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

Attendees: Bruce Atwood, Phil Covington, Paul Martini, Jerry Mason, Tom O'Brien, Mark Derwent, Dan Pappalardo, Ray Gonzalez, Ed Teiga, Dave Brewer, Dave Steinbrecher, Brad Peterson, Ross Zhelem, & Rick Pogge.

Rick began the meeting with a brief slideshow and report on his recent observing run at the LBT as part of the initial Science Demonstration Time for the LBC blue camera.

MODS Optics

Ross Zhelem reported that all of the blue channel camera-primary and collimator mirrors for both MODS have been successfully coated by Newport Thin Films. Because a lower temperature process had to be used, the enhancement possible with dielectric-coated Aluminum turned out less than usual, but still better than bare Aluminum over the wavelength region of interest for the blue channel (330-650nm). Newport is currently re-making the shipping crates so they can send us the optics with the coated surfaces properly protected, so we expect 2-3 weeks for delivry. They will send us pictures of the packing process, and will palletize all the crates so they are protected from tipping.

The blue corrector lenses have been finished and packed by Steward Mirror Lab, and are ready for shipment. We are only awaiting the authorization to ship from Peter Strittmatter pending payment of the delivery installment on this part of the order. Included in this shipment will be the final camera primary mirror with the repaired mounting fixtures.

Ross reviewed again the status of the dichroic coating witness sample returned by CSIRO, and reviewed other possible (and more expensive) options if we decide to go to a different vendor. This is a challenging coating, and Paul and Rick have been tasked with reviewing the available data and getting a recommendation to Ross.

Ross has most of the parts he needs for the optical alignment system, and will begin assembling it on the optical bench in the student lab next week. We first need to clear out the AGW camera alignment test setup and clear some space. Rick and Ross (who did the AGW work) will take care of this by Monday next week.

MODS Electronics

Dan Papallardo reported that he now has 4 channels of the first 16-axis instrument electronics (aka "IE") cabinet up and running with our dummy mechanism (consisting of a motor, 5 position sensors and a "brake" relay), and is proceeding to wire and test the remaining 12 axes. A few of the axes require additional I/O modules on the MicroLYNX controllers, and after a brief discussion, Dan will equip the last 4 axes in each IE cabinet for extra inputs so that there is excess capacity if needed. If a mechanism does not need the extra inputs, there is no penalty for having the module installed on that MicroLYNX controller. Dan should be putting in a shop order for the cabinet back plate, which he is drawing up and will give to the shop early next week.

The next mechanism to be wired and tested is the grating select turret. This consists of a rotator plus the wiring for two grating tilt mechanisms, which are wired onto the moving part of the turret using a pass-thru pigtail. We will only wire the MODS1 turrets (blue and red) at first, to make sure this all works before committing it to MODS2. The worm drives are already wired and ready to receive the pigtails. In the baseline MODS system, only 2 of the 4 positions will have grating tilt drives, the other two being fixed-tilt mounts for the imaging flats and double-pass prisms.

MODS Enclosure

Mark Derwent reported on progress on the MODS enclosure concept. They are very close to finalizing their design options using the item MB modular building kit system, and are currently working on the issue of the removability of the panels to best enable servicing. In the current design, we have a top hexagon structure, any two adjacent frames of which can be removed as free-standing units to allow us to remove an entire camera assembly, leaving the frames with the IE cabinets on the instrument. This gives us very open access to the guts of MODS without having to disconnect the mechanism controls.

We now have samples of the panel material, which is a commercial exterior sheathing made of 0.013-thick aluminum sheets bonded to corrugated polyethelyne between. Mark is looking at how to configure the panels for putting in access ports and the like that give access to key components without necessitating removing an entire panel. We will also be using the samples to evaluate its mechanical properties.

The remaining issues are working on the best way to implement the transition between the top hexagonal part of the enclosure and the dodecagon for the collmator foot, and testing gasketing options for making the enclosure light-tight. We have already learned from the 1/3-scale miniMODS setup that the item stock fastener counterbores create terrible light leaks, so we are using a different fastener that avoids this problem. Without doing this kind of scale prototyping, we would never have found such problems in advance, validating this approach to the enclosure design.

So far the concept Mark has been working with is extremely promising, and we are proceeding to a final enclosure design in the coming month. Everyone who can should come and look at miniMODS as it comes together, the enclosure looks really sharp.

MODS Software

Ray continues to work on the package build for the low-level mechanism control interfaces, and has been working with the first version of the IIF test client. Other work has been to collaborate with Dan on the power management hardware and software for the MicroLYNX controllers using the WAGO rely blocks. This will provide MODS with the necessary remote warm restart capability for each motor controller unit, either individually or all together.

CCD Detectors

Bruce reports that he has received the interface documents from e2v technologies, and so we have sent (are sending through the purchasing bureaucracy) the first progress payment for the MODS 3x8K CCDs. The interface documents Bruce received were characterized by him as the most complete he has ever seen for any CCD detector.

Other than that, Bruce continues to work on the thermal management of the head electronics boxes for the CCD controllers, primarily evaluating various options for thermal insulation for the boxes (pink antistatic foam, rigid foam board with aluminum-foil sheating, etc.). He should have a final choice soon.