Pedretti, Ettore and Traub, Wesley A. and Monnier, John D. and Millan-Gabet, Rafael and Varleton, Nathaniel P. and Schloerb, F. Peter and Brewer, Michael K. and Berger, Jean-Philippe and Lacasse, Marc G. and Ragland, Sam (2005) Robust determination of optical path difference: fringe tracking at the Infrared Optical Telescope Array interferometer. Applied Optics, 44 (25). pp. 5173-5179. ISSN 0003-6935. http://resolver.caltech.edu/CaltechAUTHORS:PEDao05
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We describe the fringe-packet tracking system used to equalize the optical path lengths at the Infrared Optical Telescope Array interferometer. The measurement of closure phases requires obtaining fringes on three baselines simultaneously. This is accomplished by use of an algorithm based on double Fourier interferometry for obtaining the wavelength-dependent phase of the fringes and a group-delay tracking algorithm for determining the position of the fringe packet. A comparison of data acquired with and without the fringe-packet tracker shows a factor of ~3 reduction of the error in the closure-phase measurement. The fringe-packet tracker has been able so far to track fringes with signal-to-noise ratios as low as 1.8 for stars as faint as m_H=7.0.
|Additional Information:||© 2005 Optical Society of America Received 9 November 2004; revised manuscript received 29 March 2005; accepted 31 March 2005. This research was made possible by a Smithsonian predoctoral fellowship and a Michelson postdoctoral fellowship awarded to E. Pedretti. The IONIC project is a collaboration among the Laboratoire d’Astrophysique de Grenoble, the Laboratoire d’Electromagnetisme Microondes et Optoelectronique, and also the Commissariat a l’Energie Atomique–Laboratoire d’Electronique de Technologie et d’Instrumentation and the Institut de Microélectronique, Électromagnétisme et Photonique, Grenoble, France. The IONIC project is funded in France by the Centre National de Recherche Scientifique and the Centre National d’Etudes Spatiales. The research and the operation of the fringe-packet tracker were supported in part by grant NAG5-4900 from NASA, by grants AST-0138303 from the National Science Foundation, and by funds from the Smithsonian Institution. This research has made use of NASA’s Astrophysics Data System bibliographic services.|
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|Deposited On:||08 Jan 2007|
|Last Modified:||26 Dec 2012 09:28|
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