Experimental Astronomy

, Volume 40, Issue 2–3, pp 545–561 | Cite as

Exoplanet atmospheres with EChO: spectral retrievals using EChOSim

  • Joanna K. Barstow
  • Neil E. Bowles
  • Suzanne Aigrain
  • Leigh N. Fletcher
  • Patrick G. J. Irwin
  • Ryan Varley
  • Enzo Pascale
Original Article


We demonstrate the effectiveness of the Exoplanet Characterisation Observatory mission concept for constraining the atmospheric properties of hot and warm gas giants and super Earths. Synthetic primary and secondary transit spectra for a range of planets are passed through EChOSim [13] to obtain the expected level of noise for different observational scenarios; these are then used as inputs for the NEMESIS atmospheric retrieval code and the retrieved atmospheric properties (temperature structure, composition and cloud properties) compared with the known input values, following the method of [1]. To correctly retrieve the temperature structure and composition of the atmosphere to within 2 σ, we find that we require: a single transit or eclipse of a hot Jupiter orbiting a sun-like (G2) star at 35 pc to constrain the terminator and dayside atmospheres; 20 transits or eclipses of a warm Jupiter orbiting a similar star; 10 transits/eclipses of a hot Neptune orbiting an M dwarf at 6 pc; and 30 transits or eclipses of a GJ1214b-like planet.


Exoplanets Atmospheric remote sensing Spectroscopy Retrieval 



JKB is supported by the Science and Technology Facilities Council and LNF by a Royal Society Research Fellowship. This work was part of the EChO Consortium Study funded by the UK Space Agency. We thank the anonymous reviewer and Professor Jacob Bean for helpful comments on the manuscript.


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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • Joanna K. Barstow
    • 1
  • Neil E. Bowles
    • 1
  • Suzanne Aigrain
    • 1
  • Leigh N. Fletcher
    • 1
  • Patrick G. J. Irwin
    • 1
  • Ryan Varley
    • 2
  • Enzo Pascale
    • 3
  1. 1.Department of PhysicsUniversity of OxfordOxfordUK
  2. 2.Department of PhysicsUniversity College LondonLondonUK
  3. 3.School of Physics and AstronomyUniversity of CardiffCardiffUK

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