The work performed from the beginning to the end of the project followed the initial plan, corresponding to the activities of all five work packages.
WP1 was aimed at developing a simulation program for identifying Raman signal returns from different chemical compounds. Raman scattering, and remote sensing theoretical models were selected from the available literature. The simulator was developed on base of lidar theory and methodology including Elastic, Raman, Polarization and Fluorescence lidar equations as well as approximations of single and multiple scattering. The basic equations and algorithms were summarized for the needs of the simulator. The simulator computed Raman lidar signals on the basis of given laser specifications (excitation wavelength, line width, pulse length) and realistic atmospheric conditions and various gas mixing conditions, and aerosol mixtures.
WP2 dealt with identification of Raman lines and cross sections of chemical compounds suitable for lidar measurements. Raman and fluorescence properties of more than 150 chemical compound were explored including gases, liquids and solid-state. As a result of the instigations cross sections of more than 30 Raman lines were selected as appropriative for detection by spectroscopic lidar. Examples of such lines are NO2 (754cm-1), C3H8 (867cm-1), O3 (1103cm-1), SO2 (1151cm-1), CO2 (1285cm-1and 1388cm-1), NO2 (1320cm-1) N2O (2223cm-1) N2 (2330cm-1), O2 (1556cm-1), H2O (liquid 1595cm-1 and vapour 3652cm-1), CH4 (2914cm-1).
WP3 was involved with the development of the laboratory experiments on the basis of the simulations results, definition of the lidar requirements, measurements of Raman lines and cross sections. A Raman/Fluorescence microscope was designed and assembled for testing of solid-state and liquid samples, as well as a suite of gas and aerosol chambers for tests of gases and aerosol particles in air. Raman/Fluorescence spectra of more than 50 samples were experimentally measured.
WP4 was focused on optimization work for the simulations and final design and specification of the spectroscopic lidar. Based on the results from WP2 and WP3 we optimized the design of the lidar spectrometer. Additional Zemax simulations were done for the lidar receiver and conjugation between lidar’s subsystems - telescopes, spectrometer, and detectors.
WP5 covered the prototyping of the spectroscopic lidar, set up and assembly, and performance testing. We developed not only a prototype, but a fully operational worldwide unique lidar system, capable of fulfilling a multitude of experiments used in lidar applications. The system is part of the newly established LITES (Lidar Innovations for Technologies and Environmental Sciences) spectroscopy facility. A number of tests were performed: the system measured for the first time ever range resolved entire pure rotational Raman spectrum of the air with better than 5cm-1.
