A Na mesospheric density lidar or ''guide star'' illuminator can be tu
ned by visually observing the pattern of laser-induced fluorescence in
side a Na illumination lamp soon after it has been turned off. Optimum
tuning occurs when the fluorescence is trapped inside the lamp and ap
pears to fill the bulb as a whole. (C) 1997 Society of Photo-Optical I
nstrumentation Engineers.