The Software PDR was held on March 22, and was attended by approximately 30 people. The meeting was chaired by Steve Kent, of the Fermi National Accelerator Lab, with John Cromer, George Jacoby, Jill Knapp and Al Conrad as the committee members. The meeting was very sucessful and marks the start of the intensive software effort. The section on software will further discuss the specific highlights of the meeting.
Optical Research Associates (ORA) was issued a contract to model the full optical system with Code 5, research optical couplants, and to do the meltsheet rebalance. They have been doing very well and did confirm the performance of the camera predicted by the original design. Their analysis indicates that the rebalance can be done by a simple re-space of the elements. At the end of the quarter we received the final piece of FK01. We are still waiting for delivery of the SK01Y (BSM51Y) glass from Ohara that was originally delivered at the wrong diameter (was received on April 25th). We will need the meltsheet data for this glass before the meltsheet rebalance can be finalized and start fabrication of the camera elements. We plan to contract ORA to do additional work to recommend a fabrication sequence and to do a tolerance study. A Purchase Order for this work will be issued early in the new quarter.
The collimator optical fabrication is nearly complete. David Hilyard has taken a series of "cuts" on the profilometer and sent the data to Terry Mast for analysis. Brian Sutin designed a null lens for the collimator, which has now been fabricated. David Hilyard is currently setting the interferometer to test the collimator with the null lens. Results of the analysis by Terry Mast and the null lens tests are expected by the end of April (received on April 29th). Further detail on the effort in optics will be covered in Section 2.1.
Work continues on the detailed design of the rotating structure, the cart, the drive disk and the inter disk. David Cowley continues to do FEA work on the structural parts and this information is being used by Eric James to fine tune the designs.
Jack Osborne continues primarily with the design of the grating holder and changer. A prototype of the grating tilt mechanism has been built and is awaiting completion of the design of the tilt drive system.
Keck/CARA has agreed to adjust the cable wrap configuration on the Keck II left Nasmyth platform to make the clearances similar to Keck I. This allows continuation of the design of DEIMOS without modifications, as the telescope design information given the DEIMOS team was that both Nasmyth platforms of both telescopes would be identical. Thank you to all at CARA who helped sort this difficulty out.
The new slit cutting NC Milling machine was delivered at the end of the quarter and is currently being commissioned. Due to the fact it can hit tighter tolerances than the 20 year old NC machine that is used normally in the instrument lab, the new machine will be used to make some of the high precision parts for the grating tilt drive mechanism.
2. Reports on Specific Areas:
2.1 Optics
2.1.1 Collimator Mirror
Aspheric grinding on the Collimator Mirror began on Nov. 29, 1995, and figuring was stopped on March 7, 1996. It was decided to target a slope tolerance of 2.2 x 10-6 radians, three times tighter than the slope specification suggested at the CDR. The conic constant was held fixed to the design value, while the radius of curvature was allowed to float as the figuring proceeded. Four sets of measurements of the mirror were taken, each with 15 diametral cuts. The data was given to Terry Mast for analysis. Terry has analyzed the data, subtracting carriage tilt and beam curvature errors and is writing a report on his findings. A two element null lens was designed and fabricated for an independent interferometric test of the figure. That test is presently underway, with results expected by the end of April. Through final conclusions must await the final reports from these two tests, preliminary indications are that the collimator meets the revised specifications. If so, it will have been finished on time and on budget.
2.1.2 Camera
The optical contract with ORA got underway. They now have the full optical design, including the Keck Telescope and the DEIMOS Spectrograph, in their input data files and have verified that the design raytraces virtually as Epps' code said it should. Their first task was to study the effect of varying the thickness of and fluid within the optical coupling gapes, and they showed that it is small. The gap size and fluid index can therefore be left unspecified until the camera cell is designed. A preliminary study also showed that the glass indices as received are close enough to the design values that there is little impact on the optical design. What small effect there is can be removed by respacing the elements. During the next quarter, we expect to receive from them full reports on the final design based on the as-received indices, a comprehensive tolerance analysis, and an initial fabrication plan. Purchase orders for these have been prepared. ORA is prepared to keep track of the design as we progress through fabrication, advising us on when each element is completed and when we can move on to the next. We plan to follow this ourselves in parallel, using Zemax, for which we have purchased a separate lap-top PC computer and program key.
So far, ORA's ability to assimilate the Epps camera design and critically analyze appear quite satisfactory. Our consultant there is Mike Rodgers.
The third and final blank of FK01 was received from Ohara and the melt data passed on to ORA. Still outstanding from Ohara are the three SK01Y blanks that will replace the undersized blanks already delivered (received April 25th). A quotation for the Sol Gel coating of the glass in the camera is expected from Jeff Bohn at Cleveland Crystals by the end of April. We will supply them with 2" diameter glass samples of each glass type in the camera, which they will coat and send back for our evaluation. We will pursue the Sol Gel coating of the calcium fluoride lenses with LLNL, rather than Cleveland Crystals, because of their reported success with this material.
2.1.3 Optical Tooling
The optical tooling for the camera lenses material has been purchased and diameters roughed out. We are awaiting the final report from ORA before we proceed with tooling fabrication or lens fabrication.
2.2 Mechanical
2.2.1 Structure
The design of the structure has substantially advanced during this quarter. Both the rotating cylinder and the carriage designs have been completed. All of the main structural components have had several design and analysis iterations before arriving at the final configuration. We are now in the process of preparing fabrication drawings for sending out to vendors for quotation.
The drive wheel has been divided into inner and outer sections to prevent out of plane forces seen by the outer areas from disturbing the accurate mounting surfaces on the inner area. The support and drive rollers for the drive mechanism have been redesigned to prevent axial forces from building up while turning the big drive disk. The carriage has been redesigned to allow installing the non-rotating electronics under the cylinder instead of in a separate vault, thus eliminating the need for an electronics vault on the Nasmyth platform. We have received a preliminary design from Keck of the new rail system to be installed on the Nasmyth platform and have designed the features needed to drive and navigate on that system. The kinematic mounts have been designed and coordinated with the structure of the Nasmyth platform. The rear bearing design has been completed and integrated with the design of the associated cable clamps and light baffles. A chain mechanism has been designed for the rear bearing area to provide gross rotational encoding as well as both software and hard mechanical rotation limits.
2.2.2 Collimator Mirror Cell
Very little has changed since the previous report. The cell design and fabrication are already substantially complete at that time. The only remaining tasks are minor changes needed to accommodate the final glass dimensions and integration into the instrument.
2.2.3 Tent Mirror Support
The tent mirror support has been designed and fabricated.
2.2.4 Camera Cell
We began experiments to develop techniques for casting the elastomeric lens mounts. We identified most of the equipment and tooling needed for this task and made several test casts. Once the techniques are satisfactory, we will cast our test doublet into a test cell for testing the sealing and other properties of the mounts with the liquid couplant. The test cell has already been designed and built.
A significant design change has been made regarding the camera and the X-motion of the flexure compensation system. We are no longer planning on moving the whole camera but rather just moving the detector within the dewar, or possibly the detector/dewar unit. This will simplify the camera mounts and reduce the mass of the moving parts.
2.2.5 Filter Wheel
The filter wheel design was already complete at the last report so no further work has been done.
2.2.6 Gratings
The grating rotator is in the detailed design phase. A full size metal and glass model has been built and is being modified for a friction drive. The grating rotator support structure has been designed and analyzed by Finite Element Analysis. The predicted deflections are less than 10% of those presented in the strawman CDR error budget. A metal structure is in fabrication now. A preliminary plan for laboratory tests of grating flexture at the sub-micron level is beginning to evolve. We plan to measure all three components of tilt and rotation during a simulated instrument revolution. 2.2.7 TV Guiders Progress was made on the conceptual design for the TV guider. A challenge is to provide offset guiding as well as direct-slit viewing in long-slit mode with just a single TV. In addition, our Science Advisory Team requested that we also be able to look directly at slit masks to place objects just as conveniently and rapidly into slitlets as in long-slit mode. We think we have found a way to meet all these requirements by imaging one large, continuous area of the focal plane. This area would be about 3' by 3' in size and would span the inner edge of the slit mask/imaging area boundary. About half the area would be on the slit mask and would also cover the long-slit for long-slit object acquisition. The other half would cover an otherwise unused area of the focal plane for object guiding. This area would be filled with a curved mirror having the same shape as the focal plane. This mirror acts as a field lens to get all the light through the camera lens asphere. The Canon 200-mm lens used in the HIRES guider gives the requisite scale, ~ 0".2 per pix, when combined with a 1K x 1K thinned SITe DDC with 24 m pixels. There are no extra relay optics in this design except for a single folding-flat mirror, and no moving parts. The only scientific is that a 1K by 1K detector cannot be used in frame-transfer mode, as the entire detector area is needed for imaging the focal plane. Thus the system must use a shutter, as with LRIS. However a 2K x 4K 15 m pixel frame-transfer CCD would solve this problem and is under discussion.
The Canon 200-mm lens has been ordered for optical testing. Discussions with NIRSPEC also indicate that their needs and DEIMOS's can be met by a common TV CCD detector, and ESI's TV plans at last checking were also similar to DEIMOS's. Discussions are underway with CARA to set the requirements for a common TV guider sensor and software system to at least these three Keck II instruments.
2.2.8 Slit Masks
The slitmask insert/extract mechanism has been given some thought. There is room to design and build a linear device and the ways and guides for moving the slitmask frame from the circulating machinery into the focal plane. We have been looking at other robots which have been used in the numerically-controlled machinery industry.
2.3 Detectors
We received a new CCD wafer run from Orbit Semiconductor. This run was a test to show that Orbit had solved their previous charge transfer problems. All of the CCDs have been tested on the wafer and the results are very encouraging. Orbit has eliminated all of the previous charge transfer problems. Here is a brief summary of the results, based on 10 degree C wafer probe tests of the 18 wafers shipped to us:
These CCDs were not DEIMOS design CCDs. However, based on these results we have released two wafer runs contained the DEIMOS design 4K x 2K CCDs. These runs should be finished around July 1st.
We continue to make steady, if slow, progress on our CCD thinning effort at Lick. We are processing several CCD wafers now, and we hope to have at least one working, thinned CCD by July and to present results at the July SSC meeting.
The Lincoln Labs CCD development effort is making good progress. According to Gerry Luppino, who is heading the consortium effort to produce these devices, the first wafer run has been completed and the yield is very high. First thinned devices from Lincoln might be expected in August.
2.4 Software
The major activity for this quarter was preparation for the software PDR held on March 22. The material presented was well received by those in attendance. While we have not yet received the report of the PDR review board, several areas needing further attention were identified either during the review or in informal comments received via e-mail shortly thereafter.
2.4.1 Budget and Schedule
Refining the DEIMOS software budget and schedule was identified as a top priority item. The effort is now in progress in combination with a similar effort for ESI.
2.4.2 CCD Readout
The CCD readout software for the 8K x 8K mosaic was identified as the highest risk area, and Conrad recommended focusing on development of DSP and low-level code for the second generation SDSU CCD controller as soon as possible. Given current expectations for delivery of this hardware, this effort probably cannot begin until late summer.
2.4.3 User Interface
Conrad also recommended putting more effort into early prototyping of user interface tools and iterating these prototypes with a selected set of future DEIMOS users. We plan to do this.
2.4.4 Quick Look / Image Display / Image Analysis
The extent to which DEIMOS image display and quick-look reduction tools should depend on IRAF or IDL appears to be the most controversial question that arose during the PDR, with comments on this topic received from Conrad, Jacoby, and Marc Davis. Both Conrad and Davis suggested that the DEIMOS team review its commitment to IRAF and consider switching to IDL, while Jacoby addressed the question of continued NOAO-funding of IRAF development and support. In an effort to respond to these concerns, we are currently working on a cost/benefit comparison of IRAF and IDL, including side-by-side benchmarks of representative DEIMOS image display and quick-look tasks. We hope to have preliminary results ready to present at the Keck II Software Coordinating Committee (SCC) meeting to be held at CARA on April 26.
The Dec-Alpha is now in service, which is being used to test various sources of the image handling software. Initial speed results are consistent with expectations.
2.4.5 Coordination with CARA
The need for close coordination between the DEIMOS team and CARA software developers was identified with respect to several key areas:
We will respond to these issues in more detail in our formal response to the official PDR review board report.
2.5 Electronics
The main areas that were addressed during this quarter include producing the mechanical specifications for the electronics components, work on the manual paddle design, ordering parts for the manual paddles, preparation for the Software PDR, and drawing updates. The issue of calibration lamps is being looked into. We have purchased a PenRay Neon lamp and power supply to be used for testing illumination uniformity. A quartz lamp set-up has also been ordered for the same purpose. Rem Stone has sent some "black" lights to test for flat-fielding purposes. Rem suggests that they might give good illumination for flat-fielding.
Work continues on fabrication of the shutter controller.
3. Report from the PI's:
Most of the PI efforts this quarter were devoted to getting the ORA optics contract underway and to supporting preparations for the Software PDR. In addition, we supervised the taking of a comprehensive new data set at the Kast spectrograph to fully explore fringing. We have a conceptual scheme to study the variation of fringe phase over the chip, which we will attempt to implement next quarter. This is preparatory to our long-term goal of removing fringing completely using the fringe-phase signature internal to each image.
4. Budget:
To the end of March 1996, $1,306,000 had been expended on the project, of which $618,000 was on labor and $688,000 was on materials and supplies. Table 1 is a summary of the budget, and the details are shown in Table 2.
During the quarter $141,200 was spent on labor and $107,370 on materials, supplies and services. The labor costs reflect the fact that optical fabrication of the collimator was in progress, mechanical design near peak manpower utilization, and electronics was working on completing the design of the motion control systems and building the shutter controller. Software put in a significant effort this quarter preparing for the Software PDR, and this rate is expected to slow a bit in the next quarter.
Significant purchases during the quarter included the NC machine and high speed spindle at $67,000, and purchases of materials for the dewars and grating assembly and drive. A Purchase order for $10,500 was given to ORA for optical design work on the camera. The budget shows a significant expenditure in Administration, which appears to be largely an error that will be corrected on the next Quarterly Report. What we were doing was setting up a number of blanket purchase orders to suppliers that we use often for less expensive items. An arbitrary lien of $2,500 was made for each of these orders against the administrative miscellaneous materials code, with the idea that as items are bought, the actual charges would be re-directed to the proper cost code. It appears that the liens were recorded as actual charges against the administration cost code.
Cost of fabrication of the collimator mirror, which is nearly complete appears to have been very nearly exactly on budget.
For the next quarterly report we plan to draw from the contingency and revise the budgets particularly for Optical Design and Instrument Reviews. The project is having a greater level of review than was thought necessary when the budget was estimated. We are now also contracting for optical design from ORA, which we did not anticipate in the budget. These new expenses will be reflected in a draw down of contingency next quarter.
5. Schedule
Figure 1 shows the project schedule. At this time, we are still planning to commission the instrument in Hawaii in the first quarter of 1998.
The following is a list of the milestones for the quarter from the last Quarterly Report, together with the progress made on them.
Milestones for Quarter 7:
1. Design of mechanical items including the structure, undercarriage, drive, grating mechanisms, and tent mirror support are continuing and will be covered at a detailed review planned for May 14th. The review committee will be composed of Dan Fabricant, Frank Melsheimer, Jerry Nelson and Terry Mast. Of the items returned in the milestones, only the slit mask insertion is still not yet ready for review.
2. The Software PDR was held on March 22, 1996, as planned.
3. The optical figuring of the collimator mirror is probably complete. Null lens testing and analysis of the final profilometer output are underway.
4. ORA progressed nearly to completion on the melt sheet rebalance of the camera optical design and is awaiting final date on the SK01Y elements. A contract is being prepared to ORA for them to recommend a camera optics fabrication sequence. Camera fabrication will certainly start next quarter.
5. The prototype of the grating tilt mechanism is being fabricated and the plan is to test it before the May review.
6. Progress was made on constructing the doublet test cell to verify the RTV/fluid coupling mount. However, construction of the final cell will extend into the next quarter.
7. The CNC slit mask cutter has been delivered.
Milestones for the next Quarter.
1. Hold the review of the DEIMOS structure planned for May 14th, and start fabrication of the structure before the end of the quarter.
2. Complete the RTV/fluid coupled test cell.
3. Start optical fabrication of the Camera elements.
4. Start fabrication of the CCD test dewar.
5. Complete a full tolerance analysis and receive a full camera fabrication report from ORA.
6. Complete design of the slit mask insertion mechanism and subject to in-house review.
7. Complete full flexure tests of the grating mount/mechanism.
8. Update the Error Budget in conformance with the a test flexure estimates.