The Ohio State University College of Mathematical & Physical Sciences Department of Astronomy

Attendees: Darren DePoy, Paul Byard, Jerry Mason, Pat Osmer, Mark Derwent, Dan Papallardo, Jen Marshall, and Rick Pogge.

Mechanical

Tom has completed the tedious process of checking Paul's CodeV optical prescription against the mechanical design of MODS, hopefully for the final time.  He felt it was improtant to re-check this before releasing the MODS welding fixtures and upper frame for fabrication.  The last time this was done thoroughly was nearly 2 years ago and some changes have been made to the optical design in that period.

Tom is happy to report that there were NO changes that affected the MODS structure and that Paul's prescription and Tom's mechanical design are coincident to within 1mm everywhere.  He also checked Paul's prescription against the detailed build drawings for the optical components and no discrepancies were found.

There were small changes (<2mm) to the camera primary mirror positions.  These are accommodated by simply changing the lengths of the adjustable-length truss rods.

In summary, no real problems were found in this most recent optical to mechanical audit, and the small changes made to the optical design are now included in the mechanical layouts.

Optics

Paul Byard has completed a preliminary front-side AGW optical specification, given in this PDF document.

Steve Miller at SOML has reported the accidental minor damage of the sidewall of one of the camera primary mirror blanks during grinding the faceplate rectangular sides. There was no damage to the front or back plates. The side panels are fairly thin (a few mm), and so fragile. Steve is evaluating the piece to see if there was any effect on the surface figure, and Tom O'Brien will be evaluating the mechanical issues. SOML reported the problem promptly and has provided us with pictures. We await further developments.

Mark Wagner (LBTPO) and Rick have discussed the baseline order blocking filters for MODS, and will start by seeing if we can replicate the the filter set used in our Boller & Chivens CCD Spectrograph at MDM. These are Corion long-pass edge filters (e.g., LG350). Paul Byard has sent an RFQ to Corion for filters in our size (182x86mm), perhaps 3mm thick.

Flexure Control System

Jen Marshall has taken delivery of a pair of small visible-light and IR cameras for use in assembling the prototype flexure compensation system, as well as delivery of the fiber-fed IR laser, a fiber-fed HeNe laser (also to be used for optical alignment), a camera framegrabber board, computer, and various optics. These will be used to assemble the first full prototype in the lab. So far, the visible camera works great, but the IR camera (an identical CCD camera to the visible except that the CCD is coated with an anti-Stokes upconversion phosphor to convert IR photons into visible light for the CCD) does not appear to work. She's started iterating with the camera vendor (Spiricon) to resolve the problem. The phosphor coating is pretty cool. If we hit it with the IR laser at close range, we can see a faint green glow.