Oct 22, 2007 SSWG #18 UKZN 1

Robert StobiePrime Focus Imaging

SpectrographStatus

• Optics repair• Schedule• Status of other fix and improvement projects• Budget

Oct 22, 2007 SSWG #18 UKZN 2

C o a tin g s

C am era C o llim a to r

M g F / so lg e l2

M g F 2

M u ltilay e r

C aF 2

S ilic a

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):

Oct 22, 2007 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.

Oct 22, 2007 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

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Fluid Sam ple Transm ission

Fluid + Material Experiments

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Polyurethane Tubing

SylG ard 184

RTV Sealant 730

Sulfuric Anodizing

Brass

P lastic Syringe

Viton

Polyurethane b ladder

Oct 22, 2007 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

Oct 22, 2007 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

320 0320 1.1

Field lens Assembly

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Oct 22, 2007 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

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Field Flattener

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Oct 22, 2007 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)

Multilayers after fluid repair

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Oct 22, 2007 SSWG #18 UKZN 9

Comparison with on-sky

• Projected improvement

– UV 10x (5x so far)

– Visible 10 - 30%

Optics Throughput

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EG 21 S litless Spec

47 Tuc Im aging

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M onochrom ator

P ro jected

Oct 22, 2007 SSWG #18 UKZN 10

Repair Schedule

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

Oct 22, 2007 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

Oct 22, 2007 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

$-

$1,000,000

$2,000,000

$3,000,000

$4,000,000

$5,000,0002002 2003 2004

PD

R

CD

R

De

liver

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E st C ost to C om pletion

U W

SAAO

R U

Tota lExpenditures

Baseline

20% Budgeted Reserve

no

w

2005 2006 2007