With the launch of planet-transit missions such as CoRoT and Kepler, it is expected that Earth-sized planets
orbiting distant stars will be detected soon. This milestone will open the path towards the definition of missions
able to study the atmosphere of Earth-sized extrasolar planets, with the identification of bio-signatures as one of
the main objectives. In that respect, both the European Space Agency (ESA) and the National Aeronautics and
Space Administration (NASA) have identified nulling interferometry as one of the most promising techniques.
Trying to minimize the cost and the technological risks while maximizing the scientific return, ESA and NASA
recently converged towards a single mission architecture, the Emma X-array. In this paper, we present the
expected science performance of this concept computed with two independent mission simulators. The impact of
different observational parameters such as planet radius and exozodiacal cloud density is specifically addressed.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.