Cool Stars 14 - Submitted Abstract # 293
This version created on 05 October 2006

Performance study of space-based infrared Bracewell interferometers


Denis Defrere, Liege University
Olivier Absil, Liege University
Charles Hanot, Liege University
Roland den Hartog, European Space Agency (ESTEC)
Malcolm Fridlund, European Space Agency (ESTEC)

The Darwin and TPF-I missions will be able to detect and to study the
atmosphere of distant worlds similar to the Earth.  Flying these
space-based interferometers will however be an extraordinary
technological challenge and a first step could be taken by a smaller
mission.  Several proposals have already been made in this context,
using the simplest nulling scheme composed of 2 beam collectors, i.e.,
the original Bracewell interferometer.  These projects, viz.  Pegase
and the Fourier-Kelvin Space Interferometer (FKSI), show very good
perspectives for the detection and characterisation of hot extra-solar
giant planets, i.e., Jupiter-size planets orbiting close to their
parent star.  In this paper, we build on these concepts and try to
optimise a Bracewell interferometer for the detection of Earth-like
planets.  Our work is based on the CNES study for a formation flying
infrared interferometer (Pegase), whose specifications have been tuned
to fit the new goal (Earth-like planets).  The major challenge is to
mitigate the influence of the exo-zodiacal emission which cannot be
suppressed by internal modulation as in the case of Darwin.  We assess
the capabilities of split-pupil configurations with phase chopping and
OPD modulation techniques, which are good candidates for such a
mitigation.  Beyond the capabilities of a modified Pegase, this paper
gives an estimation of the performance to be expected for a
space-based Bracewell infrared interferometer for the detection of
extra-solar planets.  

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