Shuttle lidar resonance fluorescence investigations. 1: Analysis of Na and K measurements

A Shuttle lidar technique based on the detection of backscattered resonance fluorescence radiation has been numerically modeled and applied to the measurements of sodium (Na) and potassium (K) number density in the upper atmosphere (80-110 km). The simulations use recently defined lidar system parameters and take into account the effect of saturation of atomic absorption due to the high intensity of laser pulses. Such an effect is shown to be important in daytime measurements, when there is a need to narrow the laser beam divergence in order to reduce the background light. When the saturation effect is important, an optimal laser beam divergence can usually be found as a result of a trade off between the reduction of signal return (due to saturation) and the reduction of background level (by narrowing the receiver field of view). A procedure for calibration of the saturation effect is discussed. The Shuttle lidar measurement capability for Na and K is compared to conventional techniques and requirements for conducting scientific investigations in the mesosphere.