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Astron. Astrophys. 331, 619-626 (1998)

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2. The IOTA interferometer and the FLUOR beam combiner

IOTA 1 is a Michelson type interferometer operated both in the visible and in the infrared. The interferometer is located at the Smithsonian Institution's Whipple Observatory on Mount Hopkins in Arizona. A complete and accurate description of IOTA can be found in  Carleton et al. (1994). First fringes were obtained on IOTA in the near infrared in 1993 (Dyck et al. 1995).

The excellent Mt. Hopkins site, the baseline, and availability of infrared instrumentation, make IOTA an outstanding facility for study of cool stars. The first IOTA scientific results (Dyck et al. 1996a) were based on classical beam combination.

Recently, a fiber recombination unit has been installed as a focal instrument at IOTA by our group. FLUOR 2 is the heir of a prototype first operated at the McMath-Pierce solar telescope of the National Solar Observatory on Kitt Peak (Coude du Foresto & Ridgway 1991). The recombination is achieved in the photometric K band with single-mode fluoride glass fibers. The single-mode fibers spatially filter the wavefronts corrugated by atmospheric turbulence. Phase fluctuations are thus traded against flux fluctuations which are monitored by auxiliary photometric outputs. It is then possible to directly calibrate and correct for the non-stationary atmospheric transfer function, alleviating severe inaccuracies in visibility calibrations which plague classical (multi mode) beam combiners (Coude du Foresto et al. 1997). Progress reports on FLUOR have been presented at several conferences (see Perrin et al. 1996a, Perrin et al. 1996b). It will be described in more detail in a forthcoming paper.

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© European Southern Observatory (ESO) 1998

Online publication: February 16, 1998