Research On Satellite Geomagnetic Data Process And Geomagnetic Model Recovery Theory And Method

Satellite geomagnetic surveying is currently the only suitable measurement to obtain the information of global geomagnetic field. Its observation data constructs a global referenced geomagnetic model and shows applicable value on military and scientific research. In the early 1980 s, the overseas has launched the geomagnetic satellites and has carried out the satellite geomagnetic data processing, modeling and other related research. However, there are no existing geomagnetic satellites specialized for geomagnetic measurement and modeling in our country, and the satellite geomagnetic surveying research in China only in its infancy. In this paper, we studied the content of data preprocessing in satellite geomagnetic surveying, geomagnetic model recovery, geomagnetic satellite networking design and other issues in detail, and the main contents are as follows:1. Aiming at the geomagnetic model that has been released, this paper reviews and summarizes the existing various geomagnetic field model. The basic equations of the geomagnetic field spherical harmonic representation are deduced by Gauss potential theory, contrasting the difference of spherical harmonic analysis between geomagnetic field and gravity field.2. Considering that traditional precision evaluations of the geomagnetic model has shortcomings, the gridding accuracy is proposed. Since the different international organizations issued their own geomagnetic model, it is necessary to come up with appropriate methods to evaluate different geomagnetic model. Nevertheless, the traditional precision evaluations of the geomagnetic model doesn’t consider the fact that the main geomagnetic model has a certain spatial resolution. Using the observation data from geomagnetic station and WMM geomagnetic model, this paper analyzes accuracy of the global and local area models(Europe, North America, China), drawing the conclusion that the geomagnetic model’s accuracy on global and local area can be represented by gridding accuracy extraordinarily.3. The satellite geomagnetic simulation system builds up an "end-to-end" closed-loop simulation system for simulating different combination of satellite geomagnetic surveying data and the research of geomagnetic field inversion algorithm. Using the ML geomagnetic spectrum combination theory, this paper simulates main geomagnetic field, crust geomagnetic field, external geomagnetic field respectively based on various geomagnetic model that has been published. The geomagnetic field information with the addition of the satellite orbit ephemeris simulation data generates geomagnetic satellite analog observation data. It can provide the original satellite geomagnetic surveying data for all kinds of upper geomagnetic field inversion simulation experiments and geomagnetic satellite network design. Due to the known original model, it’s convenient to evaluate and analyze the validity and accuracy of inversion algorithm.4. All kinds of filters in satellite geomagnetic data preprocessing methods of the global geomagnetic field inversion are systematically summarized. Moreover, the satellite geomagnetic data preprocessing and its basic steps are concluded. Also, the geomagnetic index condition, local time conditions, latitude and altitude conditions, and gross error conditions in satellite geomagnetic data screening applications are analyzed respectively.5. The main geomagnetic field, crust geomagnetic field, separation of internal and external geomagnetic field is analyzed through the satellite geomagnetic simulation system. The validity of simulation system is proved with the examples of inversion algorithm from the main geomagnetic field. At the same time, further availability of the simulation system platform is verified combining the measured data. From the example of inversion algorithm of the crustal geomagnetic field, the inter relationship curve between satellite orbit height and the largest order of crust geomagnetic field inversion is put forward. It is concluded that the external magnetic field in the geomagnetic field inversion is an important factor that cannot be ignored from the example of internal and external geomagnetic field separation. Moreover, appropriate model can be used to get rid of the influence of the external geomagnetic field.6. For the methed of Secular Variation(SV) of geomagnetic field, this paper improves the solution of the traditional geomagnetic field SV and make up for its flaws caused by merely adoption of the linear fitting. According to the observation data from ground stations and geomagnetic satellite, the geomagnetic field SV nonlinear changes is examined in detail, and new method is proposed, which is used for solving the SV of geomagnetic field directly under the utilization of satellite geomagnetic data. Then the validity and availability of new method is confirmed through the example analysis.7. Vector data of geomagnetic satellite which at high latitude are greatly influenced by geomagnetic activities, and it will cause the blank data phenomenon in polar regions during data preprocessing, which affects the precision of the geomagnetic model around the world. Aiming at this problem, the article puts forward a new method to build up the geomagnetic model combining the use of vector and scalar data. The method of how to utilize satellite magnetic scalar data is introduced, and meanwhile some related calculation formula is deduced. The simulation experiment shows that, for the final precision of the geomagnetic field inversion, the influence of disturbance at the high latitude cannot be ignored, and that the traditional data preprocessing of deleting high latitudes data can lead to severe marginal effect of the inversion results. This paper puts forward the method of recovery the geomagnetic field model with combination of scalar and vector data, which sustains the inversion precision and improves the utilization efficiency of satellite geomagnetic data at the same time.8. For satellite geomagnetic surveying and network design problems, this paper proposes a the satellite geomagnetic simulation system to emulates and discusses the characteristics of different network design such as single star geomagnetic survey, double star synchronous geomagnetic survey, triple-star network observation and four-star geomagnetic survey in the aspect of geomagnetic field inversion, and it can provide some references for our country to develop its independent geomagnetic satellite. Five network projects are designed respectively, and the inversion result and the precision of the different projects are derived from comparison of the main geomagnetic field inversion, crust geomagnetic field inversion, internal and external geomagnetic field separation. Consequently, it can be concluded that double star project is more accurate than single star project, not significantly improved. Furthermore, compared with double star, the precision of triple-star project increases a lot. However, the precision of four-star project does not obviously increase in comparison with that of the triple-star.