Turbulence-induced Zernike aberrations of optical wavefronts in partial adaptive compensation

The residual phase error after correction for turbulence-induced phase aber rations by a partially compensating adaptive optics system with a laser gui de star (LGS) as reference is computed by using the phase expansion on the Zernike polynomials. To get the most from the compensation, the limitation due to the actuator spacing of a deformable mirror, temporal lag and angula r separation between the object and the LGS (anisoplanatism effect) have be en analysed in this paper. If Fried's parameter r(0), is 10.7 cm, the tempo ral lag should be less than 2 ms for a sodium LGS. Also the higher the aber ration radial degree is, the less the actuator spacing is required. To corr ect for aberration of radial degree higher than 4 (if r(0) is 10.7 cm), the actuator spacing should be less than 300 mm.