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

Attendees: Darren DePoy, Paul Byard, Paul Martini, Jen Marshall, Mark Derwent, Jason Eastman, Ray Gonzalez, Phil Covington, Ed Teiga, Jerry Mason, Bruce Atwood, Tom O'Brien, & Rick Pogge.

Via video from Tucson: Tod Boroson (NOAO/TSIP), Mark Trueblood (NOAO/TSIP), Richard Green (LBTPO), Olga Kuhn (LBTPO), and Norm Cushing (LBTPO).

Personnel Changes

Ross Zhelem has accepted our offer to become our new optical designer. He should arrive in May.

MODS Detectors

Mark Derwent is working on the CCD dewar detector box for the first-light UA 4Kx4K CCDs, and doing the basic design for the final 3Kx8K E2V CCDs (we are still waiting the detailed mechanical specs for these devices). He has finished his checkout of the 5 dewars delivered by Meyer Tool in December. The outer vacuum shells have been sent out for anodizing: 1 black for the lab dewar, and then 2 each red and blue anodized. The dewars received include outer vacuum shell, inner radiation shield, LN₂ tank, and all the necessary fittings, electrical break-throughs and fittings for facuum gauges.

Bruce has been working on the MDM4K CCD, which is the prototype electronics for the MODS first-light 4K CCDs. He's been working on a Silicon heat spreader for the back, which should reduce stress compared to the traditional Kovar block. Bruce is currently working to procure a 5mm-thick piece of silicon for this. It was suggested that he get in contact with Jian Ge at Florida who has experience cutting Silicon and might have some pieces of the right size.

Phil Covington has finished the first post-amplifier board design. We expect at least 1 more revision before it is done, because it is a significant departure from our previous design. It has a gain stage and 2 complete video processing channels with 2-slope integrators and 18-bit ADCs. One of the big overheads in this system is resetting the integrating capacitor. The new 2-channel design lets you use one channel while resetting the other, eliminating most of this overhead. This staggered readout design will easily let us run at 300 kilopixels. Phil has now turned his attention to the clock-bias board, which is coming along nicely according to Bruce. In the end we will have electronics similar in overall architecture to what we've been using, but with entirely new aspects that will mean significant improvement in performance and flexibility.

Bruce attended a seminar run by Altera on their latest Field-Programmable Gate Array (FPGA), which includes a large number of very high-speed serial interfaces. This unit is a big departure from what we've been using, but the seminar convinced him it is what we want to use, and it will be straightforward to use it. Altera has been very helpful in giving us licenses for the unit itself, and offering hardware and a license for a PCI Express (aka PCI-X) interface. In fact, our new system will begin with a connection to a new Sequencer card designed around a PCI-X interface. This will replace our current ISA-based Sequencer which we will be happy to see go away. PCI-X is a 2.5GHz serial interface which lets you have between 1 and 16 interfaces running in parallel. This is really a "microwave" design by constrast with the more traditional digital logic design we've been using to date. Bruce believes that our application can avoid known pitfalls of this FPGA design, since we're in a regime where it should be relatively easy to apply the device. The PCI-X sequencer will not be implemented in time for the MDM4K system, but will be used for MODS.

MODS Software

Ray reported on the visit this week by Norm Cushing, the new software manager for the LBT project office. It was a very good visit. Motor control system is well on its way and the documentation is coming together. Basically Ray says he is ready for more hardware to hook up and integrate with the software, so the motor control integration can keep pace with the assembly and testing of the different mechanical components as each is brought together. Ray also reported that Alex at LBT has given him the computer hardware info he needs to configure machines for use with the IIF and TCS software interface simulators.

MODS Optics

Two more Camera Primary Mirrors have arrived today (#3 and #4) from SOML. Testing suggests they are better than the first.

The big item for discussion this week is the MODS optics progress at SOML. Pat and Tom went out to Tuscon at the end of last week to visit SOML for a review and on-site progress update with personnel at LBT and associated Steward personnel, specifically Steve Miller, J.J. Valenzuela (recent graduate of the Optical Sciences Center and now assigned to lead the MODS optics project), Jim Burge (helping with advice and internal consulting on testing and polishing).

The blue corrector lens for MODS has been in process for a very long time. Jim Burge has designed a new polishing tool that will help a great deal, able to remove a lot of material without destroying the figure it already has. SOML has made a lot of progress in the last year with using the Coordinate Measuring Machine (CMM) for profilometry - they can now do more and quicker tests, whereas before they had done only 2 diameters, and so were missing a lot of azimuth data. Overall they are still a factor of several (4-10) away from the specification and have a ways to go still.

SOML is also making an effort to improve the optical testing procedures which have been problematic to date. The null test designed by OSC has had a long history of problems (illumination, alignment, merging subapertures, correcting for geometric distortion, and corroborating optical and CMM test results, etc.). Many of these have been solved now, and Jim Burge has offered some very good suggestions on how to eliminate many of the remaining problems. We will be pressing them very hard on requiring them to demonstrate consistency between the two test methods, which has not been done in the past except by assertion. Jim's involvement will be a big help, and gives us cause for hope.

We will now be requiring monthly progress updates from SOML, in writing and by videoconference. Tom will be responsible for coordinating this for the time being, and then Ross Zhelem will take the lead once he arrives at OSU and gets settled in. We are supposed to start receiving monthly reports in April, when hopefully SOML will be able to give us an idea of the revised schedule for delivery of the MODS corrector lenses.

SOML is also working on the last (5th) camera primary. It's about to go on the machine, but it is not on the critical path with the delivery of the most recent mirrors. The 2 camera primaries we received today are much better than the first because they made a new, bigger polishing tool (factor of 2). The only problem with them is that the holes drilled in the back for the mounting system do not meet specifications for positioning tolerances. Nothing we can't work around. Still have administrative issues, as they did not notify us of the deviation.

Camera Primary #2 (first completed primary, #1 is a damaged optic acting as a mechanical sample for the IMCS testing) is setup with a mirror support in the lab. Tom is confirming experimentally that the mirror support system does not print through and distort the figure, so he setup a knife-edge test. The supports work just fine: you can't see the supports or any distortion or print through.