The NIRSpec Critical Design Review

1. The NIRSpec Critical Design Review Oct 8th 2008 - Dec 11th 2008 T. Beck (& M. Stiavelli)

2. 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

3. NIRSpec Instrument Overview • “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 - 1.8mm • II = 1.7 - 3.0mm • III = 2.9 - 5.0mm JWST Focal Plane, NIRSpec tilted by 41.5o

4. NIRSpec Instrument Overview Reflective Surfaces - FOR Filter RMA (MSA/IFU/FS) COLL Grating CAM Detector CAA (FWA) (GWA)

5. NIRSpec Instrument Overview MSA Focal Plane • 4 MSA Quadrants • IFU Entrance Aperture • Fixed Slits • New, 1.”6x1.”6 sq aperture • (IFU “Virtual Slit” Positions)

6. 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.

7. 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!)

8. ESA’s CDR Process

9. ESA’s CDR Process and Goals Board (T. Beck) (M. Stiavelli) • 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

10. 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)

11. 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.

12. 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)

13. 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)

14. 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.

15. 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 • The PLAN: • NIRSpec DM (ETU) Delivery in July 2009 (26d contingency) • NIRSpec FM mid 2010 delivery to GSFC (40d contingency)

16. NIRSpec -Operational “Issues” of Interest • MSA = A complicated component! • Stuck open/closed shutters From T. Boker’s presentation at CDR Kickoff

17. NIRSpec -Operational “Issues” of Interest

18. NIRSpec -Operational “Issues” of Interest

19. NIRSpec -Operational “Issues” of Interest

20. 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)

21. 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