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WFC3 – Critical Science Review. Science Driven CEIs Requirements. The “Critical Science Metric”. The “Critical Science Metric”. Science Driven CEIs Requirements. CEIS - Sect. 4. 4.3 Optical Performance 4.4 Spectral Performance 4.5 UVIS Channel Shutter Performance

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Wfc3 critical science review
WFC3 – Critical Science Review

Science Driven CEIs Requirements




Science driven ceis requirements
Science Driven CEIs Requirements

CEIS - Sect. 4

  • 4.3 Optical Performance

  • 4.4 Spectral Performance

  • 4.5 UVIS Channel Shutter Performance

  • 4.6 UVIS Channel Detector Requirements

  • 4.7 CCD Detector Thermal Control

  • 4.8 IR Channel Detector Requirements

  • 4.9 HgCdTe Detector Thermal Control

  • 4.10 Observational Requirements

  • 4.11 Calibration


Science driven ceis requirements1
Science Driven CEIs Requirements

  • an “astronomer friendly” view:

    • UVIS Detectors

    • IR Detector

    • Optics

    • Filters

    • Operations



Uvis detectors specs 1 2
UVIS Detectors – specs (1/2)

  • Number of detectors 2

  • Type CCD Backside Illuminated UV Coated Supplementary Buried Channels (SBC)

  • Producer Marconi (former EEV)

  • Format 2048  4096

  • Quantum Efficiency

    • Range and absolute valuesee viewgraph

    • Stability 0.2 %/hr 1s

      1.0 %/month (2% @ l< 300nm)

  • Read-out noise 4.0 e/read (3e goal) @ 4.27 min R.O.time

  • Dark current <25 e/hr/pix @ -83C for 90% of the pixels

  • Operability >99% good pixels

  • Bias stability <2 e rms during read


Uvis detectors specs 2 2
UVIS Detectors – specs (2/2)

  • Linearity >95%, correctable to >99.7%

  • Full well capacity 50,000 e/pix (85,000 goal)

  • Charge-transfer efficiency > 5E-6 @ 1620 and 40,000 e/pix

    • (see viewgraphs)

  • Pixel-to pixel response

    • uniformity better than 2%; 1% @ 400-850nm(0.5% goal)

    • stability<0.2 % over 1 hr (see Q.E.)

  • Radiation hardness

    • Absolute sensitivity <2,000 e/event

    • Stability (SAA) <0.1/e/s/pix after 5min > 90%


  • Marconi ccd q e
    MARCONI CCD – Q.E.

    200-400nm

    optimized



    Cte anomaly stis data
    CTE anomaly: STIS data

    SITe 1024  1024 CCD thinned backside

    NGC 6752, 8  20s, ‘D’ amp at the top

    Courtesy R. Gilliland (STScI)


    Cte anomaly stis data1
    CTE anomaly: STIS data

    NGC 6752, 8  20s, ‘B’ amp at the bottom

    Courtesy R. Gilliland (STScI)


    Cte losses in wf pc2
    CTE losses in WF/PC2

    “…preliminary evidence for

    accelerating growing rate.”

    (“Charge Transfer Efficiency in the

    WF/PC2 CCD Arrays”

    J. Biretta et al., June 2000 AAS)



    Improving cte for wfc31
    Improving CTE for WFC3

    M. Robbins (Marconi Apple.Tech.): “Possibility of limiting the radiation damage

    effects in CCDs”, in CCD Detector CTE workshop, STScI, January 2000

    (http://www.stsci.edu/instruments/acs/ctewg/cte_papers.html)


    2 ir detectors specs 1 2
    2. IR Detectors - specs (1/2)

    • Number of detectors 1

    • Type HgCdTe/ZnCdTe MBE on WFC3-1R MUX

    • Producer Rockwell Science Center

    • Pixel size 18 mm

    • Format 1014 1014

    • Quantum Efficiency

      • Range and absolute value see viewgraph

      • Stability 0.5 %/hr p-p; 1.0 %/month

        Minimum | Target | 100% Incentive

    • Read-out noise 17-20 | 15-17 | <15 e/pix/read @ 100KHz

    • Dark current 0.3-0.4 | 0.2-0.3 | <0.2 e/pix/s @ 150K

    • Operability 94-96 | 96-98 | >98 %

    • Bias stability <2 e rms during read


    Ir detectors specs 2 2
    IR Detectors - specs (2/2)

    • Amplifier glow <10 e/pix/read at the center

    • <400 e/pix/read at the border (<5%)

    • Linearity >95%, correctable to >99.7%

    • Full well capacity 100,000 e/pix (150,000 goal)

    • Pixel-to pixel response

      • uniformity better than 2%; 1% @ 1000-1800nm(0.5% goal)

      • stability<0.2 % over 1 hr ; <1% over 2 months

    • Radiation hardness

      • Absolute sensitivity <1,000 e/event

      • Stability (SAA) <0.1/e/s/pix after 5min > 90%



    Improvements over nicmos
    Improvements over NICMOS

    • Amplifier glow

    • Vignetting

    • Filter ghosts

    • Persistence

    • Column

    • new MUX design (WFC3-1R) > NGST development

    • no optical misalignment

    • detector tilted with respect to the chief ray

    240 s later

    • HgCdTe on ZnCdTe provide better lattice matching

    • new Conexant 0.5mm capability


    Improvement over nicmos
    Improvement over NICMOS

    Residual bias (pedestal)

    Variable DC offset, thermally driven and 1/f time variable, reduces the sensitivity.

    Present in NICMOS and in first generation of Hawaii detectors.

    • Solved with new MUX design (WFC3-1R) using reference pixels

    1014  1014

    active pixels

    1014  5 reference pixels


    3 uvis optics specs
    3. UVIS Optics specs

    • Range 200-1000 nm (200-400nm emphasis)

    • Field of view 162”  160”

    • Pixel separation/scale 39.6 mas (nominal); f/31

    • Field distortion see viewgraph; correctable to .2pix

    • Induced polarization <6.5% (<5% goal)

    • Image quality

      • encircled energy see viewgraph

      • jitter < 3 mas (1/13 pix) 1s over 1300sec

      • drift < 10 mas (1/4 pix) p-p over 2 orbits

    • Optics see viewgraph




    Ir optics specs
    IR Optics specs

    • Range 850-1700 nm (700-1900nm emphasis)

    • Field of view 123” 139”

    • Pixel size 0.121” 0137”

    • Field distortion see viewgraph; correctable to .2pix

    • Induced polarization <5%

    • Image quality

      • encircled energy see viewgraph

      • jitter < 6 mas (1/20 pix) 1s over 1300sec

      • drift < 20 mas (1/5 pix) p-p over 2 orbits

    • Optics see viewgraph






    Pupil image and ota throughput
    Pupil image and OTA throughput

    Footprints of ray bundles from nine field points 0.5 mm in front of the pupil image. The cold stop allows an annular transmission region and the hatched areas indicate areas that block light due to the oversized cold stop. The throughput efficiency of this cold mask is 95%.

    We add 10% for spiders, M1 pods, diffraction effects and alignment tolerances.

    • 15% throughput loss due to the HST obstructions, plus

    • 15% throughput loss due to the cold stop and pupil masking


    Wfc3 subsystems throughput
    WFC3 subsystems throughput

    WFC3 optics

    OTA

    detectors


    Wfc3 overall throughput
    WFC3 overall throughput

    Photon flux

    OTA

    WFC3optics

    detectors


    4 filter specs
    4. Filter specs

    UVIS IR

    • Total number of spectral components: 48 16

    • Very Broad Band 4 -

    • Broad Band 13 5

    • Medium Band 8 3

    • Narrow Band 17 6

    • Narrow Band Quad Elements 5  4 -

    • UV Prism 1 -

    • Grisms - 2




    Operations
    Operations

    • Standard observing mode IMAGING MULTIACCUM (1+15)

    • Integration time

      • Minimum (readout/buffer) 2 min. @ 4 ampli 3s @ 4 ampli

      • Longer 1 orbit (~3000 s)

    • Readout schemes

      • Subarray Y Y

      • Rebinning 2  2 N/A

      • Gain setting 1, 2, 4, 8 e/bit 1/2/4/8 e/bit

    • Overheads

      • Filter change max 60 s

      • Channel change 150 s (except power conserving mode)

      • Data Buffer 2 UVIS images OR 2 IR ramps (IR reads)

    • Calibration: on-board flat/field simulators between 2000A and 2micron must provide…

      • Uniformity within a factor 2 over both fields of view

      • Stability >99% /hr and >95% /yr

      • Flux >10,000e/10min (all filters)

    UVIS IR



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