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

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

MODS Enclosure

Mark reported on enclosure design progress. The hexagonal (top) section framework for miniMODS is now done and ready for paneling. The structure is nice and stiff with all the fixtures in place, validating the basic design. Work remaining to be done on the prototype includes testing edge tape materials (the leading candidate is aerospace polyethylene used on airplane wings) and testing the light seals and gaskets for the various overlapping regions.

Tom is working on detailed AnSys analysis of wind loading and evaluating the need for cross-bracing inside the large (5x7-foot) hexagonal section panels. So far the self-weight tests work out OK, and he is beginning the wind-loading analysis.

Overall there are a couple more weeks of work remaining, then about 1 month to get the order together (lots of parts) for item and with shipment we can expect to have most of the final enclosure parts in hand in mid- to late-May, and fabricate the enclosures for both out at the West Campus "birdhouse" facility.

MODS Instrument Electronics

Dan reported on progress with the MODS instrument wiring and electroncis. Finishing the wiring on the first Instrument Electronics Box (IEB) took 3 weeks as predicted. He has tested all 4 of the MicroLYNX controllers that have the extended I/O boards by modifying the dummy mechanism to include 6 additional mechanical switches. Proper Base I/O for all 16 controllers and extended I/O for 4 controllers of the 16 is now confirmed.

Ed has finished with the grating select wiring and tested it, and they are now fabricating the wiring harness that goes through the center hole for the grating tilt mechanisms. A program to exercise the grating select mechanism to test the harness is done. A second copy of the grating select mechanism for MODS1 is now staged for wiring after being removed from MODS1 in the basement shop.

Dan is working with the WAGO fieldbus controller to verify all of the outputs for the MicroLYNX power resets using the ethernet-based applet provided by WAGO. He has ordered new software to operate the fieldbus controller via its serial interface (the operational MODS uses the ethernet interface) to facilitate bench testing independent of the instrument network. One of the WAGO relays has been wired and tested, and Dan will now proceed to wire the remaining 15. The telemetry for the power sections is tested and working and Dan will add an RTD to provide a test temperature readout. When it is done in about 2 weeks, he will turn it over to Ray for network configuration and testing with the instrument control system software.

Work ahead includes the grating tilt mechanism wiring harness and tests, work on the Rev2 printed circuit board for the final IEB motor controller system (the current box uses the Rev1 prototype), and starting on the design of the Quad ADC printed circuit board for the IMCS quad cell.

MODS Optics

Ross reported on various optics progress over the Spring Break.

Dichroic

CSIRO continues to work on the the Dichroic. They've asked for and received an extension on projected delivery until late May, which works fine for our schedule since the dichroic is not needed until integration of the red channel.

Red Corrector Lenses

SOML reports that they have finished the figuring of the spherical side of the corrector parent, and have provided a surface map. Ross is reading their test report and verifying their estimate of the structure function they have satisfied the structure. The data consist of CMM measurements taken in 30mm steps over the 840mm diameter of the parent under reasonably stable temperature conditions (they took our suggestions of stabilizing the temperature environment of the CMM before undertaking the test). They now get 3.5-micron agreement along the horizontal axis compared to >10-microns before.

The data reveal some asymmetries like those we saw in the blue corrector, so their process is at least consistent if not ideal. They want to continue working with loose abrasive to correct this before switching to polishing, which make sense. The asymmetry appears as a planar break across the parent which makes for a 5-7 micron mismatch from one side to the other of the "break". Having this makes doing a full-aperture interferogram problematic during optical testing.

The retrosphere to be used for optical testing has been characterized. They borrowed a fast (f/2?) interferometer for the tests, and are attempting to compensate for astigmatism by additional loads on the retrosphere wiffle tree. The problem is that this has resulted in a surface which varies in time. They need to determine the cause (thermal mismatch between the glas and the metal wiffle tree?) and correct it before the retrosphere is useful as a reference optic.

Blue Camera Testing

Ross and Tom continue to work on acceptance testing of the Blue Corrector Lenses using the camera alignment system in the lab. So far they have made excellent progress, validating their measurement techniques. The current tests are designed to test the corrector lenses. Jason is working with Ross to measure the test images for FWHM and D80 both on and off-axis. Initial indications from the on-axis measurements are very promsing, and will require another week or so of work, including off-axis measurements, to complete the acceptance testing of the first lens.

MODS Detector Systems

Bruce has doing cold testing of the "black" dewar reservoir without the detector box, and with the reservoir section instrumented with RTDs. The radiation shield temperature is great, about 220K, and the gas cooling is definitely helping. The surprise so far is at the bottom of the LN2 tank where the temperature is 110K on the dry side while it is 77K on the "wet" side. He expected 85-90K, and is investigating this. Boil-off rate is about 4cu-ft/hour (8 Watts) via a coarse measure, and no leaks have been detected.

The detector box is ready to receive the 4Kx4K CCD mount package with 2 RTDs glued in for thermal testing w/o a detector proper. Bruce still needs to iterate on the "bird fence" printed ciruit board, and should be ready for cold testing at the end of this week or start of next week. These tests will let us know how cold the current system can get the detector, and how long it takes it to get to operating temperature.

Bruce and Phil are putting together an old-style Head Electronics Box (HEB) that Phil will use to test the new digital electronics in various configurations.

Phil has finished making the cables needed to test the PCIx development board, and is in the process of writing the test code. They have all of the hardware they need to go from the PC with a PCIx card installed via fibers to the Rx board in the HEB, from there to test clock-bias boards of both new- and old-style using the PCIx I/O.

Regarding the final science detectors, e2v has sent a progress report. They should have a mechanical sample with full wirebonds in about 4 weeks, and Bruce is currently iterating with them on the final spec for the electrical sample.

MODS Telescope Interface

Tom attended an LBT rotator design review in Tucson last week. The engineering team is working nearly full-time on the direct and bent Gregorian rotators. They set themselves an ambitious schedule to be done in the October/November timeframe. We will need to coordinate with them on delivery of the rigid secondary. Progress on the rotators is very encouraging, and Tom will continue to work with LBTO on this.

MODS Software

Ray reports that he has made a lot of progress renaming various package elements, and starting to work on the first IEB interfaces. He is all ready to start work with the IEB and actual mechanisms as soon as Dan can release the box to him. Over the next week Ray and Dan will work together on the final tests leading up to handoff to Ray.