CN-122017882-A - Global broadcast ionosphere time delay correction method and device based on occultation observation

CN122017882ACN 122017882 ACN122017882 ACN 122017882ACN-122017882-A

Abstract

A global broadcast ionosphere time delay correction method and device based on occultation observation comprise the steps of obtaining electronic density profile data of occultation observation inversion, carrying out quality control to obtain qualified electronic density profile data, integrating electronic density in the qualified electronic density profile data to obtain ionosphere TEC data, converting the ionosphere TEC data to a height range of foundation GNSS observation, constructing a single-layer global ionosphere spherical harmonic function model to obtain a zero-order spherical harmonic coefficient, resolving the global broadcast ionosphere function model based on the zero-order spherical harmonic coefficient to obtain a curing parameter of the global broadcast ionosphere function model, broadcasting the zero-order spherical harmonic coefficient serving as an ionosphere time delay correction parameter, and calculating an ionosphere delay correction by utilizing the ionosphere time delay correction parameter and the curing parameter. The invention gets rid of the dependence on the foundation GNSS observation network, has the advantages of simple model structure, high calculation efficiency, less broadcasting parameters, strong global coverage capability and the like, and remarkably enhances the autonomy and the robustness of the broadcast ionosphere service.

Inventors

LI MIN
YUAN YUNBIN
ZHANG WENYAO
ZHANG TING
HUO XINGLIANG

Assignees

中国科学院精密测量科学与技术创新研究院

Dates

Publication Date: 20260512
Application Date: 20251222

Claims (10)

1. The global broadcast ionosphere delay correction method based on occultation observation is characterized by comprising the following steps of: Acquiring electron density profile data of the occultation observation inversion, and performing quality control to obtain qualified electron density profile data; integrating the electron density in the qualified electron density profile data to obtain ionized layer TEC data, and converting the ionized layer TEC data to a height range observed by a foundation GNSS to obtain normalized ionized layer TEC data; Based on normalized ionosphere TEC data, constructing a single-layer global ionosphere spherical harmonic model, and obtaining a zero-order spherical harmonic coefficient through inversion estimation of the model; Constructing a global broadcast ionosphere function model, and resolving the global broadcast ionosphere function model based on zero-order spherical harmonic coefficients to obtain curing parameters of the global broadcast ionosphere function model; And broadcasting the zero-order spherical harmonic coefficient as an ionosphere delay correction parameter, and calculating an ionosphere delay correction by using the broadcasted ionosphere delay correction parameter and a curing parameter of a global broadcast ionosphere function model.
2. The global broadcast ionosphere delay correction method based on occultation observation according to claim 1, wherein the single-layer global ionosphere harmonic model is: ; In the formula, Ionospheric delay in the vertical direction; And The longitude and latitude of the puncture point under a day-fixed geomagnetic coordinate system are respectively; Is that Degree of Regularized Legend function of the order; And And the global ionosphere harmonic model coefficient to be estimated.
3. The method for correcting global broadcast ionosphere time delay based on occultation observation according to claim 1, wherein the performing quality control to obtain qualified electron density profile data comprises: calculating the relative electron density change rate between adjacent height points of each effective electron density profile; Dividing a height axis into a plurality of intervals, and counting a steady percentile index of a relative electron density change rate in each height interval for each effective electron density profile to generate a noise upper limit threshold, a sawtooth amplitude threshold and an extreme abrupt change threshold; and setting a three-level progressive judging process comprising a high noise background criterion, an extreme single-point jump criterion and an effective sawtooth structure criterion based on the noise upper limit threshold, the extreme abrupt change threshold and the sawtooth amplitude threshold, and judging that the electron density profile is invalid and rejecting if any criterion is triggered.
4. The global broadcast ionosphere time delay correction method based on occultation observation according to claim 3, wherein the calculation method of the relative electron density change rate is as follows: for each effective electron density profile, calculating the absolute value of electron density between adjacent height points: ; In the formula, Is the absolute difference of electron density; Is a height point Electron density of (a); Is a height point Electron density of (a); based on the normalization of the electron density smaller values in the two adjacent points, the relative electron density change rate is obtained: ; In the formula, Is the rate of change of the relative electron density.
5. A global broadcast ionosphere time delay correction method based on occultation observation according to claim 3, wherein said generating noise upper threshold, saw tooth amplitude threshold and extreme abrupt threshold by counting robust percentile indicators of relative electron density change rate in each altitude interval comprises: And counting 75 th percentile, 95 th percentile and maximum value of the relative electron density change rate in each altitude interval to respectively obtain first statistics, second statistics and third statistics, summarizing the first statistics, the second statistics and the third statistics of all electron density profiles in the same altitude interval, obtaining a sawtooth amplitude threshold value by taking the 75 th percentile of the first statistics, obtaining a noise upper limit threshold value by taking the 75 th percentile of the second statistics, and obtaining an extreme mutation threshold value by multiplying the 75 th percentile of the third statistics by 1.2.
6. A global broadcast ionosphere delay correction method based on occultation observation according to claim 3, wherein the high noise background criterion is: Statistics of the ratio of the relative electron density change rate to the noise upper threshold : ; In the formula, Is the relative electron density change rate; Is a height point A noise upper threshold of (2); the total number of data points in the electron density profile data; if the ratio exceeds the preset threshold, the whole electron density profile is polluted by high-frequency noise, and the electron density profile is judged to be invalid.
7. A global broadcast ionosphere delay correction method based on occultation observation according to claim 3, wherein said extreme single-point jump criterion is: if more than two height points exist in the effective height interval, the following conditions are satisfied: ; In the formula, Is the relative electron density change rate; Is a height point Is a threshold for extreme mutation; It is indicated that the electron density profile contains a non-physical abrupt change and the electron density profile is determined to be ineffective.
8. A global broadcast ionosphere delay correction method based on occultation observation according to claim 3, wherein the effective saw tooth structure criterion is: Calculating the sign change of the electron density difference sequence, and positioning potential sawtooth vertexes; For each symbol turning point, if at least one of two adjacent relative electron density change rates in front and back is not lower than a sawtooth amplitude threshold value, the symbol turning point is an effective sawtooth vertex; and counting the maximum continuous length of the effective sawtooth peak, and if the maximum continuous length is greater than or equal to a set threshold value, indicating that the electron density profile has systematic and non-physical periodic oscillation, and judging that the electron density profile has sawtooth abnormality.
9. The global broadcast ionosphere delay correction method based on occultation observation according to claim 1, wherein the normalized ionosphere TEC data The method comprises the following steps: ; In the formula, Ionosphere TEC data; TEC data from the ground to the GNSS satellite orbit altitude interval; TEC data for the ground-to-low orbit satellite orbit altitude interval.
10. A global broadcast ionospheric delay correction apparatus based on occultation observation, characterized in that the apparatus is adapted to implement the method of any one of claims 1 to 9, the apparatus comprising: the electron density profile data acquisition module is used for acquiring electron density profile data of the occultation observation inversion and performing quality control to obtain qualified electron density profile data; The ionized layer TEC data acquisition module is used for integrating the electron density in the qualified electron density profile data to acquire ionized layer TEC data, and converting the ionized layer TEC data into a height range observed by a foundation GNSS to acquire normalized ionized layer TEC data; the zero-order spherical harmonic coefficient acquisition module is used for constructing a single-layer global ionosphere spherical harmonic function model based on normalized ionosphere TEC data, and obtaining a zero-order spherical harmonic coefficient through inversion estimation of the model; the solidifying parameter obtaining module is used for constructing a global broadcast ionosphere function model, resolving the global broadcast ionosphere function model based on zero-order spherical harmonic coefficients and obtaining solidifying parameters of the global broadcast ionosphere function model; And the ionosphere delay correction acquisition module is used for broadcasting the zero-order spherical harmonic coefficient as an ionosphere delay correction parameter, and calculating the ionosphere delay correction by using the broadcasted ionosphere delay correction parameter and the curing parameter of the global broadcast ionosphere function model.

Description

Global broadcast ionosphere time delay correction method and device based on occultation observation Technical Field The invention belongs to the technical field of ionosphere time delay correction, and particularly relates to a global broadcast ionosphere time delay correction method and device based on occultation observation. Background Ionosphere is one of the most troublesome sources of error affecting the service performance of the global satellite navigation system. Broadcasting global ionospheric broadcast correction parameters in satellite navigation ephemeris is a main technical means for each satellite navigation system to realize ionospheric delay correction. In order to meet the real-time correction requirement of global single-frequency users, the main GNSS systems such as the United states GPS, the European Union Galileo, the Chinese Beidou and the like broadcast ionosphere model parameters through navigation broadcast ephemeris. The GPS adopts an 8-parameter Klobuchar model, the Galileo adopts a 3-parameter Nequick-G model, and the Beidou three-system adopts a 9-parameter Beidou global broadcast ionosphere BDGIM model. These broadcast ionosphere models play an important role in improving single frequency positioning accuracy. However, the parameter estimation of the existing broadcast ionosphere model is highly dependent on the ground GNSS observation network, and the dependence faces many challenges in practical application, so that the performance consistency and dynamic adaptability of the model in the global scope are restricted. First, the spatial distribution of global base GNSS observables is severely uneven. Existing monitoring stations are mostly concentrated in land and economically developed areas, while in wide oceans, polar regions and many developing countries, observation sites are rare or even absent. This imbalance in spatial coverage directly affects the global correction accuracy of the model. Second, in actual operation, there may be a delay or incomplete aggregation of global observation data due to restrictions related to data sharing mechanisms, operation management policies, or communication conditions. For example, nequick-G and NTCM-G models require daily assimilation of global GNSS observations to estimate ionization level parameters, which directly affect the accuracy and timeliness of model parameters if critical area data cannot be accessed in time. In order to solve the problem of insufficient data of the weak observation area, part of the system introduces a climatology background model based on long-term statistics as a supplementary means. For example, BDGIM provides TEC estimation using background field models in other areas while using primarily the GNSS data of China and surrounding areas for parameter estimation. However, such models are built based on historical average states, lacking the ability to respond to short-term changes in the ionosphere. Under the disturbance conditions such as high solar activity period or geomagnetic storm, the ionosphere state changes drastically, the climatology model is difficult to capture the dynamic characteristics of the ionosphere state, the correction effect is obviously reduced, and the model robustness is insufficient. Therefore, the core problem faced by the current broadcast ionosphere model is how to construct a novel correction model which has simple parameters, high calculation efficiency, global coverage and good dynamic adaptability on the premise of not depending on a global or regional foundation GNSS observation network, and particularly can still keep stable and reliable performance in the data sparse region and ionosphere disturbance period. In recent years, with the rapid development of low earth orbit satellite constellations such as FY-3, tianmu, obsidian, COSIC-2 and the like, ionosphere observation based on GNSS radio occultation technology shows unique advantages. The occultation observation has the characteristics of near global coverage, no limitation of geographical conditions, high vertical resolution and the like, can effectively make up the observation blank of a foundation GNSS in the areas such as ocean, polar regions and the like, and provides a new data base for constructing a global ionosphere model independent of a ground network. There have been studies attempting to refine global ionospheric spherical harmonic models using occultation data, but there are significant shortcomings. On one hand, the existing research does not fully consider the difference of the space height coverage of the occultation inversion TEC and the foundation GNSS TEC, and is difficult to directly serve GNSS single-frequency users, on the other hand, the model based on spherical harmonics generally needs more parameters (at least 16 parameters when the order is more than or equal to 3), and the parameter capacity of the current broadcasting model is far exceeded, so that real-time broadcasting is not facilita