## 3 Results and Discussion
The database could then be used to identify the pollutants in the atmosphere during practical  
Figure 1: Mie angular scattering intensity patterns from pure water for each of the size parameters in Table 2: particle size of a = 0.1 \(\upmu\)m for (**a**) \(\lambda\) = 1.064 \(\upmu\)m, (**b**) \(\lambda\) = 0.532 \(\upmu\)m, and (**c**) \(\lambda\) = 0.355 \(\upmu\)m; a particle size of a = 0.5 \(\upmu\)m for (**d**) \(\lambda\) = 1.064 \(\upmu\)m, (**e**) \(\lambda\) = 0.532 \(\upmu\)m, and (**f**) \(\lambda\) = 0.355 \(\upmu\)m and a particle size of a = 1.25 \(\upmu\)m for (**g**) \(\lambda\) = 1.064 \(\upmu\)m, (**h**) \(\lambda\) = 0.532 \(\upmu\)m, and (**i**) \(\lambda\) = 0.355 \(\upmu\)m.  
environmental monitoring exercises, whereby actual scattering patterns are collected in-situ. These are then scanned against the scattering patterns in the database to identify the scattering particle. To capture the actual scattering patterns, we propose a MIe Scattering Time-gated multi-Static LIDAR (MISTS-LIDAR) scheme. Bistatic lidar operation has been reported previously, whereby the detector (receiver) is spaced at a far distance from the source (transmitter) so that angular scattering measurements can be made [39; 40]. The MISTS-LIDAR scheme extends the concept of bistatic lidar a step further by implementing multiple detectors that can rotate through a small angle. By rotating each of the multiple detectors through an angle of 0 to 180\({}^{\circ}\), the cross-sectional scattering intensity patterns that were initially simulated could be recreated. The top view of the schematic diagram of the proposed MISTS-LIDAR experimental set-up is shown in Figure 2.  
A scattering center, for example, a smoke being emitted by a factory, is illuminated by a commercially available pulsed Q-switched laser (E), such as an Nd:YAG or Nd:YVO\({}_{4}\) laser. The importance of the laser being pulsed will be discussed later. The laser emission can be sequentially tuned to its fundamental (1.064 \(\upmu\)m), second (0.532 \(\upmu\)m), or third (0.355 \(\upmu\)m) harmonic wavelengths. The laser light source is located at a distance \(l_{0}\) from the scattering center. Furthermore, the laser is at a lower elevation compared to the scattering center such that the laser beam is directed upward toward the scattering center. The backscattered laser light is then collected by a set of multiple telescope detectors (D\({}_{0}\) to D\({}_{n}\)). The collected light then creates the MIe scattering intensity profiles, which will then be compared against the database to identify the type of scattering particle present in the scattering center that is being observed. The number of telescope detectors is correlated to the angular scattering cross-section. For example, for \(x=0.59\) or 1.18 (Figure 1a,b), at least four telescope detectors will be needed to recreate the cross-sectional scattering intensity patterns. The number of telescope detectors increases as the size parameter also increases. This is because as the size parameter increases, the scattering intensity patterns also become more complex, as shown in Figure 1. The telescope detectors are placed at known distances around the scattering center. Each detector can rotate through a telescopic angle \(0<\theta_{i}<\pi\) so that the detector (_Di_) that is tilted at an angle \(\theta_{i}\) has a distance \(l_{i}\) from the scattering center. By scanning  
Figure 2: Schematic diagram of the proposed MIe Scattering Time–gated laSer LIDAR (MISTS-LIDAR) experimental set-up for obtaining the MIe scattering angular cross sections as a function of the wavelength of the incident laser light, complex refractive index of the scatterer, and size of the scatter. E (red rectangle)—laser source, D (green rectangles) —telescope detector, \(l_{i}\)–distance between the scattering center and Di that is tilted at an angle \(\theta_{i}\), \(l_{0}\)—distance between the scattering center and the laser source.