launch vehicles, and cant predict what the launch vehicle will look like (Leisawitz). Could be close to breaking point of having monolithic primary mirror vs. something that has to be segmented and deployed.
- Going to anything bigger than 5m diameter, will have to have a deployable mirror. We are trying to put tohgether a mission that is executable today, this can be changed. We have to demonstrate mission capability that is available, and the path to get to technology that we need (Carter/Mexiner).
- Area argument is stronger. 7.2 is stronger but is sort of cute.
- Mitigate concern of knee/and psychological factor - Be just like JWST, make thermal design better. In terms of primary mirror, has same packaging scenario. Would benefit in the sense of having done this before.
- Aspect ratio 3.6 x 7.2.
- Keep telescope simple, and scale. Especially given the sensitivity estimate. JWST today is not the same as JWST 15 years ago. The size is not resonant but the psychological impact is a concern (Ennico).
- Melnick: Should scrub science cases and reduce them to a set of aspects. Whatever is released has to be well reviewed with regard to exoplanets, these are the major thrusts for Luvoir and Habex, and must pay particular attention to.
- Mexiner: Everyone is in the same boat.
- Armus: The way the interim report is written has the potential to backfire. Import to separate the requirements from Paul Hertz, may be happy with something of an order of a magnitude smaller, something smaller than 500 possibly. Whatever is released to public, should convey excitement.. Be very clear about what is required for HQ, then talk about what we are comfortable with releasing to the public. Want the community to learn about what we are doing and get excited about.
Questions Developed by Carter, Mexiner, Leisawitz
Mexiner presented overview of the sections included in the current interim report. Suggested indicating to the community that we are putting this out here, but we are still a work in progress. Re frame science cases for three, and throw the rest in discovery space. Split science into three questions (in describing the science cases)
- "How do ingredients and astrophysical processes change over cosmic time affecting properties and develipment of galaxies and black holes?"
- Simplify this question and make it punchier. Suggest to rephrase it as "how do they grow".
- Someone may not know what ingredients mean. Make the sub thing dust and metals. George has some very good comments.
- "How do the conditions for habitability arise during the process of planetary system formation?
- Should make them questions.
- Why do we have to continue with the last clause of the question? The measurements have to do with mapping out material and protoplanetary disks. Habitablity grabs peoples attention. Should maybe distill this down to something smaller.
- Following water is a major part of this questions. Water is a necessary ingredient for habitability.
- Packages habitability within planetary system alone, possibly remove habitability.
- Change it to "How does habitability arrive/arrise?
- Are we alone?
- Joqauin: Short is good. Makes one think about human life.
- Kevin: Very easy for one to make correlation to human life, short and sweet. Likes are we alone.
- Tiffany: How common are earth like planets.
- Is this something they think should be done as we compile our recommendations? Possibly.
- Include a section on discovery space, and should use a few things from the brochure.
- Roellig: Not thrilled with # three, should be rephrased to the suggestion of "how common is life?", or something else.
- Sheth: Other two questions are not in parallell with cosmic origins. Mexiner indicated that she has spoken with gravitational waves, but we aren't actually detecting gravitational waves. We were just looking at origins as dominated by core. Mexiner has inititatied discussions, and may not have something with the interim report.
- Ido Burger, a colleague of Melnicks, gave a colloquium that was remarkable. There may be spectral signatures that could be interesting. Suggested contacting modelers, they will say its beyond their scope or they may get back with us. Mexiner indicated that gravitational detections may shift out into the infra red, which may be possible.
- Sheth: There are things in black hole mergers.
- Must treat all other decadal surveys as if they are our team members.
- Suggested having Jonathan review the document.
- Sheth: Overview of what rough drafr HQ will review.
- Are science requirements described and flow effectively and efficiently, are mission requirements clearly stated, are cost requirements clearly stated.
- HQ wants to make sure we are on the right track.
- This isn't a test, HQ review is just a check in. There is no judgement.
- All the missions will be
Process for Revisions of the Interim Report.
Make revision to current interim report using the word document.
Is the rule of three going to be for the interim report or final report? We will be completely reorganizing the science section of the interim report. Mexiner will take a crack at reorganizing the document and giving it one voice.
Mexiner will be doing brutal editing.
Discuss version 2 at the AAS meeting.
Carter will follow the mission implementation section in performing her edits.
Version 1 = the current version which is comprehensive and long.
Version 2 = the reduced (i.e. 100 pages) public version of the interim report.
Dec. 15, revisions to version 1 – to be corrected by the primary authors of the section by turning track changes on the Draft Version 1 word documents now posted on the Confluence page:
|#||Action Item||Owner ||Due Date|
|1||Review the interim report.||Jonathan||12/15/2017|
|2||Settle on descion for reframing question #2. |
|3||Ask people to brainstorm (in recommending 6.5 or 5 microns).||Ruth Carter||12/15/2017 - 12/1/2018|