Array configurations for a space infrared nulling interferometer dedicated to the search for Earthlike extrasolar planets

Recent studies show that an infrared nulling interferometer dedicated to the detection and spectroscopy of exoplanetary systems must fulfill three main requirements. It must provide very strong suppression of the Fight originating from the target star and good spectral coverage (from 6 to 18 mu m) with a fixed baseline and must be able to distinguish planets from local dust disc emission without any ambiguity. We present here a solution with five 1.5 m class telescopes deployed in an elliptical array that meets all these constraints. The telescope array, whose dimensions are about 50 by 25 m, has been optimized so that the exozodiacal emission is strongly estinguished, very weakly modulated by rotation about the line of sight, and concentrated at a few even frequencies. The planet's signal, in contrast, is strongly modulated at many distinctive frequencies, A simple cross-correlation method recovers a single image of a solar system twin al 10 pc distance after about 30 hr of integration time, The spectroscopy of the planets can then be undertaken with the same baseline and would reveal absorption features of water, ozone, and carbon dioxide for an Earthlike planet at 10 pc in less than 1 mo. (C) 1997 Academic Press.