wfc3 tips july 19, 2007

1Wide Field Camera 3 Monthly Status ReviewJuly 17, 2007

WFC3 TIPSJuly 19, 2007


Summary

• WFC3 halfway through Thermal Vacuum Test #2– Team is performing excellently and test is on schedule

– Several thermal issues discovered which will require modifications

– Internal calibration lamps have multiple problems

– Great progress on closing out liens from 2004 TV test

– Currently 39 days into the maximum 72 day T/V-2 test (SES chamber must be vacated and certified for the next HST test by 9/1/2007)

• Flight detector development– Two outstanding IR flight detectors in packaging flow at Ball with

installation of one into the instrument in Dec 2007

– Unresolved problem with the Thermal Electric Coolers (TEC) for the UVIS CCD detectors

• Recovery plan in place but significant schedule concerns


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HST Internal EnvironmentTemp

Section A: Ambient Check

Section B: Bake Out

Section C: Cold #1

Section D: Hot #1

Section E: Cold #2

Section F: Hot #2

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Orbital Hot Cycle

Orbital Cycle: Cold

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WFC3 TV-2 Environmental Profile


Test Profile SegmentDetails

- Indicates Test Completed


• Verified operation of radiator heaters.

• Great progress in validating thermal model.

• Heat pipes all function as expected in 1g environment.

• Verified instrument cold start on both sides.

• Thermal performance of UVIS-2 has been stable and near nominal (compared with pre-anomaly UVIS-1).

• Achieved 145K on IR FPA in Hot and Cold environments.

• Throughput measurements show nominal optical performance.

• No SOFA errors (this issues appears to be resolved).

Highlights


System Throughput with UVIS-2

• UVIS-2 UV QE better than predicted; visible advantage vs. UVIS-1 inferred from ambient cal was an artifact of temperature and stray light

• Response of both CCDs comparable to UVIS-1 chip 1• Optics throughput appears to have held up well since 2004 run

Preliminary analysis by Tom Brown


Excellent Read Noise and Dark Current w/UVIS-2

• Like UVIS-1, UVIS-2 demonstrates “goal” level read noise of 3 e- rms, vs. spec of 4; very important in UV

• 5-10% noise penalty observed for the greater dynamic range of gain = 1.5 setting; will assess whether it is worthwhile to support both settings

Gain = 1 e-/DN UVIS-2 (T/V #2) UVIS-1 (T/V #1)

Amp A 2.93 3.02 (ambient)

Amp B 2.89 2.97 (ambient)

Amp C 2.92 2.86 (ambient)

Amp D 3.05 2.99 (ambient)

Gain = 1.5 e-/DN

Amp A 3.12 3.21

Amp B 2.99 3.25

Amp C 3.05 3.22

Amp D 3.20 3.36

Dark is <1 e/pix/hr at -79C

Preliminary T/V 2 analysis by Sylvia Baggett


IR Throughput Matches Component Measurements Remarkably Well

• No sign of the 10-15% deficit vs. component predictions seen in T/V 1

• Indicates protected-silver mirror coatings are healthy

This is the run with the best controlled background.

Earlier runs came out even higher (good), but with wider spread than we have explained (puzzling) – still investigating.

Preliminary analysis by Tom Brown

IR Throughput vs. Predictions

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Encouraging Initial Read Noise Results for IR Detector

• RMS noise is in good agreement with previous results• Must carefully assess whether there is any significant correlated noise

(some intermittent fixed pattern noise has been seen – perhaps 0.2-0.3 DN)

Preliminary T/V 2 analysis by Bryan Hilbert

Noise

(e- rms) DCL

Ball Acceptance

TestT/V 2

Quad 1 23.1 22.6 23.0

Quad 2 19.3 18.6 19.3

Quad 3 20.0 19.1 19.8

Quad 4 23.8 22.2 23.4


Alignment Stability in Spec for Cold Orbital Cycling

• Negligible drifts in response to orbital cycling in cold environment

• Note that cold cycling case is more benign than hot cycling (not yet tested)

Image Position vs. Time Thru 6 Cold Orbital Cycles


Alignment Stability in Spec for Slew in Cold Environment

• Spec is <10 mas in 200 minutes for UVIS; <20 mas for IR

• Cold environment again is likely more benign than hot environment equivalent

Image Position vs. Time Thru Slew in Cold Environment


Overnight Results for Hot Case

• Meets spec in IR

• UVIS is ~20mas over 3 hours (spec is 10mas)

• Watching long term drift – Realism of the test conditions not yet understood

• Plot by S. Baggett & D. Karakla


IR Grisms Are Now Right!

• Grisms are properly oriented (0.6° and <0.5° off vs. ~2° tolerance and previous 82° error – well done team!

• Cross-dispersion profile of continuum spectra and monochromatic images shows good FWHM – properly focused

• High thermal background seen in T/V 1 with previous G141 grism is now gone with added red blocking

• IR thermal backgrounds thru filters in general are in good agreement with Massimo Robberto model – project to nominal performance in HST OTA environment

G102 Continuum Spectrum

G141 Continuum Spectrum

Analysis by Howard Bushouse


Hardware Issues with Science Impacts

• IR 6-stage control– Out-of-spec control stability is problematic for a high dark-rate device such as

FPA129, given the strong dependence of dark rate on temperature

– Even for a lower dark rate part, there will be a transient trapping-release response to temperature changes (seen in T/V #1 with FPA64)

– The substantial calibration offset, combined with the limited temperature margins in the subsystem test, have made the team reluctant to push the FPA temperature as far as the thermal performance would permit – would be good to establish more margin in IR-3, IR-4 tests, in addition to resolving the calibration offsets

• Internal calibration system– Internal flat-field calibration, on the ground and in space is crucial for the very

rich filter set of WFC3

– Especially in UV, where no suitable diffuse, uniform sources exist in the sky

– Late turn-on of D2 (up to few minutes) is tractable, but failure to turn on would be a significant issue (there is only a single D2 lamp – no redundancy)

– The tungsten bulbs are required for a thorough ground cal with each potential flight detector, and then in orbit as well to track launch shifts or changes with time


General Detector Status

• Bar chart


UVIS Detector Assembly Status

• Two UVIS detector concerns– Short due to conductive particle on flex lead

– TEC damage

• UVIS1-prime is being reassembled after thermal anomaly occurred during acceptance testing

• UVIS2 was delivered to GSFC on March 24, installed into WFC3, and is under instrument test– probably has same TEC problems as UVIS1

• UVIS3 effort at BATC has started – CCD Flex/Carrier assemblies (short resistant)

– Significant schedule challenges


UVIS Thermal Anomaly

• Wrapping up the anomaly investigation– Conclusion: Anomaly was most likely caused by TEC column

failure due to thermally-induced stresses caused by CCD anneal, and may have been aggravated by subsequent vibration testing

– TEC failure has not been duplicated on test units thus far. However, strength varies among devices, and we appear to have selected fairly weak TECs for UVIS1 and possibly UVIS2.

• The problem will be resolved on three fronts– Reduce stresses on TEC to the extent possible

• ‘Ramp’ TEC power levels during ground test and on-orbit operation

– Strengthen future TECs to the extent possible (UVIS3 only)• Use thermally-applied nickel (TAN) plating on TE columns to increase

strength of solder joint

– Inspect the TECs more thoroughly using standardized criteria• Identify flaws that could weaken TEC


TEC Thermal Testing• ACS Qual Unit #4 instrumented and used to measure temperatures at each

TEC stage during operation– Cooldown: Current increased rapidly from 0 4.2 Amps– Warmup: Current decreased rapidly from 4.2 0 amps– Anneal:

• ‘GSFC’ process: TEC allowed to warm for 1 hour before 1.0 amps applied rapidly• ‘Ball’ process: 0.6 amps applied rapidly without a warmup period

C5 Ceramic

C1 Ceramic


UVIS3 Flow

Flex Cable Procurement

Ball Procurement

GSFC Procurement

e2v Packaging of Devices Onto Existing Chip Carrier

Assemblies

Detector Backside Processing CCD Assembly

DCL Testing UVIS3 Assembly

Ball Task

e2v Task

GSFC Task

Delivery to GSFC

Connector & Carrier Assembly

Task in progress

Task complete


CCD Performance Comparison

CCD044 was delivered to the DCL June 20, 2007

Detectors previously delivered to the DCL

#018 #178 #040 #050

Read Noise (A) e- 3 <2.7 2.2 2.1 2.1 2.3 2.4 2.4

(B) e- 3 <2.7 2.3 2.2 2.2 2.6 2.4 2.5

Dark Current e-/pix/hr @-83C

20 0.43 <5 0.13 0.1 0.37 0.38

CTE Serial (A) 0.999995 0.999997 0.999999 0.999999 0.999997 0.999999 0.999999 0.999997

Serial (B) 0.999995 0.999996 0.999999 0.999999 0.999999 0.999999 0.999998 0.999997

Parallel 0.999995 0.999999 0.999999 0.999999 0.999999 0.999999 0.999999 0.999999

QE @250nm % 40 59 51 51 41 55 36 45

@500nm % 60 68 66 63 62 69 65 63

@900nm % 23 27 27 31 32 35 31 32

Full Well ke-50 92 85 99 99 70 102 92

#044#048UVIS Build #1 UVIS Build #2

Units Spec #136


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IR Channel Wavelength Range

QE For IR4 Candidate

IR4


Dark Current For IR4 Candidate

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IR3 short location

UPSTREAM Section of leads validated by Franka, 4/07

DOWNSTREAM lead pinched under foot of

thermal shield


Instrument Integration

WFC3 Schedule9/08 Shuttle Launch

Pre-IR Detector Instrument

Level Testing (Includes T/V

test-2)

Delivery to HST I&T

8/31/07 Build Flight IR1 Detector assembly

10/1/06 – 10/16/07

EMI / EMC -2

12/20 – 12/31/07

12/3 – 12/14/07

Flight detector installation(s)

and final instrument closeout

10/24/05 – 4/5/07= NEW

= CRITICAL PATH ITEM

4/5/07 – 8/31/07

T/V test #2 (Dedicated SES chamber time)

4/17/07– 8/26/07

Build Flight IR3 Det. Assembly

5/23/06 – 5/16/07

UVIS2 Detector Installation

3/24 – 3/25/07

UVIS1 Detector Reassembly and

Test

3/2/07 – 6/07

10/1/06 – 12/3/07

Build Flight IR4 Det. Assembly

T/V test -3T/V test -3

(Dedicated SES chamber time)

12/3/07 – 2/28/081/2/08 – 02/28/08

Build Flight UVIS3 Det. Assembly

4/1/07 – 2/29/08

Detector Selection

12/3/07

UVIS3 Installation?

NET 3/3/08 – 3/14/08Final

Delivery to HST I&T

2/28/08

Acoustic -2

12/14 – 12/19/07

wfc3 tips july 19, 2007

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