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Title: First faint dual-field phase-referenced observations on the Keck interferometer
Authors: Julien Woillez, Peter Wizinowich, Rachel Akeson, Mark Colavita, Josh Eisner, Rafael Millan-Gabet, John Monnier, Jorg-Uwe Pott, Sam Ragland, Eric Appleby, Andrew Cooper, Claude Felizardo, Jennifer Herstein, Olivier Martin, Drew Medeiros, Douglas Morrison, Tatyana Panteleeva, Brett Smith, Kellee Summers, Kevin Tsubota, Colette Tyau, Ed Wetherell

Ground-based long baseline interferometers have long been limited in sensitivity by the short integration periods imposed by atmospheric turbulence. The first observation fainter than this limit was performed on January 22, 2011 when the Keck Interferometer observed a K=11.5 target, about one magnitude fainter than its K=10.3 limit. This observation was made possible by the Dual Field Phase Referencing instrument of the ASTRA project: simultaneously measuring the real-time effects of the atmosphere on a nearby bright guide star, and correcting for it on the faint target, integration time longer than the turbulence time scale are made possible. As a prelude to this demonstration, we first present the implementation of Dual Field Phase Referencing on the interferometer. We then detail its on-sky performance focusing on the accuracy of the turbulence correction, and on the resulting fringe contrast stability. We conclude with a presentation of early results obtained with Laser Guide Star AO and the interferometer.

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Lowell astronomer, project team among last recipients of Keck Interferometer time

A Lowell Observatory-led research team recently received one full night of observing time with the Keck Interferometer, a near-infrared instrument that combines the largest pair of telescopes in the world. Principal investigator Dr. Gerard van Belle of Lowell Observatory says this is the last call for proposals on the instrument, as it will soon be retired.
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NASA engineers successfully suppressed the blinding light of three stars, including the well-known Vega, by 100 times using the Keck Observatory in Mauna Kea, Hawaii. This breakthrough will enable scientists to detect the dim dust disks around stars, where planets might be forming. Normally the disks are obscured by the glare of the starlight.

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Engineers accomplished this challenging feat with the Keck Interferometer, which links the observatory's two 10-meter telescopes. By combining light from the telescopes, the Keck Interferometer has a resolving power equivalent to a football-field sized telescope. The "technological touchdown" of blocking starlight was achieved by adding an instrument called a "nuller." This setup may eventually help scientists select targets for NASA's envisioned Terrestrial Planet Finder missions. The success of those potential future missions, one observing in visible light and one in infrared, depends on being able to find Earth-like planets in the dust rings around stars.

"We have proven that the Keck Interferometer can block light from nearby stars, which will allow us to survey the amount of dust around them" - Dr. James Fanson, project manager for the Keck Interferometer at NASA's Jet Propulsion Laboratory.

That survey will begin in late 2006 after the team refines the nuller's sensitivity level. Combined information from all of NASA's planet-hunting missions will provide a complete picture of possible Earth-like planets: how big they are, whether they are warm enough for life, and if their atmospheres and surfaces show chemical signatures of current life.

"People have been talking about whether there are other earths out there for 2,500 years. Only now are we developing the technology to go find out" - Michael Devirian, manager of NASA's Navigator Program at JPL, which is investigating potential planet-exploring missions.

So far, scientists around the world have found 150 planets orbiting other stars. Most are giants, like Jupiter; none is as small as Earth. Scientists believe the best odds of finding life outside our solar system are on Earth-sized planets, particularly those with the right temperature, density and chemistry.

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