DIAL System Technical Details

The commercial Spectrasyne DIAL was based on two high energy (1.4J), 10Hz pulsed Nd:YAG pumped dye lasers. Tuneable ultraviolet and visible radiation was generated in one of the laser sets by selective use of frequency doubling and tripling crystals. The second laser set, which had an injection seeded Nd:YAG, was used to generate tuneable infrared radiation using difference frequency mixing in non-linear crystals.

The Spectrasyne DIAL system was single ended and its output beam was directed by means of a mirror steering system which rotated in two planes. The backscattered light, which returned along the same path, was collected in a cassegrain type receiving telescope and delivered to the appropriate detector through a multi-dichroic, beam splitting, collimating and focusing system.

In order to collect, store, handle and process the DIAL signals a sophisticated, high speed data communication network (hardware and software) was developed and this was also used to perform a number of ancillary control functions and to store essential spectroscopic and other databases. Software suites for data acquisition and processing were also developed.

The DIAL system was tuneable from the ultraviolet (UV) through the visible to the infrared, this enabled it to make range resolved measurements of a range of atmospheric species e.g. Nitric Oxide, Nitrogen Dioxide, Ozone, Aromatics, individual and bulk hydrocarbons. The system could potentially measure any other atmospheric specie provided it had an identifiable spectral fingerprint within the operational wavelength range of the DIAL (UV to mid IR) which was not obscured by an absorption feature from any other specie present in the atmosphere to be measured.

The Spectrasyne Differential Absorption LIDAR (DIAL) system was housed in an impressive 24 tonne mobile laboratory and was equipped with an extendible meteorological mast that was used to measure wind speed and direction, temperature and humidity and a number of remote meteorological stations. All meteorological data were displayed in real time and digitally logged for subsequent use with DIAL concentration data to produce mass emission fluxes.

Telephoto and wide angle TV cameras were used on the steering system to facilitate beam pointing, time-lapse video of the wide angle image was collected to be used if necessary to identify problems visually during subsequent data analysis.