Speaker
Description
Accurate characterisation of the aerosol extinction profile is critical for ground-based gamma-ray observatories, where atmospheric transmittance directly affects the reconstruction of gamma-ray shower energies and the observatory's acceptance. The Cherenkov Telescope Array Observatory (CTAO) requires continuous aerosol profiling with range resolution better than a few hundred metres and aerosol optical depth (AOD) accuracy of ~0.03 RMSD.
To meet these requirements, the Barcelona Raman LIDAR (BRL) is being developed as the observatory's dedicated aerosol and cloud monitor. This contribution presents the performance of the pathfinder BRL (pBRL), a 1.8m class prototype operating at two elastic wavelengths (355 nm and 532 nm) and one Raman channel (387 nm on N₂).
A dedicated LIDAR Pre-Processing (LPP) software suite was developed, incorporating novel methods for robust background subtraction, likelihood-based analog-to-photon-counting signal gluing, adaptive rebinning, and automated cloud and planetary boundary layer detection and inversion. Test campaigns were conducted near Barcelona and at the Observatorio del Roque de los Muchachos during moonlit periods. Under these non-optimal conditions, the pBRL achieved a range resolution of ~50 m for strongly absorbing dust layers, and AOD retrieval accuracy of approximately 0.05.
These results demonstrate the instrument's capability to characterise AOD profiles across the troposphere, and form the basis for the final upgraded BRL for the CTAO-N.