A) Laser light emission unit  

The Stratospheric Lidar system includes two different lasers that are used as light sources. An Excimer laser, functioning as a DIAL-ozone-Lidar, produces UV light (308 nm) which is partly converted into 353 nm radiation (via Raman cell). The Nd:YAG laser produces the 1064 nm, 532 nm and 355 nm laser lines, whereof the 355 nm light is not detected in the stratospheric system. Three mirrors are used to widen the beam coming from the Excimer laser and send it out vertically into the atmosphere. The laser beam of the Nd:YAG passes through a widening telescope before a plane mirror sends the beam vertically out into the atmosphere.  

B) Light receiving unit  

The telescope consists of a spherical mirror with a diameter of 600 mm and a focal length of 2.4 m. Due to a modified setup, a focal length of 5 m is reached. Just behind the aperture, in the focus, a chopper is mounted. The chopper blocks the backscattered light coming from the troposphere to safe the photomultipliers from oversaturation. According to the level of the chopper edge, detailed measurements in the lower / upper stratosphere can be performed. According to the position of the chopper wheel, the trigger of the laser and the signal acquisition is warranted. Via beam splitters and polarisation cubes, the separation into certain wavelengths is performed. The signals are then detected by the photomultipliers and amplified (figure: Setup of the stratospheric Lidar system)  

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