Nulling Interferometry with IRSI-Darwin: Detection and Characterization of Earth-like Exoplanets

The search for exoplanets has gained much interest since the first discovery of a planet orbiting the star 51 Peg by Mayor and Queloz in 1995. Current techniques for exoplanet detection, such as radial velocity measurements, are well suited to detect Jupiter-sized planets, but do not have enough sensitivity to discover planets similar to our Earth. The IRSI-Darwin space mission is aimed at filling this gap, by means of nulling interferometry. This special kind of interferometry is intended to suppress all the light coming from a blinding star by means of destructive interference, in order to reveal the star's potential planetary companions. Once the starlight has been properly cancelled, the thermal emission from zodiacal and exo-zodiacal dust clouds becomes the main obstacle to planet detection. Internal modulation is a recent technique devised to suppress such spurious signals. It relies on rapid modulation between the outputs of two nulling interferometers sharing the same telescopes.

In the present thesis, a comprehensive investigation of possible configurations of a
telescope array with internal modulation has been undertaken, leading to a number of new
configurations. As compared to the current {\sc Darwin} configuration, the sensitivity of
the interferometer to the planetary signal has been improved by a factor of two,
resulting in a fourfold speedup in the detection and characterization of exoplanets. The
possibility of designing a nulling interferometer on ESO's Very Large Telescope
Interferometer as a technological prerequisite to {\sc Darwin} has also been considered.
Signal-to-noise calculations have shown that this instrument could be used to
characterize exo-zodiacal clouds down to the 10-zodi level.