  Measurements of the cosmic-ray air-shower fluorescence at extreme energies
require precise knowledge of atmospheric conditions. The absolute calibration
of the cosmic-ray energy depends on the absorption of fluorescence light
between its origin and point of its detection. To reconstruct basic atmospheric
parameters we review a novel analysis method based on two- and multi-angle
measurements performed by the scanning backscatter lidar system. Applied
inversion methods, optical depth, absorption and backscatter coefficient, as
well as other parameters that enter the lidar equation are discussed in
connection to the attenuation of the light traveling from shower to
fluorescence detector.
