In the early nineties, James Spinhirne reported a revolutionary lidar concept: the Micro Pulse Lidar (MPL). His approach combined a large diameter, low pulse energy, high pulse repetition frequency transmitter with a narrow field, narrow optical bandwidth receiver to create an eye-safe visible lidar for cloud and aerosol studies. MPL systems present challenges because a significant amount of their operating range is within the overlap region, and the overlap function must be known to correctly interpret the data. Their photon-counting, Geiger-mode avalanche photodiodes are easily destroyed, the data must be corrected for count rate effects, and long averaging times are required for a reasonable signal-to-noise ratio. This paper examines a micro-pulse lidar approach using a receiver with long and short-range channels to avoid overlap corrections; photomultipliers and analog signal processing to avoid count rate effects; a significantly larger collecting aperture to decrease measurement time; a coaxial transmitter to minimize scattered light; and dual polarizations to increase the amount of information gathered on clouds and aerosols. Additional instrumentation to increase the amount of information that can be obtained from the lidar data is also examined.
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