1. 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. 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

3. JWST System Constituents
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
NIRSpec
MIRI
FGS/TF
Subsystem
(within ISIM)
Structure
Thermal
IC&DH
Flight SW
Harnessing
04/15/2004
TIPS/JIM

4. JWST Requirements Tree
Baselined
In CM Review
Drafts Available
Allocation Documents
JWST Program Plan
JWST-PLAN L1
Program
System
FGS SRD
JWST Science
Requirements Document
JWST-RQMT
JWST Mission
Requirements
JWST-RQMT
JWST Mission Operations
Concept Document
JWST-OPS
JWST Performance
Assurance Requirements
JWST-RQMT
NIRCam SRD SR MR
MOC PA
NIRSpec SRD
FGS OCD
MIRI SRD
WFS&C Requirements
Allocation Document
JWST-RQMT
EMC Control Plan
JWST-PLAN
Performance Quality
Assurance Plan
JWST-PLAN
Contamination Control
Plan
JWST-PLAN
NIRCam OCD
Budgets
WFE Rev Q 03-JWST-0405
Efficiency
Pointing
WFS
NIRSpec OCD
EMC PQ
CCP
MIRI OCD
Segment
Ground Segment
Requirements
JWST-RQMT
Flight Observatory to
Ground Segment IRD
JWST-IRD
JWST Observatory
Specification
JWST-SPEC
Observatory to Launch
Segment IRD
JWST-IRD
Launch Segment
Specification
JWST-SPEC
JWST System
Verification Plan
JWST-PLAN
JWST-ICD FG GS
OBS
JWST-ICD OL
FGC LS
OLC
Radiation Requirements
Allocation Specification
JWST-SPEC
Environmental Req’s
for the JWST Observatory
JWST-SPEC
Observatory I&T Plan
JWST-PLAN RD EV
Observatory to
GSE IRD
D36127
Fault Protection
Requirements Document
JWST-RQMT
D36128 OG
OGC FP
Element
ISIM Requirements
Document
JWST-RQMT
ISIM to OTE and
Spacecraft IRD
JWST-IRD
SC Requirements Document
JWST-RQMT
Spacecraft to OTE
ICD
D35231
OTE Specification
JWST-RQMT
SOIC
ISIM
ISIM to OTE and
JWST-ICD
IOS-IR SC
OTE
IOSC
04/15/2004
TIPS/JIM

5. 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. 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: mm, SR-21 Sensitivity
MRD Appendix A
SNR equations, conditions, and assumptions
Current draft:
JWST-MEMO
JWST-TM
JWST-TM
JWST-TM
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.
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
ISIM Requirements
Section 3.2
Allocation
The genesis of JWST Sensitivity requirements was the Level 1 Program Office at Hqs….That office directed that the mission carry out survey Observations on targets with brightness levels down to certain specified limits…..
The Science Requirements Document expanded on this and grouped the science objectives intp 4 themes, each having specific Sensitivity requirements….
Within the Mission Requirements Document, Sensitivity is addressed as Requirement # 51…
Each of the science teams for the 4 instruments has generated documents which detail out the equations, conditions, and assumptions which go into the Sensitivity calculation. These documents currently exist in draft form and will become an appendix to the Mission Requirements Document….
Certain aspects of OTE & S/C performance are key to our ability to achieve the required Sensitivities, and these parameters are captured as specific items in the Mission Requirements Document….
These (“OTE/Spacecraft Requirements”) items as well as the rest of the Sensitivity Requirements are then flowed down to the Observatory Specification….
The Observatory Spec develops additional detail on the Sensitivity Requirement, and allocates lower level requirements for the ISIM, OTE, and S/C. At this level the ISIM requirements become paramount since they are the home for the four instruments…..Detailed instrument performance requirements are developed at the next level in instrument Functional and Performance Requirements documents….
The allocation of the performance parameters which determine Sensitivity is shown in more detail in the next chart……
ISIM Requirements
Sec 3.7.1
ISIM Requirements
Sec 3.7.2
ISIM Requirements
Sec 3.7.3
ISIM Requirements
Sec 3.7.4
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
04/15/2004
TIPS/JIM

7. 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. 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. Work In Progress Sensitivity Focus and Pupil Shear Budgets
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. 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. 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. 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. 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