Title: Status of the Terrestrial Planet Finder Coronagraph TPFC :
1Status 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
2TPF-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
3Why 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
5Graded coronagraphic masks
Courtesy of John Trauger (JPL)
6Demonstrated Image Contrast
Courtesy of John Trauger (JPL)
7Terrestrial 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
8TPF-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
9TPF-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
10Schematic 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
11Strawman 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
12Instruments 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 ?
13TPF-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
14TPF-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 16TPF-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
17Illustrative 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
18Discovery Space for Basic TPF-C
Ben Lane and Sally Heap