A nulling wide field imager for exoplanets detection and general astrophysics

We present a solution to obtain a high-resolution image of a wide field with the central source removed by destructive interference. The wide-field image is created by aperture synthesis with a rotating sparse array of telescopes in space. Nulling of the central source is achieved using a phase-mask coronagraph. The full (u;v) plane coverage delivered by the 60 m, six 3-meter telescope array is particularly well-suited for the detection and characterization of exoplanets in the infrared (DARWIN and Terrestrial Planet Finder (TPF) missions) as well as for other generic science observations. Detection (S=N= 10) of an Earth- like planet is achieved in 10 hours with a 1m bandwidth at 10m. very limited (small field of view and very partial (u;v )p lane coverage), increasing the risk of confusion between an exo- planet and an anisotropy of the exozodiacal cloud. The de- tection by light modulation on a monopixel detector suers from high sensitivity to temporal variations of both the ther- mal background intensity and the light leakage from the nulled central star. In this paper, we present a solution to image (with af ull (u;v) plane coverage up to the cuto frequency) a field with the central source removed by destructive interference. The wide field of view and good (u;v) plane coverage limit the risk of confusion with background sources and exozodia- cal anisotropies. We demonstrate the importance of good (u;v) coverage and show how to achieve it in Sect. 2. The pupil densi- fication and pupil redilution techniques are presented in Sect. 3: these techniques make possible the use of a nulling corona- graph on a sparse array of telescopes. The overall behavior of the concept is studied in Sect. 4. In Sects. 5 and 6, we explore the capabilities of this concept to image Earth-like planets and study other astrophysical objects.

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