11/20/2003 TIPS/JIM

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

FGS Specification JWST-SPEC-002069

ISIM to NIRCam ICDJWST-ICD-000728

ISIM to MIRI ICD JWST-ICD-000730

ISIM to NIRSpec ICDJWST-ICD-000729

ISIM to FGS ICD JWST-ICD-000727

JWST Observatory SpecificationDRD SE-03

JWST-SPEC-002020

Element ISIM RequirementsJWST-RQMT-000835

Mission Assurance Requirements for the JWST

InstrumentsJWST-RQMT-002363

ISIM to NIRCam IRD JWST-IRD-000780

ISIM to MIRI IRDJWST-IRD-000782

ISIM to NIRSpec IRD JWST-IRD-000781

ISIM to FGS IRD JWST-IRD-000783

Sub-System

Segment

ISIM to OTE and Spacecraft IRD

DRD SE-06JWST-IRD-000640

ISIM to OTE and Spacecraft ICD

DRD SE-08JWST-ICD-001831

Observatory to Ground Segment IRD DRD SE-07

JWST-IRD-000696

Observatory to Ground Segment ICD DRD SE-09

JWST-ICD-001998

ICDH Requirements JWST-RQMT-000743

ISIM FSW Requirements JWST-RQMT-002101

ISIM Structure Requirements

JWST-RQMT-002087

NIRCam Operations Concept

(UAz DRD OPS-11)

NIRSpec Operations Concept

MIRI Operations Concept

FGS Operations Concept

JWST Level 1 Requirements

JWST-RQMT-000633

Mission JWST Mission (Level 2) Requirements

JWST-RQMT-000634

Mission Operations Concept Document

JWST-RQMT-002018

JWST Project Science Objectives and Requirements Document

(JWST-RQMT-000804)

NIRCam Specification JWST-SPEC-002049

NIRCam Science Requirements

UAz DRD SR-01

FGS Science Requirements

NIRSpec FPRDJWST-SPEC-002060

MIRI FRDJWST-SPEC-002063

MIRI Science Requirements

NIRSpec Science Requirements

Requirements Flowdown to ISIM and Instruments

11/20/2003 TIPS/JIM

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.

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MIRI SRR Review Team

Frank Schutz, Co-Chair JPL

Dennis Dillman, Co-Chair GSFC System Review Office

Klaus … , Co-Chair ESA

Steve Scott GSFC Chief Engineer

Paolo Strada ESA

Dr. David Leckrone  GSFC Space Sciences

+ several others …

11/20/2003 TIPS/JIM

InvestigationImag-ing

R~3000 Spec-trosco

R~100 Spec-troscopy

Corona-graphy

1. Pristine gas, the first stars, and the first heavy elements **2. Black holes and structure in the early Universe X*3. Formation and evolution of galaxies X* X* X*4. Lifecycle of stars in the Milky Way and other galaxies X* X* X*5. Habitats for life in the Milky Way and other galaxies X* X*6. Molecular clouds as cradles for star and planet formation X* X*7. Emergence of stellar systems X* X*8. Evolution of protoplanetary dust and gas disks into planetary systems

** ** X*

9. Evidence of planets in disks around young stars X* X*10.Census of planetary systems around stars of all ages **11. Chemical and physical properties of giant extrasolar planets12. Detect giant planets by direct imaging, and study their properties X* X*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

MIRI Plays a Key Role in Origins Roadmap

Traceability of MIRI Science and Roadmap Investigations

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• Models of spectralenergy distributions*show that NIRCammay have difficultydistinguishingtrue first light galaxies from those with older stars, or even quasars!

• MIRI data beyond 5mcan remove this uncertainty **

* technical details in the box below the figure

** drives sensitivity for 5.6, 7.7m photometry

Example 1: MIRI Will Identify True First Light Objects

Modeled young galaxies and a typical quasar, all at z = 15. The Lyman forest attenuates their outputs short of Ly andforeground damped Lyman 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.

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DUSTYENVELOPE

~ 500 AU orbit of Pluto

CIRCUMSTELLARDISK

MIRI beam@ 7m

PROTOSTAR

Example 2: MIRI Sees Through Interstellar “Windows” to Explore Protostars and Their Environments

The interiors of protostellar cocoons must be probed in the mid-infrared: two windows in the interstellar extinction near 7 and 15m providea unique opportunity to see deep inside.

November 4-5, 2003

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MIRI viewof Vega systemat 24m(model fromWilner et al. 2000)

Adequate to probedetailed predictionsof dynamical modelsand study the planetthat drives them

Example 3: MIRI Will Explore Nearby Planetary Systems and Debris Disks

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• OperationsSupport four science modesEfficiency

• OpticalSupport four science modes Wave front errors, stabilityFields of view, pixel scalesSpectral properties (filters, resolutions, etc.)Throughput, scattered and stray light rejection, minimization of artifactsCoronagraphic rejection - basic design, pointing

• Signal ChainSensitivity parameters - read noise, QE, dark current of detectors Radiometric properties - stability, linearity, dynamic range

• ThermalBackground for sensitivity - OBA < 15.5KSensitivity of detectors - SCAs < 6.9KLifetime > 5 yrsDetector anneal

Driving Requirements

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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.

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NIRCam SRR Review Team

Dennis Dillman, Chair GSFC System Review Office

Marty Davis GSFC Project Management

Tom Venator GSFC Instrument Systems/Mechanical

Steve Scott GSFC Chief Engineer

Joe Schepis GSFC Electromechanical Systems

Gene Waluschka GSFC Optics

Sachi Babu GSFC Detectors

Tony Miller GSFC Electrical Systems

Dr. David Leckrone  GSFC Space Sciences

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NIRCam’s Role in JWST’s Science Themes

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Planets

The First Light in the Universe:Discovering the first galaxies, ReionizationNIRCam executes deep surveys to find and categorize objects.Period of Galaxy Assembly: Establishing the Hubble sequence, Growth of galaxy clustersNIRCam 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 cocoonNIRCam measures colors and numbers of stars in clusters, measure extinction profiles in dense clouds

Planetary Systems and the Conditions for Life: Disks from birth to maturity, Survey of KBOs, Planets around nearby starsNIRCam and its coronagraph image and characterize disks and planets, classifies surface properties of KBOs

11/20/2003 TIPS/JIM

NIRCam Science Requirements (1 of 2)

Detection of first light objects, studying the epoch of reionization requires:

• Highest possible sensitivity – few nJy sensitivity is required.

• 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.

Observing the period of galaxy assembly requires in addition to above:

• High spatial resolution for distinguishing shapes of galaxies at the sub-kpc scale (at the diffraction limit of a 6.5m telescope at 2µm).

NIRC_X0052

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NIRCam Science Requirements (2 of 2)

Stars and Stellar Systems:• High sensitivity especially at>3m• 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

NIRC_X0044

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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 2m and 4mSelection 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

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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- 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.