040916

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FourStar meeting, September 16, 2004, Pasadena

Present: Eric Persson, Tyson Hare, Stephen Smee, Robert Barkhouser, David Murphy, Dan Kelson (AM only), Alan Uomoto

1. Agenda
2. Presentation links
3. Actions
4. Notes

Agenda

Start at 8:30 AM

1. Introduction (5 min)
2. Optical system (Barkhouser 20 min)
3. Mechanical system (Smee 20 min)
4. Steve and Robert present their results on the tolerancing analysis (1 hr). We begin to write down those tolerances that we can, in anticipation of completing the RFQ to go to Janostech. [Q: can we prepare a template RFQ (or use an existing one) and mark it up during them meeting?]
5. Break
6. Steve reviews the overall concept/FEA work that he has done on the outer dewar and IR Labs dewar (Smee 30 min).
7. We begin to brainstorm the mounting scheme(s) for all the lenses. SEP likes the radial constraint concept that was protoyped at JHU recently. Perhaps we can invent an axial constraint scheme that involves invar metering; this would be in the main camera barrel. We decide the issue of whether or not to provide adjustments of the four lenses within the barrel. We try to come up with a scheme to hold the barrel within the outer dewar.
8. Lunch
9. Continue lens mounting and metering schemes, if necessary.
10. We review the concepts and designs that SEP has developed for the filter wheels and field-flattener wheel. We discuss and decide how to hold the FF lenses radially. (Axial positions will be set via machining/shims.) SEP needs help in selecting a set of angular-contact ball-bearings for all three wheels.
11. Break
12. Other topics:
• SEP's detector mounting/focus system
• Tyson's and Steve's thermal analysis of the window/lens doublet. How to proceed with the rest of the thermal analysis.
13. Schedule and action items for completing RFQ for Janostech.
14. Other action items.

Presentation links

Main presentation including mechanical flexure analysis, new camera design, and tolerance analysis (Powerpoint file)

Actions

• Eric will call Janos on September 17, 2004, to find out if 1/5000 tolerance or radii is OK. He will also set up a telephone conference for next week, Thursday September 23, 2004 so David, Steve, and Robert can learn what's needed for the optics RFQ.
• Steve will generate mechanical drawings of the lenses for discussion with Janos.

Notes

Steve Smee & Robert Barkhouser presented their view of the instrument. Barkhouser presented an optical tolerance analysis that showed no serious optical hurdles, except, perhaps, a few 1/5000 tolerances on lens radii. These may be difficult but we don't know what Janos can do here. It was also pointed out that only the detector BFD was a * llowed to compensate for performance; perhaps some of this radius error can be made up elsewhere (spacings, for example).

They also presented a prototype roll pin lens holder and reported that lens centration on this smaller part was excellent (fractions of a thousandths of an inch). They also mentioned that the outer diameter could be turned to match the center after the roll pins were cut.

Steve and Robert were tasked with designing the vacuum window lens cell.

A thorough mechanical flexure analysis was presented, concentrating on the dewar connection to the back plate. The test case of a 20 degree rotation showed reasonable flexure performance (a pixel or so motion) that was fine for a broadband imager.

There was some discussion about how to align the instrument and a number of ideas surfaced. This does not look like it will be a major problem.

Eric showed and demonstrated his detector array mount scheme.

There was considerable discussion about the cold shield inside the dewar, especially the part between the window and the front of the camera. It was decided that this part should incorporate light baffling as well and Eric asked the Steve and Robert to generate the concepts and some drawings for those parts. Eric and Tyson will perform the thermal analysis and iterate with Steve and Robert to get it right.