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Status of the Terrestrial Planet Finder Coronagraph TPFC :

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Title: Status of the Terrestrial Planet Finder Coronagraph TPFC :


1
Status of the Terrestrial Planet Finder
Coronagraph(TPF-C)
  • Karl Stapelfeldt
  • Jet Propulsion Laboratory
  • California Institute of Technology
  • on behalf of the TPF-C Science Engineering teams

2
TPF-C is
  • NASA Universe Divisions intended next major
    optical space observatory mission
  • Optimized for high contrast and high spatial
    resolution
  • Designed for the primary goals of
  • Directly detecting Earth-like planets in the
    habitable zones (r0.7-1.5 AU) of nearby
    (distance
  • Measuring their frequency, physical orbital
    characteristics
  • Spectrally characterizing their atmospheres for
    biomarkers (O2, H20, CO2, )
  • In a pre-phase A period of technology
    development and preliminary
    design
  • Led by JPL NASA Goddard, Industry, and
    Universities participating
  • Targeting a launch in 2015

3
Why an Optical TPF mission?
  • Direct detections are an ultimate goal of
    extrasolar planet research space environment
    greatly facilitates them
  • Needed angular resolution can be achieved in
    single telescope spacecraft
  • Direct access to O2 biomarker A band at 760 nm
  • Requirements to achieve 1010 contrast now
    understood
  • Diffraction control not the key issue wavefront
    control is
  • Recent JPL laboratory demonstrations have
    achieved 109 contrast near a bright point
    source. Project goal is 1010 contrast set
    by requirement to suppress residual speckles down
    to the brightness level of the target planet

4
JPL High Contrast Imaging Testbed Proving
ground for TPF-C wavefront control
High Actuator Density Deformable Mirrors
32x32 1024 actuators
64x64 4096 actuators Four of the above
bonded to common face sheet
HCIT vacuum chamber with coronagraph optical bench
5
Graded coronagraphic masks
Courtesy of John Trauger (JPL)
6
Demonstrated Image Contrast
Courtesy of John Trauger (JPL)
7
Terrestrial Planet Targets
  • Typical coronagraph wants inner working angle
    (IWA) 4?/D between star planet
  • 8m aperture gives IWA of 62 mas allows full HZ
    search of
  • 35 stars with 90 completeness
  • Many more at lower completeness
  • Target stars are V 3-6 target planets are V
    28-31 in reflected light
  • Precision wavefront control needed to meet
    contrast requirements (equivalent to pathlengths
    of few x 0.1 Å )

?flux separation for terrestrial planets in
habitable zone of nearby FGK stars Figure by
Dennis Ebbets, Ball FAR
  • Desired sensitivity down to Mars-size planets

8
TPF-C Baseline Design Concept
  • Monolithic, off-axis primary mirror for stability
    diffraction control
  • 8x3.5m elliptical primary mirror with deployed
    secondary, for packaging in existing launch
    shrouds
  • Instruments accommodatedbetween primary mirror
    and spacecraft bus

9
TPF-C key design features
  • Provide for thermal mechanical stability
  • Thermal regulation isolation of primary
    secondary mirrors
  • Active control of secondary mirror alignment
  • Select coronagraph IWA at 4 ?/D to minimize
    sensitivity to drifts
  • L2 halo orbit
  • control vibrations
  • Large sunshade requires solar sail to balance
    radiation pressure torque

More details were given in poster earlier this
week
10
Schematic TPF-C Science Images
  • Square/symmetric dark hole is project goal
  • Dark hole corresponds to spatal frequencies
    controlled by deformable mirror
  • becomes larger at longer wavelengths
  • Outside dark hole, much brighter speckles are
    seen from uncorrected errors of the telescope
    instrument optics

VRI direct image
VRI speckle-subtracted
11
Strawman TPF-C Exoplanet Investigations
  • Planet detection survey in core star sample
    extended star sample
  • Multiple observation epochs to achieve desired
    completeness
  • Take advantage of RV SIM information to
    optimize yield
  • Confirmation of planet candidates
  • Determine orbits for confirmed planets
  • Atmospheric characterization of confirmed
    terrestrial planets spectroscopy R70 for
    detection of 0.76 ?m O2 band
  • Temporal monitoring of terrestrial planets
  • Seasonal changes, rotation rates
  • Inventory of outer planetary system constituents
    jovian planets, brown dwarfs, and
    exozodiacal/Kuiper dust
  • Atmospheric characterization of jovian planets
    and brown dwarf companions
  • Structure evolution of circumstellar disks

12
Instruments for TPF-C
  • NASA will provide facility starlight suppression
    system
  • Current baseline is Lyot coronagraph, multiple
    selectable focal plane and pupil plane masks,
    96x96 deformable mirror
  • 3.5 x 8 m telescope delivers PSF FWHM 29 mas x 13
    mas at V
  • Focal plane instruments will come out of AO
    process
  • High contrast instruments will likely include
  • Imaging with high contrast FOV of 2-3 at V band
  • Spectrograph (possibly integral field unit)
    R70-150 (to characterize
    planets speckles)
  • General astrophysics investigations
  • High contrast problems (QSO hosts, evolved star
    shells, etc.)
  • One additional instrument for deep surveys, or
    high spatial resolution spectroscopy, or ?

13
TPF-C Has Broad Science Goals
All parallel observing time will be available for
general astrophysics PLUS A fraction of the
observing time for dedicated general
astrophysics, as determined by TAC
14
TPF-C Next Steps
  • Push to the goal of 1010 image contrast in JPL
    testbed
  • Improved hardware, control algorithms, modeling
    analysis
  • New Science Technology Definition team will
    flesh out mission science requirements, develop
    operations concepts, and advise on the
    observatory design process
  • Engineering design teams will continue
    development of mission design concept telescope,
    spacecraft, thermal mechanical design issues,
    etc.
  • Instrument concept studies will take place during
    the second half of 2005 (proposals due in late
    April)
  • Mission concept report targeted for spring 2006
    completion

15
  • END

16
TPF-C Technology Priorities
  • Wavefront control DM development, testbeds,
    algorithms
  • Large monolithic primary mirror deployable
    secondary
  • Good control of mid-spatial frequency surface
    errors
  • Fast off-axis (unobscured) primary
  • Very high thermal and mechanical stability of
    telescope and instrument isolation, metrology,
    active control
  • Optical coatings
  • Overcoated Ag preferred from throughput
    considerations
  • Strongly desire reflectivity uniform to over large optics
  • Minimize or counteract induced polarization
  • Coronagraphic masks
  • Improved fabrication through characterization
    modeling
  • Designs that maximize throughput and minimize
    aberration sensitivities at the inner working
    angle

17
Illustrative General Astrophysics Camera for
TPF-C
  • Wider Field Camera, perhaps 4 FOV,
    multiple filters
  • Targeted observations to complement JWST near-IR
    and mid-IR surveys
  • Program of parallel science during planet finding
    observations
  • 50 target stars (50 of 5 yr mission) yield 18
    days of integration per field
  • With 6 x HST collecting area, will get UDF
    sensitivity on 25 b 30o fields
  • 200 comparative planetology targets (15 of
    mission time) with 3 days of integration
    HDF sensitivity on 100 b 30o fields
  • Multiple visits per target variability studies

18
Discovery Space for Basic TPF-C
Ben Lane and Sally Heap
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