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
R~3000 R~100
CoronaSpec- Specgraphy
trosco 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
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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 5mm
can remove this
uncertainty **
first light
older galaxy
quasar
frst lght, filters
older, filters
quasar, filters
10
1000003
10
2
5
10
1
Wavelength (microns)
** drives sensitivity
for 5.6, 7.7mm
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 a forest
attenuates their outputs short of Ly a and foreground damped Lyman a 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
@ 7mm
CIRCUMSTELLAR
DISK
DUSTY
ENVELOPE
PROTOSTAR
~ 500 AU
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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 15mm 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 24mm
(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:
5-s 50,000 secs
• High spatial resolution for
distinguishing shapes of galaxies at
the sub-kpc scale (at the diffraction
limit of a 6.5m telescope at 2µm).
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TIPS/JIM
z=5
HST
z=10
NIRCam
0.1
0.5
1.5
2.5
3.5
4.5
l(m
m)
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:
10
SIRTF
1
• 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.
Keck/VLT
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 l>3mm
• 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 2mm and 4mm
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-s 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