James Webb Space Telescope and its InstrumentsJames Webb Space Telescope and its InstrumentsJohn Stansberry

Steward Observatory, University of Arizona

The First Light in the Universe:Discovering the first galaxies, Reionization

Period of Galaxy Assembly: Establishing the Hubble sequence, Growth of galaxy clusters

Birth of Stars and Protoplanetary Systems: Physics of the IMF, Structure of pre-stellar cores, Emerging from the dust cocoon

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JWST’s Science ThemesJWST’s Science Themes

young solar system

Kuiper Belt

Planets

Planetary Systems and the Origins of Life: Disks from birth to maturity, Survey of KBOs, Planets around nearby stars

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

Phase A Phase B Phase C/D Phase E

Concept Development Design, Fabrication, Assembly and Test

Formulation

Authorization

NAR Launch

science operations ...

ICR

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T-NAR

JWST CapabilitiesJWST Capabilities25 m2 collecting area using a segmented primary with 6.6-m tip-to-tip diameter

Low infrared background: L2 orbit enables passive cooling to ~45K for primary mirror, ~35K for instruments

Four instruments: NIRCam, 0.6 - 5 µm imaging

NIRSpec, 0.6 - 5 µm, spectroscopy, R~100-3000 and multi-object

MIRI, 5-29 µm, camera + R~2500 integral field spectrometer

Tunable Filter, 1.7- 4.8 µm R~100

Key Design FeaturesKey Design Features• Large telescope optics• JWST’s telescope assembly is lightweight and deployable

Making its telescope lightweight and deployable makes JWST’s large size feasible.

• Telescope assembly and scientific instruments are cold The telescope and the instruments (cameras and spectrometers) attached to it need to be cold so that their own warmth does not overwhelm the faint infrared signals they are meant to detect.

• Sunshield allows the telescope and instruments to get coldThe cold telescope provides the phenomenal sensitivity in the IR.The sunshield allows the telescope and instruments to radiate their heat to the extreme coldness of deep space.

•L2 is an ideal ”Goldilocks” place for an infrared observatoryThe Sun-Earth L2 point is far enough away from the warm Earth to provide a benign thermal environment and enable efficient operations, yet close enough for easy launch and communications.

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JWST has phenomenal capabilities for new JWST has phenomenal capabilities for new astronomy!! See lower left for KBO applications.astronomy!! See lower left for KBO applications.

Instrument Design FeaturesInstrument Design FeaturesNIRCamNIRCam: images the 0.6 to 5m (1.7 - 5m prime) range

–Dichroic used to split range into short (0.6-2.3m) and long (2.4-5m) sections–Nyquist sampling at 2 and 4m–2.2 arc min x 4.4 arc min total field of view seen in two colors (40 MPixels)–Coronagraphic capability for both short and long wavelengths

•NIRCam is the wavefront sensor–Must be fully redundant–Dual filter/pupil wheels to accommodate WFS hardware–Pupil imaging lens to check optical alignment

NIRSpec: NIRSpec: Multi-object dispersive spectrograph (MOS) for 1-5 µm– R~1000 or R~100 for MOS– MOS pixels ~0.2", and cover a ~ ~3’x3’ field– Capable of observing > 100 objects simultaneously. – Several fixed slits and an IFU (3”x3”) are also available with R as high as 3000.– Being built by the European Space Agency

MIRI: MIRI: JWST’s Long Wavelength Instrument– 100x sensitivity over previous systems– Imaging and spectroscopy capability– Imager uses 1Kx1K detectors w/ 0.11”/pixel for a 1.9’x1.4’ FOV with one edge dedicated to coronagraphy– Spectrometer comprised of 4 diffraction-limited IFUs – 5 to 29m– Cooled to 7K by cryo-cooler– Combined ESA/NASA contributions

Tunable Filter/ Fine Guidance Sensor: Tunable Filter/ Fine Guidance Sensor: R~100 imaging and facility guiding

– All fields of view 2.3 x 2.3 arcmin, 68mas pixels

- Matched to NIRCAM FOV

–FGS guider passband 0.8 to 5.0 microns

No filters – may guide and do full field imaging

–FGS-TF -- ~1.7 – 4.8m -- R = 70 to 150 -- Wavelength continuously adjustable -- Coronagraph capability

Want to know more? Go to http://www.jwst.nasa.gov

2Kx2K HgCdTe 1Kx1K Si:As

The three near-infrared instruments employ 2Kx2K HgCdTe detectors from Rockwell Scientific while MIRI employs 1Kx1K Si:As detectors from Raytheon.

Prototype DetectorsPrototype Detectors

Figure to left shows sensitivity gains over a hypothetical 30-m telescope on the ground.

NIRCamSunshield

Spacecraft Bus

Warm, Sun-facing sideWarm, Sun-facing side

Primary Mirror IntegratedScienceInstrumentModule(ISIM)

Optical Telescope Element (OTE)

Cold, space-facing side

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NowNow

Reflectance spectra of KBOs showing how NIRCam filters match H2O features. NIRCam will be able to detect ice on the surfaces of very small objects. NIRSpec and MIRI will provide complete spectra from 0.6 to 28m.

Barkume et al. 2006

Barkume et al. 2006

The diamonds show 10-sigma detections using NIRCam and MIRI in 10,000 secs. The hypothetical KBO is at a distance of 45AU, has a diameter of 200 km and an albedo of 0.10.