Dr. Thomas A. Pauls Profile

Dr. Thomas A. Pauls

Radio Astronomer at Naval Research Lab

SPIE Involvement:

Author

Publications (31)

Proceedings Article | 28 July 2008 Paper

Practical coherent integration with the NPOI

Anders Jorgensen, Dave Mozurkewich, Henrique Schmitt, Robert Hindsley, J. Thomas Armstrong, Thomas Pauls, D. Hutter

Proceedings Volume 7013, 70131E (2008) https://doi.org/10.1117/12.790305

KEYWORDS: Visibility, Stars, Calibration, Phase measurement, Signal to noise ratio, Atmospheric modeling, Sensors, Photons, Solids, Interferometers

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Proceedings Article | 28 July 2008 Paper

2008 imaging beauty contest

William Cotton, John Monnier, Fabien Baron, Karl-Heinz Hofmann, Stefan Kraus, Gerd Weigelt, Sridharan Rengaswamy, Eric Thiébaut, Peter Lawson, Walter Jaffe, Christian Hummel, Tom Pauls, Henrique Schmitt, Peter Tuthill, John Young

Proceedings Volume 7013, 70131N (2008) https://doi.org/10.1117/12.788903

KEYWORDS: Data modeling, K band, Interferometry, Image restoration, Reconstruction algorithms, Visibility, Stars, Phase measurement, Image quality, Astronomical imaging

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Proceedings Article | 28 July 2008 Paper

Solving the imaging problem with coherently integrated multiwavelength data

H. Schmitt, T. Pauls, J. T. Armstrong, D. Mozurkewich, A. Jorgensen, R. Hindsley, C. Tycner, R. Zavala, J. Benson, D. Hutter

Proceedings Volume 7013, 70131H (2008) https://doi.org/10.1117/12.789487

KEYWORDS: Stars, Visibility, Calibration, Coherence imaging, Radio optics, Data integration, Interferometry, Radio interferometry, Observatories, Integrated optics

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Proceedings Article | 28 July 2008 Paper

Measurements of binary stars with coherent integration of NPOI data

Anders Jorgensen, H. Schmitt, R. Hindsley, J. T. Armstrong, T. Pauls, D. Mozurkewich, D. Hutter, C. Tycner

Proceedings Volume 7013, 701342 (2008) https://doi.org/10.1117/12.790290

KEYWORDS: Stars, Visibility, Calibration, Binary data, Phase measurement, Data modeling, Solids, Data integration, Interferometers, Spectrographs

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Proceedings Article | 28 July 2008 Paper

Recent developments in optical interferometry data standards

John Young, William Cotton, Wolfgang Gässler, Rafael Millan-Gabet, John Monnier, Thomas Pauls, Isabelle Percheron

Proceedings Volume 7013, 70134H (2008) https://doi.org/10.1117/12.788955

KEYWORDS: Standards development, Calibration, Optical interferometry, Interferometry, Interferometers, Binary data, Visibility, Optical filters, Interfaces, Data modeling

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Proceedings Article | 20 September 2007 Paper

The wide-field imaging interferometry testbed: enabling techniques for high angular resolution astronomy

S. Rinehart, T. Armstrong, Bradley Frey, J. Jung, J. Kirk, David Leisawitz, Douglas Leviton, R. Lyon, Stephen Maher, Anthony Martino, T. Pauls

Proceedings Volume 6687, 66870F (2007) https://doi.org/10.1117/12.734437

KEYWORDS: Interferometry, Interferometers, Data acquisition, Visibility, Algorithm development, Image restoration, Spatial resolution, Mirrors, Data modeling, Reconstruction algorithms

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Proceedings Article | 29 June 2006 Paper

Early type stars as calibrators for ground-based interferometry

Jinmi Yoon, Deane Peterson, Thomas Armstrong, James Clark III, Charmaine Gilbreath, Thomas Pauls, Henrique Schmitt

Proceedings Volume 6268, 626848 (2006) https://doi.org/10.1117/12.670309

KEYWORDS: Stars, Visibility, Calibration, Interferometry, Error analysis, Observatories, Michelson interferometers, Prototyping, Interferometers, Atmospheric modeling

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Proceedings Article | 29 June 2006 Paper

Characterization of the NPOI fringe scanning stroke

Anders Jorgensen, Dave Mozurkewich, James Murphy, Marc Sapantaie, J. Thomas Armstrong, G. Charmaine Gilbreath, Robert Hindsley, Thomas Pauls, Henrique Schmitt, Donald Hutter

Proceedings Volume 6268, 62684A (2006) https://doi.org/10.1117/12.672839

KEYWORDS: Metrology, Visibility, Heterodyning, Solids, Interferometers, Laser metrology, Spectrographs, Bragg cells, Polarization, Data acquisition

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We report on the results of an experiment to characterize the fringe scanning stroke on the Navy Prototype Optical Interferometer (NPOI) Fast Delay Line (FDL) strokes. The measurements were carried out during three days April 11-13, 2005 at the NPOI site near Flagstaff, AZ. The NPOI uses a heterodyne metrology laser system in its operations. It consists of a HeNe laser with a 2 MHz heterodyne component generated by an Acousto-Optic Modulator (AOM). One polarization is used as the 2 MHz clock, and the other is sent through the feed system twice and bounces off the piezo stroke modulators. We sampled both signals at 50 MHz, and obtained stroke and cart combined motion at the frequency of the stroke modulated 2 MHz heterodyne signal. By counting zero-crossings in the reference and feed system signals, a rough position (to a wavelength) can be obtained. This can be further refined to the few-nanometer level by measuring the relative phases of the reference and feed system signals. This results in approximately 4000 positions measurements per 2 ms stroke with a precision of approximately 1 nm. We recorded stroke positions for approximately 500 strokes (1 s), for all but one of the six FDLs, under a variety of conditions: different stroke amplitudes, different cart speeds, and different cart positions in the FDLs. We then analyzed these data from a total of 100 tests to understand the deviation of the actual stroke from the ideal stroke. We found that the mean stroke differs from the ideal stroke, and that consecutive strokes differ from each other. We computed the effect of the non-ideal stroke on the science data. A non-ideal stroke results in leakage of fringe power between fringe frequencies. This leakage is not significant during most normal operations of the NPOI. However, when the squared visibilities of baselines on the same spectrograph differ by large amounts (a factor of 10), care should be taken. Ideally, High- and low-visibility baselines should be placed on different spectrographs.

Proceedings Article | 28 June 2006 Paper

The wide-field imaging interferometry testbed: recent results

S. Rinehart, T. Armstrong, Bradley Frey, J. Jung, J. Kirk, David Leisawitz, Douglas Leviton, R. Lyon, Anthony Martino, Lee Mundy, T. Pauls, A. Thompson

Proceedings Volume 6268, 626836 (2006) https://doi.org/10.1117/12.672110

KEYWORDS: Interferometry, Visibility, Algorithm development, Data acquisition, Reconstruction algorithms, Interferometers, Cameras, Fourier transforms, Space telescopes, Infrared telescopes

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Proceedings Article | 28 June 2006 Paper

Using differential phases in optical interferometry

Henrique Schmitt, Thomas Pauls, Christopher Tycner, J. Thomas Armstrong, James Benson, James Clark, Robert Hindsley, Donald Hutter, Deane Peterson, Anders Jorgensen, David Mozurkewich, G. Charmaine Gilbreath, Robert Zavala

Proceedings Volume 6268, 62683B (2006) https://doi.org/10.1117/12.672396

KEYWORDS: Stars, Calibration, Phase interferometry, Optical interferometry, Observatories, Beryllium, Interferometers, Analytical research, Prototyping, Phase measurement

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Proceedings Article | 27 June 2006 Paper

Toward complex visibilities using optical interferometry: multiwavelength phase referencing

Thomas Pauls, Henrique Schmitt, Christopher Tycner, J. Thomas Armstrong, James Benson, James Clark, G. Charmaine Gilbreath, Robert Hindsley, Donald Hutter, Anders Jorgensen

Proceedings Volume 6268, 62680W (2006) https://doi.org/10.1117/12.671881

KEYWORDS: Stars, Visibility, Beryllium, Calibration, Optical interferometry, Interferometers, Phase interferometry, Observatories, Interferometry, Prototyping

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Proceedings Article | 27 June 2006 Paper

Coherent integrations, fringe modeling, and bootstrapping with the NPOI

Anders Jorgensen, Dave Mozurkewich, Henrique Schmitt, J. Thomas Armstrong, G. Charmaine Gilbreath, Robert Hindsley, Thomas Pauls, Deane Peterson

Proceedings Volume 6268, 62681H (2006) https://doi.org/10.1117/12.672829

KEYWORDS: Signal to noise ratio, Visibility, Atmospheric modeling, Calibration, Phase measurement, Solids, Stars, Instrument modeling, Data modeling, Interferometers

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Atmospheric turbulence is a major impediment to ground-based optical interferometry. It causes fringes to move on ms time-scales, forcing very short exposures. Because of the semi-random phase shifts, the traditional approach averages exposure power spectra to build signal-to-noise ratio (SNR). This incoherent average has two problems: (1) A bias of correlated noise is introduced which must be subtracted. The smaller the visibility/the fainter the target star, the more diffcult bias subtraction becomes. SNR builds only slowly in this case. Unfortunately, these most difficult small visibility baselines contain most of the image information. (2) Baseline phase information is discarded. These are serious challenges to imaging with ground based optical interferometers. But if we were able to determine fringe phase, we could shift and integrate all the short exposures. We would then eliminate the bias problem, improve the SNR, and we would have preserved most of the phase information. This coherent averaging becomes possible with multi-spectral measurements. The group delay presents one option for determining phase. A more accurate approach is to use a time-dependent model of the fringe. For the most interesting low-visibility baselines, the atmospheric phase information can be bootstrapped from phase determinations on high-visibility baselines using the closure relation. The NPOI, with 32 spectral channels and a bootstrapping configuration, is well-suited for these approaches. We will illustrate how the fringe modeling approach works, compare it to the group-delay approach, and show how these approaches can be used to derive bias-free visibility amplitude and phase information. Coherent integration provides the highest signal-to-noise (SNR) improvement precisely in the situations where SNR builds most slowly using incoherent averaging. Coherent integration also produces high-SNR phase measurements which are calibration-free and thus have high real uncertainties as well. In this paper we will show how to coherently integration on NPOI data, and how to use baseline visibilities and calibrate coherently integrated visibility amplitudes.

Proceedings Article | 23 June 2006 Paper

The Navy prototype optical interferometer: recent developments since 2004

K. Johnston, J. Benson, D. Hutter, C. Tycner, R. Zavala, N. White, J. Armstrong, T. Pauls, G. Gilbreath, R. Hindsley

Proceedings Volume 6268, 626806 (2006) https://doi.org/10.1117/12.673779

KEYWORDS: Stars, Interferometers, Observatories, Prototyping, Beryllium, Spectroscopy, Metrology, Fourier transforms, Analytical research, Calibration

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