Summary of the JWST
Integrated Science Instrument Module (ISIM)
and
Structural/Thermal Subsystem
Systems Requirements Reviews (SRRs)
Jerry Kriss
04/15/2004
TIPS/JIM
1/13
ISIM Overview
ISIM is:
• The JWST Science Instruments
• Associated Infrastructure: Structure, C&DH, & FSW
Region 1
Science 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 3
ISIM Command & Data Handling (C&DH) Electronics
FGS C&DH Electronics
04/15/2004
TIPS/JIM
2/13
JWST System Constituents
System
JWST System
Segment
Observatory
Ground
Launch
Element
Optical Telescope
Element (OTE)
Science and
Operations Center
Launch
Vehicle
Spacecraft (SC)
Institutional Systems
Payload Adapter
Integrated Science
Instrument Module
(ISIM)
Common
Systems
Launch Site
Services
NIRCam
Subsystem
(within ISIM) Structure
04/15/2004
NIRSpec
MIRI
FGS/TF
Thermal
IC&DH
Flight SW
TIPS/JIM
Harnessing
3/13
JWST Requirements Tree
Baselined
In CM Review
Drafts Available
Allocation Documents
JWST Program Plan
JWST-PLAN-000633 L1
Program
System
FGS SRD
JWST Science
Requirements Document
JWST-RQMT-002558SR
NIRCam SRD
NIRSpec SRD
JWST Mission
Requirements
JWST-RQMT-000634 MR
JWST Performance
Assurance Requirements
JWST-RQMT-000650 PA
JWST Mission Operations
Concept Document
JWST-OPS-002018 MOC
FGS OCD
MIRI SRD
Budgets
WFE Rev Q 03-JWST-0405
Efficiency
Pointing
WFS&C Requirements
Allocation Document
JWST-RQMT-002017 WFS
NIRCam OCD
EMC Control Plan
JWST-PLAN-002449
NIRSpec OCD
EMC
Performance Quality
Assurance Plan
JWST-PLAN-002412
Contamination Control
Plan
JWST-PLAN-002028
CCP
PQ
MIRI OCD
Segment
Flight Observatory to
Ground Segment IRD
JWST-IRD-000696 FG
Ground Segment
Requirements
JWST-RQMT-001056
GS
JWST Observatory
Specification
JWST-SPEC-002020
RD
Launch Segment
Specification
JWST-SPEC-001999
OL
OBS
JWST-ICD-001998 FGC
Radiation Requirements
Allocation Specification
JWST-SPEC-000871
Observatory to Launch
Segment IRD
JWST-IRD-002000
JWST System
Verification Plan
JWST-PLAN-002027
LS
JWST-ICD-002001
OLC
Environmental Req’s
for the JWST Observatory
JWST-SPEC-003149 EV
Observatory I&T Plan
JWST-PLAN-002030
Observatory to
GSE IRD
D36127 OG
D36128 OGC
Fault Protection
Requirements Document
JWST-RQMT-002450
FP
Element
ISIM Requirements
Document
JWST-RQMT-000835
ISIM
ISIM to OTE and
Spacecraft IRD
JWST-IRD-000640
ISIM to OTE and IOS-IR
JWST-ICD-001831
04/15/2004
SC Requirements Document
JWST-RQMT-002039
SC
Spacecraft to OTE
ICD
D35231 SOIC
OTE Specification
JWST-RQMT-002021
OTE
IOSC
TIPS/JIM
4/13
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
5/13
Requirements Traceability
•L1-1 Density of Galaxies, L1-2 Spectra of Galaxies
•SR-4 Diffraction-Limited imaging 2.0 mm-27 mm, SR-5 Short-l
image quality: ~75% @ 150 mas @ 1 mm, SR-21 Sensitivity
MRD Appendix A
MR-51
SNR equations, conditions,
and assumptions
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.
Current draft:
JWST-MEMO-002852
JWST-TM-002876
JWST-TM-002877
JWST-TM-002878
Sensitivity
KEY OTE/SC REQUIREMENTS
Transmission: MR-211
Image quality: MR-110,111,228
Stray light:
MR-121,122
Collecting area: MR-198
Observatory Specification: OBS-67
Allocation
ISIM Requirements
Sec 3.7.1
ISIM Requirements
Section 3.2
ISIM Requirements
Sec 3.7.2
ISIM Requirements
Sec 3.7.3
ISIM Requirements
Sec 3.7.4
NIRCam FRD
NIRSpec FRD
MIRI FRD
FGS-TF IPFRD
Derived sensitivity for
each operating mode
Derived sensitivity for
each operating mode
Derived sensitivity for
each operating mode
Derived sensitivity for
each operating mode
20% allocated margin
20% allocated margin
20% allocated margin
20% allocated margin
04/15/2004
TIPS/JIM
6/13
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
7/13
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
8/13
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
9/13
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
10/13
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
11/13
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
12/13
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.
04/15/2004
TIPS/JIM
13/13