A laser radar system for detecting atmospheric sodium using the resonance fluorescence effect is described. The lidar employs a flash lamp-excited organic dye solution laser as a transmitter. The lidar parameters are considered with a special emphasis, on the laser bandwidth because it is essential for monitoring trace atmospheric components. Laser bandwidth calculations accounting for Doppler broadening of sodium line width at mesospheric temperatures are reported. For the laser bandwidth exceeding, the Na absorption line width the uncertainty seff is shown to be not more than 2%. The concentration measurement accuracy for the trace species of interest is founds to depend on the laser bandwidth and stability.