DEIMOS

1
DEIMOS

• Presentation to the SSC
• January 25, 2001

2
Outline

• Quick overview of Budget and Schedule (web
  version has no Budget figures)
• Progress Since Last Report
• Technical Concerns
• Optical Testing
• Flexure
• Grating System
• Red CCD Status
• Schedule Details
• Budget Details

3
Summary Schedule Status

• Completion has slipped one month since our
  October report.
• Reasons for the delay
• Software slipped one month (due to sickness and
  Lick software emergencies) and is on the critical
  path.
• We discovered flexure in the detector support
  train and must remove the dewar to fix it.
• The grating transport/insertion mechanism is
  requiring substantial redesign.
• CARA cannot accept DEIMOS until Oct. 1, 2001.

4
Summary of Critical Path

• Software dominates until testing begins.
• Grating implementation and flexure repair have
  only about 2 weeks float.

5
Summary of Critical Path
6
Milestone Summary

• As of Current
• Oct 14, 2000 date
• First image of spectra Oct 24 Done
• Meeting plans to fix flexure Oct 26
  Done
• Slit mask system released to SW for functional
  tests Jan 19
• Rotation drive re-installed under SW
  control Jan 8 Jan 21
• Grating system operational Feb 5 Mar
  8
• Instrument ready for integrated systems tests Apr
  4 May 8
• Preship review June 7 July 7
• Marine Shipment Aug 9 Sept 11
• First air shipment and start of assembly Aug 21
  Oct 1
• Hoist instrument into dome Aug 24
  Oct 4
• Dewar installed Oct 3 Nov12
• First star light Oct 30 Dec 7
  (dark) or Dec 28 (full moon)

7
Progress Since Last Report

• Dewar system installed in DEIMOS (October 16)
  works well.
• Direct images and spectra taken with blue science
  mosaic.
• Flexure investigations using full mosaic detector
  completed.
• Software developed to analyze flexure and optical
  quality.
• Plan to address major source(s) of flexure
  developed.
• Major progress on grating transport/insertion
  system .
• Slit mask system under computer control.
• Calibration lamp and flat field illumination
  systems installed and tested.
• Flexure control system installed and tested.
• Dewar focus, dewar X stage, science filter wheel,
  calibration lamps, and shutter operated under
  keyword control and tested using automated
  scripts now are working systems.

8
Dewar System in DEIMOS
9
Slit mask system insertion scissor lift
10
Calibration lamps with slit mask form at bottom
of picture
11
Picture of spectra from 900 line grating
12
Other Progress

• Linux computer for rotation control purchased and
  outfitted with Galil motor control system. DEIMOS
  rotation under computer control by end of
  January.
• Engineering GUI in use.
• Leach II video boards for 16-amp operation
  received.
• Dewar ion pump power under software control.
• Hewlett-Packard temperature sensor data logged
  remotely over network 24/27 sensors installed.
• Power PC board mounted in test CCD controller for
  100 Mb ethernet video connection being tested.

13
Technical Concerns

• Fixing flexure in grating box and other sources
• Extensive redesign of grating sliders is
  required integrating grating system with all
  sliders mounted will occur late.
• Possible redesign of retraction hotdog for slit
  mask system
• Availability of high-rho CCDs for red mosaic
  testing red mosaic out of spectrograph after
  DEIMOS is shipped
• Implementing complex rotation control system
• Telescope baffling

14
Image Quality

• Image quality tested by direct images and spectra
  through pinhole/slitlet-mask. Hole diameter
  slitlet width 0.5 arcsec 4 pixels.
• All images show radial coma, with maximum length
  approximately 20 pixels at detector edges (see
  plot). In addition, a small amount of constant
  coma appears to be present.
• FWHM data on good images is about 4 pixels, as
  expected.

15
Image Quality (contd)

• Possible sources of radial coma symmetry says
  must come from camera.
• Bad aspheric surfaces on Elements 7 and 8. But
  this was not seen in Optical Shop testing.
• Improper spacing between Element 8 and Element 9
  (field flattener). This is possible, as parts
  were substituted between tests. Easy to fix.
• Possible sources of constant coma symmetry says
  must also come from camera.
• Tilt or displacement of Multiplet 4.
• Tilt or displacement of Element 9.
• Either of these can be largely nullified by the
  decentering adjustment on Multiplet 4. Easy to
  fix.
• Conclusion Greater care in installing Element 9
  and dewar (and possibly decentering Multiplet 4)
  should cure problems.

16
Picture of aberration
17
Other Optical Results

• Fringing is less than 4 peak to peak we had
  been planning on 20. Flat-fielding will be
  easier than expected.
• CCDs 1 and 4 in the blue mosaic are high-rho
  engineering-grade devices from Lot 14. They are
  exactly like the science-grade high-rho devices
  from this lot except they have a poor
  anti-reflection coating and low QE. Their PSFs
  are good, showing that the red science devices
  will have acceptably sharp PSFs.
• CCD 7 is a high-rho red-sensitive prototype from
  Phase 1 that we had been counting on. Its images
  have wings and slightly high FWHM. We no longer
  consider this suitable for the red mosaic and
  have relegated it to a spare.

18
Other Optical Results (contd)

• The wavelength calibration system contains Hg,
  Ne, Ar, Xe, Kr, Cd, and Zn lamps. There are many
  dim but highly usable spectral lines in the blue.
• The internal quartz continuum lamp is dim in the
  blue an has broad spectral features impressed
  by the fiber feed system. However, it is usable
  now and can be improved later if time permits.
• The flexure compensation spectra look good. They
  land on the FC CCDs and have spots of good
  brightness and spectral density.

19
Flexure

• Restatement of problem peak to peak image motion
  of 40 pixels (600 microns) when DEIMOS is
  rotated. Roughly 26 pixels ascribed to grating
  box. Range of motion of FC system is only 20
  pixels peak to peak.
• Progress since last report
• In-house review (Oct 26) recommended three
  strategies
• Brace existing grating box with elbow braces.
  Tried, gave little improvement.
• Remove grating box, strengthen, weld, and
  replace. Due to be implemented Feb 1, results by
  Feb. 15.
• Replace grating box with new system based on 4-5
  tripods attached directly to drive disk. We are
  beginning to study this and will implement if
  necessary.

20
Flexure (contd)

• Direct images of detector inside dewar showed 6
  pixels flexure peak to peak. Dewar is being
  removed and disassembled to fix this. Replaced
  Mar. 15.
• Analysis scheme was developed using ghost images
  and higher-order distortions to disentangle
  collimator, tent mirror, grating, and detector
  motions. Very promising.
• Present image rotation is a little less than 2
  pixels peak to peak at edge of detector. Error
  budget is 1 pixel peak to peak.

21
Grating box with slider 2 at top
22
Grating System

• All parts fabricated (original design).
• Grating tilt system is entering keyword control.
• Grating insertion system is being tested with
  slider 2 and imaging mirror.
• Clamping mechanism passed initial tests.
• Slider body flexes slightly under rotation. Needs
  reinforcing.
• Hand-off mechanism needed rework too floppy.
  New design seems to work well.
• Capture range of homing pin seems comfortably
  longer than flexure of drive-screw system.
• Final end-to-end tests of slider 2 expected next
  week.

23
Grating System (contd)

• Grating sliders are heavier than slider 2.
• Their hand-off mechanisms are harder, due to
  extra weight and grating tilt complexity.
• Slider 1 is very heavy carries 8 x 12 grating.
  Latest vignetting study indicates only 5 light
  gain.
• WE PROPOSE TO REPLACE SLIDER 1 WITH A VERSION OF
  SLIDERS 3/4.
• Concerns
• Complex redesign of sliders 3 and 4.
• Greater weight and flexure with all four sliders
  installed.
• Final integration of grating system will come
  late, after reinstallation of grating box.

24
(No Transcript)
25
Red CCD Mosaic

• The second distribution of Lot 14 MIT/LL high-rho
  devices has occurred. Our allotment of high-rho
  devices is as follows
• 6 excellent science-grade devices
• 1 very good spare, possibly science-grade if
  operated cold enough
• 1 acceptable spare (CCD 7 in blue mosaic)
• 1 B-grade device not suitable for science mosaic
• We need 1-2 more science-grade devices to fill
  out the red mosaic. Possibilities for getting
  these include
• Six more CCDs are due to be packaged from Lot 14,
  of which we would get 1.
• Luppino may be able to trade us 1-2 devices,
  depending on availability.
• We may be able to trade devices with ESO, who
  have a surplus.

26
Red CCD Mosaic (contd)

• We should know about the Luppino trade by March
  1.
• CARA have accepted our plan to assemble and
  lab-test the red mosaic AFTER the Pre-Ship
  Review, pending a review of our test plan.

27
Major Schedule Concerns

• The grating insertion mechanism re-design needs
  to be successful the full-up system with all
  sliders needs to work as well as slider 2 alone.
• Planned fixes of flexure need to work, and our
  diagnosis of the sources of flexure needs to be
  correct.
• Software continues on critical path. Delays will
  result if key software people are distracted or
  hit by illness.
• No surprises in switching to 16 amp read-out of
  the mosaic.
• We assume that we can integrate the red mosaic
  after the Pre-Ship Review.
• We have agreed with CARA to postpone mask
  fabrication at CARA until after DEIMOS
  commissioning. This eases the software schedule
  by about 3 man weeks.

28
Thumbnail of DEIMOS Schedule
29
Schedule, PS to Commissioning
30
CARA Preparations Needed

• Extend the N platform.
• Deflection of N platform under DEIMOS load.
• Design, fabricate and install the cable boom.
• Install the N tracks on the DEIMOS side.
• Increase the elevation axis telescope cable wrap.
• Test carriage mover.
• Produce a drawing for the DEIMOS lift into the
  observatory.
• Run air, glycol, co-ax fiber and power lines to
  the cable boom.
• Mount and install DEIMOS computers and disk
  drives.

31
CARA Preparations Needed (contd)

• Interface control document
• Guider work - software - Lick
• Configuring of accounts
• Data archive to tape
• Telescope interlocks
• Preparation for slit mask
• Cryogen Handling
• Documentation specification
• Commissioning and characterization, image
  reduction
• Documentation of instrument procedures
• SW for instrument control and initialization