Uwe Marksteiner

Airborne direct-detection and coherent wind lidar measurements along the east coast of Greenland in 2009 supporting ESA's Aeolus mission

The Aeolus mission of the European Space Agency (ESA) will send the first wind lidar to space to fulfill the utmost need for global wind profile observations. Before the scheduled launch in late 2013, pre-launch campaigns have to be performed to validate the measurement principle and to optimize retrieval algorithms. Therefore, an airborne prototype instrument has been developed, the ALADIN Airborne Demonstrator (A2D). In September 2009 an airborne campaign over Greenland, Iceland and the Atlantic Ocean was conducted using two instruments: the A2D and a well established coherent 2-μm lidar for aerosol and cloud backscatter. Thus, two wind lidar instruments measuring Mie and Rayleigh backscatter in parallel were operated on the same aircraft. This paper describes the analysis of wind measurement data gathered during a flight segment on 26.09.2009. A dedicated aerial interpolation algorithm is introduced taking into account the different resolution grids of the two lidar systems. Via a statistical comparison of line of sight (LOS) winds the systematic and random error of the direct-detection wind lidar A2D was assessed, yielding -0.7 m/s and 1.9 m/s for the Rayleigh and 1.1 m/s and 1.3 m/s for the Mie channel, respectively.

High spectral brightness UV laser for airborne wind-lidar observations

Laser sources employed in light detection and ranging (lidar) systems for the quantification of atmospheric parameters such as wind velocity, temperature or trace gas concentration need to fulfill a large set of strict requirements regarding their power performance as well as their spatial and spectral properties. In particular, the generation of high-energy output pulses in the UV spectral region with excellent spectral purity is mandatory for the precise measurement of wind velocities by means of direct-detection Doppler wind lidar systems. Here, the frequency stability of the laser transmitter must be better than 5 MHz to ensure low systematic errors in wind velocity of about 1 m/s. The realization of reliable, high spectral brightness laser sources is further complicated when operating in severe vibration environments such as on ships or aircraft.