Main objectives of the IAP department Optical Soundings are groundbased optical soundings of the middle and upper atmosphere (stratosphere, mesosphere, lower thermosphere) and the scientific interpretation of the processes in these atmospheric regions, but also the troposphere. Lidar instruments (LIDAR = Light Detection and Ranging) are the main experimental methods used by our department. The lidar allows active groundbased long-term determination of various atmospheric components and parameters within the altitude range of about 0-120 km altitude. Further data are obtained by in-situ detectors on board of stratospheric balloons or sounding rockets. Another important goal of our work is the modelling and theoretical interpretation of experimentally observed processes.