TIPS-JIM Meeting
20 November 2003, 10am, Auditorium
1.
Summary of the JWST MIRI and
NIRCam Systems Requirements
Reviews
Jerry Kriss
2.
Post Thermal-Vac Science
Calibration COS Update
Scott Friedman
3.
Two Strategies for Co-phasing
JWST Primary Mirror Segments:
Dispersed Hartman Sensing and
Dispersed Fringe Sensing
Anand Sivaramakrishnan
Next TIPS Meeting will be held on 18 December 2003.
Summary of the JWST MIRI and NIRCam
Systems Requirements Reviews
Jerry Kriss
11/20/2003
TIPS/JIM
Objectives of MIRI & NIRCam SRRs
↔ Establish the baseline for subsequent design and
verification activities by identifying instrument
requirements and their pedigree.
↔ Confirm that instrument requirements and
specifications meet the mission objectives.
↔ Communicate the formal SI requirements to the
review teams and to the various groups and
contractors involved in the JWST project.
↔ Identify issues and concerns and assign actions for
investigating and resolving them.
11/20/2003
TIPS/JIM
Requirements Flowdown to ISIM and Instruments
JWST Level 1 Requirements
JWST-RQMT-000633
Mission
JWST Project Science Objectives
and Requirements Document
(JWST-RQMT-000804)
Segment
Mission Operations
Concept Document
JWST-RQMT-002018
JWST Observatory Specification
DRD SE-03
JWST-SPEC-002020
Observatory to Ground
Segment ICD
DRD SE-09
JWST-ICD-001998
Element
Observatory to Ground
Segment IRD
DRD SE-07
JWST-IRD-000696
Mission Assurance
Requirements for the JWST
Instruments
JWST-RQMT-002363
ISIM to NIRCam IRD JWSTIRD-000780
ISIM to NIRCam ICD
JWST-ICD-000728
Sub-System
NIRCam Science
ISIM to OTE and
Spacecraft IRD
DRD SE-06
JWST-IRD-000640
ISIM Requirements
JWST-RQMT-000835
NIRCam Specification
JWST-SPEC-002049
ISIM to NIRSpec IRD JWSTIRD-000781
ISIM to NIRSpec ICD
NIRCam Operations
Concept
(UAz DRD OPS-11)
ISIM to MIRI IRD
JWST-IRD-000782
ISIM to MIRI ICD
JWST-ICD-000730
JWST-ICD-000729
MIRI Science
Requirements
NIRSpec FPRD
JWST-SPEC-002060
ISIM Structure
Requirements
JWST-RQMT-002087
ISIM to OTE and
Spacecraft ICD
DRD SE-08
JWST-ICD-001831
NIRSpec Operations
Concept
NIRSpec Science
Requirements
Requirements
UAz DRD SR-01
11/20/2003
JWST Mission (Level 2)
Requirements
JWST-RQMT-000634
MIRI FRD
JWST-SPEC-002063
ISIM FSW Requirements
JWST-RQMT-002101
TIPS/JIM
ICDH Requirements
JWST-RQMT-000743
MIRI Operations
Concept
FGS Operations
Concept
ISIM to FGS IRD
JWST-IRD-000783
ISIM to FGS ICD
JWST-ICD-000727
FGS Science
Requirements
FGS Specification
JWST-SPEC-002069
MIRI & NIRCam SRR Timing (1 of 2)
↔Requirements flowdown is largely complete
• IRDs in final CCB process
• Driving open issues identified and plan for resolution exists
• Requirements worked with the teams extensively over last
18 months
↔These SRRs Precede Mission/Obs/ISIM SRR
• Formal (i.e. CCB) requirements flowdown from Mission- to
SI-level documentation is not yet complete
↔This exception to the “standard” process allows
MIRI & NIRCam development to proceed on
schedule to avoid threatening the JWST launch date
11/20/2003
TIPS/JIM
MIRI & NIRCam SRR Timing (2 of 2)
↔ Risks posed by this approach are mitigated through:
• Science Working Group, which includes the Instrument PIs, has defined the
Mission-level Science Requirements
•
PIs ensured consistency between Mission- & Instrument-level Requirements
• SI Teams Participating in Working Groups which define Interface
Requirements
•
•
•
•
Interface Summit Meetings
ISIM to Telescope Interface Working Group
Line-of-Sight Working Group
Wavefront Sensing Working Group
• Drafts of all Requirements, Interface, Ops, & PA Documents have been
Released
•
Extensive pre-CCB Coordination Ongoing
–
–
•
SI Teams are Reviewing Mission & ISIM-level Documents
ISIM is Reviewing Instrument-level Documents
PIs and/or SI Team Leads are on Project- and ISIM-level CCBs
• Configuration control process in place for future changes: PI is on Project and
ISIM-level CCB.
11/20/2003
TIPS/JIM
MIRI SRR Review Team
Frank Schutz, Co-Chair
Dennis Dillman, Co-Chair
Klaus … , Co-Chair
Steve Scott
Paolo Strada
Dr. David Leckrone
+ several others …
11/20/2003
JPL
GSFC System Review Office
ESA
GSFC Chief Engineer
ESA
GSFC Space Sciences
TIPS/JIM
MIRI Plays a Key Role in Origins Roadmap
Traceability of MIRI Science and Roadmap Investigations
Imaging
Investigation
1. Pristine gas, the first stars, and the first heavy elements
2. Black holes and structure in the early Universe
3. Formation and evolution of galaxies
4. Lifecycle of stars in the Milky Way and other galaxies
5. Habitats for life in the Milky Way and other galaxies
6. Molecular clouds as cradles for star and planet formation
7. Emergence of stellar systems
8. Evolution of protoplanetary dust and gas disks into planetary systems
CoronaR~3000 R~100
graphy
Spec- Spectrosco troscopy
**
X*
X*
X*
X*
X*
X*
X*
X*
X*
X*
X*
X*
**
**
9. Evidence of planets in disks around young stars
X*
10.Census of planetary systems around stars of all ages
11. Chemical and physical properties of giant extrasolar planets
12. Detect giant planets by direct imaging, and study their properties
13., 14., 15., 16. Not major JWST impact
* Identified as a MIRI key investigation by the Origins Subcommittee
** JWST SWG has found MIRI has an important role
11/20/2003
TIPS/JIM
X*
X*
X*
**
X*
X*
Example 1: MIRI Will Identify True First Light Objects
1000000
30
Flux (nJy)
• Models of spectral
energy distributions*
show that NIRCam
may have difficulty
distinguishing
true first light
galaxies from
those with
older stars, or
even quasars!
• MIRI data beyond 5µm
can remove this
uncertainty **
first light
older galaxy
quasar
frst lght, filters
10
older, filters
quasar, filters
100000
3
10
2
5
10
1
Wavelength (microns)
** drives sensitivity
for 5.6, 7.7µm
photometry
* technical details in the
box below the figure
11/20/2003
Modeled young galaxies and a typical quasar, all at z = 15. The Lyman α forest
attenuates their outputs short of Ly α and foreground damped Lyman α systems
cause reddening of AV = 0.6 for the first light object and AV = 0.4 for the older
galaxy. The horizontal bars indicate the NIRCam and MIRI filter bands and the
relative signal levels that would be detected through them, offset for clarity.
Error bars of + 10% are also shown as fiducials.
TIPS/JIM
Example 2: MIRI Sees Through Interstellar “Windows”
to Explore Protostars and Their Environments
MIRI beam
@ 7µm
CIRCUMSTELLAR
DISK
DUSTY
ENVELOPE
PROTOSTAR
~ 500 AU
11/20/2003
November 4-5, 2003
orbit of
Pluto
TIPS/JIM
The interiors of protostellar
cocoons must be probed in
the mid-infrared: two windows
in the interstellar extinction
near 7 and 15µm provide
a unique opportunity to
see deep inside.
Example 3: MIRI Will Explore Nearby Planetary
Systems and Debris Disks
MIRI view
of Vega system
at 24µm
(model from
Wilner et al. 2000)
Adequate to probe
detailed predictions
of dynamical models
and study the planet
that drives them
11/20/2003
TIPS/JIM
Driving Requirements
• Operations
Support four science modes
Efficiency
• Optical
Support four science modes
Wave front errors, stability
Fields of view, pixel scales
Spectral properties (filters, resolutions, etc.)
Throughput, scattered and stray light rejection, minimization of artifacts
Coronagraphic rejection - basic design, pointing
• Signal Chain
Sensitivity parameters - read noise, QE, dark current of detectors
Radiometric properties - stability, linearity, dynamic range
• Thermal
Background for sensitivity - OBA < 15.5K
Sensitivity of detectors - SCAs < 6.9K
Lifetime > 5 yrs
Detector anneal
11/20/2003
TIPS/JIM
MIRI Review Summary
↔ The review board judged that the review did not
fulfill its goals.
↔ Too many unresolved issues:
• Dewar mass (20 kg over) or lifetime (3.9 yrs vs. 5 required)
• Pupil alignment errors (5.4% vs. 2%) could lead to increased
background or lower throughput (by 30%).
• Required depth of focus is now larger than can be
accommodated by MIRI design (3 mm vs. 2 mm).
• Lingering concerns about the divided NASA/ESA
management structure.
• General concerns about unsettled higher-level requirements
flowing down to the instrument level late in the process and
increasing costs.
11/20/2003
TIPS/JIM
NIRCam SRR Review Team
Dennis Dillman, Chair
Marty Davis
Tom Venator
Steve Scott
Joe Schepis
Gene Waluschka
Sachi Babu
Tony Miller
Dr. David Leckrone
11/20/2003
GSFC System Review Office
GSFC Project Management
GSFC Instrument Systems/Mechanical
GSFC Chief Engineer
GSFC Electromechanical Systems
GSFC Optics
GSFC Detectors
GSFC Electrical Systems
GSFC Space Sciences
TIPS/JIM
NIRCam’s Role in JWST’s Science Themes
The First Light in the Universe:
NIRCam
NIRCAM_X000
Modern Universe
Clusters &
Morphology
Reionoization
First Galaxies
Recombination
Forming Atomic Nuclei
Inflation
Quark Soup
Discovering the first galaxies, Reionization
NIRCam executes deep surveys to find and
categorize objects.
Period of Galaxy Assembly:
Establishing the Hubble sequence, Growth of
galaxy clusters
NIRCam provides details on shapes and colors of
galaxies, identifies young clusters
Stars and Stellar Systems: Physics of the IMF,
Structure of pre-stellar cores, Emerging from the
dust cocoon
NIRCam measures colors and numbers of stars in
clusters, measure extinction profiles in dense clouds
young solar system
Kuiper Belt
Planets
11/20/2003
Planetary Systems and the Conditions for
Life: Disks from birth to maturity, Survey of KBOs,
Planets around nearby stars
NIRCam and its coronagraph image and
characterize disks and planets, classifies surface
properties of KBOs
TIPS/JIM
NIRCam Science Requirements (1 of 2)
↔ Detection of first light objects, studying the
epoch of reionization requires:
• High spatial resolution for
distinguishing shapes of galaxies at
the sub-kpc scale (at the diffraction
limit of a 6.5m telescope at 2µm).
11/20/2003
TIPS/JIM
SIRTF
z=5
HST
z=10
NIRCam
1
0.1
0.5
1.5
2.5
3.5
4.5
l ( mm)
Performance of adopted filter set
Number of
Filters
4
5
6
Number of
Filters
4
5
6
7
4
Number of
Filters
↔ Observing the period of galaxy assembly
requires in addition to above:
Keck/VLT
10
• Fields of view (~10 square arc minute)
adequate for detecting rare first light
sources in deep multi-color surveys.
• A filter set capable of yielding ~4%
rms photometric redshifts for >98% of
the galaxies in a deep multi-color
survey.
5-σ 50,000 secs
100
nJy
• Highest possible sensitivity – few nJy
sensitivity is required.
1000
5
6
7
8
0.00
1<Z<2
0.05
2<Z<5
0.10
|Zin-Zout|/(1+Zin)
0.15
5<Z<10
0.20
NIRC_X0052
NIRCam Science Requirements (2 of 2)
↔ Stars and Stellar Systems:
• High sensitivity especially at λ>3µm
• Fields of view matched to sizes of star
clusters ( > 2 arc minutes)
• High dynamic range to match range of
brightnesses in star clusters
• Intermediate and narrow band filters for
dereddening, disk diagnostics, and jet
studies
• High spatial resolution for testing jet
morphologies
↔ Planetary systems and conditions for life
requires:
• Coronagraph coupled to both broad band
and intermediate band filters
• Broad band and intermediate band filters
for diagnosing disk compositions and
planetary surfaces
11/20/2003
TIPS/JIM
NIRC_X0044
Derived Requirements (1 of 2)
↔nJy (10-35 W/m2/Hz) sensitivity
• Detectors with read noise < 9 e-, Idk<0.01 e/sec QE>80%
• Focal plane electronics with noise < 2.5e- so detector
performance is not degraded
• High throughput instrument: ≥70% for optics, ≥85% for
filters
↔At least 7 broadband filters for redshift estimates
↔Large Field of View
• Dichroics to double effective FOV
• Large format detector arrays
↔Large well-depth on detectors
11/20/2003
TIPS/JIM
Derived Requirements (1 of 2)
↔High spatial resolution
• Nyquist sampling at 2µm and 4µm
↔Selection of intermediate and narrowband filters
• 8 R~10 filters needed to classify ices, cool stars
• At least 4 R~100 filters for key jet emission lines (want
higher spatial resolution than Canadian tunable filters)
↔Coronagraph required in all modules
• Coronagraph most important at long wavelengths
• Coronagraphic field must not reduce survey FOV
↔Need fluxes calibrated to 2%
• Requires gain stability on week time scales
• Requires on-orbit calibration plan using on stars
11/20/2003
TIPS/JIM
NIRCam’s Descope Paths (1 of 2)
↔ Descopes which would result in the largest savings (e.g.,
reducing array size from 4Kx4K to 2Kx2K, single rather than
dual wheels) precluded by WFS requirements.
↔ Could reduce number of filters and/or eliminate coronagraphy
but this saves little.
↔ Could drop redundancy requirement within each FPE box
↔ Could accept degraded detector or optical coating performance.
• This would be a descope for late in instrument development where
poorer than required performance would be accepted to maintain
schedule
• Impact unlikely to exceed a factor of 1.5 given current levels of
detector performance and assuming that essentially no AR
coatings were used.
• Not acceptable for cost savings now
11/20/2003
TIPS/JIM
NIRCam’s Descope Paths (2 of 2)
↔Only removal of the dichroics and dedicated long
wavelength channels yields any significant savings.
↔Descope would remove:
• 2 of 4 dual filter/pupil wheels
• 2 of 10 2Kx2K Focal Plane Arrays
• 2 dichroics
• 2 lens assemblies (but note that remaining lens assemblies
now have to work over 0.6-5µm rather than only
collimators working over the full range)
• 2 fold flats
• 2 of 10 Focal Plane Electronics cards
11/20/2003
TIPS/JIM
Descope Plan: Science Impacts
↔Science impacts of removal of dedicated long
wavelength arms are significant:
•
Time to execute any multi-color observation would more than
double because of having to observe all wavelengths serially
rather than in parallel. The data return from NIRCam would
effectively be cut in half.
• Ability to characterize icy surfaces and cool stars would be lost
because only one filter wheel is available and there would be
too few slots for as many intermediate band filters as NIRCam
has now.
• Long wavelength sensitivity would be degraded (10-σ point
source detection limit changes from 18.9 nJy in 10000 sec to
20.5 nJy at 4.5µm because of oversampling of the PSF).
11/20/2003
TIPS/JIM
NIRCam Review Summary
↔ The review board approved of NIRCam moving on
toward PDR, but noted several concerns:
• NIRCam wave-front error exceeds its allocation (70 nm vs.
56 nm).
• NIRCam mass exceeds its allocation (7.7 kg out of 140 kg).
• Concerns about ghosts in a largely refractive optical
design.
• Detector procurement has no independent V&V plan.
• Worried about possible complexities of event-driven
operations.
11/20/2003
TIPS/JIM
Lessons Learned (Preliminary)
↔ Note: Official review board reports and lists of
accepted RFAs have not yet been issued.
↔ Out-of-order reviews makes review boards
suspicious.
↔ Presentation style matters: a requirements review
should focus on requirements and their flowdown.
• MIRI team highlighted problems, glossed over the
successes
• MIRI team got bogged down in design details
↔ Clear, decisive management structure helps.
↔ Mission and ISIM SRRs in December may be tough.
11/20/2003
TIPS/JIM
SPACE
TELESCOPE
SCIENCE
INSTITUTE
Operated for NASA by AURA
Last COS TIPS Aug 2003
TIPS
20 Nov 2003
COS Science Calibration
& Instrument Status
COS Instrument Status
• Thermal vacuum & science calibration testing complete
– Tests of mechanism stability continuing
• All important performance requirements have been met
–
–
–
–
–
Spectral resolution
Sensitivity
Flatfield quality
Scattered light
Wavelength coverage
• COS to be moved to GSFC for storage until launch preparation
– Periodic functional and throughput tests to verify instrument
health
Friedman 2 of 25
TIPS - 20 November 2003
Thermal Vac & Science Calibration
• All testing completed at Ball Aerospace, Boulder
• Initial thermal balance tests and preliminary SI verification
(“Appendix A”) July 2-7.
– 21 tests. ~500 data files.
– Testing terminated to fix power converters and several other small
items.
• Detailed science calibration (“Appendix B”) Sept 20 – Oct 22.
– 109 tests. ~2200 data files.
– NUV first, FUV later, to allow pressure to drop to acceptable levels.
• OPUS and CALCOS processed data available with StarView.
• STScI support at Ball
– Keyes, Hartig, Sembach, Leitherer, Bohlin, Wheeler, D. Stys,
Friedman.
Friedman 3 of 25
TIPS - 20 November 2003
COS Detectors
FUV XDL detector
NUV MAMA detector
Friedman 4 of 25
TIPS - 20 November 2003
Vacuum Chamber Arrangement
COS operations
RAS/Cal
pumps
Vac chamber operations
Green Room contained
operations and data
analysis facility
COS
Vacuum chamber
Vacuum pump
RASCAL control
electronics & computer
Cal Delivery System
Calibration Delivery System
external platform provided
ultraviolet light sources.
Friedman 5 of 25
TIPS - 20 November 2003
Friedman 6 of 25
TIPS - 20 November 2003
Science Calibration Test Categories
•
•
•
•
•
•
•
•
Alignment, focus, image quality, resolution
Sensitivity
Wavelength scales
Stray & scattered light
Flat field and S/N
Detector functions
Optical stability & repeatability
Target acquisition algorithms
Friedman 7 of 25
TIPS - 20 November 2003
Optical Layout
NUV Detector Assembly
NCM
3a
NCM
3b
Ion Trap
MAMA
Tube
NCM
3c
Optics Select
Mechanism 2
MAMA
Electronics
Boards
TA1
G230L
Rotational
Acturator
G225M
FUV Detector Vacuum Assembly
SEG A
G185M
NCM
2
Pre-amps
G285M
Pre-amps
NCM1
SEG B
HVFM
Door
Mechanism
R
Ac o t a
tu t i o n
ra a
to l
r
G130M
G160M
ar r
n e to
L i tua
Ac
G140L
Shutter
Mechanism
PtNe
Lamps
D2
Lamps
Y Linear
Actuator
Optics Select
Mechanism 1
X Linear
Actuator
Aperture
Mechanism
Calibration Ass'y
Friedman 8 of 25
TIPS - 20 November 2003
Appendix B FUV Tests
test
number
70
2700
2705
2706
2740
850
2715
2725
2710
2726
2740
3600
1700
1210
1220
1230
1240
3500
2740
2300
2305
2355
2355
1265
2800
3300
2735
test
name
FUV focus sweeps
FUV HV variability
FUV HV variability
FUV HV variability
FUV dark count rate #1
Repeatability monitor #1
FUV timing threshold settings
FUV walk settings
FUV timing threshold settings
FUV walk settings
FUV dark count rate #2
FUV Accum Check
FUV cal ss flats S/N=30
FUV G130M sensitivity
FUV G160M sensitivity
FUV G140L sensitivity
FUV sensitivity with QE grid off
FUV OSM1 position checks
FUV dark count rate #3
FUV grating stability
FUV grating stability
NUV grating stability
NUV grating stability
G225M 2nd order sensitivity
FUV high local count rate
FUV BOA throughput & resloution
Geometrical Correction WCA part
day
completed
date
Thur
Thur
Thur
Thur
Thur
Fri
Fri
Fri
Fri
Fri
Fri
Sat
Sat
Sat
Sat
Sat
Sat
Sat
Sun
Sun
Sun
Sun
Sun
Sun
Sun
Sun
10/09/03
10/09/03
10/09/03
10/09/03
10/09/03
10/10/03
10/10/03
10/10/03
10/10/03
10/10/03
10/10/03
10/11/03
10/11/03
10/11/03
10/11/03
10/11/03
10/11/03
10/11/03
10/12/03
10/12/03
10/12/03
10/12/03
10/12/03
10/12/03
10/12/03
10/12/03
Test Program by D. Ebbets (Ball), E. Wilkinson (CU), and IDT.
1110
2750
1120
2741
850
3000
2306
2805
2735
1450
1460
1470
2730
2731
2306
850
1720
2100
2110
2120
850
1437
2740
2506
1730
2307
3700
3400
50
2307
50
1155
1156
FUV CDS Pt-Ne Group 1
FUV resolution, QE grid off
FUV CDS Pt-Ne Group 2
FUV dark count rate, QE grid off
Repeatability Monitor #2
FUV Cal SS flats, S/N = 100
G130M Grating Stability #1
FUV high local count rates G160M
Geom Corrections WCA
TA dispersed mode centroids
TA dispersed light phase 4
TA dispersed light phase 5
FUV geometric corrections PSA
Geom Corrections PSA 7x7 pinhole
G130M Grating Stability #2
Repeatability monitor #3
FUV flats aperture offset 2
FUV CO initial spectra
FUV scattered light
FUV high quality spectra
Repeatability monitor 4
NUV TA flooded aperture with Kr
FUV dark count rate 3
NUV flats with CDS D2 lamp
FUV flats aperture offset 3
FUV stability
NUV Efficiency Suplement
Side 2 Mechanism Verification
TA1 Focus Sweeps
NUV stability
TA1 Focus Sweeps
NUV G185M CDS Pt-Ne Spectra in N2
NUV G225M CDS Pt-Ne Spectra in N2
Mon
Mon
Mon
Mon
Mon
Mon
Mon
Mon
Tues
Tues
Tues
Tues
Wed
Wed
Wed
Wed
Wed
Wed
Thur
Thur
Thur
Thur
Thur
Thur
Fri
Fri
Sat
Sat
Mon
Mon
Tues
Tues
Wed
10/13/03
10/13/03
10/13/03
10/13/03
10/13/03
10/13/03
10/13/03
10/13/03
10/14/03
10/14/03
10/14/03
10/14/03
10/15/03
10/15/03
10/15/03
10/15/03
10/15/03
10/15/03
10/16/03
10/16/03
10/16/03
10/16/03
10/16/03
10/16/03
10/17/03
10/17/03
10/18/03
10/18/03
10/20/03
10/20/03
10/21/03
10/21/03
10/22/03
Friedman 9 of 25
TIPS - 20 November 2003
FUV G130M Spectral Resolution
Segment A
Friedman 10 of 25
Segment B
TIPS - 20 November 2003
FUV G130M Spectral Resolution
Friedman 11 of 25
TIPS - 20 November 2003
NUV G225M Spectral Resolution
30000
29000
28000
27000
lam2186
lam2217
lam2233
lam2250
lam2268
lam2283
lam2306
lam2325
lam2339
lam2357
lam2373
lam2390
lam2410
26000
25000
24000
23000
22000
21000
Requirement
20000
19000
18000
17000
2070
2170
2270
2370
2470
2570
Friedman 12 of 25
TIPS - 20 November 2003
Spectral Resolution Summary
• FUV channel
– G130M & G160M
– G140L
R > 20,000
R > 2,000
• NUV channel
– G185M
– G225M & G285M
– G230L
R > 16,000
R > 20,000
R > 1,700 (over most of bandpass)
• Bright Object Aperture (BOA) resolution degraded
– Wedge in ND filter degrades resolution by factor of ~2.5 for FUV
modes and ~4 for NUV modes.
Friedman 13 of 25
TIPS - 20 November 2003
FUV Sensitivity
Detector QE
Segment A
0.12
G140L
Appendix B measurements
0.1
cts/photon
0.08
CEI peak
0.06
component model
0.04
0.02
CEI minimum
0
1200
1300
1400
1500
1600
1700
1800
1900
λ Angstroms
Detector QE
Segment B
This point falls outside the specified wavelength
range and thus does not violate requirements.
Friedman 14 of 25
TIPS - 20 November 2003
2000
NUV Flat Structure
B
A
COS G185M NUV P-flat
1.36% Poisson rms
1000
Intrinsic detector scatter
(1σ=3.25%) within the
100x100 pixel box shown in
dashed lines
500
Pixel (dispersion)
Pixel (dispersion)
C
20,000 - 40,000
0
counts per pixel in
each stripe
500 Pixel (cross-dispersion) 1000
Friedman 15 of 25
TIPS - 20 November 2003
NUV Flatfield S/N
Normalized
ratio of first
half of
exposure to
second half
Friedman 16 of 25
TIPS - 20 November 2003
FUV & NUV Flat Fields
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TIPS - 20 November 2003
NUV Spatial Resolution
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TIPS - 20 November 2003
Optics Select Mechanism (OSM)
Optics Select Mechanism Two
• Full 360 Degree Rotation
• 101 arcsecond step size,
with selectable step rate (78
steps/sec baselined)
• Coarse and fine resolvers
provide position feedback
Ferris wheel mode
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TIPS - 20 November 2003
OSM Stability with Time
5
Helicopter mode
(typical component test results)
1 resel
4.5
4
~ 4 minutes
3.5
3
2.5
2
G160M
G130M
1.5
G140L
1
NCM-1
0.5
0
11:14:47
11:10:40
11:06:33
11:03:38
10:59:31
10:55:24
10:52:54
10:49:01
10:44:54
10:41:10
10:38:01
10:33:54
-1
10:29:47
-0.5
Time
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TIPS - 20 November 2003
G130M Segment A – Helicopter Orientation
G130M Seg A Image Motion in Helicopter Orientation
2
1.5
1
X-drift 1
X-drift 2
X-drift 3
X-drift 4
X-drift 5
X-drift 6
X-drift 7
X-drift 8
X-drift 9
Average
Motion (pixels)
0.5
-0.906 Arcseconds of Drift
0
-0.5
-1
-1.5
-2
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Time (secs)
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TIPS - 20 November 2003
G160M Segment A – Helicopter Orientation
G160M Seg A Image Motion in Helicopter Orientation
1
0.5
0
X-drift 1
X-drift 2
X-drift 3
X-drift 4
X-drift 5
X-drift 6
X-drift 7
X-drift 8
X-drift 9
X-drift 10
X-drift 11
X-drift 12
X-drift 13
Average
-01.069 Arcseconds of Drift
Motion (pixels)
-0.5
-1
-1.5
-2
-2.5
-3
-3.5
-4
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Time (sec)
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TIPS - 20 November 2003
G185M – Helicopter Orientation
G185M Image Motion in Helicopter Orientation
0
0
500
1000
1500
2000
2500
3000
3500
4000
4500
-1
-9.39 Arcseconds of Drift
Motion (pixels)
-2
YC1
YC2
YC3
YC4
YC5
YC6
YC7
Average
-3
-4
-5
-6
Time (secs)
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TIPS - 20 November 2003
OSM Stability Summary
• The OSM met stability requirements in component level
testing (helicopter mode).
• Science calibration (Ferris wheel mode): OSM1 & OSM2 did
not meet requirements in some cases.
• Post science cal GN2 testing (helicopter mode) has shown
excessive drift in some test cases.
– OSM relaxation may be due to thermal effects. Bench is not thermally
controlled in helicopter mode.
• Ball conducting additional test to further characterize problem.
• COWG and COS FIG groups will consider operational
changes to mitigate the problem. COS IS evaluating science
impacts.
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TIPS - 20 November 2003
COS Science Calibration Summary and Status
• Science calibration complete
– All instrument modes exercised.
– Instrument stimulated by continuum, emission line, and absorption line
(O2 and CO) sources.
• Performance is excellent
– Resolution, sensitivity, alignment, image quality, focus.
•
•
•
•
Flight software performed as expected
OSM stability under investigation
Expect shipment to GSFC shortly
Functional tests every 3 months; NUV throughput tests every
6 months
• OPUS and CALCOS processed thermal vacuum test data in
MAST.
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TIPS - 20 November 2003
Co-phasing JWST during commissioning
using
Dispersed Hartmann Sensing
or
Dispersed Fringe Sensing
Anand Sivaramakrishnan
Telescopes Branch, Instrument Division
Space Telescope Science Institute
methods developed by
Paul Atcheson, Scott Acton (Ball), Fang Shi (JPL)
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
From Atcheson (BATC)
Commissioning Process
– Operational Performance Assumptions
PM/SM
Deployment
OTE - 0.5 arcsec 1-σ pointing
PM segments - <100 µm, 1 arcmin wing deployment
<100 µm ROC, 0.5 arcmin tilt, 100 µm
piston
SM - <3 mm linear position, 5 arcmin tilt
Control
Sense
1. Coarse Alignment
C
>150 µm seg piston, >250 nm rms WFE
S
Commission
Accomplished
in transit to L2
(20 days)
<100 µm seg piston, <200 nm rms WFE
2. Coarse Phasing/
Fine Guiding
C
<1 µm rms WFE, <8 marcsec LOS jitter
>1 µm rms WFE range, <10 nm accuracy
S
3. Fine Phasing
C
<100 nm rms WFE setpoint
150 nm rms WFE worst case decay
Maintenance
As required
(~1 hr weekly or monthly)
4. Wavefront Monitoring
S
>>150 nm rms WFE range,
<10 nm measurement accuracy
Sensing
Sensingrequirements
requirementsat
ateach
eachstep
stepdetermine
determineinterface
interfaceparameters
parameters––FOV,
FOV,etc.
etc.
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
From Atcheson (BATC)
Where does Coarse Phasing fit
in JWST commissioning?
Before coarse phasing
At end of Coarse Alignment
< 100 micron segment piston
< 200 nm RMS wavefront error (WFE)
After guiding
After coarse phasing
At end of Coarse Phasing
< 1 micron RMS WFE
< 8 mas Line of Sight (LOS) jitter
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
Actuator
Single actuator
Gears
Large coarse motion
Small Fine motion
Cryogenic
Excellent repeatability
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
Radius of Curvature actuator
on Ball testbed telescope segment
(TBT: same basic design as JWST, smaller size)
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
Bipod Actuation
Flexures attach actuator
to back of segment
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
Single segment
on Ball testbed telescope segment
3 bipods = 1 hexapod
RoC actuator in middle
(hanging free from back surface)
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
What is Fringe Sensing?
Circular aperture
Cut it horizontally across a diameter
Offset one half by some piston error (a ‘step’ across the cut)
What is the PSF at various wavelengths?
PSFs for same piston at different wavelengths
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
From Fang Shi (JPL)
How is the Fringe Formed?
Segmented Telescope δL
DFS Grism
L
x
DFS Fringe
λ Increases
Dark Band
x
Dispersion
Final data strip on detector
DHS/DFS description, JWST Informal Monthly, November 2003
Wavefront Pistoned
Piston Corrected
Sivaramakrishnan
From Fang Shi (JPL)
DFS fringes from Keck
tbd
tbd
Red dots show 12 subaperture
locations, each seeing two segments
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
What is DHS?
Place a PRISM over the edge between two adjacent segments
prism tilts the resulting spot away from ‘on-axis’ location on detector
When sent through GRISM the spot is smeared out in λ
same as a DFS fringe
On a different pair of segments use a diffent tilt prism
this spot does not overlap the first spot
a second DFS-like fringe is created
Measure relative piston between all pairs of adjacent segments
using a single exposure
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
From Scott Acton (BATC)
DHS Simulations
-30 –20 –10 –5
0
5
10
20
30 microns
Simulation code allows user to specify:
•Center wavelength
•Width of light spectrum
•Number of discrete wavelengths in the simulation
•Percent full well in the images
•Read noise
•Dark current
•Magnitude of star (affects noise due to dark current)
•Dispersion in X and Y directions
•Image sampling parameters
DHS/DFS description, JWST Informal Monthly, November 2003
Assume pupil is 35 Sivaramakrishnan
mm dia.
DHS observing sequence - summary
1 sensing, 1 check observation (best case) ~5 worst case
•
•
•
•
Slew to target
Lock with FGS (on 5x blur)
Take two ~100s NIRCam exposures with two pupil wheel positions
Downlink data, analyze, determine segment updates
•
•
•
•
•
Upload actuator commands
Take two ~100s NIRCam exposures with two pupil wheel positions
Adjust all segments
Take two ~100s NIRCam exposures with two pupil wheel positions
Downlink data, analyze --- DONE (with good actuators)!
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
From Fang Shi (JPL)
DFS for 18-Hex Example: Segment Group
•
Two-grism approach provides optimal visibility for all
operations
–
–
–
–
–
•
•
•
2 crossed dispersed grisms in NIRcam filter wheel (may
have 1 in each of 2 channels)
7 images
First phases segments into rows
Then phases rows to each other
Fine phasing between each “big move” to remove
residual tilts
Position the groups along a 45º line so that fringes
from vertical and horizontal dispersion grism won’t
collide
The spots are (from lower left): PARKING LOT,
Group #1, #2, #3 (middle), #4 and #5
Spots are separated by 1 arcsec in x and y in the
simulations
15
16
17
14
5
4
6
18
2
8
Group #4
12
11
3
1
7
Group #5
13
10
9
Group #3
Group #2
Group #1
Tilt test segment pairs
(cyan & magenta)
away from PARKING
LOT
PARKING
LOT
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
DFS observing block - summary
7 or more iterations (best case) ~20 worst case?
·
Slew to target
·
·
Move N segment pairs out of PARKING LOT
Guide w/FGS on some spot?
·
·
·
Take two NIRCam exposures with grisms in pupil wheel
Command segment tilts to re-arrange segment pairs
Take NIRCam exposures
·
·
·
.
.
Repeat till all. required segment pairs have been observed
Downlink and analyze, prepare segment updates
Repeat 7 times (or more) till measurement meets spec
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
DHS Strengths/weaknesses
•Simple FGS operation
•Catastrophic pupil misregistration of grism assembly
is fatal
•Monotonic improvement of PSF with each iteration
•Measurement does not require actuation
•5 days to coarse phase if actuators misbehave
•Ground verification needs work during I&T
•DHS is the baseline approach
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan
DFS strength/risks
• Strengths
– Catastrophic pupil misalignment not an issue
• Risks
–
–
–
–
Non-monotonic image quality during process
Measurement requires actuation
Many more iterations with single grism
20 days to coarse phase if actuators misbehave (possibly
fatal)
• DFS is the fallback approach
DHS/DFS description, JWST Informal Monthly, November 2003
Sivaramakrishnan