Vision: A Six-telescope Fiber-fed Visible Light Beam Combiner for the Navy Precision Optical Interferometer

Abstract

Visible-light long baseline interferometry holds the promise of advancing a number of important applications in fundamental astronomy, including the direct measurement of the angular diameters and oblateness of stars, and the direct measurement of the orbits of binary and multiple star systems. To advance, the field of visible-light interferometry requires development of instruments capable of combining light from 15 baselines (6 telescopes) simultaneously. The Visible Imaging System for Interferometric Observations at NPOI (VISION) is a new visible light beam combiner for the Navy Precision Optical Interferometer (NPOI) that uses single-mode fibers to coherently combine light from up to six telescopes simultaneously with an image-plane combination scheme. It features a photometric camera for calibrations and spatial filtering from single-mode fibers with two Andor Ixon electron multiplying CCDs. This paper presents the VISION system, results of laboratory tests, and results of commissioning on-sky observations. A new set of corrections have been determined for the power spectrum and bispectrum by taking into account non-Gaussian statistics and read noise present in electron-multipying CCDs to enable measurement of visibilities and closure phases in the VISION post-processing pipeline. The post-processing pipeline has been verified via new on-sky observations of the O-type supergiant binary ζ Orionis A, obtaining a flux ratio of 2.18 ± 0.13 with a position angle of 223.9 ± 1.0 • and separation 40.6 ± 1.8 mas over 570-750 nm, in good agreement with expectations from the previously published orbit.2. Mount the 70 /20 beam splitters and accompanying beam-shear compensating windows. The beam splitters route light from the feed system to the VISION optical bench.

A Catalog of Calibrator Stars for Next-Generation Optical Interferometers

“…These catalogs were optimized for infrared interferometry, as appropriate for infrared beam combiners on the Very Large Telescope Interferometer and the CHARA array. Our catalog builds on these previous works, and extends them by optimizing a calibrator sample for the optical, as is needed by next-generation interferometers such as VISION at NPOI (e.g., Garcia et al 2016). Furthermore, of the 1523 stars in our sample, there are only 97 stars in common with the Mérand et al (2005) catalog, while only 79 overlap with Bordé et al (2002), showing we have greatly expanded the potential calibrator pool.…”

“…It is possible that a few unknown binary or multiple star systems that are only detectable via interferometry (not via radial velocity) may remain in our calibrator sample. These objects will be removed from our sample as they are observed by visible-light interferometers, such as VISION (Garcia et al 2016). …”

“…In the northern hemisphere there are two operational six-telescope interferometers, the Navy Precision Optical Interferometer (NPOI, Armstrong et al 1998) and the Center for High Angular Resolution Astronomy (CHARA, ten Brummelaar et al 2005). Each has its own assemblage of different beam combiners, such as the Visible Imaging System for Interferometric Observations (VISION, Ghasempour et al 2012;Garcia et al 2016) and NPOI classic (Armstrong et al 1998), at NPOI, and the Michigan Infrared Combiner (MIRC Monnier et al 2004), the Precision Astronomical VIsible Observations (PAVO, Ireland et al 2008), the Visible spEctroGraph and polArimeter (VEGA, Mourard et al 2009), and the CLassic Interferometry with Multiple Baselines (CLIMB, ten Brummelaar et al 2013) for the CHARA array.…”

Fibered visible interferometry and adaptive optics: FRIEND at CHARA

“…Different selections are made on the raw frames (Sorting boxes): Sorting 1 removes the frames with flashes and Sorting 2 removes frames on photometric criteria. contribution of the photon bias structures in the PS of the fringe data (Garcia et al 2016). …”

“…Using visible wavelengths is a good way to increase the angular resolution without longer baselines. Three visible instruments are in operation today: the Visible Imaging System for Interferometric Observations instrument at NPOI (NPOI/VISION), a 6T fibered combiner working with small apertures (Garcia et al 2016), the Precision Astronomical Visible Observation…”