Characterizing Earth Analogs in Reflected Light: Atmospheric Retrieval Studies for Future Space Telescopes

Y. Katherina Feng, Tyler D. Robinson, Jonathan J. Fortney, Roxana E. Lupu, Mark S. Marley, Nikole K. Lewis, Bruce MacIntosh, Michael Line

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Space-based high-contrast imaging mission concepts for studying rocky exoplanets in reflected light are currently under community study. We develop an inverse modeling framework to estimate the science return of such missions given different instrument design considerations. By combining an exoplanet albedo model, instrument noise model, and ensemble Markov chain Monte Carlo sampler, we explore retrievals of atmospheric and planetary properties for Earth twins as a function of signal-to-noise ratio (S/N) and resolution (R). Our forward model includes Rayleigh-scattering, single-layer water clouds with patchy coverage, and pressure-dependent absorption due to water vapor, oxygen, and ozone. We simulate data at R = 70 and 140 from 0.4 to 1.0 μm with S/N = 5, 10, 15, and 20 at 550 nm (i.e., for HabEx/LUVOIR-type instruments). At these same S/Ns, we simulate data for WFIRST paired with a starshade, which includes two photometric points between 0.48 and 0.6 μm and R = 50 spectroscopy from 0.6 to 0.97 μm. Given our noise model for WFIRST-type detectors, we find that weak detections of water vapor, ozone, and oxygen can be achieved with observations with at least R = 70/S/N = 15 or R = 140/S/N = 10 for improved detections. Meaningful constraints are only achieved with R = 140/S/N = 20 data. The WFIRST data offer limited diagnostic information, needing at least S/N = 20 to weakly detect gases. Most scenarios place limits on planetary radius but cannot constrain surface gravity and, thus, planetary mass.

Original languageEnglish (US)
Article number200
JournalAstronomical Journal
Volume155
Issue number5
DOIs
StatePublished - May 1 2018

Fingerprint

Earth analogs
retrieval
telescopes
extrasolar planets
ozone
water vapor
planetary mass
oxygen
samplers
Markov chains
cloud water
Rayleigh scattering
Markov chain
albedo
signal-to-noise ratio
sampler
signal to noise ratios
spectroscopy
scattering
gravity

Keywords

  • methods: statistical
  • planets and satellites: atmospheres
  • planets and satellites: terrestrial planets

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Characterizing Earth Analogs in Reflected Light : Atmospheric Retrieval Studies for Future Space Telescopes. / Feng, Y. Katherina; Robinson, Tyler D.; Fortney, Jonathan J.; Lupu, Roxana E.; Marley, Mark S.; Lewis, Nikole K.; MacIntosh, Bruce; Line, Michael.

In: Astronomical Journal, Vol. 155, No. 5, 200, 01.05.2018.

Research output: Contribution to journalArticle

Feng, Y. Katherina ; Robinson, Tyler D. ; Fortney, Jonathan J. ; Lupu, Roxana E. ; Marley, Mark S. ; Lewis, Nikole K. ; MacIntosh, Bruce ; Line, Michael. / Characterizing Earth Analogs in Reflected Light : Atmospheric Retrieval Studies for Future Space Telescopes. In: Astronomical Journal. 2018 ; Vol. 155, No. 5.
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