Publications (4)0 Total impact
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Article: High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)
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ABSTRACT: A complete census of planetary systems around a volume-limited sample of solar-type stars (FGK dwarfs) in the Solar neighborhood (ensuremath densuremath<?iensuremath> $leq$ 15 pc) with uniform sensitivity down to Earth-mass planets within their Habitable Zones out to several AUs would be a major milestone in extrasolar planets astrophysics. This fundamental goal can be achieved with a mission concept such as NEAT--the Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne extremely-high-precision astrometric measurements at the 0.05 ensuremathmuas (1 ensuremath ensuremathsigmaensuremath<?iensuremath>) accuracy level, sufficient to detect dynamical effects due to orbiting planets of mass even lower than Earth?s around the nearest stars. Such a survey mission would provide the actual planetary masses and the full orbital geometry for all the components of the detected planetary systems down to the Earth-mass limit. The NEAT performance limits can be achieved by carrying out differential astrometry between the targets and a set of suitable reference stars in the field. The NEAT instrument design consists of an off-axis parabola single-mirror telescope (D = 1 m), a detector with a large field of view located 40 m away from the telescope and made of 8 small movable CCDs located around a fixed central CCD, and an interferometric calibration system monitoring dynamical Young?s fringes originating from metrology fibers located at the primary mirror. The mission profile is driven by the fact that the two main modules of the payload, the telescope and the focal plane, must be located 40 m away leading to the choice of a formation flying option as the reference mission, and of a deployable boom option as an alternative choice. The proposed mission architecture relies on the use of two satellites, of about 700 kg each, operating at L2 for 5 years, flying in formation and offering a capability of more than 20,000 reconfigurations. The two satellites will be launched in a stacked configuration using a Soyuz ST launch vehicle. The NEAT primary science program will encompass an astrometric survey of our 200 closest F-, G- and K-type stellar neighbors, with an average of 50 visits each distributed over the nominal mission duration. The main survey operation will use approximately 70% of the mission lifetime. The remaining 30% of NEAT observing time might be allocated, for example, to improve the characterization of the architecture of selected planetary systems around nearby targets of specific interest (low-mass stars, young stars, etc.) discovered by Gaia, ground-based high-precision radial-velocity surveys, and other programs. With its exquisite, surgical astrometric precision, NEAT holds the promise to provide the first thorough census for Earth-mass planets around stars in the immediate vicinity of our Sun.Experimental Astronomy. 07/2011; -
Article: Tests of achromatic phase shifters performed on the SYNAPSE test bench: a progress report
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ABSTRACT: The achromatic phase shifter (APS) is a component of the Bracewell nulling interferometer studied in preparation for future space missions (viz. Darwin/TPF-I) focusing on spectroscopic study of Earth-like exo-planets. Several possible designs of such an optical subsystem exist. Four approaches were selected for further study. Thales Alenia Space developed a dielectric prism APS. A focus crossing APS prototype was developed by the OCA, Nice, France. A field reversal APS prototype was prepared by the MPIA in Heidelberg, Germany. Centre Spatial de Li\`ege develops a concept based on Fresnel's rhombs. This paper presents a progress report on the current work aiming at evaluating these prototypes on the SYNAPSE test bench at the Institut d'Astrophysique Spatiale in Orsay, France.01/2009; -
Article: Tests of achromatic phase shifters performed on the SYNAPSE test bench: a progress report
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ABSTRACT: The achromatic phase shifter (APS) is a component of the Bracewell nulling interferometer studied in preparation for future space missions (viz. Darwin/TPF-I) focusing on spectroscopic study of Earth-like exo-planets. Several possible designs of such an optical subsystem exist. Four approaches were selected for further study. Thales Alenia Space developed a dielectric prism APS. A focus crossing APS prototype was developed by the OCA, Nice, France. A field reversal APS prototype was prepared by the MPIA in Heidelberg, Germany. Centre Spatial de Liege develops a concept based on Fresnel's rhombs. This paper presents a progress report on the current work aiming at evaluating these prototypes on the Synapse test bench at the Institut d'Astrophysique Spatiale in Orsay, France.Schöller, Markus; Danchi, William C.; Delplancke, Françoise: Optical and Infrared Interferometry, SPIE, 70134O-70134O-11 (2008). -
Article: The NULLTIMATE test bench: achromatic phase shifters for nulling interferometry
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ABSTRACT: The NULLTIMATE project developed and realized three concepts of achromatic phase shifters for nulling interferometry. One of the concepts is based on dispersive plates made of three materials which where fully characterized regarding their refractive index and thermo-optic behavior between 100K and 330 K. The other two concepts are based on mirror optics, one of which uses the phase shift of Ã⬠when crossing a focus, the other the reversal of electric fields at reflection. An optical bench has been set up to test and characterize these phase shifters at wavelengths 2 - 2.4 üm with the option of changing to the 10 üm domain. We summarize the development of the achromatic phase shifters and report on the current status of the test bench.Danchi, William C.; Delplancke, Françoise; Rajagopal, Jayadev K.: Optical and Infrared Interferometry II, SPIE, 77342E-77342E-16 (2010).
