Experiments on laser guide stars at Mauna Kea Observatory for adaptive imaging in astronomy

Abstract

Atmospheric turbulence severely limits the resolution of ground-based astronomical telescopes. Under good seeing conditions at the best observatory sites, resolution at visible wavelengths is typically limited to about 1 arc s. During the past 15 years, adaptive optical systems with electrically deformable mirrors have been developed to compensate for turbulence1,2. Unfortunately, these systems require bright reference sources adjacent to the object of interest and can only be used to observe the brightest stars. Foy and Labeyrie3 were the first to suggest that lasers could be used to create artificial guide stars that might be suitable in controlling an adaptive imaging system. We have recently extended this concept in two ways. First, we have identified the key engineering parameters that optimize the performance of a laser-guided imaging system. Second, on the nights of 21 and 22 January 1987, we conducted experiments at the Mauna Kea Observatory on the island of Hawaii to test the feasibility of using a laser to generate an artificial guide star in the mesospheric sodium layer. Here we describe both the engineering calculations and the results of our first experiments.