Following science program selection, long range plan based on target list and visibility

1
Expected Capabilities of JWST and its Instruments
Jerry Kriss 6/2/2005
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The JWST Observatory Optical Telescope
, Diameter 6.5 m
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Observatory Performance Characteristics

• Primary mirror is 18 hexagonal segments, 6.5 m in
  diameter.
• Strehl ratio gt 0.80 at 2 micrometers
• Encircled energy gt 0.74 within 0.15 arc sec at 1
  micrometer
• Gold coating ? good response at wavelengths gt 0.6
  micrometers
• Field of regard
• Sun angles of 85135 are permitted, with roll
  of 5.
• ? gt35 sky coverage at any instant
• There is a Continuous Viewing Zone (CVZ) of 5
  about the ecliptic poles.

• Targets will be visible for gt60 days

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Overview of JWST Science Instruments

• NIRCam (Near Infrared Camera)
• 0.62.3 ?m, 2.45.0 ?m. R4, 10, 100.
• Fields of view 2 ? 2.2??2.2?
• Lyot-mask coronagraphy
• NIRSpec (Near Infrared Spectrometer)
• 0.65.0 ?m for R100. 1.05.0 ?m for R1000,
  3000.
• Micro-shutter array (3??3?), fixed slits, and
  Integral Field Unit (3??3?)
• MIRI (Mid Infrared Instrument)
• 528 ?m. R4, 10, 100, 3000.
• Imager (1.9??1.4?), Coronagraphy, Low Resolution
  Spectrometer, IFU (5??5?)
• FGS-TF (Fine Guidance Sensor-Tunable Filter
  Imager)
• 1.02.1 ?m, 2.14.8 ?m. R70150.
• Field of view 2.2??2.2?
• Coronagraphy

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The JWST Focal Plane
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JWST Limiting Sensitivities

• Sensitivity is limited by background radiation
  from the sky and telescope.
• The limiting flux (10 ?) shown is for a point
  source at the North Ecliptic Pole (minimum
  background) in a 100,000 second exposure.

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Gain in Astronomical Capability with JWST (G.
Rieke)
JWST1
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JWST Detector Performance

• NIRCam, NIRspec, and the FGS-TF use Rockwell
  H2-RG detectors.
• HgCdTe with the CdZnTe substrate removed
• Improves QE below 1 ?m
• Eliminates one form of persistence
• Molecular-beam epitaxy used to tune band gap
  for long-wavelength cutoffs of 2.5 ?m or 5.0 ?m,
  as necessary.
• Readout integrated circuit is 2040 ? 2040 plus 4
  leading and 4 trailing light insensitive
  reference pixels per row to track bias drifts.
• MIRI uses Raytheon SiAs detectors.
• Readout integrated circuit is 1024 ? 1024 plus 4
  leading and 4 trailing light insensitive
  reference pixels per row to track bias drifts.

• Raytheon performance
• QE gt50, 5 25 ?m
• Read noise lt 34 e, CDS
• Dark current lt 0.01 e/s

• Rockwell H2-RG performance
• QE gt70, 0.6 1.0 ?m gt80, 15 ?m
• Read noise lt 21 e, CDS
• Dark current lt 0.01 e/s

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The Near Infrared Camera

• 2 functionally identical (mirror image) modules

• 2 channels in each module

Filters (W ? R4, M ? R10, N?? R100)

• Sensitivity (10?, R4, 104 s)
• 1.1 ?m 10.4 nJy
• 2.0 ?m 12.1 nJy
• 4.4 ?m 24.5 nJy

• Coronagraphic masks

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The Near Infrared Spectrograph

• R1000 mode
• 1.0 - 5.0 µm
• Micro-shutter array (MSA) or fixed slits
• Covered by three 1st-order gratings
• 1.0 - 1.8 µm
• 1.7 - 3.0 µm
• 2.9 - 5.0 µm
• Sensitivity (10? in 104 s)
• 5.2 ?10-19 erg cm-2 s-1 (emission line)
• R3000 mode
• 1.0 - 5.0 µm
• Fixed slit or integral field unit
• Also uses three 1st-order gratings
• R100 mode
• 0.6 - 5.0 µm
• Micro-shutter array or fixed slits
• Covered by single dual-pass prism

Micro Shutter Array

• 4 x (384 x 185) Shutters
• Slits are 200 mas x 450 mas
• 9 arcmin2 of MSA area
• IFU is 3x3 arcsec2
• HgCdTe FPA is 2 ? (2040 ? 2040)
• Pixels are 0.1 arcsec

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The Mid Infrared Instrument (MIRI) Imager Low
Resolution Spectrometer

• MIRI Imager uses a single 1024?1024 SiAs
  detector
• Scale is 0.11 arcsec/pixel, 1.88?1.41 arcmin2
  FOV.
• Sensitivity (10? in 104 s)
• 10 µm (R5) 0.7 µJy
• 21 µm (R4.2) 8.7 µJy
• LRS uses a fixed slit and a grism at R100

MIRI Imager Filters
MIRI Imager, LRS Coronagraphs
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MIRI Integral Field Unit (IFU)

• The MIRI IFU uses two 1024?1024 SiAs detectors
• One third of each channels waveband is dispersed
  onto one half of a 1k x 1k detector, and the four
  channels are mapped onto 2 detectors.
• A full 5 to 28 mm spectrum requires 3 exposures,
  with the dichroic/grating wheels moved between
  each exposure.
• 4 channels x 3 exposures 12 (overlapping)
  spectral segments
• Sensitivity to line emission (10? in 104 s)
• 9.2 µm (R2400) 1.0 ?10-17 erg cm-2 s-1
• 22.5 µm (R1200) 5.6 ?10-17 erg cm-2 s-1

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The Tunable Filter Imager

• The FGS Tunable Filter imager has short and
  long-wave channels
• Short wavelength channel 1.0-2.1 µm, R70150
• Long wavelength channel 2.1-4.8 µm, R70150
• Optics are reflective except for the dichroic
  beamsplitter, the Fabry-Perot etalon assemblies,
  and the order-blocking filters.
• Each channel uses a 2048 ? 2048 HgCdTe detector
• FOV 2.2?2.2 arcmin2
• 0.065 arcsec/pixel
• Lyot coronagraphic occulters are similar to
  NIRCams---bars and spots.
• Sensitivity (10?, R100, 104 s)
• 1.5 ?m 357 nJy (continuum), 7.1 ?10-18 erg cm-2
  s-1 (line)
• 2.0 ?m 325 nJy (continuum), 4.9 ?10-18 erg cm-2
  s-1 (line)
• 3.5 ?m 368 nJy (continuum), 3.2 ?10-18 erg cm-2
  s-1 (line)
• 5.0 ?m 504 nJy (continuum), 3.0 ?10-18 erg cm-2
  s-1 (line)

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Further Information Contacts

• Instrument flyers on the STScI JWST web site at
  http//www.stsci.edu/jwst/docs/flyers
• The JWST Primer http//www.stsci.edu/jwst/docs/ha
  ndbooks/JwstPrimerv10_5524.pdf/docInfo
• JWST Mission Simulator (JMS) Exposure Time
  Calculator (ETC)
• http//www.stsci.edu/jwst/science/jms/jms_etc_form
  .html
• Contact Larry Petro (petro_at_stsci.edu)
• NIRCam questions P. McCullough (pmcc_at_stsci.edu)
• NIRSpec M. Regan (mregan_at_stsci.edu), or J.
  Valenti (valenti_at_stsci.edu)
• MIRI M. Meixner (meixner_at_stsci.edu), or S.
  Friedman (friedman_at_stsci.edu)
• FGS-TF A. Fullerton (fullerton_at_stsci.edu)
• FGS-Guider E. Nelan (nelan_at_stsci.edu)
• Optical Telescope Element Stefano Casertano
  (stefano_at_stsci.edu)