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

Attendees: Tom O'Brien, Bruce Atwood, Dan Pappalardo, Ray Gonzalez, Ross Zhelem, Jerry Mason, Mark Derwent, Jason Eastman, & Rick Pogge

MODS Optics

Ross reported on red corrector lens progress at SOML. The main issue this week is that overlapping CMM measurements were giving discrepant results. Tom suggested this looked like the part bent between CMM measurements, and Ross was able to reconcile two of the maps by including a cylindrical distortion term. A simple gravity bending calculation (support the 800mm part on the rim and let it sag) would predict about 6-microns of sag. The observed cylindrical term is about 4-micron of sag. The part is actually supported by a wiffle tree during CMM measurements, but if perhaps it was not put on right, you could plausibly get this much sag. Ross and SOML agree they need to understand this before rubbing more on the parent.

MODS Electronics

Dan reported that he has received the 15 Rev2 motor controller boards from the vendor. Each board is for 8 controllers. This is more than enough to equip both MODS (4 boards per MODS) plus a full 16-axis spare IE Box (2 boards) with ample spares.

The Calibration/AGW interlock minibox ha been wired up, and Dan needs to splice in the interlock cables.

Dan is investigating the calibration lamps, collecting the manufacturer's data sheets and looking at different power supply options.

MODS Opto-Mechanical Systems

Mark reported on progress with the MODS1 calibration system installation. This last week they got the calibration ring expoxied on, and will finish installing the mating bellows tomorrow. Once done, they are ready to mount the integrating sphere, which is awaiting delivery of the mask (end of next week?). 90% of the MicroLYNX low-level motion control programming for the Calibration Tower insert/retract stage is complete and being tested using the MODS2 Calibration Tower in the lab. The MODS1 Calibration Tower is already aligned, so it will be wired up in place on the structure next week (this is one of the rare instances in which we will do this - the reason is that it is already installed and aligned, and the wiring is simple enough to do without removing it from the structure, which would introduce a lot of unnecessary work).

The order for the enclosure parts went out last week and we should receive most of the parts by middle of next week. Dave Steinbrecher is currently making the custom parts for the remaining two enclosure frame joints, and should be done in time for the full parts kit to arrive from item. These will be sent out for anodizing as soon as they are done and fitted. Justin Randall will start work next Wednesday.

Tom has mounted the second blue corrector lens it is cell, and the cell in the test camera, ready for Ross to proceed with acceptance testing on Monday next week. Once this is done (1-2 days max) both lenses should be ready to send off for coating (assuming the 2nd lens passes, which is highly likely - trust but verify).

All eight of the HexTek mirrors now have their mounting flexures installed and we are ready to send off the last 4 mirrors (2 collimators and 2 camera primary mirrors) for protected silver coating for the red channels of MODS1 and MODS2 after the blue corrector lens testing is complete (one of the camera primaries is being used uncoated for those tests). Recall that all of the blue-channel mirrors (2 collimators + 2 camera primaries) have already been coated with Enhanced Aluminum.

MODS Software

Ray reported briefly on the results of last week's TCS working group videocon. Work still to be done of relevance for us is the software for rotator control. Ray has passed along our request for full control of the rotator, not just canned observational modes. Ray will also be going out to LBT later this summer to do live testing of the TCS interface code along with members of the Lucifer team.