Rayleigh lidar allows to derived temperature from 30 to 80 km. More than 30 years of continuous measurements have been performed at Observatory of Haute-Provence providing a long term cooling. Along the years of operations, the technique has been improved. The design of the lidar is described here. The emission and reception benefit for advance solutions of coupled lasers or mirrors with optical fibbers. Alignment and synchronization are also described, while noise estimates correspond to an issue when upper mesosphere want to be investigated.