DEIMOS Quarterly Report
Number 24
April 1 to June 30, 2000
The camera was installed in DEIMOS. A shipping box was also constructed that will thermally and mechanically protect it.
Testing of the dewar system continued. We have cooled the engineering mosaic 5 times in the dewar system, including twice with a radiation source to measure CTE. The mosaic gets to a temperature of -115°C when running without regulation, which is too cold for the blue science detector, but is ok for the red science detector. Temperature regulation software has been written. Several problems were identified with the dewar/detector system and have been fixed.
During the course of testing the dewar system, we electrically damaged three CCDs in the mosaic. As a result, a comprehensive review of the electronics and power-up/power-down software was performed and improvements were implemented.
The blue science mosaic was assembled and is ready for installation in the dewar in mid-July.
All components of the grating system have been fabricated. Testing of the grating system continued along with several modifications to the system. Slider #3 is being used to test tilt-drive software.
Fabrication of the new slit mask form is continuing and is expected to be complete in August.
The filter wheel was completed. Testing revealed that the drive gear ratio was inadequate, and a new gearbox was ordered.
Cladding around the electronics boxes has started.
All parts for the TV/guider system have been fabricated and assembled. The system is ready for software testing.
Design of the calibration and FC lamp systems continued, and most of the parts were ordered.
Software started to put full manpower into DEIMOS in June. Tasks were re-distributed among software and electronics staff to improve communication and fill the testing void formed by the loss of Jim Burrous. The software group has written and tested the FITS header tables containing the slit mask design information. Work on the science keywords is largely complete. The DS9 real-time display system was adopted as the official IRAF display at Lick Observatory.
2.1 Optics
The tent mirror was coated with aluminum. One tent-mirror epoxy mount failed and was re-cemented. The collimator mirror was test-fitted in its cell.
Optovac grew the replacement CaF2 crystal for Element 5 and say that this is the last large CaF2 crystal that they plan to grow. Given this information, we have elected not to have them generate the boule into lens shape, but rather take delivery of the new boule, which could then be used for another CaF2 if necessary. Altogether there are 6 CaF2 elements in ESI and DEIMOS.
RFQs were sent out to three firms for AR coatings on the front window and the clear spectroscopy filter. A quote was received back to coat the front window from Spectrum Thin Films of $44,000. This is much higher than the old quote of $20,000 from Coherent. We are waiting to get quotes from Coherent and Cleveland Crystal.
2.2 Mechanical
STRUCTURE
During the quarter we drilled many holes on the structure, which are required for electronics and cladding. Some cladding was fabricated.
CAMERA
The camera was installed in DEIMOS. The installation into the instrument proceeded smoothly with no major problems.
A storage box was constructed to protect the camera mechanically and to provide a long thermal time constant for shipping to Hawaii.
The collimator containing a dummy cell was test-fitted in DEIMOS. Considerable rework was required. The problems were corrected, and the cell passed stability and functional tests. This work delayed progress on the grating system.
FILTER WHEEL
The science filter wheel was completed and assembled, and the servo motor was installed. Initial attempts to tune the servo motor indicated that a greater mechanical reduction was required between the motor and the wheel. A 50/1 gear box was ordered and will be installed when it arrives. Only minimal mechanical changes are required to install the new gear box in the existing mechanism.
GRATINGS
Final assembly of Slider #3 (6x8 gratings) was completed. It was wired, tested and evaluated in the Electronics Shop. This is the first DEIMOS stage with dual encoding. Slider #4 (also 6x8) was assembled but not wired. Slider #2 had an aluminized dummy flat mirror installed. Slider #1 (8x12) was modified to re-locate the tilt drive to avoid interference with the telescope. The grating slide motor was tested for torque and speed at four position angles and the results posted to the website. The speeds are two to three times slower than desired, but there is room for future improvement.
Alignment of the slider shaft and grating support structure began. A fixture was designed and built to help measure the position of the shaft. The hard pads were installed onto the stationary support. Hard pads were also installed onto Slider #1, and the process of moving hardware to avoid interference at all position angles began. The main slider beam was stiffened during this quarter. The ball nut mount on Slider #2 was not stiff enough, so it was also modified.
SLIT MASK
Fabrication started on the new slit mask form. The new form eliminates vignetting and also has mounting points for the FC focal-plane fibers.
Further tests were made of flexure in the slit mask system. Flexure in the slit mask cassette holder was successfully removed by the last redesign, and the slit mask insertion mechanism basically works in all position angles.
DEWAR
The dewar system was cooled an additional 3 times with the engineering mosaic (which includes the two FC devices, making a total of 10 CCDs on the mosaic).
The dewar window was replaced with a new mount using an O-ring. This window seal was successfully tested and has been on the dewar during three cool downs. The radiation source was re-worked to eliminate stiction and is ready for testing.
During the quarter, a leak in the dewar appeared in the FC electronics feed-through plate. This plate had experienced leaks earlier and was redesigned and refabricated during this quarter.
The ion pump glow problem appears to have been solved by installing an optical baffle, and long darks are quite dark once the dewar pressure gets to low levels.
The CCD-temperature circuitry proved fragile and was replaced. The temperature regulation software is largely complete, including custom calibration curves for all 8 diodes. The regulated CCD temperatures are uniform to within 2 C. See further remarks under Software.
A resistor burned up on the power-monitor board. The board was repaired, but the failure exposed the engineering CCDs to a dangerous voltage condition. Altogether, testing has destroyed or damaged a total of three of the engineering CCDs, triggering a comprehensive review of the CCD electronics. It is suspected those uncontrolled electrical transients during power-up and power-down may have temporarily reverse-biased the gate voltages in the reset transistor in the output amplifier. Such transients might have occurred in the above power-monitor board failure, as well as in ordinary power-up/power-down operations. Redesigns are being prepared for powering up and down (see Software).
Tests were conducted of the pumping capacity of zeolite. We are concerned that water contamination may still be a problem, as a faint ring of contamination (probably water) was seen on the engineering mosaic below the edge of the dewar window at the last cooldown. We will be watching this problem during tests of the science array.
CCD MOSAIC
The blue version of the science mosiac was assembled and is ready to be installed in the dewar. It is quite flat. CTE measurements were obtained for the CCDs in the engineering array as a function of temperature. They look good.
TV GUIDER
All parts were fabricated and assembled, and the system is ready for software testing. The offset guider mirror and folding flat were polished.
2.3 Detectors
We received two Lot 14 engineering devices during this quarter. These devices are very good cosmetically but suffer from a poor AR coating. Approximately 18 more high rho CCDs remain to be tested from lot 14, which makes it probable that we will receive the one remaining device needed to fill out the four high-rho devices on the red side of the science mosaic. It is possible that we may even receive enough devices to fill an entire red science mosaic with high-rho CCDs, which is our preferred goal.
2.4 Software
Software for the early phases of the DEIMOS slit mask design and fabrication process was successfully tested. A mask was designed using the mask design software, the design was interactively submitted via the web-based mask design submission tool, the tool verified the integrity of the design and entered it into the database, and the design was recovered from the database and used to generate a plot. This completes our proof of concept for these phases of the mask design and fabrication process. The software for reading images from the flexure compensation CCDs (in non-frame-transfer mode) was successfully tested with two engineering-grade FCS CCDs mounted in the DEIMOS dewar. The FCS CCD subsystem was operated in parallel with the CCD subsystem for the science mosaic, with both subsystems able to obtain images from their respective CCDs.
The initial release of software for closing the dewar temperature servo loop was successfully tested, stabilizing the dewar temperature averaged across the 8 CCDs to within 2° C. A subsequent release will close the temperature loop individually to each CCD.
In preparation for installation of the science mosaic, additional software to provide increased protection for the CCDs has been implemented and tested, including CCD controller diagnostic software that provides a loopback test for all CCD clocks and bias voltages, and software for sequencing the CCD voltages on both power-up and power-down of the CCD controller.
The version of the DS9 image display software that incorporates the features needed to meet DEIMOS image display requirements was received from CfA Harvard on schedule in early May and successfully tested. Work commenced on building the three DEIMOS keyword libraries, with initial prototype releases expected for testing in July.
Following a survey of commercially-available quadrature generation boards, we are re-examining the design for the DEIMOS instrument rotation control system. We are now planning on using a PCI-bus based system with embedded Galil PCI boards in place of the DMC-1500 controller attached to the cradle. We believe the savings in software costs associated with this approach will outweigh the cost of the additional hardware.
With the completion of commissioning of the HIRES exposure meter in May, the bulk of our software labor is now finally available to work on DEIMOS. In addition, Will Deich, a resident programmer/analyst for Mt. Hamilton, was hired in mid-June. Once he is trained, Will Deich will be able to devote the bulk of his time to the DEIMOS software effort.
2.5 Electronics
The CCD controller for the FC system was completed and tested during the quarter. Final wiring of the major mechanical systems is largely complete, Most of the AC power system was purchased and installed. Limit switches on the cable wrap were installed, and most of the cables were loaded into the wrap.
2.6 Flexure Compensation
The FC engineering-grade CCDs were installed on the engineering mosaic and the FC controller was used to take the first FC images. Work was started on the FC fibers and light source.
2.7 Alignment
Design began on a pupil simulator to model the Keck pupil. It will sit in the parking lot at a distance of 66 feet from the focal plane and carry a hexagonal pattern of bright lights at the corners of the pupil, plus aimable lasers.
A plate was designed to mount in the central hole of the collimator mirror. It will be perpendicular to the collimator axis and will hold a cross hair and/or a two-sided mirror. It will be used for tip/tilt adjustment of the collimator mirror and also to set the axial distance of the collimator mirror from the slit mask.
An alignment plan for the slit mask form and the TV guider was devised, and necessary jigs are being designed.
[Tables and figures are not available via the web. Please contact Heather (heather@ucolick.org) for more information]
The following is a list of milestones for this quarter from the last Quarterly Report, together with the progress made on them:
1. Complete design of the calibration and FC light sources. Delayed
2. Complete design of the slit mask form and focal plane assembly. Complete
3. Complete the grating system and test it. Delayed
4. Complete cold tests of the engineering array. Nearly done
5. Complete assembly of the science mosaic, install in dewar, and test. Completed assembly, testing delayed
6. Aluminize the tent mirror. Complete
7. Complete camera testing and prepare for installation in DEIMOS. Complete
8. Install cables and glycol lines in the cable wrap. Complete
9. Start fabrication of the TV system. Started
10. Install collimator in cell. Complete
11. Hold distribution of Lot 14 CCDs. Complete
12. Complete installation of UPS's. Started
13. Test the FC signal chain, including CCDs. Complete
14. Complete the website design. Complete
15. Purchase components for the rotation drive system. Complete
16. Order test lamps for the calibration system. Complete
17. Design the fiber feeds for the FC system. Started
Milestones for the next quarter:
1. Complete design of the calibration and FC light sources.
2. Complete the grating system and test.
3. Complete fabrication and assembly of the TV system.
4. Complete cold tests of the engineering array.
5. Complete testing of science mosaic in dewar.
6. Install filter wheel in DEIMOS.
7. Install shutter in DEIMOS.
8. Test shutter with CCD controller.
9. Install tent mirror in DEIMOS with actuator.
10. Install collimator in DEIMOS.
11. Install electronics ring cladding.
12. Install Cohu camera and imaging slit plane.
13. Coarse alignment of optics and confirmation with pupil image.
14. Install 600 line/mm grating.
15. Install major electronics on rotational part of DEIMOS.
16. Install dewar in DEIMOS.
17. Install final slit mask form.
18. Install calibration lamp system.
19. Install flat field lamp system.
20. Design fiber feeds for the FC system.
21. Install FC fiber system
22. Complete UPS installation.
23. Move TV stages under key word control and test using automated scripts.
24. Move dewar stages under key word control and test using automated scripts.
25. Complete mosaic-descrambling software.
26. Complete figdisp mosaic display SW.