1. Resonant Holographic Absorption and Refraction Tomography (RHART)97-98 involves the selection excitation of one of the absorption lines of the species of interest and holographic recording of the phase shift and amplitude attenuation of the transmitted laser beam. The integrated absorption along the line of sight is measured in the image plane of the reconstructed hologram while the phase shift which is proportional to the integrated refraction can be measured by holographic interferometry. Since the absorption coefficient, a, and phase shift, $, are functions of the number density, N, and translational temperature, T, of the molecule of interest, the measurements provide a set of two equations in two unknowns, such that: a = a(T, N) , (5) + =O(T, N) . ( 6 )