<title>Wavefront Sensors For Turbulence Correction</title>

Adaptive optics is gaining acceptance as a method of reducing the degrading effects imposed on optical signals by atmospheric turbulence. One of the critical components of an adaptive optical system is the wavefront sensor, the device which measures the aberrations on the wavefront. The wavefront sensor specifications depend on the mission for which the adaptive optical system will be used and the conditions under which it will operate. Typical missions and operating conditions in which adaptive optics can be used will be presented. The error sources in a wavefront sensor will be discussed in relation to mission and operating conditions. Desirable properties of wavefront sensors will be presented. In the next section the concept of adaptive optics is briefly introduced.