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

Attendees: Darren DePoy, Jen Marshall, Paul Byard, Tom O'Brien, Amy Stutz, and Rick Pogge. All the rest are off at Rickenbacker working on the Aluminizing setup.

This is our first meeting after the Summer quarter. We held no MODS meetings, except very brief ones, during the summer as we were all over the place, including the SPIE meeting in Hawai'i. Work has proceeded on a number of fronts regardless of a lack of meetings (maybe even because of it).

There are a number of open design issues as we work towards completing the MODS design. The purpose of this meeting was to lay all of these issues on the table and then give people their tasks to follow up the discussion in subsequent meetings as we finalize the MODS design.

1. The MODS focal plane, except for the slit-mask changer and dichroic changer, still needs to be worked on. This is our highest priority.

2. Are we going to pursue (now or later) a high-resolution mode (R=15000), with or without cross-dispersion. If the latter, we need to make sure that space is preserved for a cross-dispersing mechanism. Options are:
   1. a new grism ruling mosaiced onto a prism (very expensive)?
   2. a VPH grating? Size may not be the issue so much a problem anymore, but making a low-dispersion VPH grating is. This requires low groove-frequency gratings, which apparently are very challenging to make

3. If we pursue R=15,000 modes, are such gratings actually able to be ruled? Paul is working with Thermo/RGL on designs to assess this.

4. What about very low-resolution (R=few hundred) survey modes? Should we pursue other dispersers besides direct-vision prisms, which went nowhere before? What resolutions? R=500 seems a good target.

5. What about very-high resolution double-pass modes? It was quickly decided that this really means building another instrument, e.g., say cloning Keck's ESI. Interesting, but not for MODS.

6. What about an integral field mode? This is closely coupled to the focal plane real estate, so should be considered now, even if not implemented until after the baseline MODS is commissioned. Rick and Darren have been tasked with exploring this, as our design is close enough to GMOS their IFU is a likely model for us (in fact, we might even want to consider seeing if Durham would make one for us).

7. Acquisition & Guiding is still open. We need to decide on
   1. Camera type and related packaging issues
   2. In front of slit first was one discussion, is this still correct?
   3. Do we want a single AG camera to guide anywhere in the field, both in the science field and the offset fields?
   4. Which kind of WFS do we need? What does it deliver to the TCS?

8. Calibration System concept needs to be fleshed out into a final optical and mechanical design.

9. Flexure Control System. We need to choose the IR laser, complete the projector optics design, and choose the detector. Is a quad cell OK, or do we need an imaging array?

10. What is the final instrument envelope? This needs to be sent to John Hill. JH is also starting to work with ADS on the Gregorian Ring design, so we should get into the loop on that.

11. Management Issues
    1. Current secondary mirror delivery schedule looks like August 2004.
    2. This implies an October 2004 deployment of the first-phase blue-only MODS.
    3. Darren has been tasked with developing the integration and deployment plan.

12. Mechanical Fabrication
    1. The OSU astronomy shops will be full engaged with the LBT Aluminizing system effort at Rickenbacker for the next 12 months.
    2. We need to find other people to make parts. ASU has been great so we hope for more of their help. Also working with the Chemistry Shop at OSU (good price and underutilitized by Chemistry so happy for the work).
    3. Outside vendors?
    4. Big steel work needs to be done outside, we're currently seeking bids on the main structure, will review that over the next 1-2mo and then let the contract. Tom tasked to report on this in a future meeting.

13. Detectors
    1. What is the progress with the 4Kx4K CCDs in Lesser's Lab?
    2. What about Red CCDs? We heard a lot about these at the SPIE meeting. One option is to join various runs (e.g., with Lincoln Labs) which entails some risk of coming out empty handed, or to purchase commodity deep-depletion detectors (e.g., from Marconi), which are more expensive per unit, but commodities.
    3. Do we explore other options with Lesser et al. at UofA, e.g., modifying his process to produce more red-sensitive (if not deep-depletion type) detectors.

There, that should keep us off the streets and out of the pool halls for a while.

R. Pogge, 2002 September 4