COMPENSATION OF ATMOSPHERIC OPTICAL DISTORTION USING A SYNTHETIC BEACON

ATMOSPHERIC turbulence limits the resolution of a ground-based astronomical telescope to much worse than the diffraction limit of the instrument. An adaptive-optics system, in which some part of the optical train of the telescope can be adjusted in real time, can compensate for atmospheric turbulence, but a beacon or guide-star is needed to allow measurement of the atmospheric optical distortion. It has been suggested 1 that the measurement could be achieved by means of a synthetic beacon (also called an artificial beacon, and sometimes a laser guide-star) formed by atmospheric backscatter from a ground-based laser. We have performed an experiment to demonstrate atmospheric compensation using a synthetic beacon. With a pulsed dye laser to generate the beacon and a 241-channel adaptive-optics system to perform the phase correction, we obtained almost diffraction-limited resolution of star images in the visible part of the spectrum. Our results indicate that there are no technical barriers to atmospheric compensation using synthetic beacons at ground-based observatories.