The ALFA Laser Guide Star: Operation and Results

The importance of laser guide stars to the practical usefulness ofadaptive optics cannot be understated, and yet there are veryfew working systems.This contribution discusses the current status of the ALFAlaser guide star, with regard to the particular difficulties encounteredwhile observing as well as both the expected performance and that so farachieved from scientific observations.A description is given of a number of experiments involving ALFA whichaim to determine the atmospheric turbulence and sodium layercharateristics, and demonstrate the possibility for tilt recovery fromlaser guide stars.