A) Laser light emission unit  

KARL is a backscatter-Raman-Lidar. A pulsed Nd:YAG laser emits beside the 1064 nm fundamental laser line the frequency doubled (532 nm) and tripled (355 nm) laser lines. To reduce the beam divergence, the laser beam passes through a widening telescope. A plane mirror sends the beam vertically out into the atmosphere. With the help of two step motors, the mirror can be driven into a position in which the laser beam fits best into the telescopes field of view (figure: laser light emission unit).  

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B) Light receiving unit  

While scattering generally takes place into every direction in space, a small part is exactly scattered in backward direction. The backscattered light is collected and focussed by using two parabolic telescope mirrors. The far field telescope consists of a parabolic mirror with a diameter of 30 cm and a focal length of 1.20 m. The near field telescope also consists of a parabolic mirror with 10.4 cm in diameter and a focal length of 44.5 cm. After the separation by different wavelengths (via dichroite) and polarisation directions (via two polarisation cubes) the light is detected by the photomultipliers. The data recording is carried out by different transient recorders which acquire the data in analog and / or photon counting mode. These data are saved in a computer (figure: light receiving unit).     

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