The ALS-450 is a commercial 355nm elastic lidar made by Leosphere Corporation in France. The laser emits pulses of 355nm light every 1/10 s. Designed to be all weather, the Leosphere consists of a hermetically sealed transmitter/receiver and a power supply/computer/cooler/air conditioner in a separate housing.
The principle of the lidar is very similar to the UMBC Elastic Lidar Facility and many of the routines used to analyze the Leosphere data come from the ELF heritage. Leosphere provides internal routines to display range corrected signal return, attenuated backscatter, extinction, PBL height estimation, etc. UMBC uses a slightly different processing scheme based on a modified ELF approach. The procedure to retrieve data is to start with the background corrected, range squared signal from the lidar. The signal is matched to the Rayleigh profile of the atmosphere in the range of 5-7 kilometers altitude. The system constant for the lidar is derived from that match.
Attenuated backscatter and ratio of the attenuated backscatter to Rayleigh (minus 1) are reported as primary products. A covariance wavelet transform (CWT; Compton et al., 2013) is used to determine the PBL height in a systematic fashion.
Using data from the AERONET which will be available at the NREL-Golden site, we will iteratively solve for a fixed lidar extinction to backscatter ratio, Sa, that matches the AERONET UV AOD. This will be accomplished after the end of the mission, so extinction will not be a near real time product.
The lidar is located next to the UMBC Research Trailer at the NREL-Golden site.
Note that the housing says that it is an ALS-300 but this housing was exchanged with our ALS-450 housing so that we could have adjustment capabilities to the laser head.