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Measuring Extended Structure in Stars Using the Keck Interferometer NullerThe Keck Interferometer Nuller is designed to detect faint off-axis mid-infrared light a few tens to a few hundreds of milliarcseconds from a bright central star. The starlight is suppressed by destructive combination along the long (85 m) baseline, which produces a fringe spacing of 25 mas at a wavelength of 10 m, with the central null crossing the position of the star. The strong, variable mid-infrared background is subtracted using interferometric phase chopping along the short (5 m) baseline. This paper presents an overview of the observing and data reduction strategies used to produce a calibrated measurement of the off-axis light. During the observations, the instrument cycles rapidly through several calibration and measurement steps, in order to monitor and stabilize the phases of the fringes produced by the various baselines, and to derive the fringe intensity at the constructive peak and destructive null along the long baseline. The data analysis involves removing biases and coherently demodulating the short-baseline fringe with the long-baseline fringe tuned to alternate between constructive and destructive phases, combining the results of many measurements to improve the sensitivity, and estimating the part of the null leakage signal which is associated with the finite angular size of the central star. Comparison of the results of null measurements on science target and calibrator stars permits the instrumental leakage - the "system null leakage" - to be removed and the off-axis light to be measured.
Document ID
20070019870
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
External Source(s)
Authors
Koresko, Chris
(California Inst. of Tech. Pasadena, CA, United States)
Colavita, M. Mark
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Serabyn, Eugene
(California Inst. of Tech. Pasadena, CA, United States)
Booth, Andrew
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Garcia, Jean
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 23, 2013
Publication Date
May 24, 2006
Subject Category
Astronomy
Meeting Information
Meeting: SPIE Astronomical Telescopes and Instrumentation
Location: Orlando, FL
Country: United States
Start Date: May 24, 2006
End Date: May 31, 2006
Sponsors: International Society for Optical Engineering
Distribution Limits
Public
Copyright
Other
Keywords
nulling interferometry
high - contrast imaging
exozodiacal dust

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