Space borne nulling interferometry with non-rotating telescope arrays

Abstract

Spaceborne nulling interferometry in the mid-infrared waveband is one of the most promising techniques for characterizing the atmospheres of extra-solar planets orbiting in the habitable zone of their parent star and possibly discovering life markers. One of the most difficult challenges is the control of a free-flying telescope spacecraft moving around a central combiner to modulate the planet signal. Moreover, the entire array must be reconfigured regularly to observe different celestial targets, thus increasing the risk of losing one or more spacecraft and aborting the mission before its normal end. This paper describes a simplified optical configuration in which the telescopes do not need to be rotated and the number of necessary array reconfigurations is minimized. It allows efficient modulation of the planet signal, using only making use of rotating prisms or mirrors located in the central combiner. The general principle of a Nulling interferometer with a fixed telescope array is explained. Mathematical relationships were established to determine the planet modulation signal. Numerical simulations were performed for three different arrangements of collecting telescopes. They confirmed that nulling interferometry in space did not require a rotating telescope array.