LIDAR, system

Classification of Lidar System. Lidar systems can be classified on die basis of particular optical interactions which they utilize Classes of lidar include ... 

Doppler hroadening effects also have been used to separate back scattered lidar signals into molecular and aerosol components. Characteristics of some lidar systems are summarized in Table 2. 

G. Mejean, J. Kasparian, J. Yu, S. Frey, E. Salmon, J.-P. Wolf, Remote Detection and Identification of Biological Aerosols using a Femtosecond Terawatt Lidar System, Applied Physics B 78, 535 (2004)... 

JSWILD expected to take place in FY 2001. However, it was not possible to determine from the information supplied to the committee if these events took place and what the decisions were. The Joint Service Warning and Identification Lidar System (JSWILD) has been renamed Artemis. 

Carbon dioxide lasers are widely u.scd in remote-sensing applications such as light detection and ranging (lidar). The operating principle of lidar is similar to that of radar. The lidar system transmits radiation out to a target where it interacts with and is altered by the... 

Dharmarajan and Brouwers (1987) described the use of an instrument, the atomizing trace gas monitoring system [total combustible gas (TCG) analyzer], equipped with ion-specific electrodes for measuring airborne HCl and HF. A lidar system, based on measnring backscattered light from a short pnlse of laser radiation, has been reported for determining hydrogen chloride in incinerator ship plnmes (Weitkamp 1985). 

For measurements over larger distances or in higher altitudes of the atmosphere, this absorption measurement with a retroreflector cannot be used. Here the LIDAR system, which is discussed in Sect. 10.2.2, has proven to be the best choice. 

Fig. 10.19 LIDAR-system with locally separated detector telescopes...

In this way a complete air-pollution map of industrial and urban areas can be recorded and pollution sources can be localized. With pulsed dye lasers NO2 concentrations in the parts-per-million (ppm) range at distances up to 5 km can be monitored [1457]. Recent developments of improved LIDAR systems with frequency-doubled lasers have greatly increased the sensitivity as well as the spatial and spectral ranges that can be covered [1458-1460]. 

The principle of lidar is that a laser pulse is fired into the atmosphere and as it proceeds along its path, radiation that is scattered by aerosol and other particles is directed back toward the laser where it is collected with a telescope and measured with a detector. The lidar system can be operated either in single- or multi-wavelength mode (by using a tuneable laser) so as to detect a number of different species according to the attenuation they cause at specific wavelengths. Several practical systems have been developed to monitor species such as SO2 and O3 but the instrumentation required is complex and very expensive. Analysis of the signal also requires considerable expertise. 

We would like to mention one further practical application of standard Raman spectroscopy, namely the method of Raman lidar, which is now routinely used to monitor the upper atmosphere for composition (e.g. the presence of water vapour), chemical processes (e.g. the generation or depletion of ozone (O3)), and the determination of temperature profiles at high altitudes. Although absorption and fluorescence lidar systems are also widely used, Raman lidar has the distinct advantage that it is a simultaneous multispecies measurement technique, and that only a single fixed-wavelength laser is required. 

In the first example, we present and discuss O3 measurements taken in the city of Seville, Spain, by Frejafon et al. (1998). The lidar system used in this... 

Table 28.2 Typical spedfication/operation parameters of the Lidar system utilized in the Seville measurements (from Frejafon et ai (1998))...

X = H, OH, NO, Br, Cl). These species actually control the presence and distribution of O3 in the stratosphere. A detailed description of both chemical and photochemical processes occurring in the troposphere and stratosphere can be found, for example, in the books by Wayne (1985) and Seinfeld and Pandis (1998). At the present time, there are about a dozen stratospheric O3 lidar systems (SOLS) in operation, which mainly use the DIAL technique to monitor the O3 concentration in the stratosphere. 

Besides the fixed-location lidar systems, such as the Tsukuba lidar, a number of mobile lidar instruments are operated worldwide, such as the Norwegian ALOMAR system or NASA s STROZ-LITE instrument, also used in O3 measurements. An example of measurements taken with the ALOMAR instrument is shown in Figure 28.26, providing altitude profiles for the concentration of O3. 

Figure 28.25 Typical O3 ozone number density profile versus altitude, measured on different dates after the Mount Pinatubo eruption, using the lidar system shown in Figure 28.24. For comparison, aerosol backscatter data are also shown. Data provided courtesy of H. Nakane, NIES (2006)...

DEM, with a pixel resolution of 1 m, is produced by airborne lidar system ALS50-II. DEM was used to compensate the elevation phase during SAR data processing (Liu. et al. 2012). 

---