Rayleigh Laser Guide Star Systems: Application to the University of Illinois Seeing Improvement System

Laser guide stars created by Rayleigh scattering provide a reasonable means to monitor atmospheric wavefront distortions for real‐time correction by adaptive optics systems. Because of the λ −4 wavelength dependence of Rayleigh scattering, short‐wavelength lasers are a logical first choice for astronomical laser guide star systems, and in this paper we describe the results from a sustained experimental effort to integrate into an adaptive optics system a 351 nm Rayleigh laser guide star created at an altitude of 20 km (above mean sea level) at the Mount Wilson 2.5 m telescope. In addition to providing obvious scientific benefits, the 351 nm laser guide star projected by the University of Illinois Seeing Improvement System is "stealth qualified" in terms of the Federal Aviation Administration and airplane avoidance. Because of the excellent return signal at the wavefront sensor, there is no doubt that future applications will be found for short‐wavelength Rayleigh‐scattered laser guide stars.