DEIMOS
Quarterly Report
Number 20
April
1 to June 30, 1999
Element 8 is at Coherent for optical coating. We expect it back early in the next quarter.
Camera fabrication is continuing. We have body sections 1a and 2 back from the fabricator. Detailed plans and fixturing for assembling the camera were completed. The first two elements are being assembled into their cell.
Further tests of Lot 9 and 10 MIT/LL CCDs show that many of the devices should be acceptable for DEIMOS provided they are operated at -90C. At the end of the Quarter, we decided to change our original plan (building a detector plane from initially using Orbit devices and then switching to MIT/LL devices sometime in the future) to using MIT/LL devices from the beginning and not using Orbit devices at all.
The CCD mounting scheme is being reviewed and some redesign is being carried out. After reviewing the system, we decided that the cooling circuit as designed would put undesirable forces on the CCDs. The CCD mounts were simplified by purchasing molybdenum packages from GL Scientific (Gerry Luppino).
The slit mask cassette holder modifications are complete and ready for testing.
Significant progress was made on DEIMOS software as a byproduct of software work on ESI. In this quarter we lost the services of Robert Mykland, who left to go into private business.
A detailed plan for assembling the detector and signal chain was developed and used to produce a detailed schedule for this critical path item.
2.1 Optics
During this period, the figuring of the aspheric surface on the replacement Element #8 was completed. The lens was packed and transported to Coherent for coating. (It was successfully coated and returned safely to Lick in August.)
Two filters made of BAL-12 material were ground and polished to 6.00mm thickness. These are broadband optical-path equalizers for spectroscopy mode. A paper was written and presented at the SPIE Denver Conference based on our studies on reactivity of DEIMOS components titled "Chemical Reactivity Testing of Optical Fluids and Materials in the DEIMOS Spectrographic Camera for the Keck II Telescope".
2.2 Mechanical
STRUCTURE
Fabrication during this period was done mostly by outside vendors because of
the ESI project in our shop. The cable wrap system was redesigned and new drawings
prepared for the shop. Parts were ordered from vendors.
The Nasmyth integration checking was performed. New drawings from Medeiros of the Keck II Nasmyth platform modifications were obtained. There are two sets of rolling rails, two spur gear racks and eight "kinematic" mount pads which are being installed. The elevation axis relative to the platform distance will establish the outline of the grating slide envelope. (By September, it was clear we have lost 0.5 inches of radius from the 1994 Keck II design drawings, which necessitated some modifications to our undercarriage assembly.)
CAMERA
Fabrication of the first two sections of the camera body are complete (body
Element 1, and the spacer).
Assembly of the optical elements into Body Element 1 is in progress. Developing the assembly process and quality control processes has proven very time consuming, but we now have processes that with minimal modifications can be used for the remainder of the camera. It appears these methods will allow us to meet the demanding tolerances of 0.001 inch on centroid and tip-tilt for the camera elements. Some separation areas in the RTV around the lens edge developed during curing. We decided to proceed with the assembly of Element #1 and test later for fluid leakage (none occurred).
The pre-compression scheme for mounting Element #2 was tested successfully. This element is made of CaF2 and is mounted with RTV in a metal ring. When cooled, the CaF2 shrinks more than the metal, putting it into undesirable tension. The metal ring is to be pre-compressed by an outer press-fit steel ring to maintain the CaF2 in compression down to survival temperature.
FILTER WHEEL
The filter wheel design has been reviewed, and we are sending a package of drawings
out for quote.
GRATINGS
Fixturing was developed to be used for installation and alignment of gratings
into their cells. This set of tools will be used for all future grating additions.
SLIT MASK
Modifications to the scissors jack mechanism were completed, the electronics
integrated and the mechanism bench tested. It is now ready to be re-installed
on the drive disk and be tested on the instrument.
DEWAR
The design of the backplane and the cooling circuit was reexamined to reduce
the forces put on the CCD by the cooling circuit. We decided to change the thermal
connection to the CCD to a molybdenum part that we purchased from GL Scientific.
Use of these parts necessitated the redesign of the backplane, which also caused
a redesign of the connection of the backplane to the dewar focus mechanism.
We also redesigned the thermal spider that connects the cold finger coming from
the LN2 can to the individual CCDs.
All this design is nearing completion, and parts will be purchased and fabricated in the next quarter (this was done).
CCD MOSAIC
A microscope facility for measuring the flatness of the detector mosaic was
designed, and a used, reconditioned microscope procured.
TV GUIDER
No work this quarter.
2.2 Detectors
2.3.1 Lincoln
CCDs
During the current period we tested 17 more 2Kx4K CCDs, 10 devices from lot
9 and 7 from lot 10. As expected, lot 10 CCDs show the same charge transfer
problems encountered in lot 9. However, after careful testing at various temperatures,
we now feel that we will be able to obtain enough good devices for DEIMOS if
we operate those devices relatively warm. At -90C the charge transfer efficiency
is sufficiently improved in many of the CCDs to make them usable, while the
dark current is still low enough to be small compared to the expected sky background.
Based on estimates of yields, our 3/8th share of the lot 9 and 10 should provide
us with enough good CCDs for at least the blue side of the DEIMOS mosaic.
The high resistivity lot, lot 14, is nearing completion, and we expect to begin to see some of these devices in the next period. They are not expected to exhibit the charge transfer problems of lots 9 and 10 (they did not).
Test results for lot 9 and 10 devices can be found on anonymous ftp server gardiner.ucolick.org in /pub/ccid20/, where there are individual subdirectories for each CCD. These subdirectories begin with the letters 'll9' or 'll10'.
2.3.2 Lick/Orbit
Interim Mosaic CCDs
Tests of the Orbit 2Kx4K CCDs have been completed. We have decided not to build
the Orbit interim mosaic as a cost saving measure, given that it appears we
will get enough good Lincoln CCDs by the time the instrument is ready for imaging
tests.
Initial tests of three Orbit CCDs for flexure compensation have been carried out in the test dewar. DEIMOS needs two of these CCDs. One of the flexure compensation CCDs has been extensively tested and the CCD controller software optimized for best performance. The other two flexure compensation CCDs will be tested with the optimized software as time permits.
2.4 Software
Little software activity occurred during this quarter. Steve Allen spent some
time troubleshooting problems with the DEIMOS RAID array and on generic software
infrastructure upgrades (the latter expense was shared with ESI). Dean Tucker
put in several days updating DEIMOS motor control keywords for consistency with
ESI.
2.5 Electronics
The cables that connect the CCDs to circuit boards internal to the dewar have
been designed and are out for quote. Cables for the FC CCDs are yet to be designed.
2.6 Flexure
Compensation
No report for this period.
2.7 Alignment
No report for
this period.
No report for this period
[Tables and figures are not available via the web. Please contact Heather (heather@ucolick.org) for more information]
The project budget and spending are summarized in Table 1. Details are shown in Tables 2, 3 and 4. At the end of the quarter we had spent $5.23 million on the project, or approximately 95% of the approved budget of $5.5 million.
Table 3 summarizes the expenditures on manpower. Approximately 63,000 hours of effort have been expended on the project at the end of the quarter, or about 91% of the total budgeted hours. Figure 1 graphically demonstrates the expenditure of manpower. In this quarter, we show a $72,000 lien for the cost of contract software personnel over the next year. We also had $93,000 worth of labor charges for CCD related activities backed out of the project cost, and the charges picked up by Lick Observatory. These charges were largely associated with the testing and characterization of the MIT/LL devices, which UCO/Lick Observatory is paying for.
Expenditures on materials and supplies are summarized in Table 4 and Figure 2. By the end of the quarter we had expended $2.32 million of the $2.44 million materials budget.
At the end of the quarter the SSC approved an additional $500,000 to the project budget. The present budget does not yet reflect this increase; it will be apportioned in the next quarter.
The project schedule appears in Figure 3. A milestone schedule is shown in Figure 4. At present we are showing a preship review in September 2000. This will almost certainly slip because ESI is still absorbing most of the manpower in the Lick shops. A more accurate schedule will be developed when ESI is complete. However, we understand the schedule well enough to know that the detector/dewar chain is the critical path, and we are putting manpower into that at every opportunity.
Milestones for Quarter 20
Complete design and fabricate dewar handling equipment (still in progress).
Milestones for the next quarter: