ADAPTIVE OPTICS IN ASTRONOMY

Optical observations by groundbased astronomers have long been limited by the distorting effects of the Earth's atmosphere. Primary mirrors have been polished to exquisite accuracy for telescopes with apertures as large as 10 meters, but at optical wavelengths these can deliver an angular resolution typically no better than that of a 25cm telescope, as atmospheric turbulence deforms the image on a millisecond time scale. One (highly expensive) approach to overcome this problem has been to loft instruments such as the Hubble Space Telescope above the atmosphere. Another approach, pursued by instrument builders in the astronomy community and their counterparts in the military, has been to design electrooptical systems that measure and undo the effects of clearair turbulence in real time. (See figure 1.) A number of such adaptive optic devices have already been built and operated on large groundbased telescopes, delivering neardiffractionlimited performance at infrared and visible wavelengths. With the first significant astronomical images beginning to appear from these adaptive optics systems (see the cover of this issue), the level of interest in this work is rising very rapidly in the astronomy community.The first significant astronomical images are beginning to be produced by adaptive optics systems, which are being developed at many major observatories around the world. © 1994, American Institute of Physics. All rights reserved.