Transcript JWST Project Status, AAAC

JWST Project Status
AAAC, October 12, 2005
John C. Mather
JWST Senior Project Scientist
NASA GSFC
Page 1
Topics
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•
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Science summary
Mission summary
Technology status
Test plan status
Contamination and Stray Light plan
Page 2
Top JWST Goal - Find the First Light after
the Big Bang
• How and from what were galaxies assembled?
as
seen by
COBE
?
Galaxy
assembly
?
Galaxies,
stars,
planets,
life
• 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)
The Epoch of Reionization
JW
Redshift
Neutral IGM
.
z~zi
z<zi
Wavelength
Lyman Forest Absorption
z>zi
Wavelength
Patchy Absorption
Wavelength
Black Gunn-Peterson trough
SWG Meeting, STScI, September 24 2002
4
National Aeronautics and Space
Administration
Goddard Space Flight Center
JWST Science
• End of the dark
ages: first light and
reionization
• The assembly of
galaxies
The
The Eagle
Eagle Nebula
Nebula
as as
seen
seen
in the
by HST
infrared
Galaxies in the UDF
• Birth of stars and
protoplanetary systems
• Planetary systems and the
origins of life
5
National Aeronautics and Space
Administration
Goddard Space Flight Center
4
R=100, 1-s
10,000 sec
3
2
Spectra obtained
with the JWST MIRI
on the nearest
systems can
provide detailed
insights to the
minerals in ring
particles and the
nature of
giant planets
1
R=2000, 1-s
100 sec
mJy
0
Simulated Vega Observation
6
National Aeronautics and Space
Administration
Goddard Space Flight Center
Model Picture
JWST Observatory
Architecture
Optical Telescope Element (OTE)
• Stable over total field-of-regard
• Beryllium (Be) optics with
GFRP/Boron structure
• Performance verified on the ground
Secondary Mirror (SM)
• Deployable tripod
for stiffness
• 6 DOF to assure
telescope alignment
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
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
Tower
• Isolates telescope from
spacecraft dynamic noise
Page 8
JWST Orbit about the Sun-Earth L2 and
Launch Configuration
1 week
interval
(L + 6 months) Commissioning Complete
(L + 113 days)
Initiate
Observatory
Commissioning
(L+ 41 min)
Solar Array
Deployment
(L + 4 days)
OTE
Deployment
(T0)
Launch
(L + 14 hr) High
Gain Antenna
Deployment
(L + 2 days)
Sunshield
Deployment
(L + 28 days) Initial
WFS&C Commissioning
(L + 63 days) Cool
down near steady
state; Repeat
WFS&C
Commissioning
Stowed Observatory
in 5meter shroud
Page 9
National Aeronautics and Space
Administration
Goddard Space Flight Center
Ball AMSD II Be Mirror in Optical Test
10
Primary Mirror Segment
Actuations
Actuators for 6 degrees of freedom
rigid body motion, independent of
ROC control
Lightweighted
Beryllium Mirror
Substrate
Actuator
development unit
Observatory optical quality
(mid and high spatial frequency)
is manufactured into segments
Actuator for radius
of curvature adjustment
Page 11
A NIRCam Imaging Module
A dichroic allows
simultaneous
observing at two
wavelengths.
This module’s dual
filter wheels include
pupils for wavefront
sensing.
National Aeronautics and Space
Administration
Goddard Space Flight Center
Detector Technology Development
 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
HgCdTe
NICMOS 256x256
WFC3 1024x1024
JWST Proto-type 4Kx4K
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National Aeronautics and Space
Administration
Goddard Space Flight Center
NIRSpec: 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
Filter
Wheel
Micro-Shutter
Grating/Prism
Array
Wheel
Detector
Array
Pick-off
Optics
Fore optics
Collimator
Camera
Page 15
SAT Recommendations and Response
SAT Recommendation
Action Recommended
Planned Action(s)
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.
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.
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.
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
2. "Cup Up" testing
5. Stability
6. Anisotropy
Perform Updates Every 7-10 days.
Significant relaxation and possible
elimination
7. Mission Life
Keep 10 year goal if at all possible
Note: Plan is to submit RTC's for
requirement changes in
December, 2005
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.
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
P
r
oCompletion Date
P
a
m
S
uRTC's by 12/05
L
e
e
F
eRTC's by 12/05
L
e
e
F
e
iRTC's by 12/05
M
a
t
t
G
r
eM
RTC's by 4/06
Current plan is to eliminate this requirement altogether.
a
r
LkRTC's by 12/05
e
eM
RTC's by 12/05
No changes to current plan.
i
kdone
Page 16
Technology Status
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•
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
Page 17
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.
Clean room
Plan called for 33KW He cooldown capability,
12 KW steady state, major challenges for JSC
JSC currently has 7 KW He capability
Clean room
Plan required 10 trucks of LN2/day during
cooldown
Large Risk on Cooldown Time Assumptions
Interferometers, Sources,
Null Lens and Alignment Equipment
Are in Upper and Lower
Pressure Tight Enclosure Inside of Shrouds where
Cryo Cycle Needed to Fix Problems
Page 18
JSC “Cup Up” Test Configuration
Auto-Collimating Flats
(isolators above
connected
to hard points on top of
chamber).
Telescope Cup Up
Gravity offloaded and
On Ambient Isolators
Connected to Concrete)
Center of Curvature Null
and Interferometer
Accessible from top
Focal Plane Interferometer
and sources accessible
from below
•Isolators moved outside of
shroud/vacuum
•Telescope comes in deployed on
tracks with minimal time in chamber
before pump down
Page 19
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
Page 20
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
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