The James Webb Space Telescope:
Our Megastructure in Outer Space
Andrew Bunker (Oxford University,
JWST-NIRSpec Instrument Team)
Andy Bunker, Megastructures Meeting, May 2010
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).
•
Andy Bunker, Megastructures Meeting, May 2010
NGST/JWST History
1996:
ESA invited to participate in NGST studies, 8-m
1998:
2nd NGST Conference held in Liege
Ad 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)
Andy Bunker, Megastructures Meeting, May 2010
Who Was James Webb?
Edwin Hubble
James E. Webb
Second NASA
administrator, during
Apollo
Andy Bunker, Megastructures Meeting, May 2010
What is JWST?
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6.55 m deployable primary
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Diffraction-limited at 2 µm
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Wavelength range 0.6-28 µm
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Passively cooled to <50 K
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Zodiacal-limited below 10 µm
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Sun-Earth L2 orbit
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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)
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5 year lifetime, 10-11 year goal
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2014 launch
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Andy Bunker, Megastructures Meeting, May 2010
Goddard Space Flight Centre
Northrop Grumman
Operations:STScI
Project Scientist: John Mather
Andy Bunker, Megastructures Meeting, May 2010
JWST Architecture
Integrated Science Instrument
Module (ISIM) Element
Optical Telescope
Element (OTE)
Sunshield
Spacecraft Bus
Sun
Andy Bunker, Megastructures Meeting, May 2010
ESA Contributions to JWST
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NIRSpec
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MIRI Optics Module
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ESA Provided
Detector & MEMS Arrays from NASA
ESA Member State Consortium
Detector & Cooler/Cryostat from NASA
Ariane V Launcher (ECA)
(closely similar to HST model…)
Andy Bunker, Megastructures Meeting, May 2010
Telescope
Andy Bunker, Megastructures Meeting, May 2010
Funky PSF?
Image Core
2 µm
PSF Wings
Andy Bunker, Megastructures Meeting, May 2010
Andy Bunker, Megastructures Meeting, May 2010
Orbit
Main Engine
Start 1
264 sec
Main Engine
Cut-Off 1
785 sec
~1,500,000 km
Launch
L2 orbit
achieved
L + 109 days
Initiate ISIM
testing and
certification
L + 113 days
Trajectory
correction
maneuver 1
L + 15 hrs
Sunshield
deployment
L + 2 days
Main Engine
Start 2
1694 sec
Main Engine
Cut-Off 2
2084 sec
JWST
separation
39 min
0
L2
~374,000 km
Telescope
deployment
L + 4 days
Observatory
available for
ISIM activities
L + 70 days
Observatory
first light (ISIM at safe
operating temp)
L + 59 days
Trajectory
correction
maneuver 2
(if required)
L + 25 days
Andy Bunker, Megastructures Meeting, May 2010
Sky "glow" in the near-IR
Andy Bunker, Megastructures Meeting, May 2010
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).
Andy Bunker, Megastructures Meeting, May 2010
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 1.64.9microns, 5 square arcmin
Andy Bunker, Megastructures Meeting, May 2010
JWST Imaging Sensitivity
Andy Bunker, Megastructures Meeting, May 2010
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”
Andy Bunker, Megastructures Meeting, May 2010
Slide from J. Gardner (NASA)
Andy Bunker, Megastructures Meeting, May 2010
…scientific objectives and requirements of the
James Webb Space Telescope (JWST)
Project. JWST will be a large, cold, infraredoptimized space telescope designed to enable
fundamental breakthroughs in our
understanding of the formation and evolution of
galaxies, stars, and planetary systems.
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
1.
Andy Bunker, Megastructures Meeting, May 2010
Detector Array
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2K4K FPA comprised of two 2K2K
sensor chip assemblies (SCAs)
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=0.6–5.0 µm HgCdTe detectors (Rockwell)
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FPA passively cooled to T=34–37 K
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Key Performance Parameters:
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Total noise =6 electrons rms per t=1000 seconds exposure)
QE = >80%
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NIRSpec is detector background limited in nearly all
modes (!)
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Non-stop (“up the ramp”) read and telemetry
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12 s frame time, 1 frame downlink each 50 s
Andy Bunker, Megastructures Meeting, May 2010
The European JWST Family
NIRSpec:
Arribas, Santiago (Madrid)
Bunker, Andrew (Oxford)
Charlot, Stephane (IAP)
Franx, Marijn (Leiden)
Jakobsen, Peter (ESA) - Chair
Maiolino, 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. Wright
With a large team (Too many to list here…)
Andy Bunker, Megastructures Meeting, May 2010
NIRSpec IST
Andy Bunker, Megastructures Meeting, May 2010
Physical Layout
Andy Bunker, Megastructures Meeting, May 2010
Micro Shutter Array
Active MSA Area
Mounting Frame
Fixed Slits
and
IFU Aperture
3.4’
Detector Array
3.6’
Direction of Dispersion
Single 200 mas x 450 mas slits
surrounded by 50 mas wide bars
>100 objects simultaneously
4 x 384 x 185 Shutters
9 Square Arcmin of MSA Area
Andy Bunker, Megastructures Meeting, May 2010
Andy Bunker, Megastructures Meeting, May 2010
MSA Contrast Simulation
Select Objects
(Detail)
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HDF-S Field
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MSA Contrast Simulation
Configure Slits
(Detail)
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Spoilers!
Undispersed image with
MSA mask in place
Andy Bunker, Megastructures Meeting, May 2010
MSA Contrast Simulation
Configure Slits
(larger view)
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Image Mode with
MEMS mask in place
Andy Bunker, Megastructures Meeting, May 2010
MSA Contrast Simulation
Insert Grating and Integrate
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Andy Bunker, Megastructures Meeting, May 2010
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
Andy Bunker, Megastructures Meeting, May 2010