Abstract

We describe an affordable sodium laser beacon adaptive optics system for near IR astronomical research at the Apache Point 3.5m observatory.

The successful incorporation of adaptive optics technology to major astronomical observatories for near IR and visible operation demands that these systems ultimately be: (a) functional over the entire sky, (b) affordable, maintainable, reliable, and reasonably compact, and (c) possess a well-designed user interface for ease of operation. Motivated by these considerations, we have designed a system (ChAOS) that will use a high altitude sodium beacon as a reference source. This will enable full-sky coverage as long as an 18th magnitude natural star resides within the isoplanatic patch for tip-tilt correction. The sodium star will be created with an MIT Lincoln Laboratories laser-diode-pumped sum frequency laser operating with 15W average output power at 589nm. A dc lateral shearing interferometer wavefront sensor has been designed, and is under development in our laboratory, which uses low read noise CCD arrays. Detailed calculations have been made of the performance of this wavefront sensor, a quad-cell Hartmann array system, and minimal variance (Cramer-Rao bound) wavefront sensors, for beacons formed by optimally focused Gaussian laser beams propagating through the atmosphere; results of these calculations will be summarized. A vigorous program is underway for the development of low-cost, repairable, and reliable continuous facesheet deformable mirrors. The control system, real-time wavefront digital reconstructor, and a high-voltage deformable mirror multiplex interface driver are also being built for ChAOS. An overview of these ChAOS components and the design and expectations of the integrated system will be presented.

© 1992 Optical Society of America