Study On Wind Measurement Of Atmosphere By Interferometry Technology

Atmosphere plays an important role in human beings' life. Recently, with the increasing attention on ozone hole and a series of environmental problems related to it, study on upper atmosphere has become a hot topic. Various measurement methods are adopted in this regard. Considering that airglow and aurora line in atmosphere reflects certain information of atmosphere temperature and wind velocity, passive measurement of wind applies interferometer to produce interferogram of airglow and auroral emission lines. Then the atmosphere temperature, pressure and wind velocity can be reversed from the interferential intensity. This measurement method is widely used for its great merits such as simple operating, high resolution, high detecting accuracy and almost being independent of weather. However, research on this project is still at the initial stage in our country. With the development of aerospace technology, information on atmosphere, especially upper atmosphere, is in desperate need. In this connection, to develop the technique of wind detecting of atmosphere with interferometer is of vital importance both theoretically and practically and this technique is promising to play an important role in the future and serve for spaceflight and meteorology. Under this circumstance, the upper atmospheric wind measurement technique is in-depth studied in this paper. Based upon the detailed theoretical analysis, related computer simulation is performed and crucial problems are discussed. The polarizing Michelson interferometer for wind measurement based on polarization array is proposed. Major findings and originalities of this paper are enumerated as follows:Since the choice of object source embodies the measurement target and determines some parameters of instrument, a proper choice is key to the elemental research. The characters of auroral and airglow emission lines are summarized and analyzed and information on their reacting course, emission intensity, emission altitude, and emission wavelength is elaborated. In addition, the selecting principle is pointed out. On account of the different widen principle, the emission line can be expressed by different line shape function. In the paper the line shape function relevant to atmosphere temperature is devised and the relation between pressure and temperature, wind velocity and wavelength is analyzed. Therefore, this research provides theoretical reference for wind reversion.It's acknowledged that Fabry-Perot interferometer was used earlier to detect atmosphere. Its detecting principle, reversion method and implementation method are analyzed in detail in the paper.The reversion of wind velocity of ideal condition is deduced and validated. Besides, simulation of the interferometer is carried out and predicted result is achieved. The simulation of circle to line system is realized successfully.This paper furthers its study with the analysis of Michelson interferometer, which is prevailing in wind measurement for its advantages in field-widening. Firstly, the detecting mode and reversion method are analyzed elaborately. In the light of the principle of field-widening, the best two kinds of qualified glass in China glass data base are selected and the thicknesses of the arms are calculated for the first time. The result validates the effectiveness of these two kinds of glass in field-widening. Through computer simulation, the choice is also proved correct. Then, the means to realize four steps are illustrated and new methods of rotational mirror and polarization array are put forward. The advantages and disadvantages of each method are pointed out by analyzing and comparing. Finally the data are applied to computer simulation and the reversion of interferogram shows that the perfect result achieved is coincident to the real value.In addition to the achievements mentioned above, some important problems in Michelson Doppler imaging interferometer are analyzed in detail. Firstly, the principle of selecting fixed optical path difference is proposed. It is discussed from three aspects: the limit of visibility, the limit of phase and the requirement of in-phase of near wavelengths. The optimal fixed optical path difference is discovered for given emission lines. Secondly, the influence of fixed optical path difference error and step error is analyzed. The error tolerance is achieved within allowance range. Finally, the factors influencing the uncertainty of temperature are analyzed. The quantitive relation between the uncertainty of temperature and the uncertainty of visibility is derived. It is pointed out that the uncertainty of instrument visibility and the uncertainty of apparent visibility of emission line determine the uncertainty of temperature, and means to improve the uncertainty of temperature is proposed. Research on these questions will lay the theory foundation for engineering implentment of instrument and has important innovation significance.Eventually, this paper devises a new Michelson interferometer for wind measurement based on polarization array. It combines the polarization interference technique with the technique of deriving wind from intensity measurements at sequential path differences. With this new interferometer, four interference intensities for different optical path difference image at the same time. It has many merits such as simple operating, high accuracy and making the best of optical energy. The change of polarization state of light in course of traveling is analyzed in detail in the paper. The simulation of interferometer is realized and the interferogram of different intensities is obtained. Through data processing and reversion, the result is proved in accord with the true value.