## 5 Conclusions
test sites: the campus of the Universitat Autonoma de Barcelona (UAB) and the LST-1 site, located within the northern site of the CTAO at the Observatorio del Roque de los Muchachos (ORM), La Palma, Spain. The tests were carried out under various atmospheric conditions, including clear nights, episodes of dust intrusions (calima), and even during the passage of a dust plume from a nearby volcanic eruption. The measurements allowed us to assess the robustness and stability of the instrument's performance, even though all of them were strongly hampered by strong background light, either from street lighting at UAB or the full moon at the ORM. During these observations, the pBRL operated with two elastic lines at 355 nm and 532 nm and one Raman line at 387 nm. A second Raman line at 607 nm requires a dedicated PMTs with acceptable photon-detection efficiency in that range, which was not available for the tests. Similarly, the near-range optics described in Ballester et al. (2016) could not yet be used. Nevertheless, the performance of this yet incomplete set of detection lines could be positively assessed: the Raman line could be used for independent and reliable extinction profiles of the ground layer above 400 m distance, with a range resolution of only 50 m for the strongly absorbing layer of volcanic dust debris and about 500 m for the cloud layer located above it. In addition, the Raman line successfully helped us determine the backscatter profiles and associated LIDAR ratios with similar range resolutions, which already meet the strict CTAO requirements. Both elastic lines could be used to determine the extinction profile of different types of ground and dust layers and clouds. For layers limited by the free troposphere from below and above, the extinction profile, together with an estimate of the LIDAR ratio, could be delivered independently of the Raman signal, using the technique of iterative Klett inversion. The accuracy of that LIDAR ratio retrieval was, however, still hampered by the low gain at which the PMTs were operated at the ORM and by the strong moonlight. Nevertheless, Angstrom exponents could be successfully obtained with resolutions significantly better than the CTAO requirement of 0.3 RMSD (although we have not yet been able to determine its accuracy with sufficient precision). The data analysis was able to carry out such atmospheric characterization for ranges above about 400 m, independent of the LIDAR's zenith pointing angle. For even lower distances, the two elastic near-range lines will need to be used in the future and be inverted using the LIDAR ratios obtained above, where the Raman line is already available. The instrument in its current configuration reaches a maximum range of about 35 km in the elastic channels and a maximum range of 20 km in the Raman channel. When operated at maximum gain, strong overdriving of the Licel transient receiver readout (LOTR) has resulted in some low-amplitude ringing of the photon-counting baseline, which can be corrected by our analysis, but should be remedied in the future by upgraded hardware, such as a laser of lower power but higher repetition rate and additional protection to avoid the direct diffuse reflection of laser light from the guiding mirrors onto the primary mirror. Gated PMTs for the elastic lines are an additional improvement. To obtain these results, a complete data processing and analysis software suite has been developed: the LIDAR PreProcessing (LPP) software. The LPP includes advanced statistical techniques for offset determination, signal gluing, ringing detection, absolute calibration, and elastic and Raman signal inversion, several of which are original and presented for the first time.