Target signatures for laser altimeters: an analysis

The statistical characteristics of short laser pulses of less than 1 cm which have been reflected from the ground are examined. Expressions are derived for the mean and temporal covariance of the received pulse for a direct detention receiver, taking into consideration the effects of laser speckle, shot noise, and surface profile of the target. The results are used to compute the means and variances of the total received energy, propagation delay, and rms width of the received pulse, and indicate that for laser altimeters, the surface profile and nadir angle have a significant influence on the received pulse shape. Thus, for very short transmitted pulses, small nadir angles, and small laser divergence angles, the expected received pulse shape is identical to the surface profile probability density function.