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

Attendees: Darren DePoy, Paul Byard, Jen Marshall, Dan Pappalardo, Mark Derwent, Jason Eastman, Ray Gonzalez, Jerry Mason, Bruce Atwood, Tom O'Brien, Pat Osmer, Ross Zhelem, & Rick Pogge.

Via video from Tucson: Mark Trueblood (NOAO/TSIP)

Yes, in fact, we haven't had a meeting since March 7...

New Team Member

Welcome to Ross Zhelem who arrived last week as our new optical designer. Ross comes to us from the Mount Stromolo Observatory (ANU), and is originally from the Ukraine.

MODS Optics

Tom reported on recent developments at SOML regarding progress on the MODS corrector lens figuring and other MODS optics. One of the main issues has been the optical testing setup at SOML, which could not produce fringes to the edges of the part. After some work with the current configuration, Jim Burge and J.J. Valenzeula have designed a reconfigured test and ordered a new holographic test plate that should allow a full aperture test. The assembly of the components and setting up the new testing system is in progress at this writing.

Steve Miller at SOML decided to send the MODS blue corrector parent to QED Technologies, Inc. in Rochester, New York, for Magnetorheological Finishing (MRF), and advanced computer-controlled polishing technique (see the QED webpage for more information). This work is going on in parallel with the efforts to assemble the new optical testing system.

Other news is that we have heard that work is beginning on the spherical side of the red corrector lens parent, and that work on the 5th and final Camera Primary Mirror is in progress.

With Ross' arrival at OSU, he will be taking over most of the oversight on the MODS optics progress at SOML for OSU.

MODS Mechanical Systems

Tom reported on progress in MODS assembly and testing. Currently they are working on the AGW stage hardware, writing up both of the X-axis drive systems, and then one of the Y-axis drives for testing. Tom has completed simple cold testing of both stage axes, after some rebuilding following problems with the original ball-screw mechanism. The new approach works better, and we will have some spare ball-screws to boot. The next big push is to assemble one of the AGW units, and get it going with the motor control system and begin integrating and testing the optics with the LBT-provided cameras.

MODS CCD Detectors

Bruce and Pat commented briefly on the on-going contract negotiations with e2v technologies for purchase of the 3Kx8K science CCDs for MODS. These are needed for MODS2 integration, and so far we are on schedule provided there are no big delays in the final contract steps.

Bruce did a little show-and-tell with one of the 4Kx4K CCD detector mounts. The system is a variation on a previous OSU theme of a set of PC board standoffs from the detector mount proper with our "bird cage" wiring design. Differences with the MODS4K version are use of a 6mm-thick block of Silicon "adhesively bonded" (aka, "glued") to the back of a gold-coated Kovar detector package. This design reduces stress on the CCD because the Silicon block has the same thermal expansion properties as the silicon in the CCD itself. Bruce acquired the blocks from a vendor who provided them as 4-inch round parts that a local shop sawed into the desired square shape. We did not have any luck acquiring Silicon blocks from the group at UFl.

The 3Kx8K packaging details are still being worked out, but they will be different, based on an Invar block that will come with a set of mechanical shims to precisely establish the distance to the active surface of the CCD, and mechanical connections machined into the back of the Invar block for mounting, cold straps, etc., much like other e2v packages.

Finally, Phil Covington (away today) has been making lots of progress on the Clock-Bias board for the MODS system. So far it looks very nice, and will include a lot of the new technologies described in previous reports. It may not be ready for the MODS commissioning 4K CCDs (though it is not needed for that system, it would be nice), but it will be online for the eventual 3Kx8K system.