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

Attendees: Darren DePoy, Jerry Mason, Pat Osmer, Mark Derwent, Tom O'Brien, Dan Pappalardo, Bruce Atwood, and Rick Pogge.

MODS Front-Side AGW Units

Darren & Rick reported on the outcome of a MODS/LBTPO video conference held on Friday, June 27 to discuss MODS AGW camera and science detector issues. Rick, Darren, & Chris Morgan participated for OSU, while Mark Wagner, Mike Lesser, Peter Strittmatter, and Guido Brusa were on hand in Tuscon for the LBTPO.

To summarize, we will be adopting the Steward CCD camera for both the off-axis guider and slow Wavefront Sensor (the 12x12 SH sensor) for the MODS front-side AGW units. These are the same facility cameras that will be used by the Potsdam/LUCIFER AGW units.

From the MODS perspective, we are providing a mounting point for the off-axis guider and wavefront sensing cameras, optics to create images (except for the microlens array which is part of the WFS camera), and the mechanisms for an XY position stage to carry the cameras, focus mechanisms, and a filter wheel for the off-axis guider. We are also mounting the camera readout electronics on the MODS electronic crate. We are also responsible for providing the software for the mechanism control, and will work with the LBT programming staff to provide the interface hooks for the LBT-GSC system (i.e., we tell them how to talk to our front-side camera stage, focus mechanisms, and filter wheel through our controller and provide the interface stub codes to accomplish this). We are not responsible for the software for camera control (e.g., data acquisition and retrieval), guiding from images, WFS measurements from images, etc. Those functions will be taken care of by LBTO facility software.

To help us test the system, LBTPO will be sending us a complete camera unit (camera head, cable, SDSU-2 "Leach" controller, Shuttle PC computer, fiber optics pair, and liquid coolant recycling unit) to use for testing and integration of the Steward cameras in MODS. This will also give us valuable experience working with the SDSU-2 controllers. There is an effort afoot at Steward to adapt these cameras to use a controller used at Magellan which will reduce the unit cost of the system. This change should be transparent to us.

An action item for Tom and Chris Morgan is to determine what size of camera cable we need. The stock AGW cameras for LBT come with 1-meter cables, but Mike Lesser says they can be up to 2-meters long, and we should figure out what we need and tell him so he can make our cables to the correct length.

For the SH WFS system, we will be using the Steward camera with a 12x12 lenslet array bonded to the CCD as adopted by LBTPO for the Potsdam/LUCIFER AGW units. Paul Byard will be working to refine the optical design to provide images to this camera. An action item is to understand what modifications are required at some future date to introduce a normal Steward camera (e.g., one without the bonded lenslet array) into the system with a detatched lenslet array (our original design) in the event the bonded-lenslet cameras do not prove suitable for MODS. This latter is a concern for us, and we want to make sure we can preserve some flexibility in the future.

MODS Science Detectors

Towards the end of the videocon it was getting late in Columbus, so we had a somewhat briefer discussion of MODS science CCD detectors. For first-light/commissioning activities, we have agreed to use single 4Kx4K CCDs to be packaged by Mike Lesser for MODS. OSU and Steward would then begin working together to identify better "final" detector solutions for MODS that would make best use of its capabilities. The ideal device does not exist as an off the shelf unit, but could be designed and fabricated with an additional infusion of thought and grant money. We will begin actively exploring the best detector options for MODS, but in the meantime will have single 4Kx4K detectors in hand and ready to go for MODS1 first light and commissioning activities.

A remaining issue to be discussed is whether we want to accept Steward's offer of a "complete package" that would include not just the detectors but also associated Leach SDSU-2 controllers and dewar integration, or whether we want just the package detectors and we will provide our own detector controller and do our own dewar integration. There are a number of aspects to this proposal that must be discussed and resolved this summer. In particular, we have no in-house experience with SDSU-2 controllers, and the lower effective costs to OSU may be offset by the not inconsiderable additional labor required for our personnel to learn a completely new system and integrate it into our data-taking system. Understanding and resolving these questions is a major action item for the summer.

Mechanical

Mark Derwent reported on the bid from Indian Creek Fabricators on the upper structure. The price is right, so we are ordering two upper structures (at a cost of about $18K each if we do both now, $21K if done separately, so we save about $5K this way), plus a handling fixture used to fabricate the structure (another $22K). Parts of the handling fixture will be incorporated into the first MODS instrument cart. Delivery times are about 3 months for the first structure. Indian Creek has also agreed to store the second structure for us at their plant for no cost until we are ready to use it.

This sounds great to everyone, and is right on our budget predictions, so we will place an order for the structure with them.

Because of a shift of resources to the Aluminization project, the only design work going on for MODS is detailing of the instrument top hatch (the "dark slide") and the calibration system.