The NIRSpec Critical Design Review

Oct 8th 2008 - Dec 11th 2008

T. Beck (& M. Stiavelli)

The NIRSpec CDR

• Quick NIRSpec instrument overview

• Brief Overview of ESA’s CDR process and goals

• NIRSpec CDR Results

• Next Steps & Schedules

• Some Operational “Issues” of interest

NIRSpec Instrument Overview

JWST Focal Plane, NIRSpec tilted by 41.5o

“The most complicated instrument ever to fly in space”

• Multi-Object Spectrograph Mode (MOS) with an MSA

• Integral Field Unit (IFU)

• 4 Fixed Slits + 1 Broad Aperture

R~100, 1000 and 3000 spectroscopy over 3 Bands:I = 0.7 - 1.8mmII = 1.7 - 3.0mmIII = 2.9 - 5.0mm

NIRSpec Instrument Overview

Reflective Surfaces -

FOR Filter RMA (MSA/IFU/FS) COLL Grating CAM Detector(FWA) (GWA)

CAA

NIRSpec Instrument Overview MSA Focal Plane

• 4 MSA Quadrants

• IFU Entrance Aperture

• Fixed Slits

• New, 1.”6x1.”6 sq aperture

• (IFU “Virtual Slit” Positions)

ESA’s CDR Goals• Verify that the instrument system performance will meet both the scientific

and functional requirements

• Verify that the instrument detailed design is robust, shows adequate margins, and is compliant with product assurance reqs

• External and internal interfaces are defined/documented in the relevant ICDs

• Instrument verification/test plans are realistic and adequate

• The instrument level qualification plan is complete, satisfactory and complies with the subsystem qualification plans.

• The instrument schedule is realistic with adequate margin

• The identified risks are thoroughly assessed with clearly defined mitigation plans

• PA practices are fully implemented

• Ops concept is defined and is consistent with Flight SW architecture

• Commanding and control of the instrument is properly defined in FSW

• Critical technologies have been identified and performance demonstrated.

ESA’s CDR Process• CDR Board + 5 “Panels”

• Document Delivery to Panel and Board members (late September 2008)

• CDR “Kickoff” Meeting = 1 day of instrument presentations, 1 day of face-to-face meeting with the panels (Oct. 8-9, 2008)

• Panel members are tasked with identifying “Review Item Discrepancies” (RIDs) = discrepancies/inconsistencies/errors in documentation, design or instrument performance vs. requirements

• One month of document reading with weekly telecons between panel members - RIDs continuously input into online tracking system.

• Colocation Meeting - All RIDs from all panels discussed among the large group and actions determined

• Board Meeting - Final presentations on findings, issues from RIDs flagged with actions noted. (Dec. 11th 2008).

• Final Board Report released to team (yesterday!)

ESA’s CDR Process

ESA’s CDR Process and Goals

• ESA led review, co-chaired by NASA Independent Review Office• 18 Board members from ESA , NASA and STScI

• 60 Panel members from ESA , NASA, IST, and STScI

Board

System Design

Overall Science & Func Perfo

Calibration

Operations

FDIR

Budgets

Schedule

Overall AIV

Panel # 1SYSTEM PANEL (SP)

R. MeynartG. Bagnasco

Structure Design

Mechanicms Design

Thermal Design

Relevant Perfo

MGSE

Relevant AIV

PANEL # 2MECH-THERMAL PANEL( MP)

R. BureoJ.C. Salvignol

Optical Design

Relevant Perfo

OGSE

Relevant AIV

PANEL # 3OPTICAL PANEL (OP)

B. HarnishM. Te Plate

Electrical Design

Harness Design

SW Design

Relevant Perfo

EGSE

Relevant AIV

PANEL # 4ELEC-SW PANEL (EP)

F. MarlianiP. Rumler/P. Strada

Quality Assurance

Product Assurance

Cleanliness & Contamination

Risk Management

Safety

PANEL # 5PA PANEL (PP)

M.v. EesbeekM. Falcolini

(M. Stiavelli)(T. Beck)

NIRSpec CDR Results• During the Reviews, Panels came up with a total of:

– 192 RIDS• 70 RIDS Classified as “Major”

• 92 RIDS Classified as “Minor”

• ALL RIDS have either been Closed or accepted with a well defined action

• NO Items were elevated to the Board for Resolution

• (At the time of the NIRSpec Instrument CDR, the MSS subsystem had not had it’s CDR - this is taking place TODAY & TOMORROW at GSFC)

NIRSpec CDR Results• Issues Highlighted by the CDR Board:

– Grating Wheel Assembly (GWA) Wavefront Error is significantly out of spec - continued troubleshooting, updates in budgets

– Refocus Mechanism Assembly (RMA) deforms at cryogenic temperatures causing WFE (coated on back, have SiC backups)

– Board requests a report by February 2009 on the recent failure of the RMA gearbox lifetime testing

– HAWAII 2RG performance - Detector Noise and sensitivity degradation due to radiation damage still not established

– MSS CDR delayed until January - after NIRSpec CDR, which resulted in a lack of proper documentation on the MSS. Board requests a report by Feb. 2009 on conclusions from the MSS CDR - incl. clear analysis of MSS problems and qualification plans/status.

– Schedule delays in some elements (e.g., GWA) will impact flight model tests - now planned to perform FM cryo tests in two phases.

NIRSpec CDR Results• Issues Highlighted by the CDR Board:

– Stray light reduction mask - out of field stray light may be blocked by a static, oversized pupil mask positioned in front of the FWA, board endorsed feasibility study for implementing such a mask.

– Concern regarding software validation flow from ICE/MSS/DS through to ISIM level, recommends that the project define and describe in detail an appropriate NIRSpec FSW validation process based on top-level requirements.

– Performance Budgets are not yet consolidated and verified with measurement values - requests that budgets are maintained and updated systematically as new data become available. (incl. GWA WFE, FOR WFE, Detector noise/sensitivity/dark current).

– Total of 70 actions assigned to Astrium, ESA and NASA on “Major” RID items - (many = updates to qual plans and verification matrix for consistency with test plans)

NIRSpec CDR Results• Total of 70 actions assigned to Astrium, ESA and NASA

on “Major” RID items, including:– many = updates to qual plans and verification matrix for

consistency with test plans, error budgets– Report from NASA on Prasedymium-Iron-Boron for use in the

MSS magnet arm, risk due to corrosion, brittleness, contamination and loss of magnetic strength

– Confirmation that acrylic adhesive Y966 can be used at cryo-temperature (reports of risk due to lack of adhesion)

NIRSpec CDR Results• CDR Board Conclusions:

– The NIRSpec CDR will be satisfactorily concluded when the recommendations highlighted (previously) and actions from the CDR panel teams have been addressed and concluded.

– The board requests a report on the status of the identified major issues and RID actions by May 2009.

NIRSpec - The Future• DM (Demonstration Model) ambient tests ongoing, cryotests in

Spring 2009 (Focal plane detector at MSA plane)

• FM (Flight Model) plan with schedule mitigation has been developed – Main deliveries: grating wheel assembly, filter wheel assembly, micro-

shutter subsystem, detector subsystem– Plan for dual cryogenic test with intermediate refurbishing – Likely to be implemented for grating wheel

Old Baseline (1 Cryo test)

New Baseline 2 Cryo Tests

Old Baseline (1 Cryo test)

New Baseline 2 Cryo Tests

• The PLAN:

• NIRSpec DM (ETU) Delivery in July 2009 (26d contingency)

• NIRSpec FM mid 2010 delivery to GSFC (40d contingency)

NIRSpec -Operational “Issues” of Interest

• MSA = A complicated component! – Stuck open/closed shutters

From T. Boker’s presentation at CDR Kickoff

NIRSpec -Operational “Issues” of Interest

NIRSpec -Operational “Issues” of Interest

NIRSpec -Operational “Issues” of Interest

NIRSpec -Operational “Issues” of Interest

• “Plugging” moves quadrants into useable space - (NOTE: most of the MSA quads considered for flight aren’t quite as bad as the ENG-grade images presented in images here)

NIRSpec -Operational “Issues” of Interest

• MSA Quad lifetime tests show that shutters can become stuck open/closed during operations, after many moves of the MSA magnet arm– MSA open/closed shutters may change over time!– MSA Quadrant heating (heat to ~270K) unsticks the

shutters and returns the MSA to it’s nominal performance– MSA Quadrant heating may need to take place after

every ~2000 moves (TBD/TBR!)– NIRSpec will be unusable during the heating process

(nominal duration TBR!, but on order of ~15hrs).– We may need an updatable map of stuck open/closed

shutters that can be updated in the APT MSA planning tool