This is the first of approximately 12 quarterly reports that will be generated during the course of this project. The principle activity during this quarter is preparation of the Preliminary Design Review (PDR) Report, background materials, and preparation for the meeting. The PDR is one of five major reviews planned for the project. The other reviews are: the Software PDR, Critical Design Review, the Software Critical Design Review, and the Pre-Ship Review.
The PDR report is coming together and is planned to be mailed out to the reviewers and the community at the end of October. It was a major effort by the project team as it sets the frame for the project design with in the budget constraints approved in May by the SSC. Many areas that had not been previously defined in any detail are explored and will be reported on. These included the Flexure Compensation System, the TV Viewing/Guiding Systems, and the split in the Software effort between Instrument Control and Data handling.
A full size structural model was started and is scheduled to be completed before the PDR. The model is intended to demonstrate the size and placement of the various major elements, and is planned to be used for structural analysis and testing of the rotational drive system. We plan to reuse as many of the model's parts in the final structure as possible including the bearings, the disk, and the steel.
The design and shop drawings for the detector shutter were completed, with the part being scheduled for completion, again, before the PDR. This shutter is considerably larger than any commercially available fast shutter, and will be tested extensively before being incorporated into DEIMOS.
Requests for Quotes have been sent to three potential suppliers of laser cutters for Slit Mask generation.
We are on schedule for the PDR, chaired by Dan Fabricant. The review is scheduled for Nov 15th at UCSC.
2. Status of Risk Items
We have identified 8 major risk areas. It is our intention to update the status of each area in each Quarterly Report. More areas may be added as experience warrants.
2.1 Flexure Control
Harland Epps and Brian Sutin have started to investigate this area of the spectrograph in some detail. The first major result of this investigation was that the tent mirrors which reside in the spectrograph between the collimator and the gratings cannot compensate for flexure in the optical train perpendicular to the axis of dispersion. The reasons for this and the consequences will be presented in the PDR report. Active flexure control of a different element of the optical train is necessary, and active control is being considered.
An initial pass at predicting the mechanical stiffness of the spectrograph has indicated that the native flexure of mechanical parts can be expected to be in the range of 10 times the goal of 1.5 microns. The conclusion is that either an active Flexure Compensation system is required for the instrument to meet its design goals or a non-fringing CCD system will be necessary.
2.2 Optics Fabrication
The main perceived risk is breakage of the CaF2, which costs approximately $25,000 per blank. We will have Opto-Vac edge-finish and rough-grind each piece to minimize our total exposure.
The aspheric camera elements are comparable in difficulty to previous aspherics we have made, but there is a cumulative risk to schedule and budget in doing a total of six CaF2 elements.
2.3 Slit Mask Changer
Our plan is to design and fabricate a prototype early in the project. In doing so we will be able to extensively test and improve the mechanism before completing the remaining two for the spectrograph. The prototype is ultimately planned to be used in conjunction with the Laser Cutter to load the masks into the cutting plain.
2.4 Detector Mosaic
The baseline detectors are beyond the current state of the art. An independent two-pronged development attack is being mounted from separate Keck funds at essentially no cost to DEIMOS. If these paths fail, we will install small interim double mosaics of size 2kx8k to permit efficient single-object spectroscopy and minimal long-slit capability (4 min). This would require 4 detectors total and would likely not exhaust the detector budget. Money saved would be banked for future developments. This strategy would satisfy single-object users but would be a major blow to our own program of multi-slit spectroscopy of faint galaxies.
2.5 CCD Data Handling
The data rate is 16 times greater than the current LRIS and HIRES systems, which are our previous benchmarks. To a great extent we are relying on future computer hardware improvements that are not on the market yet. These include bigger and faster disks, faster CPUs, more memory, faster networks, and more capacious archive media. We are also relying on the inclusion of particular upgrades in the second-generation Leach CCD controllers. On the positive side, failure is more graceful than other high-risk items.
2.6 Total Sofware Burden
The total instrument system is highly software intensive, more so than either HIRES or LRIS. Operating efficiency depends to a great extent on the availability of convenient software packages (e.g., object acquisition and centering, rapid spectrograph setup and focussing, telescope focus monitor). Many of these software tasks are new and involve higher data rates, quick-look display and analysis of huge images, on-line analysis of TV images, etc. Each task is in itself little problem, but the total requirements are large. Careful priorities need to be set. To compensate, other software elements are familiar given previous experience with HIRES, including motor control, the basic architecture of the Leach controllers, and the architecture of the data-handling system.
2.7 Slit Mask Cutter
This is a high-technology piece of expensive equipment that is vital to the multi-slit mode. On the positive side, we plan to purchase this item early and exercise it in the lab.
2.8 Total Budget Overrun
Again the concern is not for any one task but rather that the total instrument contains many difficult challenges. There is little fat in the budget to deal with a major disaster. We propose to address this by putting the most difficult tasks up front where possible, where they can get early attention. However, some items such as detectors are paced by considerations beyond our control.
3. Goals and Schedule for Next Quarter
An outline of the project schedule is attached, together with a more detailed look and the activities in the period from July 1, 1994 to Feb 1, 1995.
Mid next quarter the PDR will be held, and following an orderly cleanup from that review, we will start detailed mechanical design. Early in this time period we are expecting to do extensive testing on the model frame and rotational drive system. Fabrication and testing of the shutter is scheduled to begin during this quarter.
Assuming that it is approved at the PDR, we plan to order the optical glass for three cameras with the exception that CaF2 would be ordered only for one.
4. Budget
Attached to this report is a budget summary. As of September 30, 1994; $59,058.84 has been spent on this project.
The budget summary is taken directly from the budget approved in May 1994. It does not include any of the contingency, which will be allotted as needed to specific areas during the course of the project. When contingency money is allotted, the particular cost center will be highlighted in the summary and footnoted. The footnote will explain the amount of contingency money applied to the cost center, the percentage difference from the original estimate, and the reason for the difference. A separate line of the summary will show the contingency fund, the original amount and the amount committed.
The major man power effort occurred in support of the PDR review, but was dispersed to the individual areas of effort in the budget. One area that has expended a large percentage of its estimated effort is the generation of the Slit Mask Frame. This frame will be fabricated on the CNC mill, and a major part of the effort is in producing the program. As this part has a center of curvature outside the mill's cutting area, new programing had to be bought and learned. This has been done, and the remainder of the effort is expected to be straight forward. A new level of effort will need to be estimated for this item for the next quarter, and the budget adjusted accordingly.
In terms of percentages, we have used about 1.4% of the budgeted effort, and if we expend effort linearly through the course of the project we would have used about 6%. The general trend of using effort at less than the linear rate is expected to continue through 1995, until start of Optical fabrication.
The major materials/supplies expenditures during the quarter were for the electronics vault, and the bearings for the instrument rotator. An external contract to do finite element analysis of camera lens elements was completed by Bruce Bigelow.