MRI: Development of Adaptive Optics Upgrade for the CHARA Array - Phase II

Georgia State University Research Foundation, Inc., Atlanta GA

Investigators

Abstract

On the summit of Mt. Wilson overlooking Los Angeles sits a Y-shaped array of six 1-m aperture telescopes. Unlike telescopes located on other mountaintops, these six are not used independently of each other, but are instead used in unison to effectively form a single larger telescope, an interferometric array, in which the optical and near-infrared light from each of the telescopes is combined with the light from its neighbors. Operation of the six 1-m telescopes as an interferometric array results in the ability to detect finer details (spatial resolution) in astronomical sources than would be possible if the 1-m telescopes were utilized individually. With physical separations between the six 1-m telescopes ranging from 33 to 331 meters, spatial resolutions better than 1 milliarcsecond are achieved. This far exceeds the resolution of the largest ground-based and orbiting telescopes, and is even an order of magnitude better than will be possible with the extremely large telescopes (ELTs) currently under development. Since construction of the Mt. Wilson array was completed in 2005 by Georgia State University's Center for High Angular Resolution Astronomy (CHARA), the Mt. Wilson interferometric array has yielded the first direct detection of gravity darkening on a single star, the first angular diameter for a halo population star, the first image of a single, main-sequence star, the first direct image of an interacting binary, and first images of the expanding fireball around a nova just 15 hours after its discovery. The funded work will significantly improve the interferometric array's ability to detect faint targets (sensitivity) and scientific throughput by completing an adaptive optics upgrade for each of the six 1-m telescopes. The sensitivity will be improved by 0.5 to 3 magnitudes, depending on the seeing conditions, and the scientific throughput will be enhanced by a factor of 3-5. Access to the Mt. Wilson interferometer is afforded to consortium members but also to the general astronomical community through an open allocation process managed by the National Optical Astronomy Observatory (NOAO). Through the array, CHARA is training the next generation of scientific and technical experts in the field of interferometry, and scientific results emerging from the facility are incorporated in undergraduate courses as well as public outreach activities. Funding for completing the Mt. Wilson optical/near-IR interferometer upgrade is being provided through the Major Research Instrumentation (MRI) program of the NSF. The funded work will complete the first major facility upgrade of the CHARA array since initial construction. Georgia State's Dr. T. ten Brummelaar and collaborators have carefully considered the most cost-effective approaches to enhance the sensitivity of the instrument. The principal goal of the funded work is to add deformable mirrors (DM) to each of the six 1-m telescopes, completing the development and implementation of full, fast AO capabilities at each telescope. Together, these modifications should yield sensitivity increases 0.5 to 3 magnitudes at H band, and increase the number of nights of high-quality data by about a factor of 3 in the summer and 5 in the winter, with the integration time required to reach a specific SNR reduced by a factor of up to 3. New important areas of study include the study of highly reddened targets such debris disks around young stars, T-Tauri disks, and accretion flows onto YSOs.