11/20/2003 TIPS/JIM Summary of the JWST MIRI and NIRCam Systems Requirements Reviews Jerry Kriss

11/20/2003 TIPS/JIM Objectives of MIRI & NIRCam SRRs  Establish the baseline for subsequent design and verification activities by identifying instrument requirements and their pedigree.  Confirm that instrument requirements and specifications meet the mission objectives.  Communicate the formal SI requirements to the review teams and to the various groups and contractors involved in the JWST project.  Identify issues and concerns and assign actions for investigating and resolving them.

11/20/2003 TIPS/JIM FGS Specification JWST-SPEC ISIM to NIRCam ICD JWST-ICD ISIM to MIRI ICD JWST-ICD ISIM to NIRSpec ICD JWST-ICD ISIM to FGS ICD JWST-ICD JWST Observatory Specification DRD SE-03 JWST-SPEC Element ISIM Requirements JWST-RQMT Mission Assurance Requirements for the JWST Instruments JWST-RQMT ISIM to NIRCam IRD JWST- IRD ISIM to MIRI IRD JWST-IRD ISIM to NIRSpec IRD JWST- IRD ISIM to FGS IRD JWST-IRD Sub-System Segment ISIM to OTE and Spacecraft IRD DRD SE-06 JWST-IRD ISIM to OTE and Spacecraft ICD DRD SE-08 JWST-ICD Observatory to Ground Segment IRD DRD SE-07 JWST-IRD Observatory to Ground Segment ICD DRD SE-09 JWST-ICD ICDH Requirements JWST-RQMT ISIM FSW Requirements JWST-RQMT ISIM Structure Requirements JWST-RQMT NIRCam Operations Concept (UAz DRD OPS-11) NIRSpec Operations Concept MIRI Operations Concept FGS Operations Concept JWST Level 1 Requirements JWST-RQMT Mission JWST Mission (Level 2) Requirements JWST-RQMT Mission Operations Concept Document JWST-RQMT JWST Project Science Objectives and Requirements Document (JWST-RQMT ) NIRCam Specification JWST-SPEC NIRCam Science Requirements UAz DRD SR-01 FGS Science Requirements NIRSpec FPRD JWST-SPEC MIRI FRD JWST-SPEC MIRI Science Requirements NIRSpec Science Requirements Requirements Flowdown to ISIM and Instruments

11/20/2003 TIPS/JIM MIRI & NIRCam SRR Timing (1 of 2)  Requirements flowdown is largely complete IRDs in final CCB process Driving open issues identified and plan for resolution exists Requirements worked with the teams extensively over last 18 months  These SRRs Precede Mission/Obs/ISIM SRR Formal (i.e. CCB) requirements flowdown from Mission- to SI-level documentation is not yet complete  This exception to the “standard” process allows MIRI & NIRCam development to proceed on schedule to avoid threatening the JWST launch date

11/20/2003 TIPS/JIM MIRI & NIRCam SRR Timing (2 of 2)  Risks posed by this approach are mitigated through: Science Working Group, which includes the Instrument PIs, has defined the Mission-level Science Requirements PIs ensured consistency between Mission- & Instrument-level Requirements SI Teams Participating in Working Groups which define Interface Requirements Interface Summit Meetings ISIM to Telescope Interface Working Group Line-of-Sight Working Group Wavefront Sensing Working Group Drafts of all Requirements, Interface, Ops, & PA Documents have been Released Extensive pre-CCB Coordination Ongoing – SI Teams are Reviewing Mission & ISIM-level Documents – ISIM is Reviewing Instrument-level Documents PIs and/or SI Team Leads are on Project- and ISIM-level CCBs Configuration control process in place for future changes: PI is on Project and ISIM-level CCB.

11/20/2003 TIPS/JIM MIRI SRR Review Team Frank Schutz, Co-ChairJPL Dennis Dillman, Co-ChairGSFC System Review Office Klaus …, Co-ChairESA Steve ScottGSFC Chief Engineer Paolo StradaESA Dr. David Leckrone GSFC Space Sciences + several others …

11/20/2003 TIPS/JIM MIRI Plays a Key Role in Origins Roadmap Traceability of MIRI Science and Roadmap Investigations

11/20/2003 TIPS/JIM Models of spectral energy distributions* show that NIRCam may have difficulty distinguishing true first light galaxies from those with older stars, or even quasars! MIRI data beyond 5  m can remove this uncertainty ** * technical details in the box below the figure ** drives sensitivity for 5.6, 7.7  m photometry Example 1: MIRI Will Identify True First Light Objects Modeled young galaxies and a typical quasar, all at z = 15. The Lyman  forest attenuates their outputs short of Ly  and  foreground damped Lyman  systems cause reddening of A V = 0.6 for the first light object and A V = 0.4 for the older galaxy. The horizontal bars indicate the NIRCam and MIRI filter bands and the relative signal levels that would be detected through them, offset for clarity. Error bars of + 10% are also shown as fiducials.

11/20/2003 TIPS/JIM Example 2: MIRI Sees Through Interstellar “Windows” to Explore Protostars and Their Environments The interiors of protostellar cocoons must be probed in the mid-infrared: two windows in the interstellar extinction near 7 and 15  m provide a unique opportunity to see deep inside. November 4-5, 2003

11/20/2003 TIPS/JIM MIRI view of Vega system at 24  m (model from Wilner et al. 2000) Adequate to probe detailed predictions of dynamical models and study the planet that drives them Example 3: MIRI Will Explore Nearby Planetary Systems and Debris Disks

11/20/2003 TIPS/JIM Operations Support four science modes Efficiency Optical Support four science modes Wave front errors, stability Fields of view, pixel scales Spectral properties (filters, resolutions, etc.) Throughput, scattered and stray light rejection, minimization of artifacts Coronagraphic rejection - basic design, pointing Signal Chain Sensitivity parameters - read noise, QE, dark current of detectors Radiometric properties - stability, linearity, dynamic range Thermal Background for sensitivity - OBA < 15.5K Sensitivity of detectors - SCAs < 6.9K Lifetime > 5 yrs Detector anneal Driving Requirements

11/20/2003 TIPS/JIM MIRI Review Summary  The review board judged that the review did not fulfill its goals.  Too many unresolved issues: Dewar mass (20 kg over) or lifetime (3.9 yrs vs. 5 required) Pupil alignment errors (5.4% vs. 2%) could lead to increased background or lower throughput (by 30%). Required depth of focus is now larger than can be accommodated by MIRI design (3 mm vs. 2 mm). Lingering concerns about the divided NASA/ESA management structure. General concerns about unsettled higher-level requirements flowing down to the instrument level late in the process and increasing costs.

11/20/2003 TIPS/JIM NIRCam SRR Review Team Dennis Dillman, ChairGSFC System Review Office Marty DavisGSFC Project Management Tom VenatorGSFC Instrument Systems/Mechanical Steve ScottGSFC Chief Engineer Joe SchepisGSFC Electromechanical Systems Gene WaluschkaGSFC Optics Sachi BabuGSFC Detectors Tony MillerGSFC Electrical Systems Dr. David Leckrone GSFC Space Sciences

11/20/2003 TIPS/JIM NIRCam’s Role in JWST’s Science Themes young solar system Kuiper Belt Planets The First Light in the Universe: Discovering the first galaxies, Reionization NIRCam executes deep surveys to find and categorize objects. Period of Galaxy Assembly: Establishing the Hubble sequence, Growth of galaxy clusters NIRCam provides details on shapes and colors of galaxies, identifies young clusters Stars and Stellar Systems: Physics of the IMF, Structure of pre-stellar cores, Emerging from the dust cocoon NIRCam measures colors and numbers of stars in clusters, measure extinction profiles in dense clouds Planetary Systems and the Conditions for Life: Disks from birth to maturity, Survey of KBOs, Planets around nearby stars NIRCam and its coronagraph image and characterize disks and planets, classifies surface properties of KBOs

11/20/2003 TIPS/JIM NIRCam Science Requirements (1 of 2)  Detection of first light objects, studying the epoch of reionization requires: Highest possible sensitivity – few nJy sensitivity is required. Fields of view (~10 square arc minute) adequate for detecting rare first light sources in deep multi-color surveys. A filter set capable of yielding ~4% rms photometric redshifts for >98% of the galaxies in a deep multi-color survey.  Observing the period of galaxy assembly requires in addition to above: High spatial resolution for distinguishing shapes of galaxies at the sub-kpc scale (at the diffraction limit of a 6.5m telescope at 2µm). NIRC_X0052 Number of Filters Performance of adopted filter set Number of Filters |Z in -Z out |/(1+Z in ) 1<Z<22<Z<5 5<Z<10 5-  50,000 secs

11/20/2003 TIPS/JIM NIRCam Science Requirements (2 of 2)  Stars and Stellar Systems: High sensitivity especially at  >3  m Fields of view matched to sizes of star clusters ( > 2 arc minutes) High dynamic range to match range of brightnesses in star clusters Intermediate and narrow band filters for dereddening, disk diagnostics, and jet studies High spatial resolution for testing jet morphologies  Planetary systems and conditions for life requires: Coronagraph coupled to both broad band and intermediate band filters Broad band and intermediate band filters for diagnosing disk compositions and planetary surfaces NIRC_X0044

11/20/2003 TIPS/JIM Derived Requirements (1 of 2)  nJy ( W/m 2 /Hz) sensitivity Detectors with read noise 80% Focal plane electronics with noise < 2.5e- so detector performance is not degraded High throughput instrument:  70% for optics,  85% for filters  At least 7 broadband filters for redshift estimates  Large Field of View Dichroics to double effective FOV Large format detector arrays  Large well-depth on detectors

11/20/2003 TIPS/JIM Derived Requirements (1 of 2)  High spatial resolution Nyquist sampling at 2  m and 4  m  Selection of intermediate and narrowband filters 8 R~10 filters needed to classify ices, cool stars At least 4 R~100 filters for key jet emission lines (want higher spatial resolution than Canadian tunable filters)  Coronagraph required in all modules Coronagraph most important at long wavelengths Coronagraphic field must not reduce survey FOV  Need fluxes calibrated to 2% Requires gain stability on week time scales Requires on-orbit calibration plan using on stars

11/20/2003 TIPS/JIM NIRCam’s Descope Paths (1 of 2)  Descopes which would result in the largest savings (e.g., reducing array size from 4Kx4K to 2Kx2K, single rather than dual wheels) precluded by WFS requirements.  Could reduce number of filters and/or eliminate coronagraphy but this saves little.  Could drop redundancy requirement within each FPE box  Could accept degraded detector or optical coating performance. This would be a descope for late in instrument development where poorer than required performance would be accepted to maintain schedule Impact unlikely to exceed a factor of 1.5 given current levels of detector performance and assuming that essentially no AR coatings were used. Not acceptable for cost savings now

11/20/2003 TIPS/JIM NIRCam’s Descope Paths (2 of 2)  Only removal of the dichroics and dedicated long wavelength channels yields any significant savings.  Descope would remove: 2 of 4 dual filter/pupil wheels 2 of 10 2Kx2K Focal Plane Arrays 2 dichroics 2 lens assemblies (but note that remaining lens assemblies now have to work over 0.6-5µm rather than only collimators working over the full range) 2 fold flats 2 of 10 Focal Plane Electronics cards

11/20/2003 TIPS/JIM Descope Plan: Science Impacts  Science impacts of removal of dedicated long wavelength arms are significant: Time to execute any multi-color observation would more than double because of having to observe all wavelengths serially rather than in parallel. The data return from NIRCam would effectively be cut in half. Ability to characterize icy surfaces and cool stars would be lost because only one filter wheel is available and there would be too few slots for as many intermediate band filters as NIRCam has now. Long wavelength sensitivity would be degraded (10-  point source detection limit changes from 18.9 nJy in sec to 20.5 nJy at 4.5µm because of oversampling of the PSF).

11/20/2003 TIPS/JIM NIRCam Review Summary  The review board approved of NIRCam moving on toward PDR, but noted several concerns: NIRCam wave-front error exceeds its allocation (70 nm vs. 56 nm). NIRCam mass exceeds its allocation (7.7 kg out of 140 kg). Concerns about ghosts in a largely refractive optical design. Detector procurement has no independent V&V plan. Worried about possible complexities of event-driven operations.

11/20/2003 TIPS/JIM Lessons Learned (Preliminary)  Note: Official review board reports and lists of accepted RFAs have not yet been issued.  Out-of-order reviews makes review boards suspicious.  Presentation style matters: a requirements review should focus on requirements and their flowdown. MIRI team highlighted problems, glossed over the successes MIRI team got bogged down in design details  Clear, decisive management structure helps.  Mission and ISIM SRRs in December may be tough.