01/15/2004 TIPS/JIM

Summary of the JWST Mission and ObservatorySystems Requirements Reviews,

andMicro-Shutter Array (MSA) Confirmation Review

Jerry Kriss

01/15/2004 TIPS/JIM

SRR Objectives

Confirm that mission-level and observatory requirements meet the project objectives

Confirm observatory-level specifications are sufficient to meet the project objectives

Validate that the mission architecture concept can support the functional, operational, interface and performance requirements

Show that the requirements have been flowed down and are understood at the next level.

01/15/2004 TIPS/JIM

SRR Review Team

Dennis Dillman, Chair GSFC System Review OfficeSteve Graham GSFC Project ManagementAlain Berinstain CSATed Harper CSAJacques Louet ESAColin Jones ESASteve Scott GSFC Chief EngineerAlexander Krimchansky GSFCGene Waluschka GSFC OpticsSachi Babu GSFC DetectorsTom McCarthy GSFC ThermalMark Fontaine GSFCJoe Schepis GSFC ElectromechanicalPeiman Maghami GSFCMinh Phan GSFCDr. Mal Niedner  GSFC Space Sciences

01/15/2004 TIPS/JIM

NIRCam SRD

NIRSpec SRD

MIRI SRD

FGS SRD

JWST Requirements Tree

JWST-ICD-002001 JWST-ICD-001998

JWST Program PlanJWST-PLAN-000633Program

System

JWST PerformanceAssurance Requirements

JWST-RQMT-000650

JWST ScienceRequirements Document

JWST-RQMT-002558

JWST Mission OperationsConcept DocumentJWST-OPS-002018

Segment

Performance QualityAssurance Plan

JWST-PLAN-002412

Contamination ControlPlan

JWST-PLAN-002028

JWST ObservatorySpecification

JWST-SPEC-002020

Environmental Req’sfor the JWST Observatory

JWST-SPEC-003149

EMC Control PlanJWST-PLAN-002449

WFS&C RequirementsAllocation DocumentJWST-RQMT-002017

Ground SegmentRequirements

JWST-RQMT-001056

JWST SystemVerification Plan

JWST-PLAN-002027

Launch SegmentSpecification

JWST-SPEC-001999

Flight Observatory toGround Segment IRD

JWST-IRD-000696

Observatory to LaunchSegment IRD

JWST-IRD-002000

NIRCam OCD

NIRSpec OCD

MIRI OCD

FGS OCD

Radiation RequirementsAllocation SpecificationJWST-SPEC-000871

ISIM to OTE and

JWST-ICD-001831

Fault ProtectionRequirements Document

JWST-RQMT-002450

ISIM to OTE and Spacecraft IRD

JWST-IRD-000640

OTE SpecificationJWST-RQMT-002021

SC Requirements DocumentJWST-RQMT-002039

ISIM RequirementsDocument

JWST-RQMT-000835

Element

Spacecraft to OTE ICD

D35231

L1

SR

JWST MissionRequirements

JWST-RQMT-000634MR MOC PA

GS OBS

ISIM

EVRD

WFSCCPPQ

EMC

OL

OLC

LS

FP

FG

FGC

IOS-IR

IOSC

OTESOICSC

BaselinedIn CM ReviewDrafts AvailableAllocation Documents

BudgetsWFE Rev Q 03-JWST-0405

EfficiencyPointing

D36128

Observatory to GSE IRDD36127 OG

OGC

Observatory I&T PlanJWST-PLAN-002030

01/15/2004 TIPS/JIM

JWST Science Requirements (John Mather presenting)

Four themes: • First Light • Assembly of Galaxies • Birth of Star and Planetary Systems • Planetary Systems and the Origins of Life

Level 1 Mission Success Criteria: • Density of galaxies • Spectra of galaxies • Physical and Chemical properties of young stellar objects • Observing time---5 yr mission, 1.1e9 s on target • Telescope > 25 m2 • Strehl ratio > 0.8 at 2 m • Encircled energy > 0.74 within 0.15 arc sec at 1 m, stable for > 24 hrs. • Thermal environment zodi limited 0.6 -- 10 m

Example of how Level 1 requirements flow down: 1st-light objects are rare (<1 arcmin-2) ==> large, unvignetted FOV with low distortion.

01/15/2004 TIPS/JIM

Requirement Changes Since the Delta-MDR

Redesigned sun shield---smaller, better clearances, simpler deployment – but, it could make mission planning more difficult.

Upgrade the power system to accommodate ISIM power needs.

01/15/2004 TIPS/JIM

Requirements Still in Work Moving targets. Quantitative requirements are TBD,

depending on cost. Sensitivity. New numbers developed, but CCB on hold

pending NGST replan contract change. Mass allocations are TBD pending resolution of the ISIM

Electronics Compartment (IEC) study. Ariane 5 change not yet flowed down (no expected impact). FOV offsets not yet flowed done (no expected impact). Reliability. Recent MRD change says goal is 92% for

Spacecraft+OTE. Goal for whole observatory is pending. OTE to ISIM structural interface definition. X vs. Ka-band study. [Should finish soon in favor of Ka.]

01/15/2004 TIPS/JIM

Key Issues

Concept for locating ISIM electronics in Region 2 is not viable. • FPEs must be within 6m of focal planes, in Region 2 • Adding ICE boxes advantageous

• "Saddle-bag" configuration won't work. (Too massive; thermal problems.) Further work underway. (IEC trade study. Will take FPE

rqmnts into account.) Mass Allocations

• Current mass reserves are at 21%. Would like to be at 25%. Biggest problem areas are the IEC accommodation, and the sun shield containment system.

• Spacecraft is 250 kg over its allocation• OTE is 405 kg over its allocation• MIRI dewar is 20 kg over its allocation; NIRCam is 7 kg too heavy.

01/15/2004 TIPS/JIM

(ISIM Region 1)

(ISIM Region 2)

(ISIM Region 3)

01/15/2004 TIPS/JIM

SRR Summary Results

The board thought that the review was excellent. ~60 Requests for Action (RFAs) generated. Major issues in the RFAs:

• Request for an Observatory-level TV test.

• Request for deployment tests in TV.

• Desire to make several of the Mission/Obs rqmnts less vague and more verifiable (e.g., those related to event-drive ops).

• Need to do a better flow down of the efficiency rqmnt and tie it in to data quality and reliability in a more comprehensive way.

• Fault handling requires more development.

01/15/2004 TIPS/JIM

Micro-Shutter Array (MSA) Confirmation Review

Held 12/18/03 at GSFC to assess whether the MEMS micro-shutter array should be the slit-defining mechanism for NIRSpec.

Successes:• Fabricated 128 x 64 arrays (flight will be 384 x 175)• Demonstrated 2-D addressing• Implemented light shields• Performed cryogenic life tests• Measured pixel failure rate at end-of-life• Measured open/closed shutter contrast ratio [2,000-

10,000 warm; ~200 cold (due to shutter curvature)]• Performed an acoustic test

01/15/2004 TIPS/JIM MSA Backside

100 m

Magnetic Stripes on MSA Frontside20 m MSA Light Shields

100 m

01/15/2004 TIPS/JIM

Micro-Shutter Array (MSA) Confirmation Review

Concerns:• Yield is still low• Light shields frequently break off• Shutters curve and bend when cooled• Life testing does not meet <10% of rows with a failed-

open shutter• Crude acoustic/shake tests increase rate of failed-opens

Further development needed, but optimism prevails. The MSA remains the preferred approach, and the European

selection is proceeding on this basis.