Robert Stobie Prime Focus Imaging Spectrograph Status

1
Robert StobiePrime Focus Imaging
SpectrographStatus

• Optics repair positive progress
• UV efficiency
• Some (repair-caused) problems beamsplitter,
  detector
• Status of other fix and improvement projects
• Schedule

2
Optics Reprise Throughput/ Ghosts

• Instrument removed (Nov 2006), optics shipped
  to Pilot Group in Calif (Dec)
• Disassembled into multiplets, throughput
  measured by monochromator (Feb - Apr 2007)

• Three problems
• Yellow ghost due to coating problem on dewar
  window
• Grey loss in camera triplet
• UV loss in contaminated lens fluid of four
  multiplets

3
1,2 fixed

• Field flattener (ghost). Bad coating polished
  off by Janos, new coating applied by Spectrum
  Thin Films (with new moisture repellant
  overcoat). Satisfactory.
• Camera triplet contact. Backed off pressure,
  contact and grey loss vanished, has not
  reappeared.

4
3 Repair (still) "in work"

• Found absorption in lens fluid (Cargille LL5610)
  due to polyurethane expansion bladders, and
  (lesser extent) viton O-Rings. After several
  false starts
• Disassemble multiplets, clean, replace expansion
  polyurethane bladders and viton O-rings
• Use LL5610 fluid except for Collimator Field
  Lens and Triplet LL3421 a better choice for
  common NIR beam
• (Aug - Sept) Four of five multiplets repaired.
  During reassembly of the last, two surfaces of
  first CaF2 element in collimator triplet ("OL5")
  damaged by technician error!

5
OL5 Replacement almost done

• Recovery
• use existing spare blank
• Pilot to cover blank, figuring, coating costs
• figuring by TORC done (promised 2 months
  actual 4 1/2 months)
• solgel coating by Cleveland Crystals almost
  done. (promised 4 weeks actual 7 weeks).
  (Considered Lick Obs hardened solgel coating too
  risky they do not have experience with large
  CaF2 pieces)
• resume with triplet assembly at Pilot next week
  (where we were last Sept)

6
Polarizing Beamsplitter

• Was shipped to Pilot with main optics to solve
  fluid leak problem
• With resolution of UV optics problem, realized
  beamsplitter would have same problem, verified
  severe UV loss
• (Nov) Flushed fluid, fixed leak, replaced
  bladder. Verified UV transmission recovered.
• (Nov) seal on front side lost. disassembled top
  layer, cleaned, realigned.

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Beamsplitter - 2

• (Feb) Repotting attempt leaves voids. 4 of 9 top
  prism wedges removed, cleaned, realigned
• (Mar) Repotting attempt succeeds, except 3 corner
  top prism wedges cracked when removing mold.
• Recovery plan
• Pilot Group covering costs
• possible repair with index-matching glue
  (Lambrecht)
• possible replacement using spare blank, or new
  blanks
• 3-6 months? does not affect main RSS
  reinstallation, only polarimetry commissioning

8
Detector

• Problem with poor temperature stability being
  remedied with new bucking heater
• (Jan) Due to poorly mated connector, heater came
  on without control loop working heater
  evaporated, leaving contamination film on CCDs
  and (temporary) dewar window
• Recovery
• redesigned heater control Done
• send CCD mosaic to E2V for cleaning Done
• build up a QE measuring system at SAAO visible,
  points at 320 and 355nm, plus flat field In work
• will not hold up RSS reassembly

9
RSS Fixes/ Improvements

• Slitmask mechanism
• severe reliability problems due to difficulty of
  aligning magazine, carrier, and focal plane chute
• redesigned, rebuilt, integrated with instrument
  under test
• Grating stage flexure
• out-of spec flexure perpendicular to dispersion
• repaired current grating stage purchased new,
  improved one flexure being tested
• Etalon flexure
• ring centers do not flex the same dual etalon
  difficulty
• improve etalon "seat". Done
• Fix guider interference (limits field) Parts
  manufactured needs assembly and calibration

10
RSS Fixes/ Improvements - 2

• Electronics brackets redesign for easier
  maintainance. Done
• Improve baffling
• moving baffle damage, maintainability. Material
  received
• payload/ instrument interface. Done
• High level software.
• PCON/ PDET Coding nearing completion. TCS I/F
  next
• Should be ready to test during reassembly
• Detector fast readout modification (last SSWG).
  Done, Tested
• Instrument air humidity improvement
• found air dewpoint 12 C ! risked dewar window
  fogging.
• maintained dryer, lines. Dewpoint at payload now
  -10 - -30

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Repair Schedule

• UW optics reintegration support team Alan Shier
  (Pilot Group), Marsha Wolf (NIR project)
• Reintegration schedule
• No earlier than 28 July 17 Sept
• Return for lift when telescope is ready

Schedule