Polarization and atmospheric backscatter coefficient measurements.

Recently, it was pointed out that polarization effects must be considered in hard target calibration of lidars. A vector theory of radiometry is developed, and it is demonstrated for a real nonideal target that the reflectance is a matrix quantity and not a scalar quantity, and all its components must be measured. These concepts can be extended to actual field measurements of the volume backscatter coefficients. The volume backscatter coefficient at range R is an averaged (4 x 4) matrix, which is averaged over the sampling depth dR = ctau/2. The transmitted beam is polarized in a definite sense, the received beam is still polarized, and both are represented as (4 x 1) Stokes vectors so that the interaction must be represented by a (4 x 4) matrix called the volume backscatter coefficient beta. Present experiments are in error for data are considered a scalar quantity with only one value not a matrix with sixteen components. Some of these components may be zero but many are not.