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Proceedings Paper

Design and expected performances of the SCAO-WFS module of SIMPLE, the high-resolution near-infrared spectrometer for E-ELT
Author(s): A. Tozzi; E. Oliva; M. Le Louarn; L. Origlia
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Paper Abstract

We present and discuss the design and expected performances of the SCAO-WFS module of SIMPLE, the highsd resolution near-infrared spectrometer for the E-ELT which is designed to operate in the wavelengths range 0.84-2.5μm with an entrance slit width of 27mas which yields a spectral resolving power of R=130,000. We analyze both pyramid and SH wave-front sensors operating at near-infrared wavelengths (1-2 μm). The main results can be summarized as follows. - Good levels of AO correction can only be achieved within a few arc-sec of the reference star. The primary applications of SCAO correction are therefore observations where the science object is compact and bright enough to be used as reference star, feeding the WFS via a beam-splitter. We concentrate on a WFS operating at nearinfrared wavelengths because many of the scientific targets of SIMPLE are intrinsically very red. - The pyramid WFS provides better performances than the SH, because it is less affected by aliasing errors. - The quality of AO correction is almost independent on the wavelength at which the wave-front is sensed. Therefore, we simplify the design the WFS module by not including the K-band, i.e. operating in the 1.0-2.1μm range. Extension to shorter wavelengths is also possible but requires exchanging the atmospheric dispersion compensator. - Using a pyramid WFS with 84x84 sub-apertures one can achieve remarkably high values of light-concentration in the slit, i.e. ~70% in K and ~40% at 0.9μm. - The limiting magnitude for the 84×84 WFS is about 13.5+2.5•log(η), where η is the fraction of stellar light sent to the WFS by the beam-splitter. - Somewhat fainter limits, i.e. magnitudes ~14.0+2.5•log(η), can be achieved by changing the camera optics of the WFS and sampling 42×42 sub-apertures.

Paper Details

Date Published: 29 July 2010
PDF: 12 pages
Proc. SPIE 7736, Adaptive Optics Systems II, 77363V (29 July 2010); doi: 10.1117/12.856478
Show Author Affiliations
A. Tozzi, INAF-Osservatorio Astrofisico di Arcetri (Italy)
E. Oliva, INAF-Osservatorio Astrofisico di Arcetri (Italy)
M. Le Louarn, European Organisation for Astronomical Research in the Southern Hemisphere (Germany)
L. Origlia, INAF-Osservatorio Astronomico di Bologna (Italy)


Published in SPIE Proceedings Vol. 7736:
Adaptive Optics Systems II
Brent L. Ellerbroek; Michael Hart; Norbert Hubin; Peter L. Wizinowich, Editor(s)

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