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Robert Stobie Prime Focus Imaging Spectrograph Status

Robert Stobie Prime Focus Imaging Spectrograph Status. Optics repair Schedule Status of other fix and improvement projects Budget. Optics Reprise: Throughput/ Ghosts. Instrument removed (Nov 2006), optics shipped to Pilot Group in Calif (Dec)

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Robert Stobie Prime Focus Imaging Spectrograph Status

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  1. Robert StobiePrime Focus Imaging SpectrographStatus • Optics repair • Schedule • Status of other fix and improvement projects • Budget SSWG #18 UKZN

  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 SSWG #18 UKZN

  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. SSWG #18 UKZN

  4. #3: Repair (still) "in work" • Found absorption in lens fluid (Cargille LL5610) due to polyurethane expansion bladders, and (lesser extent) viton O-Rings • Original plan (May - July): flush/ replace fluid with LL3421 (viton compatible), replace bladder with polyethylene • Can be done without disassembling multiplets, although index slightly low • Plan A: Did not work • fluid gaps too small, some could not be flushed • ethanol flushing agent sometimes fogged test NaCl pieces SSWG #18 UKZN

  5. Plans B, C (and D) • Plan B: Disassemble multiplets, clean, replace expansion polyurethane bladders and viton O-rings • Back to LL5610 fluid (better index match) 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! • Plan C: Recovery • use existing spare blank (thanks to CDR panel!) • Pilot to cover blank, figuring, coating costs • figuring underway by TORC • considering Lick Obs hardened solgel coating • 3 - 6 month delay • Plan D (in case this one breaks!): regrind damaged element SSWG #18 UKZN

  6. Throughput – Collimator • Field Lens repair: UV loss was very small - repaired as precaution • Triplet repair: interrupted by accident: projection shown • Doublet repair • UV loss gone except slight dip at 350 nm • ~10% grey loss still seen SSWG #18 UKZN

  7. Throughput - Camera/ Spec • Quartet Repair. Looks good. • Triplet Repair • surface contact fix remedies grey loss • fluid repair improves UV, leaves ~15% loss at 320 nm • Project visible ~5% below FPRD spec, 30% low at 320 nm SSWG #18 UKZN

  8. Remaining UV loss - multilayer coatings? • Notice that all elements having Spectrum Thin Film multilayer coatings (including singlet field flattener after recoat) have "ripples", one in the UV. • Suspect absorption effect, not caught with reflectivity witness • Small effect not worth risk and cost of disassembly, polish off coat, recoat, etc • Effect may also be in SALTICAM • If true, should not be seen in repaired collimator triplet (solgel/ MgF2) SSWG #18 UKZN

  9. Comparison with on-sky • Projected improvement • UV 10x (5x so far) • Visible 10 - 30% SSWG #18 UKZN

  10. Repair Schedule • With departure of Eric Burgh, new UW optics reintegration support team: Alan Shier (Pilot Group), Marsha Wolf (NIR project) • Reintegration schedule • No earlier than: 7 Feb - 31 Mar • With 3 month contingency: 1 May - 23 June Schedule SSWG #18 UKZN

  11. RSS Fixes/ Improvements • Slitmask mechanism • severe reliability problems due to difficulty of aligning magazine, carrier, and focal plane chute • redesigned, rebuilt; sensor electronics board iteration • Grating stage flexure • out-of spec flexure perpendicular to dispersion • repaired current grating stage; purchased new, improved one • Etalon flexure • ring centers do not flex the same: dual etalon difficulty • improve etalon "seat". Done • Fix guider interference (limits field): Done • Improve baffling • moving baffle damage, maintainability. Material received • payload/ instrument interface. Material received; design complete • High level software. Design Complete; coding in progress • Detector fast readout modification (last SSWG). Done SSWG #18 UKZN

  12. Cost to Completion • Does not include ~$40K repair overrun due to additional work disassembling multiplets ("Plan B") • Replacement of damaged element OL5 borne by Pilot Group • Still predicting CTC ~20% over CDR budget SSWG #18 UKZN

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