FIELD EXP E REAG CALIBRATED RDR OPTICAL DEPTH V1.0

Total instantaneous optical depth was obtained from the data through use of Beer's Law, as follows. The set of observations for one channel are plotted as natural logarithm of instrument voltage versus secant of incidence angle (i.e., Langley Plot).

This allows one to solve for the equivalent instrument voltage that would be obtained above the atmosphere (the plot intercept) and the optical depth (the plot slope). Instantaneous optical depths were then derived by using this intercept and solving for optical depth using pairs of voltage values acquired close together in time.