LIDAR (LIght Detection And Ranging) is a remote sensing device that uses the light pulses emitted by lasers to observe the atmosphere. The light pulses are scattered at the same wavelength (Rayleigh or Elastic LIDAR) or at different wavelength (e.g. RAMAN LIDAR) by the molecules or particulate of the atmosphere.
The BAQUNIN LIDAR has been designed and assembled using both custom-made and commercial equipments. Laser source, sensors, electronics and optics are commercial items, while frames and optomechanics were designed and built in the mechanical workshop of the Physics Department. The controlling software has been developed by the laboratory personnel. This modular approach allows a regular upgrading of each component and gives the possibility to add to the basic instrument new acquisition channels, in order to improve the system performance. Presently the system includes a large power pulsed laser, emitting 3 wavelengths, 4 receivers and 12 acquisition channels. A Quanta Ray Pro-290-30 laser produces pulses at three wavelengths, 1064, 532 and 355 nm. The three beams are directed to the vertical direction by adjustable mirrors and prisms. For safety reason and to prevent that laser light leakages could be picked up by the receivers, the beams travel inside black enclosures throughout the path from the laser head to the hatch in the roof. The LIDAR signals are collected by four receivers:
Raman Receiver: a large telescope for collecting the signals in the UV range (elastic backscattering at 355 nm and 355-nm exited Raman backscattering from atmospheric N2 and H2O);
IR Receiver: a medium size telescope for collecting the elastic backscattering at 1064 nm;
532 Low Range Receiver: a small size telescope for collecting elastic backscattering at 532 from closer altitude range.
532 High Range Receiver: a medium size telescope for collecting the elastic backscattering at 532 nm from the medium altitude range;
The acquisition system is based on 6 Transient Recorders TR20@LICEL. Each TR20 is equipped with an ADC as well as a Photon counter. Altogether 12 channels are available for the signals acquisition.
The analogic channels are dedicated to the acquisition of the stronger elastic backscatter signals, while the photon counting is the method to digitalize the weak Raman backscattering from atmospheric water vapor and molecular nitrogen. LIDAR can be operative in no-rain day and night conditions.
From the inversion of the signals is possible to carry out the following atmospheric parameters:
1) Tropospheric vertical profiles of the Aerosol and Cloud Backscatter Coefficients at 355, 532 and 1064 nm;
2) Tropospheric vertical profiles of Aerosol and Cloud Extinction Coefficients at 355;
3) Tropospheric vertical profiles of Aerosol and Cloud Polarization Ratio at 532;
4) Aerosol and Cloud Optical Depths;
5) Altitude and thickness of Aerosol and Cloud Layers;
Tropospheric vertical profiles of the Water Vapor Mixing Ratio.
PI: Marco Cacciani, <a href=”mailto:email@example.com” target=”_blank” rel=”noopener noreferrer”>firstname.lastname@example.org</a>