INSTRUMENTS ,

The lidar of the Energy, Environmental and Technological Research Centre (CIEMAT) of Madrid joined EARLINET in April 2005. It also participates in EARLINET-ASOS. In the transmitter it uses a Q-switch pulsed Nd:YAG laser and doubled in frequency which generates pulses of 20 mJ with a duration of less than 10 ns. The receiver telescope has a diameter of 30 cm and it uses a photomultiplier tube to detect the backscattered optical signal. By means of a periscope system, it can sweep the line of vision 360º in azimuth and 180º in elevation. The system is permanently mounted in a vehicle. The system is modular and admits the implementation of new capacities; in fact, it is planned to incorporate soon a new channel to measure radiation backscattered by the atmospheric nitrogen due to the Raman effect. This lidar instrument also admits an alternative configuration as a differential absorption system (DIAL), to measure the concentration of chemical species in the atmosphere. In this mode of operation, the Nd:YAG laser is used to pump a colorant laser that emits pulses of around 10 mJ, tuneable within a wavelength range between 280 and 470 nm, permitting the detection of gases such as SO₂, NO₂ and O₃.