Andrew Bunker (Oxford University, JWST-NIRSpec Instrument Team)

Andy Bunker, Megastructures Meeting, May 2010

Andrew Bunker (Oxford University,JWST-NIRSpec Instrument Team)

The James Webb Space Telescope:Our Megastructure in Outer Space


NGST/JWST History• Coordinated NASA, ESA and CSA Studies

since 1997• JWST is consistent with the scientific

program for a “Large Infrared-Optimized Space Telescope”, described in the report “HST and Beyond” (Dressler 1996), and

• the program for the “Next Generation Space Telescope”, which was given top priority by the National Academy of Sciences survey “Astronomy and Astrophysics in the New Millennium” (McKee & Taylor, 2001).


NGST/JWST History

1996: ESA invited to participate in NGST studies, 8-m

1998: 2nd NGST Conference held in LiegeAd Hoc Science Working Group (ASWG)

1999: Design Reference Mission completed

2001: ESA NIRSpec and MIRI Studies initiated

2002: NGST renamed JWST, Ariane V Launcher

2003: Telescope reduced to 6.5-m

2005: “Tiger team” re-scope: PSF at 1micron not science driver

2007: Technology Ready

2008: Start of phase C/D (construction)

2014: Launch (Cycle 1 observations begin 2015)


Who Was James Webb?

James E. Webb Second NASA administrator, during ApolloEdwin Hubble


What is JWST?

• 6.55 m deployable primary

• Diffraction-limited at 2 µm

• Wavelength range 0.6-28 µm

• Passively cooled to <50 K

• Zodiacal-limited below 10 µm

• Sun-Earth L2 orbit

• 4 instruments• 0.6-5 µm wide field camera (NIRCam)• 1-5 µm multiobject spectrometer (NIRSpec)• 5-28 µm camera/spectrometer (MIRI)• 0.8-5 µm guider camera (FGS/TF)

• 5 year lifetime, 10-11 year goal

• 2014 launch

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Goddard Space Flight CentreNorthrop GrummanOperations:STScIProject Scientist: John Mather


JWST Architecture

Optical Telescope

Element (OTE)

Integrated Science Instrument

Module (ISIM) Element

Spacecraft Bus

Sunshield

Sun


ESA Contributions to JWST

• NIRSpec• ESA Provided• Detector & MEMS Arrays from NASA

• MIRI Optics Module• ESA Member State Consortium• Detector & Cooler/Cryostat from NASA

• Ariane V Launcher (ECA)

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(closely similar to HST model…)


Telescope


Funky PSF?

Image Core

PSF Wings

2 µm


0

Orbit

~1,500,000 km

~374,000 km

Trajectory correction

maneuver 1 L + 15 hrs

Trajectory correction

maneuver 2 (if required) L + 25 days

L2 orbit achieved

L + 109 days Launch

Telescope deployment

L + 4 days

Observatory first light (ISIM at safe

operating temp) L + 59 days

Initiate ISIM testing and certification

L + 113 days

Sunshield deployment

L + 2 days

Observatory available for

ISIM activities

L + 70 days

L2

Main EngineStart 1264 sec

Main EngineCut-Off 1785 sec

Main EngineStart 21694 sec

Main EngineCut-Off 22084 sec

JWSTseparation39 min


Sky "glow" in the near-IRSky "glow" in the near-IR


MIRI - mid-infrared instrument 5 < λ < 27 μm

Cryocooler to 7K; Broad-band imaging; 2sq arcmin

R=3000 spectroscopy; also has a coronograph

European Consortium, ESA & JPL (50/50).


NIRCAM : 1-5micron imager (U of Arizona)

10 square arcmin, two channels at once

Uses Hawaii-2KRG arrays

FGS-TFI (Fine Guidance Sensor & Tunable Filter Imager), Canadian Space Agency

Can take 1% narrow-band images over 1.6-4.9microns, 5 square arcmin


JWST Imaging Sensitivity

1 10Wavelength (µm)

Sunshield Scatter> 10 µm

PSF Grows

Mid-IR DetectorDark Current

Gold Coatings< 0.6 µm

105 s, R ~ 3, S/N=10

11 nJy ~AB = 31.4


NIRSpec

• 3 x 3 arcmin FOV

• 1-5 µm coverage

• R~1000, R~100 multiplexed

• >100 sources simultaneously

• Configurable slit width/length

• MEMS array - “build your own slitmask in space”


Slide from J. Gardner (NASA)


1. The End of the Dark Ages: First Light and Reionization

2. The Assembly of Galaxies

3. The Birth of Stars and Protoplanetary Systems

4. Planetary Systems and the Origins of Life

…scientific objectives and requirements of the James Webb Space Telescope (JWST)

Project. JWST will be a large, cold, infrared-optimized space telescope

designed to enable fundamental breakthroughs in our understanding of

the formation and evolution of galaxies, stars, and planetary systems.


Detector Array• 2K4K FPA comprised of two 2K2K

sensor chip assemblies (SCAs)

• =0.6–5.0 µm HgCdTe detectors (Rockwell)

• FPA passively cooled to T=34–37 K

• Key Performance Parameters:• Total noise =6 electrons rms per t=1000 seconds exposure)• QE = >80%

• NIRSpec is detector background limited in nearly all

modes (!)

• Non-stop (“up the ramp”) read and telemetry• 12 s frame time, 1 frame downlink each 50 s


The European JWST FamilyNIRSpec: Arribas, Santiago (Madrid)

Bunker, Andrew (Oxford)Charlot, Stephane (IAP)Franx, Marijn (Leiden)Jakobsen, Peter (ESA) - ChairMaiolino, Roberto (Rome)Moseley, Harvey (NASA/GSFC)Rauscher, Bernie (NASA/GSFC)Regan, Mike (STScI)Rix, Hans-Walter (MPIA)Willott, Chris; Crampton, David (HIA)

SWG: Lilly, Simon (ETH)McCaugrean, Mark (ESA)Wright, Gillian (Edinburgh)

MIRI: co-PI: G. WrightWith a large team (Too many to list here…)


NIRSpec IST


Physical Layout


Micro Shutter Array

Active MSA Area3.6’3.4’Mounting FrameDetector ArrayFixed Slits and

IFU Aperture

Direction of Dispersion

4 x 384 x 185 Shutters 9 Square Arcmin of MSA

Area

Single 200 mas x 450 mas slitssurrounded by 50 mas wide bars

>100 objects simultaneously


MSA Contrast Simulation

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HDF-S Field

Select Objects(Detail)





Undispersed image with MSA mask in place

Spoilers!

Configure Slits(Detail)





Configure Slits(larger view)

Image Mode with MEMS mask in place





Insert Grating and Integrate


Why are we bothering?

Want to find the sources which reionized the Universe, and chart

the history of galaxy (mass) assembly & star formation

Lyman-alpha (if it emerges at all pre-Gunn Peterson)

then it will be a good way to find galaxies, but the flux does not

tell us the star formation rate (but EW might provide clues to the

IMF). Pop III???

Looking at longer wavelengths for other diagnositc lines (also get

reddening, metallicity)

Couple with NIRCAM SEDs

Brightest sources: some hope of velocity dispersions

Want overall luminosity functions, EW distributions

Andrew Bunker (Oxford University, JWST-NIRSpec Instrument Team)

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Transcript of Andrew Bunker (Oxford University, JWST-NIRSpec Instrument Team)