Status of the James Webb Space Telescope () Observatory ESTEC Mark Clampin Observatory Project Scientist mark.clampin@nasa.gov Goddard Space Flight Center
HUBBLE and its Precursors SPITZER 2.4-meter T ~ 270 K 0.8-meter T ~ 5.5 K 123 x 136 λ/d1.6μm~ 0.14 6.5-meter T ~ 40 K 132 x 164 λ/d2μm~ 0.06 114 x 84 λ/d20μm~ 0.64 312 x 312 λ/d5.6μm~ 2.22 324 x 324 λ/d24μm~ 6.2 Wavelength Coverage 1 μm 10 μm 100 μm HST Spitzer
: How It Works Integrated Science Instrument Module (ISIM) 5 Layer Sunshield Cold Side: ~40K Primary Mirror Secondary Mirror Solar Array Spacecraft Bus Hot Side Sun
18 18Primary PrimarySegments Segments (Composite (Compositefigure) figure) 23.7 23.7 8.1 8.1 Secondary Secondary 14.5 14.5 14.9 14.9 Tertiary Tertiary 17.5 17.5 9.4 9.4 Fine FineSteering Steering 14.7 14.7 8.7 8.7 s Optical System Telescope Optics Completed the AOS (w/tertiary a 3 cryogenic cycles: aligent m AOS provides stray light mitigat Full Fullscale scale model model Mirror Mirror Mirror Measured Measured Uncertainty Uncertainty (RMS (RMSSFE) SFE) (RMS (RMSSFE) SFE) Total Total (RMS (RMS SFE) SFE) Requirement Requirement (RMS (RMS SFE) SFE) 18 18Primary PrimarySegments Segments (Composite (Compositefigure) figure) 23.7 23.7 8.1 8.1 25.0 25.0 25.8 25.8 Secondary Secondary 14.5 14.5 14.9 14.9 20.8 20.8 23.5 23.5 9.4 9.4 19.9 19.9 23.3 23.3 8.7 8.7 17.1 17.1 17.5 17.5 Measured UncertaintyTertiary Total Requirement Tertiary 17.5 17.5 (RMS SFE) (RMS SFE)Fine (RMS SFE) (RMS SFE) FineSteering Steering 14.7 14.7 18 PM Segments (Composite Figure) 23.6 8.1 25.0 25.8 Secondary 14.7 13.2 19.8 23.5 Tertiary 18.1 9.5 20.5 23.2 FSM 13.9 Full Fullscale scale model model 4.9 14.7 Aft-Optics System 18.7
Predicted Image Quality Diffraction Limited: Strehl > 0.8 (WFE 150 ) F070W F444W F115W F200W Log Scale Linear Scale
Encircled Energy F115W F200W
Observing Constraints l Field of Regard is an annulus with rotational symmetry about the L2-Sun axis, 50 wide l Sun angle constraints yield 35% instantaneous sky coverage Full sky coverage achieved over a sidereal year l Observations interrupted for: North Ecliptic Pole 5 45 Continuous Coverage Zone North Orbit maintenance station-keeping burns Toward the Sun 360 7 Momentum management reaction desaturation burns Continuous Coverage Zone South
Observing Constraints l Field of Regard is an annulus with rotational symmetry about the L2-Sun axis, 50 wide l Sun angle constraints yield 35% instantaneous sky coverage Full sky coverage achieved (b) over a sidereal year l Observations interrupted for: Sun Orbit maintenance 8 station-keeping burns Momentum management (c) reaction desaturation burns Sun
Optical Stability Optical stability modeling based on worst case hot-cold slew Wavefront error changes will be smaller when the telescope executes a real observing program. e.g. Gersh-Range and Perrin (2015) (a) Hot-Cold slews (b) Simulated observing program Pointing Angle (Degrees) 140 120 100 80 0 5 10 15 20 25 Time (Days) Pointing Angle (Degrees) 140 130 120 110 100 90 80 0 50 100 150 200 250 Time (Days) RMS WFE () 50 40 30 20 10 RMS WFE () 50 40 30 20 10 0 0 5 10 15 20 25 Time (Days) 0 0 50 100 150 200 250 Time (Days)
Sky Background should be zodi-limited at λ < 10 μm Background levels will include contribution from stray light Meet requirements @ 20 μm: 174 MJy/Sr vs 200 MJy/Sr req.
Pointing Predicted performance for offset precision from 0-45 currently expecting < 5.3 mas Fine steering mirror offsets will be employed for offsets of <60 mas to deliver ~mas precision Pixel response function mapping Coronagraphy Slit mapping
Telescope Structure Pathfinder Backplane Flight Backplane
Pathfinder Backplane The pathfinder is a backplane section with a secondary mirror support structure (SMSS) Verify SMSS deployment Tests integration of primary mirror segment installation with two flight spare mirror segments, plus flight-spare secondary mirror Pathfinder is scheduled for three cryogenic tests during 2015 in Chamber-A at JSC Verify optical test equipment
Primary Mirror Integration Ambient Optical Ambient Optical Aligent Stand Aligent Stand Mirror Installation dry-run Mirror Installation dry-run
Sunshield Membranes Five flight-like Template Membrane layers manufactured Template layers tensioned to flight-like configuration - 3-D membrane shapes measured by Lidar - Critical for layer-to-layer spacing thermal performance - Edge aligent thermal performance & stray light Flight membranes under construction (#3 completed) Tensioned to 3x flight tension for shape measurement by Lidar (3x tension counteracts gravity sag)
Spacecraft Bus Structure Complete GIMBALED ANTENNA ASSY +J3 -J2 PANEL SOLAR ARRAY LOW GAIN ANTENNA BUS HARNESSES TIAL REFERENCE UNIT (2X) (2) Cryocooler Radiator Panel BUS STRUCTURE WITH INTEGRATED PROPULSION COMPONENTS +J2 PANEL STAR TRACKER ( 3X) +J2 +J1 Star Tracker Radiator Panel FINE SUN SENSOR (2X) REACTION WHEEL WITH ISOLATOR ASSY (6X)
Integration: Path to Launch
How Do We Test the Telescope? Cryogenic Optical Test will be conducted at JSC s Chamber A Goals of Cryogenic Optical Test Optical workmanship - check on assembly of the telescope e.g. mechanical interference Optical aligent - are we inside the capture range of the telescope s active optics? Thermal balance - will the telescope cool to 40K?
Chamber Isolator Units OTIS Test Preparations Cryo Position Metrology Center of Curvature Optical Assembly
Dry Run testing w/chamber-a 1) Dry run test- phasing two mirrors on pathfinder 2) Dry run imaging with AOS 3) Test thermal monitoring equipment
Overall Commissioning Schedule Month 1 Month 2 Month 3 Month 4 Month 5 Month 6 Observatory Deployments Telescope Phasing Observatory& Instrument Commissioning Phased Instrument power-on with Temp. Observatory check-out & calibrations Attitude control, acquisition, thermal... Instrument check-out and calibration
will do transformational science and change our view of the Universe Launch 2018
Where To Follow Web pages www.jwst.nasa.gov webbtelescope.org Social Media Webcam ibook itunes www.jwst.nasa.gov/webcam.html
Operations Ariane 5 Upper Stage Injects Into Direct Transfer Trajectory Communications Coverage Provided For all Critical Events SOC Available 24 Hours, 7 Days per Week Until Telescope Phased Observatory Upper Stage Separation Observatory Deployments - Solar Array - High Gain/ Medium Antennas - Sunshield - Optical Telescope Element L2 Point L2 Lissajous Orbit Ariane 5 Launch System S-Band Tlm Link ( 2Kbps) S-Band Ranging S-Band Tlm Link ( 2Kbps) S-Band Cmd Link (0.25 Kbps) S-Band Ranging L2 Transfer Trajectory Ka-Band Science Link ( Selectable 7, 14, 28 Mbps) S-Band Tlm Link (Selectable 0.2-40 Kbps) S-Band Cmd (Selectable 2 and 16 Kbps) S-Band Ranging Nominal 4 Hour Contact Every 12 Hours Communications Services for Launch (TDRS, ESA, Malindi) Deep Space Network NASA Integrated Services Network Space Telescope Science Institute Science & Operations Center Ariane PPF S5 GSFC Flight Dynamics Facility
Phasing the Telescope OTE Deployment / First Light (Image Mosaic) SM Focus Sweep Segment Identification NIRCam First Light After Segment-Image Array After Global Aligent Segment Search Commissioning DHS (20 edges) Segment-Image Array Global Aligent Image Stacking After Image Stacking After Coarse Phasing Coarse Phasing (DHS) Pupil Imaging Single Field Fine Phasing Multi-Field Fine Phasing After SF Fine Phasing Wavefront Monitoring & Maintenance