The multi-wavelength lidar system for tropospheric aerosol characterization,  PEARL (Potenza EArlinet Raman Lidar), operative at CNR-IMAA since August 2005  has been designed to provide simultaneous multi-wavelength aerosol  measurements for the retrieval of optical and microphysical properties of the  atmospheric particles and water vapour mixing ratio profiles. The system has been operative until 2014.

This system is the result of the upgrade of a preexisting lidar system,  operative since May 2000 in the frame of EARLINET. It's based on a 50 Hz  Nd:YAG laser source emitting at 1064, 532  and 355nm. An optical system based  on mirrors, dichroic mirrors and 2X beam expanders, separates the three  wavelengths allowing to optimize the energy and the divergence for each  wavelength. The beams are mixed again in order to get the collinearity of the  three wavelengths and to transmit them simultaneously and coaxially with  respect to the lidar receiver.

 

The backscattered radiation from the atmosphere is collected by a F/10  Cassegrain telescope (0.5m diameter, 5m focal length) and forwarded to the  receiving system, equipped with 17 optical channels.   Three channels are devoted to the detection of the radiation elastically backscattered from the atmosphere at the three laser wavelengths; three  channels for the Raman radiation backscattered from the atmospheric N2  molecules at 387 nm and 607 nm and H2O molecules at 407 nm. Two further  channels detect the polarized components of the 532 nm backscattered light.  Each of these channels is further split into two channels differently  attenuated for the simultaneous detection of the radiation backscattered from  the low and high altitude ranges in order to extend and optimize the signal  dynamic range. For the elastic backscattered radiation at 1064 nm the  detection is performed by using an APD detector and the acquisition is  performed in analog mode. For all the other acquisition channels, the  detection is performed by means of photomultipliers and the acquisition is in  photoncounting mode. The vertical resolution of the raw profiles is 7.5m for  1064 nm and 15m for the other wavelengths, whereas the temporal resolution is  1 min.

At present, the system is used for laboratory test and research.

 

Contact person: Giuseppe D'Amico