Feasibility of Laser Systems for Aircraft Landing Operations Under Low Visibility Conditions

The effects of currently recommended eye-safety standards and of atmospheric scattering on the potential application of lasers to the low-visibility aircraft approach and landing operational environment are assessed. It is concluded that these two criteria are serious handicaps in any proposed development of a laser landing guidance system. The two criteria are interrelated: the application of high power, narrow beam lasers to overcome the large attenuation in dense fog increases the eye-safety hazard, whereas a lowering of laser power to guarantee eye-safety drastically reduces the distance over which the laser beam can be used effectively. Since the scattering coefficient during conditions of fog is essentially independent of wavelength, no laser wavelength that also falls within an absorption-free 'window,' appears to be significantly better than any other wavelength as far as penetration in fog is concerned.