OPTICAL REMOTE-SENSING OF SURFACE-ROUGHNESS THROUGH THE TURBULENT ATMOSPHERE

Using a CO2, cw, coherent lidar, we have measured the surface roughnes s of diffuse targets through 1000 m of turbulent atmosphere. The techn ique measures the phase fluctuations of the speckle field at the recei ver and relates the measured phase variance to the surface roughness. Measurements were made with aluminum targets that had been sandblasted with 8-, 16-, and 30-grit material and also with a flame-sprayed alum inum target. It was found that a linear relationship exists between th e standard deviation (SD) of the unwrapped phase fluctuations and the SD of the target surface-height fluctuations. Good results were obtain ed with modest transmitter power and small receiver optics in just a f ew seconds of averaging time.