Mid-InfraRed Instrument (MIRI)
Delta-Systems Requirements
Review: March 9
Margaret Meixner
MIRI support scientist
Result of MIRI delta-SRR
MIRI project successfully completed the delta System Requirements Review.
The review board was very complementary of the extensive preparation of the
requirements documentation and the systematic documentation of the flow
down of the requirements. The hard work of the entire MIRI Team was
acknowledged and commended.
MIRI Delta Systems Requirements Review 9 March 2004
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MIRI has four Science Modes
1. Photometric Imaging
3. Coronagraphy
2. Low Resolution Spectroscopy
MIRI Delta Systems Requirements Review 9 March 2004
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MIRI has four Science Modes
4. Integral Field Unit Spectroscopy
MIRI Delta Systems Requirements Review 9 March 2004
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MIRI in the System
REGION 1
REGION 2
REGION 3
(37 K)
(75-300 K)
(300 K)
T
V
T
Dewar I/Fs
Under review
Routine Monitoring
Discretes / Passive Analog
T
T
Launch-Critical
Discretes /Passive Analog
DCE
RS-422 / 1553B
(TBD)
S
S/C
CTP
MIRI
FSW
(TBD)
Thermal Straps
MIRI Dewar
(6.65 K @ FPM Strap I/F
6.85K @ OBA Strap I/F)
FPE
SpaceWire
1553B
Thermal Switch
T Temperature Transducer
V Valve Actuator
S
ICE
IC&DH
MIRI
FSW
MIRI OBA
(7 K)
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System Requirement Review
 Held on Nov 4 and 5, 2003 at JPL
 First Instrument SRR on JWST. The higher level flow downs were not
complete
 Was held before ISIM and Observatory SRRs
 Board requested delta SRR to address issues raised in the board report
 Received 97 RFAs
MIRI Delta Systems Requirements Review 9 March 2004
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After MIRI SRR
 45 RFAs were reassigned internally
 NIRCam successfully completed their SRR
 MIRI prepared plan for addressing the Board comments
 Observatory Successfully completed their SRR
 ISIM SRR scheduled for March 16
 MIRI delta SRR scheduled for March 9
 Established the content and the format for delta SRR in consultation with
the review board
 Delta SRR package distributed on Feb 24
MIRI Delta Systems Requirements Review 9 March 2004
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Review Board Report Summary – Part I
 The working relationships between the MIRI principals, JPL and ESA,
appear to be excellent
 The science requirements in particular appear to be clearly understood
 The MIRI team provided a clear depiction of open issues affecting the
instrument system.
 It was observed that the MIRI team, which is spread over the globe with
multiple centers and institutional participants, is obviously fully operational
and is filled with an enthusiastic spirit.
 The MIRI team has a clear definition of the instrument design at this early
stage of the project.
 The MIRI project has an excellent, very capable team.
 There appears to be an excellent understanding and flowdown of the
science requirements. There was clearly a thorough
knowledge of the source of the science requirements and how the
requirements flowdown to the subsystems.
MIRI Delta Systems Requirements Review 9 March 2004
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Board Report Summary – Part II
Group a) 1,3,4,5,9 and 11
1.
The flow down from the SciRD to the instrument system and subsystem
architecture was spotty
3
Few presenters discussed the derived, flow down of the requirements,
instead they presented designs that reflected their approach to meeting
the assumed requirements.
4
Consistency of the OBA design approach with the requirements was
not made clear to the Board.
5
Uncertainties plague the definition of the requirements. The JWST
project made changes in its requirements documentation, the System
IRD, which was not available to the MIRI team in time to be incorporated
in the material presented at the MIRI SRR. This situation impacted the
ability of the MIRI Team to convince the Board that it had a clear grasp
of the requirements and the impact of the requirements on the system
design.
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Observatory Requirements
JWST Program Plan
JWST-PLAN-000633 L1
Program
System
JWST Science
Requirements Document
JWST-RQMT-002558SR
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
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
Performance Quality
Assurance Plan
JWST-PLAN-002412
NIRSpec OCD
EMC
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
JWST System
Verification Plan
JWST-PLAN-002027
OL
OBS
JWST-ICD-001998 FGC
Radiation Requirements
Allocation Specification
JWST-SPEC-000871
Observatory to Launch
Segment IRD
JWST-IRD-002000
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
SC Requirements Document
JWST-RQMT-002039
SC
Spacecraft to OTE
ICD
D35231 SOIC
OTE Specification
JWST-RQMT-002021
OTE
IOSC
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ISIM Requirements
JWST Observatory
Specification
JWST-SPEC-002020
OBS
Segment
Fault Protection
Requirements Document
JWST-RQMT-002450
FP
Element
Mission Assurance Requirements
For the JWST Instruments
JWST-RQMT-002363
ISIM Requirements
Document
JWST-RQMT-000835
MAR
ISIM
ESA JWST Product Assurance
Requirements Document
ESA-JWST-RQ-64
ISIM to OTE and
Spacecraft IRD
JWST-IRD-000640
ISIM to OTE and IOS-IR
JWST-ICD-001831
IOSC
PAR
CSA Performance Assurance
Requirements CSA-TBD
NIRCam IRD
JWST-IRD-000780
ISIM to OTE and INCU
JWST-ICD-000728
INCC
NIRSpec IRD
JWST-IRD-000781
ISIM to OTE and INSU
JWST-ICD-000729
MIRI IRD
JWST-IRD-000782
ISIM to OTE and IMU
INSC
JWST-ICD-000730
IMC
FGS IRD
JWST-IRD-000783
ISIM to OTE and
JWST-ICD-000727
IF
IFC
Subsystem
NIRCam Functional
Requirements Document
JWST-SPEC-002049
NRC
NIRSpec Functional
Requirements Document
JWST-SPEC-002060
NRS
ISIM Structure Requirements
JWST-RQMT-002087
IST
MIRI Functional
Requirements Document
JWST-SPEC-002063
MIR
ISIM Flight
Software Requirements
JWST-RQMT-002101
FGS Instrument Performance
and Functional Requirements
JWST-SPEC-002069
FGS
ICDH Requirements
JWST-RQMT-000743
IFSW
MIRI Delta Systems Requirements Review 9 March 2004
ICDH
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JWST Requirements Flow Down to MIRI
Element
S/C Requirements
JWST-RQMT-002039
SC
S/C FSW
Xxxx-xxx-xxxxxx
ISIM to OTE and
Spacecraft IRD
JWST-IRD-000640
ISIM to OTE and IOS-IR
ISIM Requirements
JWST-RQMT-000835
ISIM
Mission Assurance Requirements
For the JWST Instruments
JWST-RQMT-002363
MAR
ISIM FSW
JWST-RQMT-002101
IFSW
JWST-ICD-001831 IOSC
Subsystem
ESA JWST
Product Assurance
Requirements Document
ESA-JWST-RQ-64
PAR
MIRI Functional
Requirements Document
(JWST-SPEC-002063)
JPL D-24158
MIR
MIRI Mission
Assurance Plan
JPL D-25631
MIRI IRD
JWST-IRD-000782
IMU
MAP
MIRI System Requirements
(JPL) D-25646
SYS
Component
MIRI OBA Requirements
EC MIRI-RS-00001
OBA
MIRI Dewar Requirements
JPL D-25641 DWR
MIRI FSW Requirements
JPL D-24160
MFSW
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JWST Requirements Trace to MIRI FRD
Rationale
{OBS-552} The science instruments and FGS
guider channels minimum unvignetted field of
views in the OTE focal plane shall be equal
to, or greater than the values shown in the
table below. Table 3-15. Field of View
Science Instrument FOV (arc-minutes) MIRI
2.4 x 2.4
 Minimum unvignetted field of view for imaging and
spectroscopy.
ISIM-235 Field of View
The science instruments and FGS guider
channels minimum unvignetted field of views in
the OTE focal plane shall be equal to, or greater
than the values shown in the table below.
MIRI is 3.5 square arc-minutes. (1.87 x 1.87
arc-min)
Allocation
MIRI Allocation
ISIM-520
MIRI Field of View
The minimum effective science field of
view for the MIRI modules is 3.5 (TBR)
sq arc min. (1.87 x 1.87 arc-min)
MIRI FRD
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Critical Issues List








Sensitivity
Pupil shear
Focus tolerance
Image quality - WFE/FWHM
Contamination
Dewar mass
Target acquisition
Observing efficiency
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Dewar Mass
 Requirement: The MIRI Cryo Dewar shall have a mass allocation of 208 kg,
including cryogen, dewar mounting structure and margins. (RS-4.4-SYS0003)
 Issue: The estimated mass of a Dewar that meets the Dewar performance
requirements is greater than the allocation (228kg versus the 208kg
allocation).

5 year Operational lifetime after cool down and commissioning (FRD 3.5.2)

Instrument heat lift of 60mW (RS-4.5-SYS-0005)
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Dewar Mass Requirement Trace
{OBS-637} ISIM Mass
ISIM-322
Rationale
 ISIM set the total mass allocation for MIRI for each region
of the ISIM in the MIRI-ISIM IRD
ISIM Mass
The mass of the ISIM shall not exceed 1,630
kilograms (TBR).
 The MIRI Requirements Document allocated the Region
1 mass of MIRI. 103kg were allocated to the OBA and
208kg to the Dewar.
 Balance of the dewar mass is kept as system margin in
the MIRI System Requirements Document (RS-4.4-SYS0001)
MIRI
Allocation
IMU-817 Region 1 Component Allocations
The MIRI Region 1 Assembly shall have a
mass less than 311 kg, excluding external
harnesses.
Component
Allocation
SysRD RS-4.4-SYS- 0003 Dewar Mass
Dewar RS-DWR-4.2-0012
The MIRI Cryo Dewar shall have a mass
allocation of 208 kg, including cryogen, dewar
mounting structure and margins.
Mass: The total mass of the dewar including
its supports to the ISIM at launch, including
the margins as specified below shall not
exceed 197.6kg.
MIRI Delta Systems Requirements Review 9 March 2004
Mass
16
Options
Current baseline estimate is 228kg.

Detailed trade studies have shown opportunity
for 10-15kg mass reduction
1.
Heat redistribution from FPM strap to OA
strap
2.
Warmer OA interface temperature
3.
OBA cooled by ISIM to 40K
4.
On pad liquid helium cooling available
5.
Warmer end of life detector temperature
6.
Combine options 1 and 3
7.
Combine options 1 and 4
8.
Combine options 1 and 5
9.
Combine options 1, 3 and 4
10.
Combine options 1, 3, and 5
single option
combination of options
240
230
Mass (kg)

220
210
200
190
0
2
4
6
8
10
Option
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Status
 Dewar RFP ready for release(March 2004)

Will get Dewar vendor on board by May

Options and trades will be settled once we have Dewar vendor on board to validate the
mass estimates and options.
 Based on vendor assessment we will revisit the Mass availability from ISIM
.
 Trades:






Heat redistribution from FPM strap to OM strap
• Has been accepted as new baseline.
Warmer OA interface temperature
• Will be assessed, based on vendor response.
OBA cooled by ISIM to 40K
• Under review with ISIM ICD team
On pad liquid helium cooling available
• Visit to Ariane Space in April
Warmer end of life detector temperature
• 0.2K increase to the detector operating temperature has been accepted.
Combine cases
• Can combine cases 1 and 5 (14kg net savings)
• Additional cases will be combined if net system savings found. Decision by May
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Target Acquisition Status
 High Level requirements to support target acquisition will be worked out
by MIRI PDR.
 The target acquisition software will be written by the ISIM FSW group to
requirements specified by the MIRI science team.
 A working group is being established by the Project to work the details
of target acquisition requirements with all instrument teams
represented. Ray Kutina (STScI) will lead the working group. Meetings
will start by the end of March.
 Algorithms for centroiding will also be worked out by this group.
 The IC&DH software implementation of target acquisition is scheduled
for fall of ‘05, so there is some time to work out the IC&DH details.
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Requirement Traceability for Observing Efficiency
{OBS-629} ISIM Efficiency
Rationale
ISIM 524
MIRI Efficiency
After commissioning, the ratio of prime exposure
time on scientific targets to total elapsed time, for
the MIRI instrument, shall be greater than 95%
(TBR) over a 5-year mission.
 MIRI Operations Concept Document, section 6, outlines
a Month in the Life of MIRI, which is a very top level, very
approximate operational scenario to estimate the time for
MIRI operations. This operational scenario assumes a
heavy weight on long exposures. We derived a 92%
efficiency, however, given the uncertainty in operational
scenario, we add margin and list a 89% efficiency for
MIRI.
 Telescope slews and similar operations are not counted
against the MIRI operational efficiency
MIRI Allocation
FRD 3.4.1
Setup, Cleanup and Mode
Switching
The MIRI operational efficiency shall
be greater than 89 (TBR)%….
FRD 3.4.3
Detector Annealing Efficiency
…specification within 2 hours
(TBR) of the end of a detector
annealing procedure.
FRD 2.4.2.3
Spectral Calibration Stability
Wavelength calibration shall be
required no more often than once
per week …
FRD 3.3.9
Instrument Turn-on Time
… obtain science data within 30
minutes of turn on.
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Observing Efficiency Status
 The observing efficiency budget has been recognized as a project wide
open issue and will be re-evaluated based on meetings of the
observing efficiency working group led by Lionel Mitchell (GSFC).
 Mitchell led a technical interface meeting on Friday, Feb. 27 to discuss
observing efficiency with a project wide working group, including
representatives from the project, OTE, space craft, ISIM, instrument
teams and SOC. This meeting was an information exchange in which
the instrument teams discussed the assumptions made for observing
efficiency estimates.
 The efficiency requirements are being re-cast in terms of overheads for
the ISIM and SI subsystems. Due March 15, MIRI is working on an
overhead time request for its operations.
 This work, which began last October with the OTE and S/C will be
continued with incorporation of an operational scenario based on a
design reference mission (DRM) that is being developed at STScI with
expectation of completion in the summer.
 The observing efficiency working group is looking at operations
assumptions and not instrument design.
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RFA Categories
Legend for Categories for all 97 ( including withdrawn):
1- Flow down from level 1 to FRD/IRD (ISIM lead),
include critical issues
23
2 - Flow down to MIRI subsystems (MIRI lead)
5
3 - Software programmability
2
4 - In process tasks (design advisory)
7
5 - Mass management
5
6 - Sensitivity models
2
7 – Advisory and/or to be completed by PDR
25
8 – clarification
12
9 - Various/specific
4
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Summary
 JWST has completed requirements flow down to MIRI Instrument
 MIRI requirements documents are in place
 Project has excellent flow down and tracking process
 All of the critical issues are being addressed; many have been closed out.
 Most of the RFAs have been addressed. The remaining will be tracked to
MIRI PDR.
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