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28 June 2006 A combined nulling and imaging pupil-plane beam-combiner for DARWIN
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The primary goal of DARWIN is to detect earth-like extrasolar planets and to search for biomarkers. This is achieved by means of nulling interferometry, using three free-flying telescopes and a Beam-Combiner (BC) hub. DARWIN will be able to perform astrophysical imaging with high spectral and spatial resolution. Should one of Darwin's telescope flyers fail, then Darwin's capability of detecting earth-sized exo-planets is dramatically reduced. However, with only two telescopes the imaging mode can continue operating with minimal performance degradation, thus ensuring mission success. This work describes a trade-off study between four conceptual three-beam BC's, that are capable of performing both as a nuller and as an imager. A proposed breadboard design will demonstrate end-to-end Fringe-Tracking (FT) and Optical Path-Length (OPL) control. The BC concept is based on a pupil-plane (Michelson) beam combination scheme. Pupil-plane imaging BC's offer a large overlap in terms of optical layout with the nulling BC concept, making it possible to develop a combined nulling- and imaging BC. This means that a reduced number of optical components can be used compared to a scheme with separate BC's. The BC concept inherently compensates for unequal OPL's, which in ground-based interferometers is compensated for by long stroke Optical Delay Lines (ODL's).
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ron P. H. Haaksman, Cor P. de Vries, Jan-Willem den Herder, L. L. A. Vosteen, Henk Bokhove, and Arjan L. Mieremet "A combined nulling and imaging pupil-plane beam-combiner for DARWIN", Proc. SPIE 6268, Advances in Stellar Interferometry, 62682Q (28 June 2006);

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