An evaluation of the resonant fluorescence lidar technique as a method of measuring ion density during ionospheric barium releases is presented. We find that it is technically feasible to measure ion densities of 104 cm-3 at an altitude of 200 km with a time resolution of 0.5 s by using a ground-based laser and telescope. One application of the lidar technique would be observation of the critical ionization velocity effect at nighttime, without the complication of solar illumination. Criteria useful for evaluating the feasibility of other experiments are presented.