04/15/2004 TIPS/JIM 1/13

Summary of the JWST

Integrated Science Instrument Module (ISIM)and

Structural/Thermal Subsystem

Systems Requirements Reviews (SRRs)

Jerry Kriss

04/15/2004 TIPS/JIM 2/13

ISIM OverviewISIM is:• The JWST Science Instruments • Associated Infrastructure: Structure, C&DH, & FSW

Region 1Science Instrument Optics Assemblies Near Infrared Camera (NIRCam) Near Infrared Spectrometer (NIRSpec) Mid Infrared Instrument (MIRI), & Dewar Fine Guidance Sensor and Tunable Filter (FGS/TF)Optical Bench Structure Radiators and support structure (NGST supplied)

Region 2 Focal Plane Electronics (FPE)Instrument Control Electronics (ICE, MCE, DCE)

Region 3ISIM Command & Data Handling (C&DH) ElectronicsFGS C&DH Electronics

04/15/2004 TIPS/JIM 3/13

JWST System Constituents

SystemSystem

SegmentSegment

ElementElement

Subsystem(within ISIM)Subsystem(within ISIM)

JWST System

Observatory Ground Launch

Optical TelescopeElement (OTE)

Spacecraft (SC)

Integrated ScienceInstrument Module

(ISIM)

Structure

Science andOperations Center

Institutional Systems

CommonSystems

LaunchVehicle

Payload Adapter

Launch SiteServices

NIRCam NIRSpec MIRI FGS/TF

Thermal IC&DH Flight SW Harnessing

04/15/2004 TIPS/JIM 4/13

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

04/15/2004 TIPS/JIM 5/13

ISIM SRR Objectives

Confirm that ISIM-level requirements meet the mission objectives.

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

Confirm that the preliminary system design is ready to proceed.

04/15/2004 TIPS/JIM 6/13

Requirements Traceability

Allocation

KEY OTE/SC REQUIREMENTS

Transmission: MR-211Image quality: MR-110,111,228Stray light: MR-121,122Collecting area: MR-198

•L1-1 Density of Galaxies, L1-2 Spectra of Galaxies •SR-4 Diffraction-Limited imaging 2.0 mm-27 mm, SR-5 Short-limage quality: ~75% @ 150 mas @ 1 mm, SR-21 Sensitivity

MR-51 Sensitivity

The observatory system shall be capable of reaching the sensitivity performance levels shown in the following table when observing a position on the celestial sphere that exhibits 1.2 times the minimum Zodiacal light background power.

MRD Appendix A

SNR equations, conditions, and assumptions

Current draft:JWST-MEMO-002852

JWST-TM-002876JWST-TM-002877JWST-TM-002878

Observatory Specification: OBS-67

NIRCam FRD

Derived sensitivity for each operating mode

20% allocated margin

NIRSpec FRD

Derived sensitivity for each operating mode

20% allocated margin

MIRI FRD

Derived sensitivity for each operating mode

20% allocated margin

FGS-TF IPFRD

Derived sensitivity for each operating mode

20% allocated margin

ISIM Requirements Sec 3.7.4

ISIM Requirements Sec 3.7.3

ISIM Requirements Sec 3.7.2

ISIM Requirements Sec 3.7.1

ISIM RequirementsSection 3.2

04/15/2004 TIPS/JIM 7/13

Open Trade Studies

Pupil Imaging Lens in NIRCam• Concluded in favor of including a pupil imaging lens.

OTE/ISIM Mechanical Interface• Concluded in favor of mounting the ISIM to the OTE BSF.

ISIM Decontamination• Concluded in favor of preventing contamination by managing cooldown.

Reheating ISIM and instruments rejected as an option.

MIRI Dewar• Baseline is dual solid hydrogen dewar w/ tactical cooler on the pad.

• To be concluded after dewar contractor selected.

ISIM Electronics Compartment (IEC) Accommodation• Outstanding mass and thermal problems. TBD by 8/2004.

OTE Simulator (OSIM)• To be concluded by mid-summer

04/15/2004 TIPS/JIM 8/13

Key Issues & Challenges

MIRI SRR• Delta-SRR successfully accomplished 9 March 2004

• Demonstrated proper Requirements flowdown• Answered all RFAs

Instrument Electronics Accommodations Trade• Lacking Observatory architectural solution to housing ISIM electronics that

meets all thermal, structural, and electrical performance requirements• Trade study underway to develop new concept for electronics compartment

• Goal to keep all Instrument electronics boxes in Region 2• Planned completion date July 04

System Mass• Observatory Mass Budget has only 9% unallocated reserve

• Estimates currently exceed allocations

• ISIM allocation includes growth contingency• Tracking SIs and Subsystem mass estimates and contingency usage monthly

• Mass evaluation and reallocation (if necessary) in September following:• Conclusion of IEC Trade Study• Conceptual Design of MIRI Dewar

04/15/2004 TIPS/JIM 9/13

Work In Progress

Sensitivity• Mission Rqmts Document and Observatory Spec update required to reflect

current OTE and Instrument designs.

Focus and Pupil Shear Budgets• Tentative agreement; CCRs to Interface Rqmts Docs in process.

Accommodation of NIRCam non-common-path Wavefront Error• Methodology defined; CCRs to Instrument Interface Rqmts Docs in process

Coronagraphy • Existing Level 1 Requirement for Coronagraphy to be flowed to lower level

requirements documents (Mission Observatory ISIM)

• NIRCam, MIRI, and FGS/TF concepts already include coronagraphy

Stray Light and Thermal Emissions Budget• Working group defining format and allocations for flowdown of Mission-level

requirement

04/15/2004 TIPS/JIM 10/13

Plans to ISIM SDR

Complete Trade Studies Key Procurements

• Select NIRSpec Contractor Team

• Select MIRI Dewar Manufacturer

• Select Structure Manufacturer

• Select Single Board Computer Supplier

Documentation

• Complete CCB Process for:

• ISIM, SI, and ISIM Subsystems Requirements Documents

• Flight and ETU ISIM Integration and Test Plans

• MIRI, NIRSpec, FGS Joint Project Implementation Plans

• Develop drafts of:

• SI Interface Control Documents

Achieve TRL6 for Detector Technologies Complete Instrument and Subsystem SRRs and PDRs

04/15/2004 TIPS/JIM 11/13

ISIM SRR Summary Results

The board thought that the review was excellent. 23 Requests for Action (RFAs) generated. Major issues raised by the review board:

• ISIM urged to speed up I&T timeline to meet up with OTE Pathfinder at Plumbrook.

• Worried about piecemeal approach to contamination control. • Worried that redundancy and cross strapping is being done to

excess, without careful thought. • The connection with Ariane Space is still missing, and it can affect

many requirements. • Desire to make several of the ISIM FSW rqmnts less vague and more

verifiable.• Need to do a better flow down of the efficiency rqmt and tie it in to

data quality and reliability in a more comprehensive way.• Fault handling requires more development.

04/15/2004 TIPS/JIM 12/13

Structural/Thermal Subsystem SRR

Structure • Provides kinematic interface to Optical Telescope Element• Supports Instrument Optical Assemblies and maintains alignment• Composite carbon-fiber (M55J) construction with metal (Ti) fittings

Structural system risks:• Thermal distortion at cryogenic temperatures.

• Mitigation: Math Model Development plus test program.

• Metal-composite joint survivability.• Mitigation: early and extensive test program.

Thermal Control Subsystem• Maintains thermal environments for instruments, structure, and electronics• Heat Straps, Thermal Switches, MLI, Heaters, & Sensors• Heat straps connect to radiators for passive cooling

(radiators are NGST-provided)• MIRI dewar is provided by MIRI/JPL

Thermal system risks:• Managing cool down so that it is rapid enough to enable commissioning within

the first 6 months.• Managing relative thermal profiles to avoid contamination.

04/15/2004 TIPS/JIM 13/13

Structural/Thermal SRR Summary

Review was successful. ~20 RFAs generated. Major concern of the panel:

• Little/no flight history for cryogenic applications of composite structures, especially composite joints.

• Urged an even more aggressive and earlier testing program than described by the team.