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

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

Optics

Ross reports that SOML is continuing work on the red corrector, and his next major teleconference will be after next week's OptiFab meeting in Rochester.

Last week we had a videocon between OSU and SOML (2007 May 2) to review the map of the red corrector lens parent aspheric surface. SOML has accepted Ross' re-analysis and map of the surface as the basis for subsequent rubbing to correct the obvious high spots. They will start with a test region in the middle of the piece (away from where we will ultimately cut the lenses from the parent). The goal is to remove 2-microns per rubbing session and then measure progress with the CMM. Once this rate of removal is verified, they will proceed on to try to remove the 7-micron ripples in the parent, using Ross' solution as the hit map. After each processing run, we will receive the raw CMM data for analysis, and then iterate with SOML personnel on the next steps.

Ross also reported on his design for the exit port window for the calbration system integrating sphere. A clear fused-silica optical flat without AR coating will be used to cover the 100mm diameter port on each integrating sphere. A circle made of either delrin or metal to create the center spot mask. Ross will be seeking quotes, and iterating with Tom on the best option for the mask material.

In order to pass light from the IMCS IR laser to the quad cell in the detector focal plane, a hole has been drilled through the filter wheel above each filter position. To prevent visible light from passing through this hole onto the CCD, a small IR filter that passes laser light but blocks visible light will be used at each location. For 2 channels in 2 MODS, this means we need 32 such filters. Jason and Ross finished testing of samples of visible-blocking filters, and have identified a vendor. Ross is seeking a quote for purchasing 32 filters plus spares and will make up an order on his return from OptiFab.

Finally, we have received revised quotes for the corrector lens AR coatings from ZC&R, and for the protected silver coatings for the remaining MODS mirrors from Newport Thin Films. Ross needs to finish acceptance testing of the second blue corrector lens before sending both to ZC&R for coating, and we need to clear space on the optical bench in the downstairs lab to install the mounting flexures in the mirrors preparatory to sending these to NTFC for coating.

MODS Electronics

Dan has finished work on the Rev2 motor control board, including all of the cleanup work and the reset relay position. After testing he has decided to adopt the automotive relay as the most robust solution for the MicroLYNX motor reset circuit. He also has spaces for the "crazy controller" components, which in the first iteration we will simply jumper across before committing to a specific solution for those components. He has ordered 15 boards (each board controls up to 8 motors), as well as ordering components needed for 10 copies. This will equip both MODS (4 boards/MODS) plus a complete spare IE Box. He expects a 2 week turnaround including shipping. He has also ordered the frame kits for the IE boxes from item, and will need some shop time to have the various panels for the IE boxees built.

Dan also reported on lifecycle testing of the grating select mechanism pass-through wiring harness for the grating tilt mechanisms. Both concepts passed with flying colors, and we have adopted and are making up the nylon-sock version. Ed will wire up one complete Grating Turret, and then turn to making more 15-foot cables for lab testing with the 16-axis box before wiring another turret.

Dan's next major task it to spec and design the interlock cable for the Calibration Tower/AGW Stage interrupt relay interlock.

MODS Enclosure

Mark reports that he is nearly done with the CAD drawings for the MODS enclosure, and will make up the bill of materials for the first orders next. Dave Steinbrecher has installed 4 of the 6 sides of the fixed hexagon ring on MODS1, with the last 2 portions being the most challenging modifications to deal with mechanical interferences with the mounting spheres and structural members. Dave is making the custom mounting blocks and should be done later this week.

The next task on the enclosure is to finish work on the prototype and complete light testing and then clear it from the downstairs lab. They want to do one more procedure run with the 2-panel removal process to complete the full-size design.

MODS Detector Systems

Bruce reported that he encountered some unexpected issues with the procedures they'd worked out for mounting the field flattener lenses on the detector box (reminder: the camera field flatteners double as the dewar window for the CCD detector system). Work with the mechanical sample had problems and cracked the part. We know what is wrong now, and so won't risk destroying the good windows.

e2v Technologies has sent us the mechanical sample of the 3x8K devices, we should get them soon, but not before Bruce departs for Chile on May 18th (back May 31).

MODS Software

Ray is concentrating on the LBT TCS interface, working to a new interface control document from LBTO, as well as working on procedures for using the 16-axis IE box testing coming up. In particular, he is working out testing protocols for simulating mechanism collisions without actually letting them hit in the lab (i.e., setup the mechanisms with the flight wiring physically well-separated, and then work through failure modes with the software and hardware interlocks between overlapping mechanisms).