The MkIV employes a double-passed optical configuration for compactness and to provide passive shear compensation. Ne laser at 10kHz. Column abundances were derived using the GFIT algorithm, developed at JPL for the analysis of solar absorption spectra. Initial vertical profiles were based on balloon measurements, which were then stretched or squashed until the measured HF absorption was matched. These profiles were then scaled in order to derive the vertical column abundances.
Accuracies are more difficult to determine.
1989 - 1'st balloon flight, Ft. Sumner, New Mexico. 1990 - 2'nd balloon flight, Ft. Sumner, New Mexico. 1991 - 3'rd balloon flight, Ft.