Research On Ionospheric Spectral Imaging Remote Sensing Technology

The ionosphere is the ionized part of the Earth’s upper atmosphere,which is mainly located in the altitude range of 60km～1000km from the ground.The formation of ionosphere is mainly due to ionization of upper atmosphere components caused by short-wave radiation and high-energy particles from the Sun.The ionosphere is a region of the atmosphere with very specific electrodynamic properties,and its distribution of electron density affects the transmission of radio waves.At the same time,this layer connects the lower atmosphere to the higher space environment such as the magnetosphere,and responds to solar-terrestrial space weather events,thus affecting human activities.Therefore,the study on the ionosphere occupies a very important position in space environmental weather researches.Ionosphere is studied in a slightly different way by researchers than they do other regions of the atmosphere.As well as to study the composition of the ionosphere,researchers can also use the interaction between the ionosphere and electromagnetic waves to detect the ionosphere.In addition,the optical spectral remote sensing method has also become an important method used for ionospheric exploration in recent decades.The exploration of the ionosphere through optical remote sensing methods can obtain information about the spectral radiation of H,O,N₂,O₂ and other particles in the ionosphere.With the help of inverse system,the spectral irradiance of the ionosphere can be applied to calculate the concentration distribution of different particles at different heights in the ionosphere,thus enabling the analysis and monitoring of ionospheric activity.At present,ionospheric remote sensing is mainly performed in the far-ultraviolet band,where the ionospheric radiation is pure and the inversion algorithm is more mature.The excitation spectrum also exists in oxygen A-band,which is suitable for ionospheric spectral remote sensing.Remote sensing of the ionosphere using both far-ultraviolet and oxygen A-band bands can increase the dimension of remote sensing data acquisition,introduce more spectral data into the inversion system,enhance the observation capability of oxygen atom concentration in the ionosphere,and improve the efficiency of ionospheric remote sensing observation.In this paper,an ionospheric imaging spectroscopy detection method is proposed focusing on the above requirements.Using this method,the ionospheric irradiance data can be obtained simultaneously in both limb and nadir directions,covering the far ultraviolet and oxygen A-band.The theoretical research and experimental verification are performed from the design of the exploration method,the analysis of key parameters,the design and simulation of the optical machine,the laboratory test and calibration,and the field test of the instrument.The main research contents of this paper are as follows:（1）Research on ionospheric optical remote sensing and inversion theory.By analyzing the relationship between ionospheric activity,ionospheric concentration of various particles and ionospheric glow reaction intensity,the basic method of inversion is collated in this research,which is used for calculate ionospheric parameters and ionospheric activity from ionospheric spectral remote sensing data in two bands,far-ultraviolet and oxygen A-band.Then,using the inversion theory,the performance parameter requirements of remote sensing instruments are analyzed,and the key technical parameters of the ionospheric imaging spectral exploration system are determined.（2）Design of a far-ultraviolet（FUV）ionospheric imaging spectrometer.Firstly,based on the remote sensing detection requirements,the optomechanical design of the FUV ionospheric imaging detector was developed.The targeted design was carried out mainly for the features of low optical efficiency and large influence of stray light in the FUV band.Subsequently,finite element simulations of the spectrometer are carried out in this paper to verify the instrument design schemes,as well as to provide the thermal design index.Finally,the fabrication and integration of the prototype of the FUV ionospheric imaging spectrometer are also performed.（3）Design of an oxygen A-band ionospheric imaging spectrometer.Firstly,based on the demand of remote sensing detection,the instrument design of the oxygen A-band ionospheric imaging spectrometer was performed,mainly for the objectives of instrument miniaturization and hyperspectral observation.Subsequently,thermo-optical simulations of the instrument were performed to confirm the validity of the design.Finally,the fabrication and integration of a prototype oxygen A-band ionospheric imaging spectrometer was also performed.（4）Testing and calibration of the ionospheric spectral imaging remote sensing system.First,the calibration requirements of the detection system are analyzed from the consist of imaging spectral instrument remote sensing data.Then,the calibration method is studied in three parts:spectral calibration,radiometric calibration and geometric calibration.The results of the design and integration of the detection system prototype are verified by calibration tests.Finally,the functions of the oxygen A-band ionospheric imaging spectrometer prototype were also verified in the field test.