Mr. Brian M. Sun Profile

Brian M. Sun

at New Mexico Institute of Mining and Technology

SPIE Involvement:

Author

Publications (4)

Proceedings Article | 24 July 2014 Paper

Design and implementation of the NPOI database and website

K. Newman, A. Jorgensen, M. Landavazo, B. Sun, D. Hutter, J. Armstrong, David Mozurkewich, N. Elias, G. van Belle, H. Schmitt, E. Baines

Proceedings Volume 9146, 914630 (2014) https://doi.org/10.1117/12.2057186

KEYWORDS: Databases, Stars, Interfaces, Precision optics, Interferometers, Binary data, Observatories, Analytical research, Astronomical imaging, Astronomy

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Proceedings Article | 24 July 2014 Paper

The new classic data acquisition system for NPOI

B. Sun, A. Jorgensen, M. Landavazo, D. Hutter, G. van Belle, David Mozurkewich, J. Armstrong, H. Schmitt, E. Baines, S. Restaino

Proceedings Volume 9146, 914620 (2014) https://doi.org/10.1117/12.2057013

KEYWORDS: Data acquisition, Field programmable gate arrays, Photons, Imaging systems, Spectrographs, Computing systems, Observatories, Clocks, Detection and tracking algorithms, Analytical research

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Proceedings Article | 24 July 2014 Paper

Progress toward unprecedented imaging of stellar surfaces with the Navy precision optical interferometer

A. Jorgensen, D. Mozurkewich, H. Schmitt, G. van Belle, D. Hutter, J. Clark, J. Armstrong, E. Baines, K. Newman, M. Landavazo, B. Sun, S. Restaino

Proceedings Volume 9146, 91460A (2014) https://doi.org/10.1117/12.2055789

KEYWORDS: Visibility, Stars, Telescopes, Interferometers, Data acquisition, Image resolution, Signal to noise ratio, Spectrographs, Precision optics, Imaging arrays

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We present progress on the stellar surface imaging project recently funded by the U. S. National Science Foun- dation. With the unique layout of the Navy Precision Optical Interferometer (NPOI) in combination with data acquisition and fringe-tracking upgrades we expect to be able to substantially exceed the imaging fidelity and resolution of any other interferometer in operation. The project combines several existing advances and infras- tructure at NPOI with modest enhancements. For optimal imaging there are several requirements that should be fulfilled. The observatory should be capable of measuring visibilities on a wide range of baseline lengths and orientations, providing complete Fourier (UV) coverage in a short period of time. It should measure visibility amplitudes with good SNR on all baselines as critical imaging information is often contained in low-amplitude visibilities. It should measure the visibility phase on all baselines. The technologies which can achieve this are the NPOI Y-shaped array with (nearly) equal spacing between telescopes and an ability for rapid configuration. Placing 6-telescopes in a row makes it possible to measure visibilities into the 4th lobe of the visibility function. By arranging the 12 available telescopes carefully we can switch, every few days, between 6 different 6-station chains which provide symmetric coverage in the Fourier plane without moving any telescopes, only by moving beam relay mirrors. The 6-station chains are important to achieve the highest imaging resolution, and switching rapidly between station chains provides uniform coverage. Coherent integration techniques can be used to obtain good SNR on very small visibilities. Coherently integrated visibilities can be used for imaging with standard radio imaging packages such as AIPS. The commissioning of one additional station, the use of new data acqui- sition hardware and fringe tracking algorithms are the enhancements which are making this project a reality. The New Classic data acquisition system, based on a powerful Stratix FPGA and fast Direct Memory Access module, upgrades the existing Classic beam combiner to allow for continuous data recording across all baselines available with 6 telescopes. It also provides the computing power and software environment necessary for im- plementing the 6-station, 5-baseline fringe-tracking algorithms. In separate papers we discuss the New Classic data acquisition system and the fringe-tracking algorithms in greater detail. In this paper we will focus on an overview of the project. We will describe the observation planning, logistics of the observations, and discuss the current status of the project including preliminary results and simulations of expected future results.

Proceedings Article | 24 July 2014 Paper

6-station, 5-baseline fringe tracking with the new classic data acquisition system at the Navy Precision Optical Interferometer

M. Landavazo, A. Jorgensen, B. Sun, K. Newman, David Mozurkewich, G. van Belle, Donald Hutter, H. Schmitt, J. Armstrong, E. Baines, S. Restaino

Proceedings Volume 9146, 914621 (2014) https://doi.org/10.1117/12.2057278

KEYWORDS: Signal to noise ratio, Data acquisition, Interferometers, Precision optics, Spectrographs, Detection and tracking algorithms, Optical tracking, Image resolution, Imaging systems, Stars

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The Navy Precision Optical Interferometer (NPOI) has a station layout which makes it uniquely suited for imaging. Stellar surface imaging requires a variety of baseline lengths and in particular long baselines with resolution much smaller than the diameter of the target star. Because the fringe signal-to-noise ratio (SNR) is generally low on such long baselines, fringe-tracking cannot be carried out on those baselines directly. Instead, baseline bootstrapping must be employed in which the long baseline is composed of a number of connected shorter baselines. When fringes are tracked on all the shorter baselines fringes are also present on the long baseline. For compact sources, such as stellar disks, the shorter baselines generally have higher SNR and making them short enough that the source is unresolved by them is ideal. Thus, the resolution, or number of pixels across a stellar disk, is roughly equal to the ratio of the length of the long baseline to the length of the short baselines. The more bootstrapped baselines, the better the images produced. If there is also a wide wavelength coverage, wavelength bootstrapping can also be used under some circumstances to increase the resolution further. The NPOI is unique in that it allows 6-station, 5-baseline bootstrapping, the most of any currently operating interferometer. Furthermore, the NPOI Classic beam combiner has wavelength coverage from 450 nm to 850 nm. However, until now, this capability has not been fully exploited. The stellar surface imaging project which was recently funded by the National Science Foundation is exploiting this capability. The New Classic data acquisition system, reported separately, is the hardware which delivers the data to the fringe-tracking algorithm. In this paper we report on the development of the fringe-tracking capability with the New Classic data acquisition system. We discuss the design of the fringe tracking algorithm and present performance results from simulations and on sky observation.

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