A method is described for increasing the efficiency of an laser emitter based on the frequency summation. The emitter is designed to generate narrow-band radiation with a wavelength of λ ~ 589 nm, consisting in continuous automated correction of the established pumping energy levels and the actuation moments of Q-switches. The aim of the work is to reduce the time jitter of the summed radiation pulses and thereby increase the efficiency of generating of the desired frequency.
At the Siberian Lidar Station in V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences in Tomsk (56.5 N, 85.0 E), a lidar is operated to measure the ozone vertical distribution in the upper tropospherelower stratosphere, to study the ozone dynamics in the tropopause region, and to investigate the stratosphere-troposphere exchange. In this work, we compare R7207-01 PMT, operated on this lidar jointly with amplifiers-discriminators C3866 of HAMAMATSU firm for signal recording, against H12386-210 PMT units at the wavelength pair of 299/341 nm. It is shown that the new H12386-210 PMT units are promising for ozone sensing at the wavelength pair of 299/341 nm.
The paper considers a block diagram of a photodetection system based on a new version of the four-channel photon counter "PHCOUNT-4" used for precision lidar measurements of atmospheric temperature. The results of using the new capabilities of the analog part of the photon counting system, which makes it possible to automatically record the amplitude distribution of single-electron pulses of each of the photodetectors installed in the channels and determine the optimal discrimination threshold, are described. It is shown that setting the optimal discrimination thresholds makes it possible to achieve a small spread in the end-to-end quantum efficiency of each of the channels
The paper discusses the problem of ensuring the linearity of photo registration of the lidar signal of molecular scattering on the main lidar of the Siberian lidar station (SLS) based on a unique mirror with a diameter of 2.2 m. To reduce the dynamic range of signal changes, it is proposed to use a mechanical shutter based on a disk obturator to cut off the near zone of the lidar signal in the altitude range of 0÷30 km. A high-speed brushless motor was used as an obturator driver. The synchronization signal was generated by a Hall sensor. Bench and full-scale tests of the obturator were carried out. It is shown that the error of the Hall sensor does not affect the delay and duration of the shutter opening.
The paper considers the problems of optimization of the molecular scattering signal registration system at the Siberian lidar station for the photon counting mode. The modern element base makes it possible to design recorders with a gigahertz counting rate that allow to implement hardware methods for evaluating and accounting for the effect of dead time. Modified photon counting systems allow more efficient use of algorithms of the nonlinear distortion correction. Simulation of operation of a photon counter with various methods of recording events and methods of processing the recorded signals is performed. A method is proposed for determining the value of the dead time and evaluating the limits of applicability of the photon counting mode of the modified counter. A quantitative assessment of the advantage when using various correction formulas is carried out in comparison with the classical photon counting.
The paper considers the equipment and methodology for remote determination of the vertical distribution of atmospheric temperature up to altitudes of 90 km. The technique is based on the lidar measurements of the vertical profile of the molecular density of the atmosphere using the Rayleigh scattering effect. The results obtained on the modernized Rayleigh scattering channel of the lidar based on the main mirror of the Siberian lidar station with a diameter of 2.2 m are demonstrated. The atmospheric temperature profile obtained from the lidar data is compared with the temperature profile of a satellite radiometer in the altitude range of 40-90 km.
The efficiency of application of the combined photodetection technique for recording the lidar signals of the main mirror of the Siberian Lidar Station (SLS) is evaluated. It is shown that under the lidar signal recording in the photon counting mode, nonlinear distortion of the lidar response is observed in the altitude range from 1 to 26 km. It is shown in that the use of a combined method of the lidar signal recording can significantly expand the range of the detection linearity in the photon counting mode. Experimental testing of the lidar recording system was carried out under the detection of signals of various intensities.
The concept of an airborne IR differential absorption lidar for the study of methane in the atmosphere (in particular, in the Russian sector of the Arctic) is presented. The description of the main nodes and elements of the transceiver part of the IR lidar is given. The results of calculation of informative methane sensing wavelengths for polar latitudes are presented.
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