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Front end of the SPIRou spectropolarimeter for Canada-France Hawaii Telescope

2012; SPIE; Volume: 8446; Linguagem: Inglês

10.1117/12.925410

1996-756X

L. Parès, J.‐F. Donati, M. Dupieux, T. Gharsa, Yoan Micheau, M. Bouyé, Bruno Dubois, G. Gallou, Driss Kouach, Gregory Barrick, Shiang‐Yu Wang,

Superconducting and THz Device Technology

SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a nextgeneration instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goal of detecting Earth-like planets around low-mass stars and magnetic fields of forming stars. The unique scientific and technical capabilities of SPIRou are described in a series of seven companion papers. In this paper, the Front End of the instrument is presented. Positioned at the Cassegrain Focal plane of the telescope, the front end is constituted of an atmospheric dispersion corrector, a field viewer with an image stabilization unit (0.03 arc seconds RMS stabilization goal), a calibration wheel and an achromatic polarimeter unit based on Fresnel Rhombs. The polarimeter permits the circular and linear polarization analysis. The retardance of the Fresnel rhombs is nominal to better than 0.5% in the whole spectral domain. The evaluation and the reduction of the thermal background of the Front end is a challenging part of the instrument.