ALADIN Doppler Wind Lidar and Related Programs at EADS Astrium
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ALADIN Doppler Wind Lidar and Related Programs at EADS Astrium Didier Morancais, Frédéric Fabre, and Yves Toulemont EADS Astrium, 31 rue des Cosmonautes, Toulouse, 31402 Cedex, France ABSTRACT The Atmospheric Laser Doppler Instrument (ALADIN) is the payload of the ADMAEOLUS mission, which will make direct measurements of global wind fields. It will determine the wind velocity component normal to the satellite velocity vector. The instrument is a direct detection Doppler Lidar operating in the UV, which will be the first of its kind in space. ALADIN is now in its final construction stage: the integration of the Flight Model is on-going. Most of the subsystems have been integrated; the payload performance and qualification test campaign will commence. This paper describes the ALADIN development status and the results obtained at this stage. This regards the receiver performance, the telescope development and the challenges of the laser. The paper will also provide insights on the ATLID instrument design which is the backscatter lidar for the EarthCARE mission. This lidar program is starting its detailed design phase. The ALADIN and ATLID instruments are developed by EADS Astrium Satellites for the European Space Agency.
AEOLUS MISSION ALADIN (figure 1) is a Doppler Lidar operating in the near ultra-violet spectral region using backscatter signals from aerosol at low altitude and from air molecules at high altitudes. ALADIN will produce more than 3 thousand wind profiles per day, each one providing wind velocity from ground up to 30 km altitude: this is equivalent to the worldwide radiosonde system currently used by meteorological offices. The wind profile vertical resolution is 500 m at low altitude and 2 km at the highest altitudes. The wind measurement accuracy is better than 1m/s in the Planetary Boundary Layer and better than 2 m/s in the Troposphere. The wind profile data will be processed and delivered in less than 3 hours after the measurements. The measurement principle is shown in figure 2. The satellite trajectory is a Low Earth Orbit at 400 km altitude with sub-satellite point motion around 7 km/s. The instrument points towards the Earth with a 35° slant angle versus the Nadir direction, oriented across-track. It measures the projection of the horizontal wind onto the inclined line-of-sight, for every altitude. In order to obtain high accuracy, 700 wind profiles are averaged during 7 seconds, which corresponds to a 50 km line on ground. This measurement is repeated every 28 seconds, which corresponds to every 200 km along the orbit.
Figure 1. Artist’s view of AEOLUS satellite © ESA
Figure 2. Measurement principle of the Atmospheric Laser Doppler Instrument (ALADIN)
ALADIN DESIGN OVERVIEW The ALADIN instrument [1], [2] emits laser pulses towards the atmosphere and measures the Doppler shift of the return signal, backscattered from different altitudes in the atmosphere. The instrument emits the pulses at the 355 nm wavelength with a high power solid-state laser [3] featuring high efficiency
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