The paper considers the problem of solving the inverse problem of retrieval of the vertical distribution of atmospheric temperature from a Rayleigh scattering lidar signal in a high spectral resolution lidar. It is shown that the lidar signal, filtered from the aerosol scattering signal using a molecular filter, acquires a parasitic dependence on the atmospheric temperature due to a change in the width and shape of the Rayleigh scattering line contour. Signal distortions have a significant effect on the result of retrieval of the vertical temperature distribution and do not allow using the standard signal processing technique. To eliminate the influence of the signal filtering effect, the advanced temperature retrieval algorithms should be applied.
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 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 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 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 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 discussed. A two-stage procedure for the remote estimation of temperature by molecular backscattering is proposed, which makes it possible to estimate the temperature both in a free atmosphere and in a cuvette in which the relationship between the temperature and pressure does not fit into the barometric model. Calculations have shown that the accuracy of the temperature profile retrieval depends on the choice of the calibration point and its error. The calculation of the profile by formula, when the calibration point is chosen at the upper part of the sounding path, has greater stability and accuracy compared to calculations by formula with the calibration point chosen at the beginning of the path.
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.
This paper describes a pulsed coherent Doppler lidar, recently created at the Wave Propagation Laboratory of the Institute of Atmospheric Optics SB RAS (WPL lidar). The WPL lidar was tested in atmospheric experiments. Comparison of the results of joint measurements of the radial velocity by the WPL lidar and Stream Line lidar showed their satisfactory agreement. From measurement of radial velocities by the WPL lidar at various azimuth angles (that is, with the use of the conical scanning), the height profiles of wind velocity and wind direction angle in the atmospheric boundary layer have been retrieved.
The results of computer simulation of the lidar overlap functions obtained by the ray-tracing method for a transceiver optical system with four receiving apertures are presented. It is shown that when using a multi-element transceiver based on a combination of four receiving apertures of different diameters, the lidar sensing range from 5 to 3000 m can be obtained with a dynamic range of the lidar return not more than 10. A prototype of the Raman lidar based on the four-aperture transceiver is created. A comparison is made of the calculated values of the lidar returns for a given overlap function of the transceiver with the experimental values of the lidar Raman signals for a uniform atmosphere. The comparison results confirm the correctness of the calculation method and can be used as a criterion when adjustment of the transceiver.
The "LOZA" small-size lidar is described. The lidar is intended for field measurements of the optical state of the troposphere, including situations of its arrangement onboard an aircraft-laboratory or a research vessel. The lidar carries out sounding of the atmosphere at two wavelengths of radiation from a solid-state laser of 1064 and 532 nm. Optical selection of lidar signals at these wavelengths is performed by two identical telescopes. In the visible channel, the signal is divided into two orthogonal polarized components, as well as a Raman signal at a wavelength of 607 nm is separated. The lidar signals are recorded by means of HAMAMATSU photomultipliers tube in analogue and photon-counting modes. In the IR channel, the signals at λ = 1064 nm are recorded by means of the C30956E-TC avalanche photodiode designed by Perkin Elmer.
The paper summarizes the experience to create the counting of the registration system pulse avalanche photodiode. The authors suggested a technical solution that allows the hardware to carry out registration in both analog and in the photoelectron pulse registration regime. The paper substantiates the idea of how the use of modern microcontroller solutions, provides a flexible registration system with user-defined time parameters (or probe pulses) accumulation start timing cutoff near zone, sensing range, signal range resolution. Such a view would be of interest to specialists in the development of devices for receiving signals in lidar systems.
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