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JWST Project StatusAAAC, October 12, 2005
John C. MatherJWST Senior Project Scientist
NASA GSFC
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Topics
• Science summary• Mission summary• Technology status• Test plan status• Contamination and Stray Light plan
Top JWST Goal - Find the First Light after the Big
Bang• How and from what were galaxies
assembled?
• What is the history of star birth, heavy element production, and the enrichment of the intergalactic material?
• How were giant black holes created and what is their role in the universe?
• Three instruments to do this: NIRCam (NASA/CSA), NIRSpec (ESA), MIRI (ESA/consortium/NASA), plus FGS-TF (CSA)
as seen by COBE
Galaxies,stars,planets,life
Galaxyassembly
?
?
4SWG Meeting, STScI, September 24 2002
JWJWThe Epoch of Reionization
Redshift
Wavelength Wavelength Wavelength
Lyman Forest Absorption
Black Gunn-Peterson trough
Patchy Absorption
z<zi
z~zi
z>zi
.
Neutral IGM
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National Aeronautics and Space AdministrationGoddard Space Flight Center JWST Science
The Eagle Nebula as seen by HST
The Eagle Nebulaas seen in the infrared
• Birth of stars and protoplanetary systems
• Planetary systems and the origins of life
Galaxies in the UDF
• End of the dark ages: first light and reionization
• The assembly of galaxies
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National Aeronautics and Space AdministrationGoddard Space Flight Center
-sec
mJy
R=2000, 1-100 sec
Spectra obtainedwith the JWST MIRI on the nearest systems can provide detailed insights to the minerals in ring particles and the nature ofgiant planets
Simulated Vega Observation
National Aeronautics and Space AdministrationGoddard Space Flight Center
Model Picture
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JWST Observatory Architecture
Secondary Mirror (SM)• Deployable tripod
for stiffness• 6 DOF to assure
telescope alignment
Optical Telescope Element (OTE)• Stable over total field-of-regard• Beryllium (Be) optics with GFRP/Boron structure
• Performance verified on the ground
Primary Mirror (PM)• 18 (1.315 m) hex segments• Simple semi-rigid WFS&C for phasing
• 6 degree of freedom rigid body• Radius corrections
•Deployable chord fold for thermal uniformity
Tower• Isolates telescope from
spacecraft dynamic noise
ISIM • NIRCam, NIRSpec, MIRI & FGS• Enclosure for FPE• Simple Kinematic interface
Sunshield• Passive cool ISIM/OTE to ~40K• Limits momentum buildup
Spacecraft Bus• Isolates reaction wheel noise
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JWST Orbit about the Sun-Earth L2 and Launch Configuration
(T0) Launch (L + 63 days) Cool
down near steady state; Repeat WFS&C Commissioning
(L + 28 days) Initial WFS&C Commissioning
(L+ 41 min) Solar Array Deployment
(L + 14 hr) High Gain Antenna Deployment
(L + 6 months) Commissioning Complete
(L + 113 days) Initiate Observatory Commissioning
(L + 4 days) OTE Deployment
(L + 2 days) Sunshield Deployment
1 weekinterval
Stowed Observatory in 5meter shroud
(T0) Launch (L + 63 days) Cool
down near steady state; Repeat WFS&C Commissioning
(L + 28 days) Initial WFS&C Commissioning
(L+ 41 min) Solar Array Deployment
(L + 14 hr) High Gain Antenna Deployment
(L + 6 months) Commissioning Complete
(L + 113 days) Initiate Observatory Commissioning
(L + 4 days) OTE Deployment
(L + 2 days) Sunshield Deployment
1 weekinterval1 weekinterval
Stowed Observatory in 5meter shroud
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National Aeronautics and Space AdministrationGoddard Space Flight CenterBall AMSD II Be Mirror in
Optical Test
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Primary Mirror Segment Actuations
Lightweighted Beryllium Mirror Substrate
Actuator for radius of curvature adjustment
Actuators for 6 degrees of freedom rigid body motion, independent of ROC control
Actuator development unit
Observatory optical quality (mid and high spatial frequency) is manufactured into segments
A NIRCam Imaging Module
A dichroic allows simultaneous observing at two wavelengths.
This module’s dual filter wheels include pupils for wavefront sensing.
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National Aeronautics and Space AdministrationGoddard Space Flight CenterDetector Technology Development
NICMOS 256x256
HgCdTe
WFC3 1024x1024 JWST Proto-type 4Kx4K
NICMOS and IRAC arrays have demonstrated the basic detector architecture but with lower performance and smaller formats.
TRL 4 achieved Feb 2002 with JWST performance levels achieved
TRL 5 achieved Feb 2003 with JWST size 2Kx2K devices, mosaicing
Astronomical Image with prototype, Sept. 2003
Flight detectors being manufactured
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National Aeronautics and Space AdministrationGoddard Space Flight CenterNIRSpec: ESA & Astrium
• > 100 Objects Simultaneously• 9 square arcminute FOV
• Implementation:– 3.5’ Large FOV Imaging Spectrograph– 4 x 175 x 384 element Micro-Shutter Array– 2 x 2k x 2k Detector Array– Fixed slits and IFU for backup, contrast– SiC optical bench & optics
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NIRSpec Schematic
Fore optics CollimatorCamera
Micro-Shutter Array Grating/Prism
WheelDetector
ArrayFilter
Wheel
Pick-offOptics
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SAT Recommendations and Response
SAT Recommendation Action Recommended Planned Action(s)
ProCompletion Date
1. Prioritize 1.7-28um Imaging and Spectroscopy
Eliminate low priority modes if they reduce risk and future cost
Planning to eliminate 1.1 micron sensitivity requirement at MRD level. 1 Tunable Filter module in FGS will be eliminated and FGS mass allocation reduced by 80Kg.
Pam SuRTC's by 12/05
2. "Cup Up" testing Pursue planning for "Cup Up" testing and any other I+T savings
"Cup Up" cryo approach has been made the baseline although additional work is needed to fully demonstrate feasibility. A separate trade study is also under way to see if the optical test configuration can be simplified.
Lee FeRTC's by 12/05
3. Eliminate 1um Encircled Energy and modify stability requirement to every 2% photometric accuracy at 2um.
Delete L.1 1um EE Requirement, Rewrite EE Stability
Updated plan is to eliminate the 1um Encircled Energy Requirement altogether. Working with prime contractor on redefinition of stability spec at 2um which could be accompanied by a Field of Regard reduction to keep it cost neutral.
Lee FeiRTC's by 12/05
4. Relaxation of Scattered Light Requirements
Relax particulate requirements to L. 720 (PM) and 630 (SM) - note: need to confirm the eventual relaxation is made consistent with the sensitivity relaxation recommended by the SAT
Team will consider particulate impacts from the Cup Up trade, SSDIF I+T trade, Ariane assessment and will recommend a reduction to the sensitivity and stray light relaxation commensurate with that needed. Will consider particle size distribution and cleaning.
Matt GreRTC's by 4/06
5. Stability Perform Updates Every 7-10 days.
Project is evaluating best approach to mitigating stability risk (see presentation). Updating every 7-10 days will be implemented if appropriate. Recent creep data suggests that structural stability will not require this relaxation. Thermal
Mark RTC's by 12/05
6. AnisotropySignificant relaxation and possible elimination Current plan is to eliminate this requirement altogether.
Lee RTC's by 12/05
7. Mission Life Keep 10 year goal if at all possible No changes to current plan.
Mikdone
Note: Plan is to submit RTC's for requirement changes in December, 2005
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Technology Status
• All technologies to be ready for by Non-Advocate Review (NAR)
• Key technologies:– Mirrors - flight mirror blanks made and being
machined; EDU being polished; operator error (due to an unexpected feature in the machine) at Axsys drilled hole in one blank, no effect on schedule
– Detectors - TRL 5 achieved in 2003, all performance specifications met; some HgCdTe detectors disintegrated, apparently due to insufficient cleaning prior to bonding to BCS (Balanced Composite Substrate); new recipe verified by repeated thermal cycles
– Microshutters - GSFC - recipe found for keeping shutters flat at room temperature and cold; on track with all needed tests
– ASICs - all performance specifications met; final foundry run starting with revised masks
– Cryocooler - will select contractor in January
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Baseline “Cup Down” Tower Configuration at JSC (Before)
Most recent Tower Design shows an Inner Optical Tower supported by a Outer structure with Vibration Isolation at the midplane. Everything shown is in the 20K region (helium connections, etc. not shown) except clean room and lift fixture.
Plan called for 33KW He cooldown capability, 12 KW steady state, major challenges for JSC
JSC currently has 7 KW He capability
Plan required 10 trucks of LN2/day during cooldown
Large Risk on Cooldown Time Assumptions
Clean room
Clean room
Interferometers, Sources,Null Lens and Alignment EquipmentAre in Upper and LowerPressure Tight Enclosure Inside of Shrouds whereCryo Cycle Needed to Fix Problems
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Telescope Cup UpGravity offloaded andOn Ambient Isolators Connected to Concrete)
Auto-Collimating Flats(isolators above connectedto hard points on top of chamber).
Center of Curvature Null and Interferometer Accessible from top
Focal Plane Interferometer and sources accessible from below
JSC “Cup Up” Test Configuration
•Isolators moved outside of shroud/vacuum•Telescope comes in deployed on tracks with minimal time in chamber before pump down
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Contamination Plan
• “Cup Up” test at JSC is not a major contaminant source
• Launch effects are major driver– Ariane meeting planned for this fall– Particle generation by sunshield rubbing during launch?
• We will be able to clean mirrors• Need independent review of all models, assumptions,
methods• Detail required: cleaned mirrors have different
particle size distributions and different BRDF shapes than before cleaning
• Goal is twofold:– Cost-effective particulate contamination plan– Consistency with SAT assumptions regarding sensitivity losses
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Summary
• All review committees endorse JWST plans• Scientific descope recommended by SAT accepted
and being implemented• Cost control and risk reduction approach
endorsed by SAT and IPAO reviews• Replan in progress for new launch date and
budget• Technology progress excellent, will be ready
for NAR