Automated lidar transmitter for multiparameter investigations within the Arctic atmosphere

The transmitter system of the ALOMAR Rayleigh/Mie/Raman lidar (RMR lidar), part of the ALOMAR facility at the island Andoya (69 degrees N, 16 degrees E) in Northern Norway, is presented, Long-term and multiparameter observati ons of the Arctic middle atmosphere on a climatological basis require a com plex and automated transmitter system, To obtain winds using the Doppler me thod, two identical power systems driven by one single seeder system have b een chosen. The seeder frequency is actively stabilized against an iodine a bsorption line with remaining fluctuations of less than 10(-8). Each power system can be used with its own steerable receiving telescope, moveable in elevation as well as azimuth, Using both systems in alternating operation o n a pulse-by-pulse basis of the lasers, two wind components can be obtained simultaneously. Trends in the power laser beam positions are corrected by a direction control system leading to fixed axes of the laser beams before transmission into the atmosphere. The achieved beam pointing stability at t he original beam diameter is better than +/-20 mu rad, which guarantees the beam to remain inside the very narrow field-of-view (FOV) of the receiving telescope and supports full daylight capability of the lidar, The whole tr ansmitter system is controlled by computers, thus avoiding optical adjustme nts for months.