Post on 30-Dec-2015
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.