Daytime mesopause temperature measurements with a sodium-vapor dispersive Faraday filter in a lidar receiver.

Using a dispersive Faraday bandpass filter, we have upgraded our Na temperature lidar to be capable of 24-h operation. Along with a transmitting telescope to reduce the laser beam divergence to 0.2 mrad, the initial use of this unique narrow-band filter in a lidar receiver allowed us to reduce the detected daytime sky background to a level previously encountered at night, making routine daytime temperature measurements in the mesopause region a reality. The implementation, characterization, and results of what we believe are the first daytime mesopause temperature measurements are reported.