FIRST, a fibered aperture masking instrument
I. First on-sky test results
1 LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, Paris Sciences et Lettres, 5 place Jules Janssen, 92195 Meudon, France
2 Carl Sagan Center at the SETI Institute, 189 Bernardo Av., Mountain View, CA 94043, USA
3 Department of Astronomy, University of California at Berkeley, Hearst Field Annex, B-20, Berkeley, CA 94720-3411, USA
4 ISAS/JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara 252-5210, Japan
5 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, 38041 Grenoble, France
6 University of California Observatories/Lick Observatory, PO Box 85, Mount Hamilton, CA 95140, USA
7 W. M. Keck Observatory, 65-1120 Mamalahoa Hwy, Kamuela, HI 96743, USA
8 Canada-France-Hawaii Telescope, 65-1238 Mamalahoa Hwy, 96743 Kamuela, HI, USA
Received: 24 November 2011
Accepted: 16 March 2012
Aims. In this paper we present the first on-sky results with the fibered aperture masking instrument FIRST. Its principle relies on the combination of spatial filtering and aperture masking using single-mode fibers, a novel technique that is aimed at high dynamic range imaging with high angular resolution.
Methods. The prototype has been tested with the Shane 3-m telescope at Lick Observatory. The entrance pupil is divided into sub-pupils feeding single-mode fibers. The flux injection into the fibers is optimized by a segmented mirror. The beams are spectrally dispersed and recombined in a non-redundant exit configuration in order to retrieve all contrasts and phases independently.
Results. The instrument works at visible wavelengths between 600 nm and 760 nm and currently uses nine of the 30 43 cm sub-apertures constituting the full pupil. First fringes were obtained on Vega and Deneb. Stable closure phases were measured with standard deviations on the order of 1 degree. Closure phase precision can be further improved by addressing some of the remaining sources of systematic errors. While the number of fibers used in the experiment was too small to reliably estimate visibility amplitudes, we have measured closure amplitudes with a precision of 10% in the best case.
Conclusions. These first promising results obtained under real observing conditions validate the concept of the fibered aperture masking instrument and open the way for a new type of ground-based instrument working in the visible. The next steps of the development will be to improve the stability and the sensitivity of the instrument in order to achieve more accurate closure phase and visibility measurements, and to increase the number of sub-pupils to reach full pupil coverage.
Key words: instrumentation: high angular resolution / techniques: interferometric / planetary systems / stars: individual: Vega
© ESO, 2012