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Characterization of Extrasolar Planets via Direct Detection with an Enhanced Coronagraphic Terrestrial Planet Finder
Eric B. Ford (U Florida)
in collaboration with Sara Seager (MIT), Edwin L. Turner (Princeton), Enric Palle, Pilar Montanes-Rodriguez, Manuel Vazquez (IAC) Astrophysics 2020: Large Space Missions Beyond the Next Decade Space Telescope Science Institute November 14, 2007


Direct Detection

TPF-C TPF-I

Artwork Boownset of.NA02 c r urte y al 20 SA


Close et al.

Direct Detections

Chauvin et al.

Charbonneau et al.

Neuhauser et al.


The Solar System from Voyager


Direct Detection


Could we distinguish Earth from Venus or Mars?

Images courtesy of NASA


Optical Spectra & Potential Biomarkers


Planet mass & radius (albedo) Atmospheric mass (Rayleigh) O2 (760nm A-band) O3 (580, 320nm) H2O (940, 820, 720nm) CO2 (1050nm, if abundant) CH4 (890, 790nm, if abundant) Red Edge (~700-750 nm)

Traub et al. 2001


Why are TPF missions on hold?




Cost/Risk/Need for Further Technology Development Cost matters, but TPF-C's budget is not the whole problem Evidently, other projects are perceived as higher priority and/or a better value How could this be changed? Convince decision makers to change budget priorities Accomplish some interesting science with smaller budget Accomplish much more interesting science, even if this would require a larger budget


Why Direct Detection?
Measurements Picture of 2+ Fuzzy Dots






Capabilities & Implications Confirm Indirect Detections, Orbits, Equilibrium Temp. Identify Planets with Different Photometric Variability "Surfaces": Oceans/Continents, Surface/Atmosphere; Weather Measure Composition of Spectrum of Planet Atmosphere & Abundances Signatures of Life: Search for Disequilibrium Chemistry: Polarization of Scattered Light Detect Oceans, Distinguish Cloud/Ice Cover


Choice of Size for TPF-C






Scientific capabilities increase rapidly with size of primary Astronomers want largest observatory possible/practical Previously, the maximum size (~8m major axis) was set by the Space Shuttle cargo bay, not science requirements Ares V would enable a much larger primary mirror (~16m major axis) and greater mass for instruments Can we envision a new mission so much more impressive than TPF-C, that the mission would be deemed a higher priority and/or a better value (despite a greater cost)?


Advantages of a Larger Aperture for TPF-C


Can Search More Stars to Greater Distances (~D3 ) Faster Survey, More Time for Follow-Up Sensitive to Planets in Habitable Zone of More/Fainter Stars Smaller Inner Working Angle (at Fixed Wavelength) Lower Mass Stars, Fewer Visits/Star for Significant Null Result, Improved Orbits, Efficient Recovery on Future Visits


TPF-C Observability of Planets in HZ
For a blind search:


Require observations at 5 (11) epochs to rule out a planet in the habitable zone which is inside the inner working radius 50% of time at 2 (3) level. For asymmetric mirror, need observations with multiple orientations at each epoch



Ford; see also Brown 200x


Advantages of a Larger Aperture for TPF-C




Can Search More Stars to Greater Distances (~D2 ) Faster Survey, More Time for Follow-Up Sensitive to Planets in Habitable Zone of More/Fainter Stars Smaller Inner Working Angle (at Fixed Wavelength) Lower Mass Stars, Fewer Visits/Star for Significant Null Result, Improved Orbits, Efficient Recovery on Future Visits Higher S/N & Spectral Resolution Longer Wavelengths (at Fixed Inner Working Angle) O2 (1.27µm), H2O (1.14, 1.41, 1.86µm), CO2 (1.45, 1.57, 2µm), CH4(1.66, 2.3µm), NH3(2µm)


Near-IR Spectra & Biomarkers

Kaltenegger et al. 2006


Advantages of a Larger Aperture for TPF-C






Can Search More Stars to Greater Distances (~D2 ) Faster Survey, More Time for Follow-Up Sensitive to Planets in Habitable Zone of More/Fainter Stars Smaller Inner Working Angle (at Fixed Wavelength) Lower Mass Stars, Fewer Visits/Star for Significant Null Result, Improved Orbits, Efficient Recovery on Future Visits Higher S/N & Spectral Resolution Longer Wavelengths (at Fixed Inner Working Angle) O2 (1.27µm), H2O (1.14, 1.41, 1.86µm), CO2 (1.45, 1.57, 2µm), CH4(1.66, 2.3µm), NH3(2µm) Higher S/N & Temporal Resolution Precise Rotation Period: Maintain Rotational Phase for Temporal Surface Mapping


Detecting Surface Features

Ford et al. 2001

Fraction of Surface

NASA/Mars Global Surveyor


Variability of Other Worlds

Ford et al. 2001

Time (d)


Variability in Cloud Cover
Average difference between maximum & minimum cloud coverage over a two week period. Significant variability in some locations (e.g., North America) But over much of the Earth, cloud formations change gradually

Palle et al. submitted to ApJ


Is it Possible to Measure the Rotation Period of the Earth from Optical Variability?

Model w/ clouds Model w/o clouds

Palle et al. submitted to ApJ


How Precisely could we measure Earth's Rotation Period?

Palle et al. submitted to ApJ


Folded Light Curves

Palle et al. submitted to ApJ


How Big would TPF-C Need to Be?

Earth/Sun @ 5pc Earth/Sun @ 10pc

Palle et al. submitted to ApJ


Questions

NASA//Marrs Glloball Surrveyorr NASA Ma s G oba Su veyo