DEIMOS
Quarterly Report
Number 25
July 1 through September 30, 2000
During this quarter, the major optics were installed in the spectrograph, and we saw first light with a Cohu TV detector in place of the dewar system. We also installed the collimator, the tent mirror, and the imaging mirror in slider #2 of the grating system. Preliminary checks of the image quality and alignment look good.
The shutter and filter wheels were installed in DEIMOS, as was the piezo actuator on the dummy tent mirror (side B). The major electronics were installed in the electronics ring, which was then covered with insulation and cladding.
Cold tests on the engineering array were completed. The blue science array was installed in the dewar, and testing was completed in the CCD lab. Before the science array was installed, further hardware and software modifications were made to the dewar system to protect the CCDs against transient conditions on power up and power down.
We made the first flexure measurements and found that we had about 40 pixels peak to peak of flexure in the x direction, as seen by the detector. In the y direction the flexure appears to be about 6 pixels peak to peak. More than half of this flexure seems to be in the structure that attaches to the drive disk which supports the grating sliders. Considerable effort is being directed to finding and rectifying the sources of flexure. The original goal was to have native flexure less than 6 pixels peak to peak as seen by the detector. With flexure compensation operating, the final goal was to have motion on the detectors of less than 0.5 pixels peak to peak. To achieve this final goal will almost certainly require a fully functional flexure compensation system.
The mosaic display and descrambling software was completed (FIGDISP version), allowing the full mosaic to be displayed all at once. Software continued development of the motor control software, and the dewar stages, TV filter wheel, and focus stages were tested under keyword control using automated scripts. The shutter was tested with the CCD controller.
2.1 Optics
No report this quarter.
2.2 Mechanical
Structure
Cladding of the electronics ring was completed this quarter.
Camera
No report this quarter. The camera is in DEIMOS.
Filter Wheel
The gear-reduction drive was installed in the filter wheel, and the wheel was installed in DEIMOS, run under software control, and tested.
Gratings
The grating slide-drive system includes the slide, slide drive, insertion hardware and several clamps. Considerable progress was made on aligning and strengthening this system. The system delivers one of the four sliders to three hard points on the grating box, which is in turn mounted to the drive disk. The range of travel of the "hand-off" system is limited, so the sliders must approach the hard points accurately and with little flexure in different PAs. A method using the Davidson autocollimator and various tooling pieces was developed to position the hard points accurately relative to the drive disk, and the slide drive relative to the hard points. Each slider must be separately aligned. The alignment work revealed flexure in the slide drive system that called for further stiffening. The main linear bearing shaft was modified to gain more clearance within the slider ball bushings once a slider is in position, and the cam-follower track was modified to increase clearance between it and the sliders once mounted. Finally, a stiffening truss was designed and fabricated to keep the main slide beam straight. Work was then halted on the grating system to allow for flexure tests (see Flexure below).
Slit Mask
At the end of the quarter, work was restarted on integrating and testing the mechanical parts of the slit mask system. No new results were achieved within the report period. Final machining was completed on the permanent slit mask form.
Dewar
The ion pump now produces some detectable glow with the science array (because the dewar was opened, spoiling the vacuum). However, the pump current is less with each pump down. Water absorption tests with the zeolite canister were completed, and capacity seems adequate for many years' operation at Keck. The shutter was tested with the CCD controller.
Early in the quarter, the dewar and LN2 can were test-fitted in DEIMOS. The dewar is now complete, and the focus and x stages have been tested under keyword control. The focus stage is sticky, and a 4-1 gear reduction will be installed later. The dewar, LN2 can, and shutter will soon be installed in DEIMOS with the blue science array.
CCD Mosaic
Final lab testing was completed of the blue science mosaic in the dewar system. The CCD in position 1 was a device that was originally used in ESI until its connector became delaminated. This device was repaired by Gerry Luppino, but some of the conductive epoxy caused high-resistance shorts across adjacent bond pads. The device in position 4 was mechanically damaged during installation. Both devices were replaced by Lot 14 engineering devices. All 8 CCDs are now operating, with 16 working amplifiers. An extensive series of Fe55 x-ray images to determine the CTE characteristics of the CCDs in the mosaic was obtained using the full mosaic readout mode. Dark current and gain tests were completed in the lab. Linearity tests will be completed in the spectrograph.
TV Guider
Both stages (filter and focus) were tested under software control during this quarter.
Calibration System
All parts have been fabricated for the calibration system and will be installed next quarter.
2.3 Detectors
See CCD mosaic.
2.4 Software
A major rework was required on the motor control software, caused by a previous decision several months ago to replace the manual hand-paddle control with push buttons near each stage. Those complications were unforeseen and caused the loss of several weeks in the motor-control schedule.
Updates to support simultaneous readout of the full mosaic were applied to the CCD controller DSP software, the CCD VME crate software, and the software that runs on the instrument computer (lickserv and figdisp). The full mosaic can now be read out in 70 seconds in single-amplifier mode, although actual display of the image currently requires 140 seconds due to constraints imposed by the 10-Mbit/sec ethernet between the VME crate and instrument controller. (The ethernet on the VME crate will be upgraded to 100-Mbits/sec later this year.) On-the-fly data compression was also implemented for the pixel data flow across the ethernet. A rebuild of the VxWorks kernel for the VME crate was needed to allow proper addressing of the full mosaic image. Full mosaic images (approximately 140 megabytes in size) can now be written to and read back from the DEIMOS raid disks in under 10 seconds. The ability to cleanly abort an in-progress readout of the full mosaic has been successfully tested.
A simulated test of dual-amplifier readout of the full mosaic was performed, even though we have not yet received the additional four video processor boards needed to digitize 8 more CCD amplifiers. The simulated test demonstrated that the CCD controller and VME crate hardware and software were able to drive the fiber optic cable and write CCD pixel data into the crate's VMEbus memory at the full 2 megapixel/second rate. It also demonstrated that the 16-amplifier mosaic descrambling software is functioning correctly. The four Leach II video processor boards for 16-amp operation were ordered. Once they are received, installed and the CCD controller is reconfigured, full mosaic readout time will drop to 39 seconds.
Further improvements were made to the power-up diagnostic software in all CCD controllers (hardware modifications are described under Electronics). Diagnostic readback is provided of all of the hundreds of clock and bias voltages generated by the controller. During controller power-up, if any generated clock or bias voltage is measured to be out of range, the power-up sequence is aborted before any invalid voltages can be applied to the CCD mosaic. These diagnostics have protected the science mosaic and have allowed us to identify and repair problems in some of the CCD cabling and connectors. No further damage to the CCDs has occurred.
The standby UPS that powers the CCD subsystem was replaced by a constant on-line UPS so that the CCD controllers and science mosaic will be completely isolated from any power-line events. Software has been implemented to insure a graceful powerdown of the mosaic in the case of extended power outage.
Initial releases of the DEIMOS motor control keyword library and dispatcher software are now being used to operate five DEIMOS stages under keyword control: dewar focus, dewar x-stage, science filter wheel, tv focus, and tv filter wheel. These stages have also been exercised via the Ktest automated test suite.
The DS-9 real time display package (with DEIMOS-specific features included) was built and tested under Linux and Solaris. Slitlet outlines were successfully displayed on the overlay graphics plane at the correct points in a simulated DEIMOS image.
A DEIMOS slit mask was successfully milled using the DEIMOS slit mask design software. The mask design software produced a FITS file which was submitted via the web page, sanity checked, and ingested into the data base. The submitted design was obtained from the database and used to generate the mill control code that produced the actual mask.
Permission was received from CARA to use a Linux-based PC system to provide rapid realtime communication between DEIMOS PA rotation and the Keck II DCS. The PC and other pieces have been received and the system is being assembled. A Galil motor-control PCI card will be used in a Pentium-based Linux box that will be booted diskless from the DEIMOS supervisory computer. Delivery of this hardware is expected at the start of Q26, and software development for that subsystem will commence at that time.
2.5 Electronics
The major components were installed on the electronics ring, and a large fraction of general wiring within the spectrograph was completed.
During testing of the full mosaic readout software, an intermittent problem was identified in the SDSU second-generation fiber optic interface boards (VMEINF-2) used in the CCD VME crates. One of several PAL chips on these boards appears to overheat when a large volume of data is passed through this board at a rate exceeding 1 million pixels/second (as is the case for a full mosaic readout), resulting in corruption of the image data. Replacement of this PAL chip with a lower-power version appears to fix the problem.
The amplifiers driving the voltages to the heater resistors in the dewar were updated to the same compensation scheme as the ESI CCD controller to eliminate oscillations at large heater voltages. First, op-amps were recompensated to eliminate oscillations on the circuitry used to drive the heater resistors in the dewar. Second, components were added to the dewar temperature sensing circuit to prevent it from overloading the analog muxes used to monitor bias and clock voltages. Resolving this second problem was essential to the successful implementation of the CCD controller power-up diagnostics (see Software).
To further insure proper power-up/power-down sequencing to both the science mosaic and flexure compensation CCD controllers, more modifications were made to the power monitor board. Relays for the +/- 16 volt supplies in the science mosaic CCD controller power supply were replaced with 12 volt activated relays to allow the power monitor board full control of the power monitoring.
Grating tilt stage #3 has been wired and tested. A new set of both normal and reverse stage interconnect boxes have been designed, built and tested for the Gurley encoder stages. Shorting blocks were built to protect the CCD's when they are disconnected. The power monitor card EPLD has been updated and tested.
2.6 Flexure Compensation
The science FC CCDs were successfully operated cold in the science mosaic, and X-ray images were obtained. There do not appear to be any significant readout noise issues resulting from operation of the FC and science mosaic subsystems within the same dewar, provided that the two subsystems do not read out at the same time. Ports were completed for the focal plane FC fiber mounts, and the FC light source is under construction.
2.7 Alignment
The pupil simulator was used to check the alignment of the collimator, tent mirror and imaging mirror. The pupil landed on the grating system almost exactly where it was planned. Alignment is adequate for this stage of assembly and testing
A first test of flexure was made by placing the small Cohu TV camera in the rear of the camera (without Element 9 or the dewar window). A light source illuminated a pinhole on a slit mask, the spectrograph was rotated, and image motion was measured on the Cohu. We detected roughly 40 pixels of flexure peak to peak, mostly in the X direction (perpendicular to dispersion), plus 6 pixels peak to peak in the Y direction (parallel to dispersion). More than half of the flexure seems to be in the grating box, the structure that holds the hard points for the grating mount and attaches to the drive disk. This was established by putting an x-brace within the "U" of the grating box, which removed 22-26 pixels of flexure. From other tests, we estimate that 3-5 pixels is coming from collimator tilt, 6 pixels from the detector in the dewar, and about 1 pixel from camera tilt. As much as a third of the flexure (14 pixels) is unaccounted for.
An in-house review of flexure is planned on October 26 to discuss these measurements and recommend solutions. The total range of the flexure compensation system is only 20 pixels peak to peak, so flexure must be more than halved to get the system to work (the goal for passive flexure was originally 6 pixels peak to peak). It appears that implementing the closed-loop FC software will indeed be necessary to achieve the ultimate image-stability goal of 0.5 pixels peak to peak in each coordinate.
A three-day visit was held with CARA staff in Santa Cruz to review instrument commissioning. A joint task list was developed. The design of the carriage-mover mechanism was altered to move it from the underside of DEIMOS to the rear of the structure to improve servicing accessibility. Access to electronic components in the undercarriage was also improved. Discussions started on telescope alignment and baffling. The most serious concern is CARA's schedule, which showed that DEIMOS commissioning would collide with the Laser Project, necessitating a delay of DEIMOS delivery to March 1, 2002! As that would be disastrous for the DEEP Survey, all parties agreed to revisit the schedule with the aim of bringing the delivery date forward to October 1, 2001.
[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. Complete
2. Complete the grating system and test. Delayed due to flexure tests
3. Complete fabrication and assembly of the TV system. Complete
4. Complete cold tests of the engineering array. Complete
5. Install science mosaic in dewar and test. Complete
6. Install filter wheel in DEIMOS. Complete
7. Install shutter in DEIMOS. Complete
8. Test shutter with CCD controller. Complete
9. Install tent mirror in DEIMOS with actuator. Complete
10. Install collimator in DEIMOS. Complete
11. Install electronics ring cladding. Complete
12. Install Cohu camera and imaging slit plane. Complete
13. Coarse alignment of optics and confirmation with pupil image. Complete
14. Install 600 line/mm grating. Complete (clamped only)
15. Install major electronics in rotational part of DEIMOS. Complete
16. Install dewar in DEIMOS. Complete (first week of October)
17. Install final slit mask form. Complete
18. Install calibration lamp system. Complete
19. Install flat field lamp system. Complete
20. Design fiber feeds for the FC system. Complete
21. Install FC fiber system. Delayed - to be installed next quarter
22. Complete UPS installation. Complete
23. Move TV stages under key word control and test using automated scripts. Complete
24. Move dewar stages under key word control and test using automated scripts. Complete
25. Complete mosaic descrambling software. Complete
26. Complete figdisp mosaic display SW. Complete
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.