The basic function of any space propulsion system is to produce as high a propellant exhaust velocity as is possible for that technology. Therefore, in seeking to improve the performance of any propulsion system, a measurement of the radial distribution of the axial velocity component at the engine exit plane is invaluable. A simultaneous measurement of the radial distribution of the atom temperature will also provide insight into engine operation. This paper describes a non-intrusive technique for obtaining these measurements and presents some preliminary results of a radial survey in an arcjet engine plume. The technique involves a measurement of the doppler shift of an optically thin line, resulting from recombination and relaxation processes in the high Mach number stream, for velocity determination. The atom temperature can be calculated from a measurement of doppler broadened line widths.