20 October 2004 Adaptive DFT-based fringe tracking and prediction at IOTA
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Abstract
An automatic fringe tracking system has been developed and implemented at the Infrared Optical Telescope Array (IOTA). In testing during May 2002, the system successfully minimized the optical path differences (OPDs) for all three baselines at IOTA. Based on sliding window discrete Fourier transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on off-line data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately 2.0 milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. Preliminary analysis on an extension of this algorithm indicates a potential for predictive tracking, although at present, real-time implementation of this extension would require significantly more computational capacity.
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Edward Wilson, Edward Wilson, Ettore Pedretti, Ettore Pedretti, Jesse Bregman, Jesse Bregman, Robert W. Mah, Robert W. Mah, Wesley Arthur Traub, Wesley Arthur Traub, } "Adaptive DFT-based fringe tracking and prediction at IOTA", Proc. SPIE 5491, New Frontiers in Stellar Interferometry, (20 October 2004); doi: 10.1117/12.552979; https://doi.org/10.1117/12.552979
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