New diagnostic techniques to measure the fundamental plasma properties of an arcjet are being developed collaboratively between the University of Southern California and Air Force Phillips Laboratory. The diagnostics described here are for measuring velocity and density, principal parameters that describe the plasma state within an arcjet. Velocity measurements are being obtained from a new technique we have named Current Modulation Velocimetry (CMV). A current spike applied to the arcjet input current generates an optical emission event that is observed to travel downstream with the propellant flow. Observing this event at two axial locations, a fixed distance apart, provides an average bulk velocity of the gas flowing out of the arcjet nozzle. Species density measurements are to be obtained using Pulsed Electron Beam Fluorescence. A pulsed beam of focused electrons bombard a gas sample causing the resulting emitted fluorescence to be proportional to the local species density. Proper calibration with known samples can then provide absolute density values. Velocity measurements are being conducted on the standard NASA Lewis 1kW arcjet using hydrogen propellant.