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Proceedings Paper

Design of a four mirror astrometric telescope for light bending measurements
Author(s): Davide Loreggia; Mario Gai; Sebastiano Ligori; Alberto Vecchiato; Mario G. Lattanzi
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Paper Abstract

We present a new design of a four mirrors telescope for astrometric measurement to be used in the GAME mission, currently under study at the Astronomical Observatory of Turin, Italy. The main aim of GAME - Gamma Astrometric Measurement Experiment - is to measure the γ parameter of the Parameterized Post- Newtonian formulation by looking at the deflection of light produced by the Sun's gravitational curvature, as in the Dyson, Eddington et al. 1919 experiment, using a dedicated, space based dual-field telescope. A first design has been presented in recent years, based on a Cassegrain scheme with a mask in front of the primary mirror to realize multiple aperture Fizeau interferometry. The new design still implements a Fizeau interferometer, but the telescope layout is based on a Korsch-like scheme with four conical mirrors, long focal length, and without the use of exotic surfaces (aspheric or polynomial) as adopted in other long focal astrometric instruments. A different combination scheme of the two lines of sight makes the dimensioning of the primary mirror more relaxed allowing us to work with smaller surfaces and therefore to achieve a more compact payload configuration. The design of the instrument and the masked interferometry approach allow us to maximize the astrometric performances and at the same time to improve the baffling, minimizing the amount of stray light from the Sun. In this paper we describe the mission profile, the observation principle, the new instrument layout and the expected performances.

Paper Details

Date Published: 5 August 2010
PDF: 12 pages
Proc. SPIE 7731, Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave, 77311U (5 August 2010);
Show Author Affiliations
Davide Loreggia, INAF, Osservatorio Astronomico di Torino (Italy)
Mario Gai, INAF, Osservatorio Astronomico di Torino (Italy)
Sebastiano Ligori, INAF, Osservatorio Astronomico di Torino (Italy)
Alberto Vecchiato, INAF, Osservatorio Astronomico di Torino (Italy)
Mario G. Lattanzi, INAF, Osservatorio Astronomico di Torino (Italy)

Published in SPIE Proceedings Vol. 7731:
Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave
Jacobus M. Oschmann Jr.; Mark C. Clampin; Howard A. MacEwen, Editor(s)

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