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, & Rick Pogge.

Brad began the meeting by announcing to the MODS Team that effective Feb 1 Rick Pogge will become the Vice Chair for Instrumentation, and that because of Pat Osmer's departure to become the dean of the Graduate School, Rick is now the PI for MODS effective immediately.

This is our first regular team meeting in a while. We will be holding regular team meetings (every 1-2 weeks as required) from now on as we enter into the integration and testing phases of MODS1.

MODS Optics

Tom reported on MODS optics for Ross Zhelem who is away this week. We had a videoconference with Steward Mirror Lab (SOML) last week. The first blue corrector lens is cut and ready to ship, the second requires some finishing and should also be ready to ship within a couple of days. Once Peter Strittmatter gives the go-ahead, we should receive the blue correctors within a couple of weeks. They are also done with the last of the camera primary mirrors (redrilling was required on the mounting points).

The Red Corrector lenses are in progress, but we don't need them right away. SOML reports a 2-3 month slip in their original schedule so a conservative estimate is that we will receive them in June(?). Ross continues to monitor progress weekly with SOML personnel, and we continue holding monthly videoconferences to keep abreast of overall progress.

With the blue correctors finally in hand, we can plan the assembly of the first MODS camera and get it optically aligned. This is a big milestone for the project. The initial alignment will be done with an uncoated corrector lens and camera primary, and after we have made good images, these will be shipped to Newport Thin Films for coating.

Tom and Ross are getting ready for mounting and testing the optics when they arrive, and Mark and Ross have designed an adapter for a small CCD camera to use for making test images at various locations in the camera focal plane. Ross has various parts of the optical test setup in hand and will be assembling the test rig in the student lab optical bench in the coming weeks.

In other optics news:

• Ross visited Newport Thin Films in California last month to check on the blue reflection coatings for the blue channel mirrors. The coating is not as good as their original theoretical projection for enhanced aluminum, but it is still better than bare aluminum over the relevant wavelength region and we will go with what they can deliver, and the overcoated aluminum will be more durable and stable in the long run. Coatings have so far only been done on witness samples before we give the final go-ahead on the mirrors themselves.
• Ross received the first witness samples of the dichroic from CSIRO. To recall, our dichoric is a blue-pass/red-reflection dichroic with a cross-over wavelength of around 550nm. The witness sample was measured in our lab at its 30-degree operating angle. The blue part of the spectrum had some problems that made it less efficient and had some nasty bumps. Ross and CSIRO have reviewed the measurements and they are going to modify their process and send another sample. We hope this will converge quickly. Note that this is a challenging coating to produce and we expected iterations (which is why we're working first with witness samples), and projections are favorable to achieve a coating that will perform to our specifications.

MODS Mechanisms

Tom reported on MODS mechanism status. Right now there is a lot of wiring going on. We are about 2/3 of the way through wiring up mechanisms for both MODS1 and MODS2, with the most difficult systems (the slit mask system and focal-plane assemblies) still to come. The most recent suite completed are the 4 camera shutters. All have been wired, verified, and life tested and are ready to go. We can operate them under software control, and directly via electronic triggers from the detector head electronics system.

Very little fabrication remains except for the enclosure (report by Mark below). The main tasks ahead are mounting the large optics, prisms, and all of the red optics.

The focus ahead will be on assembly of the first blue camera and making images. We will need a graduate student to help with data analysis once we get to the optical testing phases.

MODS Software

Ray reported on MODS software progress. Most of the main mechanism control modules and the interprocess communications and event logging system is done and documentation is nearly complete. It is now ready to starting bringing mechanisms online one-by-one during the assembly and testing phases.

Control computer has been purchased and is becoming an operational system. The system install scripts still need some work, but progress is good. Ray is not in the process of integrating all of the components of the system.

Ray, Jerry, and Rick have been continuing to work with the LBT software working group, attending monthly videoconferences, and contributing to development of the telescope instrument interfaces. We successfully got a working TCS simulator system running after many problems and false starts, on both the LBT and OSU sides (firewalls are not always your friend), and have begun development of the MODS interface software using the LBT IIF libraries. A prototype IIF interface agent was successfully compiled this morning, and testing with the local LBT TCS simulator will proceed over the next few weeks. A use-case analysis of the MODS/TCS interaction is in final draft and will be sent to Norm Cushing at LBT tomorrow for review by the software working group at the February videcon.

MODS Instrument Electronics

Dan reported on progress on the MODS instrument electronics. All of the large orders are complete and delivered. We have about 100 MicroLYNX intelligent stepper-motor controllers in hand, and have modified the first set for inclusion in the first (of 4) 16-channel instrument electronics (IE) boxes. The modification is to remove the cooling fan and machine a vent port in the cover, since we have our own heat management system for the IE. Assembly of the first IE box is proceeding very well. Dan expects to have one axis up and running fully this week for testing of all the wiring, power, etc., and once that work is complete he will proceed to bring up each of the other 15 axes in turn. A second revision of the printed circuit boards is expected from this exercise, and rev2 boards will be used in the next 3 IE boxes (as well as retrofitting the first box as required).

The next tasks are incorporating the non-mechanism electronics into the IE box, starting with the IMCS laser controllers, and to begin working on the lamp and other non-mechanism electronics packages.

CCD Detectors

Bruce reported on CCD detector status. An observing run in November at MDM with a 4Kx4K CCD from the same batch as the 2 first-light MODS 4Ks revealed a problem with the device. Mike Lesser examined it and found the QE was 70% instead of >90% as when it left his lab, and other problems had developed. Bruce sent him the 2 MODS 4Ks for checking, and these had similar problems (though we are still awaiting a detailed report from Mike). We have a new 4K that doesn't work in MPP mode (which we don't care about) that Bruce is going to be testing in the MDM4K system, and then we will proceed to decide what to do for MODS. It is not yet a critical problem, and Bruce remains on top of things.

e2v say they should be delivering an electrical sample to us by end of May of this year (this is about 1 month late), but that it will be a back-side thin device instead of the originally planned front-side thick device for electrical testing. This is OK by us. The delays are not critical.

Bruce's current work is on thermal management of the detector electronics boxes. He has it down to about 110W in the current system, most of which will be taken off with the LBT glycol system. These boxes are nestled inside MODS, and so we don't want any heat leakage into the instrument. He has ordered samples of an aluminum-clad foam insulation material that looks particularly promising for the head electronics box enclosure. Some issues remain, but so far everything is on track.

Phil Covington has finished work on the clock-bias and post-amplified boards from the MkIX detector controller system. These incorporate the new dual-channel ADCs. These have been tested and are now being integrated into the head electronics box. He is now turning to working on the digital electronics using the demo boards from Altera. Unlike our earlier fiber-optics system, these are 2GHz tranceivers and run with higher power. Part of working with the Altera demo board is learning what does and doesn't work, and Phil has made excellent progress understanding the Altera programming. We will use the demo board in the first working systems.

All of the dewars have been assembled and various rework required has been finished by Dave Brewer. These are now ready for testing. Mark and Dave have completed all of the work on the 6 detector-box sections of the dewar all of which were built in house.

Detector system tasks coming up:

• Finish the power supply design and get the long-lead time parts ordered.
• Start vacuum and thermal tests with the Black test dewar.

MODS Enclosure

The last big design problem for MODS is the light-tight enclosure for the instrument. Mark Derwent reported on progress, which has been considerable. They have purchased ITEM construction parts and are assembling a 1/3-scale model of the enclosure in the shop, affectionately known as "miniMODS". The top section will be a hexagon, mating to a dodecagon for the long collimator section. Current concept for the panels is to use 15-mil aluminimum with a polyethelene fill - it looks like aluminum sheet and plastic corrugated cardboard, but is very strong and has good weight and thermal properties. It is a commonly used construction material. Test pieces have been ordered from a vendor for evaluation with miniMODS in the coming months. Most of the expensive joint parts in miniMODS can be recycled into the full enclosure. The IE boxes and head-electronics boxes all integrate very well within the current design and present no problems.

Analysis of the current design for wind-loading and self-weight models are very promising, so progress has been excellent. The remaining challenges are working out ingress points and keeping the weight in control. There is still a lot of work to do, but things are going great.

MODS Slit Masks

A document describing the MODS mask cutting requirements was given to Mark Wagner at LBTPO in December. Dave Thompson at LBTPO has been tasked with combining the MODS and LUCIFER requirments into a mask cutting machine requirements document and overseeing the procurement of the machine for LBTO. They should be issuing an RFQ soon. The main challenge is that MODS and LUCIFER use different mask materials, and both planar and spherical blank shapes.

We have ordered 50 Nicoloy blanks from NiCoForm of Rochester NY for testing for MODS. These masks will be coated. Tom also inquired about larger unit orders, the projected cost of a 200-unit order is approximately $115 per mask. In about 6 months we will be far enough along with working with this material to begin discussions with LBTO about ordering blank mask supplied.

Paul Martini has agreed to be the lead on the mask design system, and to help with estimates of our "burn rate" for masks to help LBTO plan for maintaining supplies of blanks.