May 19, 2008SSWG #19 Göttingen1 Robert Stobie Prime Focus Imaging Spectrograph Status Optics repair positive progress: –UV efficiency –Some (repair-caused) problems: beamsplitter, detector Status of other fix and improvement projects Schedule

May 19, 2008SSWG #19 Göttingen2 Optics Reprise: Throughput/ Ghosts 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 Instrument removed (Nov 2006), optics shipped to Pilot Group in Calif (Dec) Disassembled into multiplets, throughput measured by monochromator (Feb - Apr 2007):

May 19, 2008SSWG #19 Göttingen3 #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.

May 19, 2008SSWG #19 Göttingen4 #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 CaF 2 element in collimator triplet ("OL5") damaged by technician error! Original OL5: R.I.P.

May 19, 2008SSWG #19 Göttingen5 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 CaF 2 pieces) –resume with triplet assembly at Pilot next week (where we were last Sept)

May 19, 2008SSWG #19 Göttingen6 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.

May 19, 2008SSWG #19 Göttingen7 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

May 19, 2008SSWG #19 Göttingen8 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

May 19, 2008SSWG #19 Göttingen9 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

May 19, 2008SSWG #19 Göttingen10 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

May 19, 2008SSWG #19 Göttingen11 Repair Schedule 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