---++[[111018_Team_Meeting_4][<]]IRMS mini-Study Team Meeting #5 - Optical Design mini-Review [[111101_Team_Meeting_6][>]] Date: Tues, Oct 19, 2011<br> Time: 1pm - 3pm PDT<br> Location: Caltech, Cahill room 126<br> *Participation (tentative)* |*Attending*: Matthews, Weber, Dekany, Konidaris| |*Call-in*: Mobasher, Ellerbroek, Pazder | |*Unavailable*: Simard| *Dial-in* * (U.S. & Canada): (866) 217-1869<br> * Conference Code: 9147077081<br> * From China: 8008708911 (or perhaps 4006700523) *Agenda* * 1300 - 1310 Goals of this review - Rich * 1310 - 1400 IRMS optical design concept relative to MOSFIRE - Nick * [[http://www.oir.caltech.edu/twiki_oir/pub/TMT/IRMS/OpticalDesign/Optics_Design_Review.pptx][Presentation (.pptx)]] * 1400 - 1420 Optomechanical impact of optical design changes - Bob * [[http://www.oir.caltech.edu/twiki_oir/pub/TMT/IRMS/OpticalDesign/Mechanical_Changes_Required_Due_to_Proposed_IRMS_Rx_V2.pptx][Presentation (.pptx)]] *Minutes* * Rich described the goal of this meeting as assessing whether the MOSFIRE optical design approach can be made to work as IRMS behind NFIRAOS * There are many optical issues that we will need to address in the fullness of the project, but for now, should we continue with the current mini-Study, have we enough confidence? * Nick pointed out that MOSFIRE has been in construction phase for 5 years beyond DDR, when the design was 'complete' - MOSFIRE is a very difficult instrument to build * Nick elected to optimize for sharp slit images in spectrograph mode, allowing a blurred PSF to fall onto the slit, and with only a 'flip' of the CSU effective curvature (no change to radius) * This decision needs to be revisited in terms of slit coupling losses * John recommended that the full NFIRAOS model be included in Nick iterations in the future, to confirm results end-to-end * Initial ghost analysis shows the situation essentially no worse than for MOSFIRE, but there will in the future be more thought necessary about ghosting, the potential for persistence effects, etc. * Bob reported that the optical design changes recommended by Nick require only minor rework of the structure * The largest cost impact will be re-drawing the production drawings for the small dimensional changes. * Rich wondered if the changes are so small, should we forego the thermal study planned in this phase? * Keith pointed out the additional of an external OIWFS probe arm (if adopted as our design baseline) could be a larger impact to the thermal budget than the optics changes in the cryostat. * After discussion, all concurred the situation looked good, and the IRMS team should continue with the remainder of the mini-Study *Outstanding Actions* * Nick will parameterize a set of PSFs to be requested from Brent and the TMT AO team * Nick will then evaluate the differential impact on slit coupling losses of several design choices, such as sharp slit edge imaging onto the detector. * Also key is the question, is the potential benefit of re-engineering the CSU for a different cylindrical curvature (e.g. 5 slit levels vs. 3) worth even opening a discussion with CSEM? * Nick will included the NFIRAOS model in future design iterations, or at least verify the independence of results to NFIRAOS details (except for field curvature, which is essential).
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Topic revision: r7 - 2011-11-01 - RichardDekany
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