The 8-channel multi-spectral lidar system is the third lidar station conceptually designed at RSLAB since the birth of the lidar research activity in 1993. The stations is formally a 3β+2α+1WV+2δ elastic/Raman aerosol/water-vapor system (see figure below). In emission, a 350-mJ energy Nd:YAG is used to simultaneously emit at the 1064-nm (near infrared, NIR) and 532-nm (visible, VIS) wavelengths.
The 3β+2α+1WV+2δ notation stands for
- 3 elastic channels (355-, 532- and 1064-nm wavelength)
- 3 Raman channels (two channels, 387- and 607-nm wavelength in response to N2 532-nm excitation and, one channel, 407-nm in response to water vapor 532-nm excitation)
- 2 depolarization channel (355- and 532 –nm wavelength).
The RSLAB multi-spectral lidar station:
- simultaneously emits at 355-, 532-, and 1064-nm wavelength using a Nd:YAG laser as the fundamental source.
- has full Ethernet control over the Internet.
- Simultaneous analog/ photon-counting acquisition
- Unmanned unattended operation including system operation disable upon aircraft detection.
- 4-quadrant overlap factor self-alignment.
A 6-channel polychromator (see figure at the bottom) is used to separate 3 elastic returns (355, 532 and 1064 nm) and 3 inelastic-Raman returns (387, 607, and 407-nm wavelength). This enables independent inversion of the optical parameters, namely, aerosol extinction and backscatter and, subsequently of the lidar ratio and Ångström coefficients (i.e., the aerosol wavelength dependency coefficient) as well. The water-vapor Raman shift upon 355-nm wavelength excitation, has also been included for water vapor atmospheric profiling
Fig. 1. UPC Raman lidar wavelength-selective receiving set-up.