Search for extraterrestrial planets: The DARWIN mission

Abstract

The DARWIN mission is primarily devoted to the detection of earth-like exoplanets and the spectroscopic characterization of their atmospheres for key tracers of life. We will review the current instrumental concept, which is based on an interferometric array of six free-flying telescopes, passively cooled to 40 K, operating in the 6-18 micron wavelength range. The angular resolution of DARWIN can be matched to a broad variety of observational scenarios by resizing the array between diameters of 50 m and 500 m. The flux of the parent star, which normally would overwhelm the planetary signal, is suppressed by a factor of 106 by destructive interference (nulling) over the full optical bandwidth, as the beams are combined. Then, the planetary signal can be separated from the zodiacal background signature by modulating the optical response of the interferometer. ESA is carrying out an extensive technology development programme to bring DARWIN-related technology to a maturity level in the three key areas of Formation Flying, Cryogenic Cooling and Mechanisms, and Nulling Interferometry. We report on the current status of optical development activities within this program, which includes the development of optical metrology, achromatic phase shifters, amplitude and polarization control devices, nulling interferometer demonstrators, mid-IR single-mode waveguides and advanced waveguide coupling devices.