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

Attendees: Darren DePoy, Jen Marshall, Pat Osmer, Mark Derwent, Dan Pappalardo, Jerry Mason, Paul Byard, Tom O'Brien, Dave Steinbrecher, Dave Brewer, Ralph Belville, Bruce Atwood, and Rick Pogge.

Paul reported on the current state of the MODS optics fabrication.

Steve Miller at SOML sent us a more detailed report on the accident back in September in which the MODS blue camera primary was damaged by a ball bearing being dropped onto the spherical surface of the lens from a height of 1.5-meters. The ball bearing bounced around on the glass, leaving deep (0.015-inch) "dings" in in the surface. Apparently work was being done above the lens on a mounting for some test fixture without proper safety precautions to protect the optic below.

They report having some trouble re-assembling the test reing, but are going forward, and do not yet have any post-accident measurements of the figure of the lens to report yet.

One of our options is to refigure the spherical surface of the parent to make it thinner by 0.5mm or so and polish out the dings. Paul's preliminary analysis with Code-V suggests that this could be done without impacting on the performance, and in fact it might even lead to marginal improvement in the error function for the optic. We could also cut and then repolish, but we need to fully explore the implications and issues before deciding on a course of action.

Camera Primary Mirror #4 was damaged during finishing work on the mounting bosses located in the midplane of the mirror support structure. One of the bosses was fractured, apparently be a tool failure (a tool that was used too much). We have decided that mechanically we cannot trust this mirror, so we are going to send out our spare (#5) Camera Primary mirror which is defective, but annealed so the defect won't cause problems, and have SOML polish it to spec to stand in for the now rejected Camera Primary #4. Camera Primary Mirror #5 has been generated and edged already, and it still needs fine griding and polishing. We have also asked SOML to edge the damaged Camera Primary Mirror #4 so we can use it as an engineering a test piece, and to flow UV epoxy into the cracks to stabilize it. We expect to take delivery of the pieces by the end of the year.

Finally, we have received two of the three coating quotes we have out for bid. These are for the AR and reflection coatings for the MODS optics.

Mark has ordered parts for the Calibration System tower from the shop in Worthington, we should see these in November. The new Grating Select Turret gears are done in the shop downstairs, and the machinists are doing the thread generation now. Tom has the other half of the calibration system (the light baffle and optics mounts) about ready to go out for bid.

Tom reports that the multislit mask assembly is coming together nicely in the lab downstairs. The insert/retract mechanism works great. The mask select mechanism has been tested with a full load with the brake and they're making good progress.

The parts for the AGW camera stage are out for fabrication at COW, and all purchased commercial parts have been received. The remaining tasks are to finish detailing the focus mechanism and guider field stop, then the next steps are to completed the designs for the optics and camera mounts, and finally the AGW filter wheel. We already have the first set of optics received (these are purchased lenses).

Darren reports that the contract for the TSIP grant has been signed with NOAO, and we can start spending money. He is now working to coordinate the TSIP and LBTPO reviews into one (to save everyone time). The first joint review may be in January or February of 2005 (December may not work for all parties).

The remainder of the meeting was devoted to a discussion of non-MODS instrument issues that need to be reviewed.