Ionized layer electron density inversion method, device, system, equipment and medium

Abstract

The embodiment of the invention provides an ionization layer electron density inversion method, device, system and equipment and a medium. The method specifically comprises the following steps: determining a target area of electron density inversion; obtaining observation data corresponding to the signal link in the target area; the signal links comprise a first signal link from a GNSS satellite to a ground station, a second signal link from the GNSS satellite to a low earth orbit satellite, and a third signal link from the low earth orbit satellite to the ground station; determining the slant total electron content corresponding to the signal link according to the observation data corresponding to the signal link; solving an ionized layer chromatography function according to the oblique total electron content corresponding to the signal link so as to obtain an electron density value of a grid in the target area; the ionized layer chromatography function is used for representing a mapping relation between the oblique total electron content and the electron density value of the grid. According to the embodiment of the invention, the inversion precision of the ionosphere electron density can be improved.

Description

Technical Field

[0001] Embodiments of the present application relate to the field of satellite navigation technology, and in particular, to an ionospheric electron density inversion method, apparatus, system, equipment and medium. Background Art

[0002] The ionosphere is a part of the atmosphere that contains a large number of free electrons. The movement of these free electrons can significantly affect the propagation of radio waves. From the perspective of satellite applications and understanding the dynamics of the ionosphere, it is particularly important to determine the real-time distribution of IED (Ionospheric Electron Density).

[0003] Ionospheric tomography is a method of inverting the three-dimensional electron density in space using the total electron content of the oblique path, which can capture the details of the local distribution and changes of the electron density. Related technologies usually divide the ionospheric space into multiple grids based on the tomographic observation information provided by the ground monitoring station network, combined with ray tracing technology, and transform the electron density inversion problem into a mathematical problem of solving the unknown electron density in the grid. By establishing the ionospheric tomography equation, the total electron content of the oblique path is linked to the electron density in the grid and the intercept of the ray in the grid, and then the ionospheric tomography equation is solved using a suitable algorithm to obtain the electron density distribution.

[0004] However, the insufficient number of ground monitoring stations and other reasons lead to the insufficient number and uneven distribution of ionospheric observation rays, which in turn brings about the problem of ill-posed solution of the ionospheric tomography equation. Summary of the invention

[0005] The embodiment of the present application provides an inversion method for ionospheric electron density, which can improve the inversion accuracy of electron density.

[0006] Correspondingly, an embodiment of the present application also provides an ionospheric electron density inversion system, an ionospheric electron density inversion device, an electronic device and a machine-readable medium to ensure the implementation and application of the above method.

[0007] In order to solve the above problems, the present application discloses an inversion method for ionospheric electron density, the method comprising: Determine the target area for electron density inversion; Acquire observation data corresponding to signal links in the target area; the signal links include: a first signal link from a GNSS satellite to a ground station, a second signal link from a GNSS satellite to a low-orbit satellite, and a third signal link from a low-orbit satellite to a ground station; Determining the oblique total electron content corresponding to the signal link according to the observation data corresponding to the signal link; According to the oblique total electron content corresponding to the signal link, the ionospheric tomography function is solved to obtain the electron density value of the grid in the target area; the ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

[0008] In order to solve the above problems, the embodiment of the present application discloses an ionospheric electron density inversion system, including: a GNSS satellite, a low-orbit satellite, a ground station and a data center; The GNSS satellite transmits a satellite signal to the ground station using a first signal link; the first signal link is a signal link from the GNSS satellite to the ground station; The GNSS satellite transmits a satellite signal to the low-orbit satellite using a second signal link; the second signal link is a signal link from the GNSS satellite to the low-orbit satellite; The low-orbit satellite transmits a satellite signal to the ground station using a third signal link; the third signal link is a signal link from the low-orbit satellite to the ground station; The data center determines a target area for electron density inversion; obtains observation data corresponding to a signal link in the target area; determines the oblique total electron content corresponding to the signal link based on the observation data corresponding to the signal link; solves an ionospheric tomography function based on the oblique total electron content corresponding to the signal link to obtain the electron density value of the grid in the target area; the ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

[0009] In order to solve the above problems, the embodiment of the present application discloses an ionospheric electron density inversion device, the device comprising: A region determination module, used to determine the target region for electron density inversion; An observation data acquisition module is used to acquire observation data corresponding to a signal link in a target area; the signal link includes: a first signal link from a GNSS satellite to a ground station, a second signal link from a GNSS satellite to a low-orbit satellite, and a third signal link from a low-orbit satellite to a ground station; A link electron content determination module, used to determine the oblique total electron content corresponding to the signal link according to the observation data corresponding to the signal link; The electron density solving module is used to solve the ionospheric tomography function according to the oblique total electron content corresponding to the signal link to obtain the electron density value of the grid in the target area; the ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

[0010] The embodiment of the present application further discloses an electronic device, including: a processor; and a memory, on which executable code is stored. When the executable code is executed, the processor executes the method described in the embodiment of the present application.

[0011] The embodiment of the present application further discloses a machine-readable medium on which executable code is stored. When the executable code is executed, a processor executes the method described in the embodiment of the present application.

[0012] The embodiment of the present application also discloses a computer program product, including a computer program / instruction, which implements the aforementioned method when executed by a processor.

[0013] The embodiments of the present application include the following advantages: In the technical solution of the embodiment of the present application, the number and distribution of observation rays in the ionosphere are optimized by introducing low-orbit satellites. On the one hand, at the space orbit level, a second signal link is established between the low-orbit satellite and the GNSS satellite, increasing the number of observation rays between the GNSS and the low-orbit satellite. On the other hand, in the dimension of space-to-earth communication, a third signal link is established between the low-orbit satellite and the ground station, increasing the number of observation rays between the low-orbit satellite and the ground station. On another hand, the dynamic operation characteristics of the low-orbit satellite improve the distribution of observation rays in the tomography area.

[0014] The optimization of the number and distribution of the above-mentioned ionospheric observation rays can provide richer and optimized data resources for solving the ionospheric tomography function. Therefore, the embodiment of the present application can effectively overcome the ill-posed problem of solving the ionospheric tomography equation caused by the insufficient number and uneven distribution of ionospheric observation rays. On this basis, the embodiment of the present application can improve the inversion accuracy of the electron density, that is, it can improve the accuracy of the electron density value obtained by inversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of an ionospheric electron density inversion system according to an embodiment of the present application; Figure 2 is a schematic diagram of observation rays within a time window of a tomography region of the ionosphere in one embodiment of the present application; Figure 3 It is a schematic flow chart of the steps of an ionospheric electron density inversion method according to an embodiment of the present application; Figure 4 It is a structural schematic diagram of an ionospheric electron density inversion device according to an embodiment of the present application; Figure 5 It is a schematic diagram of the structure of a device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0016] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0017] The electron density inversion method of the embodiment of the present application can be used to obtain the electron density distribution in the three-dimensional space of the ionosphere. This method can not only provide a basis for satellite navigation, but also effectively correct the ionosphere error, thereby significantly improving the positioning accuracy. Moreover, this method helps to monitor the weather changes in the ionosphere space, and also has a positive role in promoting the study of ionosphere dynamics.

[0018] Related technologies usually divide the ionosphere space into multiple grids based on the tomographic observation information provided by the ground station network, combined with ray tracing technology, and transform the electron density inversion problem into a mathematical problem of solving the unknown electron density in the grid. However, due to the insufficient number of ground stations and other reasons, the number of ionosphere observation rays is insufficient and unevenly distributed, which in turn leads to the problem of ill-posed solution of the ionosphere tomography equation.

[0019] In view of the technical problem of ill-posed solution of ionospheric tomography equation in related technologies, the embodiment of the present application provides an inversion method for ionospheric electron density, which specifically includes: Determine the target area for electron density inversion; Acquire observation data corresponding to signal links in the target area; the signal links include: a first signal link from a GNSS satellite to a ground station, a second signal link from a GNSS satellite to a low-orbit satellite, and a third signal link from a low-orbit satellite to a ground station; Determine the oblique total electron content corresponding to the signal link according to the observation data corresponding to the signal link; According to the oblique total electron content corresponding to the above signal link, the ionospheric tomography function is solved to obtain the electron density value of the grid in the above target area; the above ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

[0020] The embodiment of the present application performs an inversion of the ionospheric electron density based on the observation data of multiple signal links. Specifically, the embodiment of the present application obtains the observation data of three signal links, namely, GNSS satellite to ground station, GNSS satellite to low-orbit satellite, and low-orbit satellite to ground station, and obtains the oblique total electron content corresponding to the three signal links; and uses the mapping relationship between the oblique total electron content represented by the ionospheric tomography function and the grid electron density value to solve the electron density value.

[0021] The embodiments of the present application optimize the number and distribution of observation rays in the ionosphere by introducing low-orbit satellites. On the one hand, at the space orbit level, a second signal link is established between the low-orbit satellite and the GNSS satellite, increasing the number of observation rays between the GNSS and the low-orbit satellite. On the other hand, in the dimension of space-to-earth communication, a third signal link is established between the low-orbit satellite and the ground station, increasing the number of observation rays between the low-orbit satellite and the ground station. On another hand, the dynamic operation characteristics of the low-orbit satellite improve the distribution of observation rays in the tomography area.

[0022] The optimization of the number and distribution of the above-mentioned ionospheric observation rays can provide richer and more optimally laid out data resources for solving the ionospheric tomography function. Therefore, the embodiment of the present application can effectively overcome the ill-posed problem of solving the ionospheric tomography equation caused by the insufficient number and uneven distribution of ionospheric observation rays. On this basis, the embodiment of the present application can improve the inversion accuracy of the electron density.

[0023] System Example Reference Figure 1 , shows a schematic structural diagram of an ionospheric electron density inversion system according to an embodiment of the present application, the system specifically comprising: a GNSS satellite 101, a low-orbit satellite 102, a ground station 103 and a data center 104.

[0024] The GNSS satellite 101 transmits a satellite signal to the ground station 103 using a first signal link; the first signal link is a signal link from the GNSS satellite 101 to the ground station 103; The GNSS satellite 101 transmits a satellite signal to the low-orbit satellite 102 using a second signal link; the second signal link is a signal link from the GNSS satellite 101 to the low-orbit satellite 102; The low-orbit satellite 102 transmits a satellite signal to the ground station 103 using a third signal link; the third signal link is a signal link from the low-orbit satellite to the ground station; The data center 104 determines a target area for electron density inversion; obtains observation data corresponding to a signal link in the target area; determines the oblique total electron content corresponding to the signal link based on the observation data corresponding to the signal link; solves an ionospheric tomography function based on the oblique total electron content corresponding to the signal link to obtain an electron density value of a grid in the target area; the ionospheric tomography function is used to characterize a mapping relationship between the oblique total electron content and the electron density value of the grid.

[0025] In the embodiments of the present application, GNSS (Global Navigation Satellite System) is an air-based radio navigation and positioning system that can provide users with all-weather three-dimensional coordinates, speed and time information at any location on the surface of the earth or in near-Earth space. The GNSS system provides positioning, navigation, timing and communication services to users worldwide by deploying a group of GNSS satellites in Earth orbit. Examples of GNSS systems may include: GPS (Global Positioning System) and BeiDou system. It can be understood that the embodiments of the present application are not limited to specific GNSS systems.

[0026] GNSS satellite 101 is an important part of the global navigation satellite system. GNSS satellites orbit the earth and provide a variety of services to users on the earth's surface or in near-earth space by transmitting radio signals. These services mainly include all-weather three-dimensional coordinates (longitude, latitude, altitude), speed and time information.

[0027] The low-orbit satellite 102 refers to an artificial satellite whose orbit is relatively close to the earth's surface. Generally, the orbital altitude of the low-orbit satellite 102 (e.g., 200-2000 km) is relatively low, and compared with high-orbit satellites (such as geostationary orbit satellites), low-orbit satellites have a shorter orbital period. This enables them to cover most areas of the earth in a short period of time, and because they are closer to the earth, the signal transmission loss is relatively small.

[0028] In the embodiment of the present application, the low-orbit satellite works in conjunction with the GNSS satellite and the ground station to play a key role in the inversion process of the ionospheric electron density. The low-orbit satellite can increase the number of ionospheric observation rays and improve the ray distribution, which is specifically manifested in the establishment of a second signal link between the low-orbit satellite and the GNSS satellite, and a third signal link between the low-orbit satellite and the ground station, thereby providing data support for more accurately solving the ionospheric tomography function.

[0029] The ground station 103 is a facility set on the surface of the earth for receiving and transmitting signals related to satellite communications. In an embodiment of the present application, the ground station can receive signals transmitted from GNSS satellites and low-orbit satellites. It plays an important role in the ionospheric electron density inversion system. On the one hand, it is one of the receiving ends of traditional ionospheric observation rays. On the other hand, when working in coordination with low-orbit satellites, it can increase the number of observation rays by establishing new signal links and provide raw observation data to the data center. These data can be used to invert the ionospheric electron density after processing. The ground station is usually equipped with professional satellite communication equipment, such as antennas, signal receivers, and data transmission devices, to ensure that satellite signals can be accurately received and processed.

[0030] The data center 104 may be a facility for centralized processing, storage and management of data from various satellites (GNSS satellites and low-orbit satellites) and ground stations. In the ionospheric electron density inversion system, the data center receives signal data transmitted from ground stations and low-orbit satellites. The data center integrates, analyzes and calculates these signal data to obtain the electron density value of the grid in the target area. The data center plays the role of a data hub in the entire system and is a key link in realizing the inversion of ionospheric electron density. It ensures the effective use of data and the smooth progress of the inversion process.

[0031] It should be noted that the ground station may be deployed with a ground station receiver, which is used to receive the first satellite signal transmitted by the GNSS satellite and may also be used to receive the second satellite signal transmitted by the low-orbit satellite. A satellite side receiver may be deployed on the low-orbit satellite side, which may be used to receive the third satellite signal transmitted by the GNSS satellite. The satellite side receiver may be a GNSS receiver. When the GNSS receiver receives the third satellite signal from the GNSS satellite, it will record the relevant parameters of the third satellite signal, such as the arrival time, phase, frequency and other information of the third satellite signal.

[0032] Among them, for the first satellite signal transmitted by the GNSS satellite and received by the ground station, its propagation path is: GNSS satellite->ionosphere->atmosphere->ground station receiver.

[0033] For the second satellite signal transmitted by the low-orbit satellite and received by the ground station, its propagation path is: low-orbit satellite -> ionosphere -> atmosphere -> ground station receiver. This is because after the second satellite signal is sent from the low-orbit satellite, it needs to pass through the ionosphere and atmosphere before it can be received by the ground station receiver deployed at the ground station.

[0034] For the third satellite signal transmitted by the GNSS satellite, its propagation path is: GNSS satellite -> ionosphere -> satellite-side receiver. The third satellite signal is sent from the GNSS satellite, also passes through the ionosphere, and is finally received by the satellite-side receiver on the low-orbit satellite side.

[0035] In a specific implementation, the ground station receiver can be a LEO (Low-Earth-Orbit) receiver. With its global flight characteristics in low-Earth orbit, LEO receivers can break through the visual limitations of ground stations and monitor the ionosphere over ocean areas. They can receive satellite signals from GNSS satellites or low-orbit satellites from different positions and angles, obtain rich observation data, and improve signal reception range and redundancy.

[0036] The communication method between the ground station receiver and the data center can be a wired communication method based on optical fiber, or a wireless communication method such as microwave communication, satellite communication link, etc.

[0037] The embodiment of the present application does not limit the communication method between the satellite side receiver and the data center. For example, the satellite side receiver first transmits the data of the third satellite signal to the ground station, and then the ground station transmits the data of the third satellite signal to the data center. Alternatively, the satellite side receiver can use the interplanetary link of the low-orbit satellite constellation to transmit the data of the third satellite signal to other low-orbit satellites that can communicate with the data center, thereby completing the data transmission.

[0038] Reference Figure 2 , showing a schematic diagram of observation rays in a time window of a tomography region of the ionosphere of an embodiment of the present application. Among them, the GNSS satellites specifically include: GNSS satellite i, GNSS satellite j and GNSS satellite k, etc. The low-orbit satellites specifically include: low-orbit satellite A, etc. The ground stations specifically include: ground station a, ground station b, ground station c and ground station d, etc.

[0039] The tomographic region can refer to a specific spatial range for layered analysis of the ionosphere. It is a three-dimensional spatial region that divides the ionosphere into small units according to the dimensions of altitude, longitude, latitude, etc. The divided unit area is the tomographic region. The tomographic region can be all or part of the target area.

[0040] The low-orbit satellite A passes through the tomography region. The observation rays appearing in the tomography region specifically include: The black solid line 201 represents the ray between the GNSS satellite and the ground station; The red, green, and blue solid lines 202 represent the rays that appear between the low-orbit satellite A and the ground station during its operation; The red, green and blue dashed lines 203 represent the rays that appear during the operation of the GNSS and the low-orbit satellite A.

[0041] The embodiment of the present application does not limit the length of the time window. For example, the length of the time window can be 1 hour.

[0042] Method Embodiment refer to Figure 3 , shows a schematic flow chart of the steps of an inversion method for ionospheric electron density according to an embodiment of the present application, and the method may specifically include the following steps: Step 301, determining a target area for electron density inversion; Step 302: Acquire observation data corresponding to signal links in the target area; the signal links specifically include: a first signal link from a GNSS satellite to a ground station, a second signal link from a GNSS satellite to a low-orbit satellite, and a third signal link from a low-orbit satellite to a ground station; Step 303: determining the oblique total electron content corresponding to the signal link according to the observation data corresponding to the signal link; Step 304: Solve the ionospheric tomography function according to the oblique total electron content corresponding to the above signal link to obtain the electron density value of the grid in the above target area; the above ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

[0043] The inversion method of ionospheric electron density of the embodiment of the present application can be used to obtain the electron density distribution in the three-dimensional space of the ionosphere. The method can be executed by a data center. Of course, the embodiment of the present application does not limit the specific execution subject of the method.

[0044] In step 301, the target area refers to a specific area that is pre-set and has a clear time and space range during the inversion process of the ionospheric electron density.

[0045] The embodiment of the present application determines the target area by means of a preset latitude range (such as 15°N–55°N), a preset longitude range (such as 70°E–130°E), and a preset altitude range (generally 100-2000 km). The preset longitude and latitude ranges specify the corresponding geographical location on the earth, and the preset altitude range covers the D layer, E layer, F layer, and other layers of the ionosphere.

[0046] As a unit structure divided based on a specific spatial resolution, the important role of the grid is to refine the vast target area to facilitate more accurate observation and analysis of the specific values, distribution differences and change trends of electron density at different horizontal geographical locations, thereby reflecting the characteristics of electron density changes caused by factors such as geographical environment.

[0047] The specific spatial resolution can be determined by those skilled in the art based on actual application requirements. In one example, the specific spatial resolution covers both horizontal resolution and elevation resolution. The horizontal resolution is set to 2.5° latitude * 5° longitude, and grid cells are divided according to this horizontal resolution with the help of longitude and latitude lines to achieve regional refinement. The elevation direction uses 50 kilometers as the elevation resolution. Starting from 100 kilometers, a grid is divided every 50 kilometers to help more finely grasp the changes in electron density at different positions and altitudes.

[0048] The target area corresponds to a specific time resolution, which is specifically expressed as time intervals of 5 minutes, 15 minutes, half an hour or 1 hour. The purpose is to continuously observe and record the dynamic changes of ionospheric electron density over time in the target area according to these time intervals, ensuring that the observation of electron density changes is also detailed and comprehensive enough on the time axis.

[0049] In step 302, in the presence of the ionosphere, when the satellite signals transmitted by the first signal link from the GNSS satellite to the ground station, the second signal link from the GNSS satellite to the low-orbit satellite, and the third signal link from the low-orbit satellite to the ground station pass through the ionosphere, the electrons in the ionosphere will produce effects such as refraction, delay, and phase change on the satellite signals. By using corresponding receivers to capture the characteristic changes of these satellite signals due to the influence of the ionosphere during the transmission of each signal link, the corresponding observation data can be obtained. These observation data reflect the influence of the ionosphere on the satellite signals, which can be used for subsequent inversion of the correlation analysis of the ionospheric electron density.

[0050] In the specific implementation, the characteristic changes include: changes in pseudorange observations due to the influence of geometric distance, clock error, tropospheric and ionospheric delays, hardware delays, and observation noise; and changes in carrier phase observations due to the above factors and wavelength, ambiguity, resulting in phase offset, fluctuation, ambiguity, etc.

[0051] In a specific implementation, the above observation data specifically includes: first signal link observation data, second signal link observation data and third signal link observation data; The first signal link observation data specifically includes: first pseudorange observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite, and first carrier phase observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite; The second signal link observation data specifically includes: second pseudorange observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite, and second carrier phase observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite; The third signal link observation data specifically includes: the third pseudo-range observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite And the third carrier phase observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite.

[0052] For the first signal link, the process of obtaining the observation data corresponding to the signal link in the target area specifically includes: Step A1, determining the first pseudorange observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite according to the geometric distance between the ground station receiver and the GNSS satellite, the clock error of the ground station receiver, the clock error of the GNSS satellite, the first tropospheric layer mapping function, the tropospheric zenith delay, the ionospheric delay of the GNSS satellite, the pseudorange hardware delay of the ground station receiver at frequency i and frequency j, the pseudorange hardware delay of the GNSS satellite at frequency i and frequency j, and the first pseudorange observation noise corresponding to the GNSS satellite; Step A2: Determine the first carrier phase observation value of frequency i and frequency j from the GNSS satellite received by the ground station receiver based on the geometric distance between the ground station receiver and the GNSS satellite, the clock error of the ground station receiver, the clock error of the GNSS, the first stratum mapping function, the tropospheric zenith delay, the ionospheric delay, the phase hardware delay of the ground station receiver at frequency i and frequency j, the phase hardware delay of the GNSS satellite at frequency i and frequency j, the wavelength of the GNSS satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the first signal link, and the first phase observation noise corresponding to the GNSS satellite.

[0053] Wherein, formula (1) shows the calculation process of the first pseudorange observation value.

[0054]

[0055] In formula (1), represents the first pseudorange observation value of frequency i received by the ground station receiver from the GNSS satellite; Indicates the geometric distance between the ground station receiver and the GNSS satellite; the geometric distance can be calculated based on the broadcast ephemeris information of the GNSS satellite and the position of the ground station receiver.

[0056] c represents the speed of light; Indicates the clock error of the ground station receiver. The ground station receiver can be compared with other reference clocks (such as the high-precision clock of the ground base station) to determine the clock error of the ground station receiver.

[0057] Indicates the clock error of the GNSS satellite. The GNSS satellite provides its own clock error in its broadcast ephemeris information.

[0058] Represents the first-layer mapping function; the first-layer mapping function is related to the delay characteristics of the troposphere and is usually determined based on local meteorological data (such as temperature, air pressure, humidity, etc.) and empirical models.

[0059] Represents the tropospheric zenith delay; the calculation method of the tropospheric zenith delay is similar to the tropospheric mapping function and also depends on meteorological data and empirical models.

[0060] Represents the ionospheric delay coefficient.

[0061] Represents the ionospheric delay of the GNSS satellite; the ionospheric delay can be estimated using an ionospheric model.

[0062] represents the pseudorange hardware delay of the ground station receiver at frequency i; the pseudorange hardware delay is usually determined by the hardware characteristics of the ground station receiver. In some high-precision positioning applications, the pseudorange hardware delay can be determined by calibration methods.

[0063] represents the pseudorange hardware delay of the GNSS satellite at frequency i; the pseudorange hardware delay of the GNSS satellite is usually provided by the satellite manufacturer.

[0064] Represents the first pseudorange observation noise corresponding to the GNSS satellite. This is a random error term, the size of which is related to the performance of the ground station receiver and the observation environment, and is usually determined by statistical methods during the positioning solution process.

[0065] Formula (2) shows the calculation process of the first carrier phase observation value.

[0066]

[0067] in, represents the first carrier phase observation value of frequency i received by the ground station receiver from the GNSS satellite; Represents the phase hardware delay of the ground station receiver at frequency i; its determination process is similar to that of the pseudorange hardware delay, which is determined by the hardware characteristics of the ground station receiver and may require calibration.

[0068] represents the phase hardware delay of the GNSS satellite at frequency i; it can be provided by the satellite manufacturer.

[0069] represents the wavelength of the GNSS satellite at frequency i, which is a known parameter determined by the satellite signal frequency.

[0070] Represents the ambiguity of frequency i on the first signal link; the ambiguity is usually an integer. During the positioning solution process, a search algorithm (such as least squares method, integer least squares method, etc.) can be used to determine the ambiguity.

[0071] It represents the first phase observation noise corresponding to the GNSS satellite. This is a random error term, and its processing method is similar to that of the first pseudorange observation noise.

[0072] For the second signal link, the process of obtaining the observation data corresponding to the signal link in the target area specifically includes: Step B1, determining the second pseudorange observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite according to the geometric distance between the low-orbit satellite and the GNSS satellite, the clock error of the low-orbit satellite, the clock error of the GNSS satellite, the ionospheric delay of the GNSS satellite, the pseudorange hardware delay of the low-orbit satellite at frequency i and frequency j, the pseudorange hardware delay of the GNSS satellite at frequency i and frequency j, and the second pseudorange observation noise corresponding to the GNSS satellite; Step B2: determine the second carrier phase observation value of frequency i and frequency j from the GNSS satellite received by the ground station receiver based on the geometric distance between the low-orbit satellite and the GNSS satellite, the clock error of the low-orbit satellite, the clock error of the GNSS, the ionospheric delay of the GNSS satellite, the phase hardware delay of the low-orbit satellite at frequency i and frequency j, the phase hardware delay of the GNSS satellite at frequency i and frequency j, the wavelength of the GNSS satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the second signal link, and the second phase observation noise corresponding to the GNSS satellite.

[0073] Wherein, formula (3) shows the calculation process of the second pseudorange observation value.

[0074] (3) in, represents the second pseudorange observation value; Indicates the geometric distance between the low-orbit satellite and the GNSS satellite; the geometric distance can be calculated based on the broadcast ephemeris information of the GNSS satellite and the broadcast ephemeris information of the low-orbit satellite.

[0075] Represents the clock error of a low-orbit satellite. A low-orbit satellite provides its own clock error in its broadcast ephemeris information.

[0076] Represents the ionospheric delay of the GNSS satellite.

[0077] represents the pseudorange hardware delay of the low-orbit satellite on frequency i. The pseudorange hardware delay of the low-orbit satellite is usually provided by the satellite manufacturer.

[0078] Represents the second pseudorange observation noise corresponding to the GNSS satellite, that is, the observation noise generated when the low-orbit satellite measures the second pseudorange observation value in the process of receiving the second satellite signal from the GNSS satellite. In one example, the process of determining the second pseudorange observation noise includes: first determining the actual pseudorange observation value corresponding to the second satellite signal; then, calculating the theoretical pseudorange observation value; then, determining the second pseudorange observation noise based on the actual pseudorange observation value and the theoretical pseudorange observation value, as well as the error equation. The error equation is a mathematical expression that not only simply calculates the error of each observation, but also links the error to other variables that may affect the observation results. These variables may include changes in the receiver position, changes in clock errors, etc.

[0079] Formula (4) shows the calculation process of the second carrier phase observation value.

[0080]

[0081] in, represents the second carrier phase observation value; represents the phase hardware delay of the low-orbit satellite at frequency i; represents the ambiguity of frequency i on the second signal link; It represents the second phase observation noise corresponding to the GNSS satellite, and its determination process refers to the determination process of the second pseudorange observation noise.

[0082] For the third signal link, the process of obtaining the observation data corresponding to the signal link in the target area specifically includes: Step C1, determining the third pseudorange observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite according to the geometric distance between the ground station receiver and the low-orbit satellite, the clock error of the ground station receiver, the clock error of the low-orbit satellite, the second tropospheric mapping function, the tropospheric zenith delay, the ionospheric delay of the low-orbit satellite, the pseudorange hardware delay of the ground station receiver at frequency i and frequency j, the pseudorange hardware delay of the low-orbit satellite at frequency i and frequency j, and the third pseudorange observation noise of the low-orbit satellite; Step C2: determine the third carrier phase observation value of frequency i and frequency j from the low-orbit satellite received by the ground station receiver based on the geometric distance between the ground station receiver and the low-orbit satellite, the clock error of the ground station receiver, the clock error of the low-orbit satellite, the second tropospheric mapping function, the tropospheric zenith delay, the ionospheric delay of the low-orbit satellite, the phase hardware delay of the ground station receiver at frequency i and frequency j, the phase hardware delay of the low-orbit satellite at frequency i and frequency j, the wavelength of the low-orbit satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the third signal link, and the third phase observation noise corresponding to the low-orbit satellite.

[0083] Wherein, formula (5) shows the calculation process of the third pseudorange observation value.

[0084] (5) in, represents the third pseudorange observation value of frequency i received by the ground station receiver from the low-orbit satellite; The geometric distance between the ground station receiver and the low-orbit satellite; represents the second tropospheric mapping function; represents the ionospheric delay of the low-orbit satellite; represents the pseudorange hardware delay of the ground station receiver on frequency i; represents the pseudorange hardware delay of the low-orbit satellite on frequency i; The third pseudorange observation noise of the low-orbit satellite is represented by the third pseudorange observation noise, and its determination process refers to the determination process of the second pseudorange observation noise.

[0085] Formula (6) shows the calculation process of the third carrier phase observation value.

[0086] represents the third carrier phase observation value of frequency i received by the ground station receiver from the low-orbit satellite; Represents the geometric distance between the ground station receiver and the low-orbit satellite; represents the phase hardware delay of the low-orbit satellite at frequency i; represents the wavelength of the low-orbit satellite at frequency i; represents the ambiguity of frequency i on the third signal link; It represents the third phase observation noise corresponding to the low-orbit satellite, and its determination process refers to the determination process of the second pseudorange observation noise.

[0087] In step 303, in the fields of satellite communication, satellite navigation, etc., satellite signals are affected by free electrons in the ionosphere when passing through the ionosphere. STEC (Slant Total Electron Content) refers to the total electron content in the column from the satellite to the receiver along the satellite signal propagation path (slant direction), which is an important ionospheric parameter.

[0088] In the embodiment of the present application, the observation data specifically includes: pseudorange observation values ​​and carrier phase observation values; the process of determining the oblique total electron content corresponding to the above-mentioned signal link according to the observation data corresponding to the above-mentioned signal link specifically includes: Step D1, determining a first geometry-independent combination corresponding to the pseudorange observation values ​​and a second geometry-independent combination corresponding to the carrier phase observation values ​​according to the pseudorange observation values ​​and the carrier phase observation values ​​corresponding to the signal link at different frequencies; Step D2: Determine the oblique total electron content corresponding to the signal link using a phase smoothing pseudorange method according to the first geometry-independent combination and the second geometry-independent combination at different epochs.

[0089] In step D1, GF (Geometry-Free) combination is a data combination method that mainly reflects the influence of non-geometric factors such as ionospheric delay by performing specific linear combination of observation data of different frequencies (such as pseudorange observations and carrier phase observations) in the process of satellite navigation and positioning data processing, so that the combined result is independent of geometric related factors such as the geometric distance between the satellite and the receiver, the clock difference between the satellite and the receiver, etc. The first pseudorange observations of frequency i and frequency j, and the first carrier phase observations of frequency i and frequency j can provide data support for the calculation of GF combination.

[0090] Formula (7) is a calculation formula for the first geometrically independent combination corresponding to the pseudorange observation value. The first geometrically independent combination corresponding to the pseudorange observation value is equal to the difference between the pseudorange observation values ​​of different frequencies; the first geometrically independent combination corresponding to the pseudorange observation value is also equal to the product of the ionospheric coefficient and the slant path ionospheric parameter minus the differential code deviation at both ends of the transmission.

[0091] Formula (8) is a calculation formula for the second geometrically independent combination corresponding to the carrier phase observation value. The second geometrically independent combination corresponding to the carrier phase observation value is equal to the difference between the carrier phase observation values ​​of different frequencies; the second geometrically independent combination corresponding to the carrier phase observation value is also equal to the product of the wavelength and the ambiguity of the geometrically independent combination minus the product of the ionospheric coefficient and the slant path ionospheric parameter.

[0092] (7) (8) in, represents the first geometrically independent combination; represents the ionospheric coefficient; represents the slant path ionospheric parameters; DCBr represents the differential code deviation at the receiving end; Indicates the differential code deviation at the transmitting end; represents the wavelength of the geometry-independent combination, which can be determined from the frequency of the satellite signal; represents the ambiguity of the geometry-independent combination, which can be obtained using the estimation algorithm.

[0093] , They represent the pseudorange observation values ​​at different frequencies. In satellite navigation systems, multiple frequencies are usually used for signal transmission. Signals of different frequencies have different propagation characteristics in the ionosphere. These are the original pseudorange observation data. The subscript r represents the receiving end, and the superscript s represents the transmitting end. 2 and 1 are used to distinguish the pseudorange observation values ​​corresponding to different frequencies. , They represent the carrier phase observation values ​​at different frequencies respectively.

[0094] (9) (10) f 1 Represents the first frequency among different frequencies, f 2 Represents the second frequency among different frequencies; VTEC (Vertical Total Electron Content) represents the total number of electrons in a column of unit cross-sectional area along the vertical direction in the ionosphere.

[0095] MF represents the ionospheric projection function, and its determination process is shown in formula (11).

[0096] (11) in, represents the height of the thin layer; Re represents the radius of the earth; represents the orbital altitude; Z represents the nadir angle.

[0097] In step D2, the phase-smoothed pseudorange method aims to combine the characteristics of pseudorange observations that have no integer ambiguity but low precision and carrier phase observations that have high precision but integer ambiguity. After obtaining the corresponding geometrically independent combinations of the two at different epochs, the high precision of the carrier phase observations is used to optimize the pseudorange observations. Since these geometrically independent combinations mainly reflect the ionospheric delay, and the ionospheric delay is related to the oblique total electron content, the oblique total electron content corresponding to the signal link can be determined more accurately.

[0098] In a specific implementation, step D2 determines the oblique total electron content corresponding to the signal link using a phase smoothing pseudorange method according to the first geometry-independent combination and the second geometry-independent combination at different epochs, and specifically includes: Step D21, determining the phase smoothed pseudoranges at different epoch times according to the first geometry-independent combination and the second geometry-independent combination at different epoch times; Step D22, solving the slant path ionosphere parameters and the differential code deviations at both ends of the transmission according to the phase smoothed pseudoranges corresponding to different epochs and the corresponding relationship between the phase smoothed pseudoranges and the slant path ionosphere parameters and the differential code deviations at both ends of the transmission; Step D23, determining the total oblique electron content of the signal link at the preset epoch time according to the phase smoothed pseudorange corresponding to the preset epoch time and the differential code deviation at both ends of the transmission.

[0099] In step D21, the epoch is a time reference point, which refers to a specific moment or the starting point of a time period selected when performing observation or data processing.

[0100] At different epochs, the first geometry-independent combination and the second geometry-independent combination play an important role. The first geometry-independent combination is based on pseudorange observations, and the second geometry-independent combination is based on carrier phase observations. They have removed or reduced the impact of geometry-related factors, focusing on non-geometric factors such as ionospheric delay. Combining the two, the high-precision characteristics of carrier phase observations can be used to smooth the pseudorange observations, thereby obtaining phase-smoothed pseudoranges at different epochs.

[0101] The phase smoothed pseudorange corresponding to epoch time k+1 is specifically shown in formula (12).

[0102] (12) Wherein, k is a positive integer; represents the phase smoothed pseudorange at the k+1th epoch; represents the first geometrically independent combination; represents the second geometrically independent combination; represents the average of the differences between the first geometrically independent and second geometrically independent combinations over the first k epochs; represents the ionospheric coefficient; represents the slant path ionospheric parameters; Indicates the differential code deviation at the receiving end; Indicates the differential code deviation of the transmitting end. It should be noted that the differential code deviation of the two transmission segments can remain unchanged within a time period (such as 24 hours).

[0103] In step D22, formula (7) presents the relationship between the first geometrically independent combination and the slant path ionosphere parameters, the differential code bias of the receiving end, and the differential code bias of the transmitting end. Formula (8) presents the relationship between the second geometrically independent combination and the slant path ionosphere parameters, wavelength, ambiguity, etc. Formula (12) presents a more detailed computational relationship between the phase smoothed pseudorange and the slant path ionosphere parameters, the differential code bias of the receiving end and the transmitting end at different epochs.

[0104] Based on formula (7), formula (8) and formula (12), the embodiment of the present application can construct a group of equations with the slant path ionospheric parameters and the differential code deviations at both ends of the transmission as unknown variables, and solve the group of equations using methods such as the least squares method to obtain specific results of the slant path ionospheric parameters and the differential code deviations at both ends of the transmission.

[0105] In step D23, because there is a certain correspondence between the oblique total electron content and the phase smoothing pseudorange and the differential code deviation at both ends of the transmission, the oblique total electron content of the signal link at the preset epoch time can be determined based on the correspondence.

[0106] Formula (13) shows an example of the correspondence between the total slant electron content, the phase smoothed pseudorange, and the differential code deviation at both ends of the transmission. This correspondence subtracts the differential code deviation at both ends of the transmission from the phase smoothed pseudorange corresponding to the preset epoch time to obtain the total slant electron content of the signal link at the preset epoch time.

[0107] (13) in, Indicates the total electron content in the oblique direction at the preset epoch. Indicates the phase smoothed pseudorange at the preset epoch.

[0108] In the entire processing flow, the determination of the preset epoch moment is not fixed, but rather has considerable flexibility, and can be judged and selected by personnel familiar with the professional knowledge and technology in this field according to actual application requirements.

[0109] Generally speaking, the more epochs involved in the smoothing operation, the smaller the noise contained in the resulting phase-smoothed pseudorange will be. This is a very important characteristic basis for improving data quality.

[0110] Based on the above characteristics, in some specific cases, in order to obtain higher quality and better quality data, a data screening strategy will be adopted, that is, discarding the first p STEC values ​​and retaining Np STEC values. Here, N has a clear meaning. It represents the total number of epoch moments in a complete time period, covering all epoch situations that can be considered and processed in the period; and p represents the number of epoch moments that need to be discarded. Its specific value is not fixed and can be determined by professional and technical personnel in this field according to actual conditions, such as the overall characteristics of the data, the accuracy requirements of subsequent calculations and analysis, and past practical experience. By selectively discarding and retaining the STEC values ​​corresponding to some epochs, the entire processing flow can be optimized, thereby ensuring that the subsequent related calculations and analyses can be carried out smoothly based on more reasonable and accurate data.

[0111] It should be noted that the above-mentioned method of using phase smoothing pseudorange to determine the oblique total electron content corresponding to the signal link is only an optional embodiment of the method for determining the oblique total electron content, and is not to be understood as a limitation of the method for determining the oblique total electron content. In fact, those skilled in the art may use other methods to determine the oblique total electron content. For example, other methods may include: non-differential non-combination method, or ambiguity fixed solution method, etc.

[0112] Among them, the non-difference non-combination method directly uses dual-frequency observations to determine the oblique total electron content. It does not perform linear combination operations to eliminate errors such as ionosphere errors, but instead comprehensively considers many factors such as the geometric distance between the satellite and the receiver, satellite clock error, receiver clock error, ionospheric delay and tropospheric delay based on the original observation data. In the processing process, the approximate value of the geometric distance is obtained through the satellite ephemeris, and the tropospheric delay model is used to process the tropospheric delay. Then, based on the intrinsic relationship between ionospheric delay and STEC, combined with reasonable estimates of other factors, STEC is solved.

[0113] The ambiguity fixation solution method mainly relies on the integer ambiguity in the carrier phase observation. In the carrier phase observation, the phase observation value of the integer ambiguity and the fractional part are included. For dual-frequency carrier phase observation, it is necessary to consider factors such as geometric distance, satellite clock error, receiver clock error, ionospheric delay, tropospheric delay, etc. to construct the observation equation. The key to this method is to fix the integer ambiguity, and through techniques such as wide lane combination and narrow lane combination, the integer ambiguity is determined as a known quantity. After that, combined with the treatment of other errors such as tropospheric delay, STEC is solved according to the observation equation. Because the carrier phase observation accuracy is relatively high, when the integer ambiguity is fixed accurately, a higher-precision STEC result can be obtained.

[0114] In step 304, the ionospheric tomography function is solved according to the oblique total electron content corresponding to the above signal link to obtain the electron density value of the grid in the above target area.

[0115] The total oblique electron content reflects the total amount of electrons accumulated along the direction of the signal link when the satellite signal passes through the ionosphere. The ionospheric tomography function characterizes the mapping relationship between the total oblique electron content and the electron density value of the grid. The ionosphere can be imagined as a three-dimensional structure composed of many small grids, each with its own electron density value. When the satellite signal passes through the ionosphere, the signal link passes through these grids.

[0116] Assuming that the ionosphere is divided into L×m×h grids at equal intervals, that is, divided in longitude, latitude and altitude, the electrons in a single grid are considered to be uniformly distributed in a short period of time, and the electron density value at the center of the grid can be solved. L, m, and h can all be positive integers.

[0117] As shown in formula (14), for the signal link from ground station receiver k to low-orbit satellite s, the total slant electron content is equal to the integral of the electron density on the link: (14) in, It represents the total slant electron content on the signal link from the ground station receiver to the low-orbit satellite; represents the electron density value; represents the line element along the integration path, that is, a small length on the integration path.

[0118] Discretize formula (14): It is equivalent to the sum of the products of the intercept of the signal link passing through the inside of the grid and the electron density value corresponding to the grid: (15) in, Indicates the first A grid, and They represent the intercept of the signal link passing through a certain grid and the electron density of the corresponding grid respectively; represents the error term.

[0119] Collect all link information in the tomography area of ​​the ionosphere and construct the ionosphere tomography function: (16) Where m is the total number of signal links, n is the total number of grids, The column vector formed by the total diagonal electron content of the signal link; Represents the column vector corresponding to the electron density value to be solved; Represents the intercept of the signal link passing inside the grid.

[0120] In a specific implementation, the process of determining the intercept of the first signal link passing through the grid includes: determining the position of the GNSS satellite based on the broadcast ephemeris information of the GNSS satellite; determining the altitude angle, azimuth angle and ionospheric piercing point coordinates corresponding to the first signal link based on the position of the GNSS satellite and the position of the ground station; determining the intercept of the first signal link passing through the grid based on the altitude angle, azimuth angle and ionospheric piercing point coordinates corresponding to the first signal link.

[0121] First, the coordinates of the ionospheric puncture point define the specific spatial position of the first signal link entering the ionosphere. The altitude angle and azimuth reflect the extension direction of the first signal link in space, that is, the angle information of its spatial direction. In this way, based on the spatial geometric relationship, the coordinates of the ionospheric puncture point can be used as the starting point, and the straight line equation can be constructed according to the extension direction of the signal link, and then the coordinates of the intersection of the straight line equation and the grid boundary can be obtained. On this basis, according to the distance formula between two points, the intercept of the first signal link inside the grid can be accurately calculated based on the obtained intersection coordinates.

[0122] In a specific implementation, the process of determining the intercept of the second signal link passing through the grid includes: determining the position of the GNSS satellite based on the broadcast ephemeris information of the GNSS satellite; determining the position of the low-orbit satellite based on the broadcast ephemeris information of the low-orbit satellite; determining the altitude angle, azimuth angle and ionospheric piercing point coordinates corresponding to the second signal link based on the position of the GNSS satellite and the position of the low-orbit satellite; determining the intercept of the second signal link passing through the grid based on the altitude angle, azimuth angle and ionospheric piercing point coordinates corresponding to the second signal link.

[0123] In a specific implementation, the process of determining the intercept of the third signal link passing through the grid includes: determining the position of the low-orbit satellite based on the broadcast ephemeris information of the low-orbit satellite; determining the altitude angle, azimuth angle and ionospheric piercing point coordinates corresponding to the third signal link based on the position of the low-orbit satellite and the position of the ground station; determining the intercept of the third signal link passing through the grid based on the altitude angle, azimuth angle and ionospheric piercing point coordinates corresponding to the third signal link.

[0124] The embodiment of the present application may use an iterative algorithm or a non-iterative algorithm to solve the ionospheric tomography function.

[0125] Among them, the iterative algorithms specifically include: additive algebraic reconstruction algorithm, multiplicative algebraic reconstruction algorithm, etc.; the non-iterative algorithms specifically include: matrix singular value method, Kalman filtering, etc.

[0126] When the additive algebraic reconstruction algorithm is used, the solution of the ionospheric tomography function can be expressed as: (17) in, Indicates STEC rays; Indicates A grid; Indicates the number of iterations; Represents the relaxation factor, with a value range of ; Indicates STEC rays in The intercept within the grid. It represents the electron density value of the jth grid after k+1 iterations. The solution of the ionospheric tomography function can be specifically: the electron density value of each grid in the tomography area.

[0127] The electron density values ​​of each grid in the tomography area can be used for ionosphere-related research and practical application scenarios. In ionosphere-related research, the electron density value is the key to building an ionosphere model, which helps to understand the structure and characteristics of the ionosphere, and can also be used to study ionosphere physical processes. In satellite communication scenarios, electron density values ​​can be used to predict signal propagation and compensate for signal delays to improve communication quality; in satellite navigation scenarios, electron density values ​​can be used to calculate ionosphere delays and improve positioning accuracy. Electron density values ​​can also be used to monitor ionosphere changes caused by solar activity, and can also be used to establish early warning models to provide early warning services for related industries and reduce losses from space weather disasters.

[0128] In summary, the inversion method of the ionospheric electron density of the embodiment of the present application optimizes the number and distribution of observation rays in the ionosphere by introducing low-orbit satellites. On the one hand, at the space orbit level, a second signal link is established between the low-orbit satellite and the GNSS satellite, increasing the number of observation rays between the GNSS and the low-orbit satellite. On the other hand, in the dimension of space-to-earth communication, a third signal link is established between the low-orbit satellite and the ground station, increasing the number of observation rays between the low-orbit satellite and the ground station. On the other hand, the dynamic operation characteristics of the low-orbit satellite improve the distribution of observation rays in the tomography area.

[0129] The optimization of the number and distribution of the above-mentioned ionospheric observation rays can provide richer and more optimally laid out data resources for solving the ionospheric tomography function. Therefore, the embodiment of the present application can effectively overcome the ill-posed problem of solving the ionospheric tomography equation caused by the insufficient number and uneven distribution of ionospheric observation rays. On this basis, the embodiment of the present application can improve the inversion accuracy of the electron density.

[0130] It should be noted that, for the method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the embodiments of the present application are not limited by the described order of actions, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0131] Based on the above embodiment, this embodiment also provides an ionospheric electron density inversion device, referring to Figure 4 As shown in the structural schematic diagram, the device specifically includes: a region determination module 401, an observation data acquisition module 402, a link electron content determination module 403 and an electron density solution module 404.

[0132] Wherein, the region determination module 401 is used to determine the target region for electron density inversion; An observation data acquisition module 402 is used to acquire observation data corresponding to a signal link in a target area; the signal link includes: a first signal link from a GNSS satellite to a ground station, a second signal link from a GNSS satellite to a low-orbit satellite, and a third signal link from a low-orbit satellite to a ground station; A link electron content determination module 403 is used to determine the oblique total electron content corresponding to the signal link according to the observation data corresponding to the signal link; The electron density solving module 404 is used to solve the ionospheric tomography function according to the oblique total electron content corresponding to the signal link to obtain the electron density value of the grid in the target area; the ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

[0133] Optionally, the observation data includes: first signal link observation data, second signal link observation data and third signal link observation data; The first signal link observation data includes: first pseudorange observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite, and first carrier phase observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite; The second signal link observation data includes: second pseudorange observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite, and second carrier phase observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite; The third signal link observation data includes: the third pseudo-range observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite And the third carrier phase observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite.

[0134] Optionally, the observation data acquisition module 402 includes: A first observation data acquisition module is used to determine the first pseudorange observation value of frequency i and frequency j received by the ground station receiver from the GNSS satellite according to the geometric distance between the ground station receiver and the GNSS satellite, the clock error of the ground station receiver, the clock error of the GNSS satellite, the first stratus mapping function, the tropospheric zenith delay, the ionospheric delay of the GNSS satellite, the pseudorange hardware delay of the ground station receiver at frequency i and frequency j, the pseudorange hardware delay of the GNSS satellite at frequency i and frequency j, and the first pseudorange observation noise corresponding to the GNSS satellite; The second observation data acquisition module is used to determine the first carrier phase observation value of frequency i and frequency j from the GNSS satellite received by the ground station receiver based on the geometric distance between the ground station receiver and the GNSS satellite, the clock error of the ground station receiver, the clock error of the GNSS, the first stratum mapping function, the tropospheric zenith delay, the ionospheric delay, the phase hardware delay of the ground station receiver at frequency i and frequency j, the phase hardware delay of the GNSS satellite at frequency i and frequency j, the wavelength of the GNSS satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the first signal link, and the first phase observation noise corresponding to the GNSS satellite.

[0135] Optionally, the observation data acquisition module 402 includes: A third observation data acquisition module is used to determine the second pseudorange observation value of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite according to the geometric distance between the low-orbit satellite and the GNSS satellite, the clock error of the low-orbit satellite, the clock error of the GNSS satellite, the ionospheric delay of the GNSS satellite, the pseudorange hardware delay of the low-orbit satellite at frequency i and frequency j, the pseudorange hardware delay of the GNSS satellite at frequency i and frequency j, and the second pseudorange observation noise corresponding to the GNSS satellite; The fourth observation data acquisition module is used to determine the second carrier phase observation value of frequency i and frequency j from the GNSS satellite received by the ground station receiver based on the geometric distance between the low-orbit satellite and the GNSS satellite, the clock error of the low-orbit satellite, the clock error of the GNSS, the ionospheric delay of the GNSS satellite, the phase hardware delay of the low-orbit satellite at frequency i and frequency j, the phase hardware delay of the GNSS satellite at frequency i and frequency j, the wavelength of the GNSS satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the second signal link, and the second phase observation noise corresponding to the GNSS satellite.

[0136] Optionally, the observation data acquisition module 402 includes: a fifth observation data acquisition module, for determining the third pseudorange observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite according to the geometric distance between the ground station receiver and the low-orbit satellite, the clock error of the ground station receiver, the clock error of the low-orbit satellite, the second tropospheric mapping function, the tropospheric zenith delay, the ionospheric delay of the low-orbit satellite, the pseudorange hardware delay of the ground station receiver at frequency i and frequency j, the pseudorange hardware delay of the low-orbit satellite at frequency i and frequency j, and the third pseudorange observation noise corresponding to the low-orbit satellite; The sixth observation data acquisition module is used to determine the third carrier phase observation value of frequency i and frequency j from the low-orbit satellite received by the ground station receiver based on the geometric distance between the ground station receiver and the low-orbit satellite, the clock error of the ground station receiver, the clock error of the low-orbit satellite, the second tropospheric mapping function, the tropospheric zenith delay, the ionospheric delay of the low-orbit satellite, the phase hardware delay of the ground station receiver at frequency i and frequency j, the phase hardware delay of the low-orbit satellite at frequency i and frequency j, the wavelength of the low-orbit satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the third signal link, and the third phase observation noise corresponding to the low-orbit satellite.

[0137] Optionally, the observation data includes: pseudorange observation values ​​and carrier phase observation values; the link electronic content determination module 403 includes: A geometry-independent combination determination module, used to determine a first geometry-independent combination corresponding to the pseudorange observation value and a second geometry-independent combination corresponding to the carrier phase observation value according to the pseudorange observation values ​​and the carrier phase observation values ​​corresponding to the signal link at different frequencies; The phase smoothed pseudorange processing module is used to determine the oblique total electron content corresponding to the signal link using a phase smoothed pseudorange method according to a first geometrically independent combination and a second geometrically independent combination at different epochs.

[0138] Optionally, the phase smoothing pseudorange processing module includes: A phase smoothed pseudorange determination module, used to determine the phase smoothed pseudoranges at different epoch times according to the first geometry-independent combination and the second geometry-independent combination at different epoch times; A differential code deviation solving module is used to solve the slant path ionosphere parameters and the differential code deviations at both ends of the transmission according to the phase smoothed pseudoranges corresponding to different epochs and the corresponding relationship between the phase smoothed pseudoranges and the slant path ionosphere parameters and the differential code deviations at both ends of the transmission; The oblique total electron content calculation module is used to determine the oblique total electron content of the signal link at a preset epoch time according to the phase smoothing pseudorange corresponding to the preset epoch time and the differential code deviation at both ends of the transmission.

[0139] Optionally, the phase smoothed pseudorange corresponding to the epoch time k+1 is specifically:

[0140] Wherein, k is a positive integer; represents the phase smoothed pseudorange at the k+1th epoch; represents the first geometrically independent combination; represents the second geometrically independent combination; represents the average of the differences between the first geometrically independent and second geometrically independent combinations over the first k epochs; represents the ionospheric coefficient; represents the slant path ionospheric parameters; Indicates the differential code deviation at the receiving end; Indicates the differential code deviation at the transmitting end.

[0141] Optionally, the oblique total electron content calculation module is specifically used to subtract the differential code deviation at both ends of the transmission from the phase smoothed pseudorange corresponding to the preset epoch time to obtain the oblique total electron content of the signal link at the preset epoch time.

[0142] Optionally, the first geometry-independent combination corresponding to the pseudorange observation value is equal to the difference between pseudorange observation values ​​of different frequencies; the first geometry-independent combination corresponding to the pseudorange observation value is also equal to the product of the ionospheric coefficient and the slant path ionospheric parameter minus the differential code deviation at both ends of the transmission; The second geometrically independent combination corresponding to the carrier phase observation value is equal to the difference between the carrier phase observation values ​​of different frequencies; the second geometrically independent combination corresponding to the carrier phase observation value is also equal to the product of the wavelength and the ambiguity of the geometrically independent combination minus the product of the ionospheric coefficient and the slant path ionospheric parameter.

[0143] Optionally, the ionospheric tomography function is specifically:

[0144] Where m is the total number of signal links, n is the total number of grids, The column vector formed by the total diagonal electron content of the signal link; Represents the column vector corresponding to the electron density value to be solved; Represents the intercept of the signal link passing inside the grid.

[0145] Optionally, the process of determining the intercept of the first signal link passing through the interior of the grid includes: Determine the position of the GNSS satellite according to the broadcast ephemeris information of the GNSS satellite; determine the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the first signal link according to the position of the GNSS satellite and the position of the ground station; According to the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the first signal link, the intercept of the first signal link passing through the inside of the grid is determined.

[0146] Optionally, the process of determining the intercept of the second signal link passing through the inside of the grid includes: Determine the position of the GNSS satellite according to the broadcast ephemeris information of the GNSS satellite; determine the position of the low-orbit satellite according to the broadcast ephemeris information of the low-orbit satellite; determine the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the second signal link according to the position of the GNSS satellite and the position of the low-orbit satellite; According to the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the second signal link, the intercept of the second signal link passing through the inside of the grid is determined.

[0147] Optionally, the process of determining the intercept of the third signal link passing through the inside of the grid includes: Determine the position of the low-orbit satellite according to the broadcast ephemeris information of the low-orbit satellite; determine the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the third signal link according to the position of the low-orbit satellite and the position of the ground station; According to the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the third signal link, the intercept of the third signal link passing through the inside of the grid is determined.

[0148] The embodiment of the present application further provides a non-volatile readable storage medium, in which one or more modules (programs) are stored. When the one or more modules are applied to a device, the device can execute instructions (instructions) of each method step in the embodiment of the present application.

[0149] The present application embodiment provides one or more machine-readable media, on which instructions are stored, and when executed by one or more processors, an electronic device executes one or more of the methods described in the above embodiments. In the present application embodiment, the electronic device includes various types of devices such as terminal devices, servers (clusters), etc.

[0150] In another embodiment of the present invention, a computer program product including instructions is provided. When the computer program product is run on a computer, the computer is enabled to execute any of the methods described in the above embodiments.

[0151] The embodiments of the present disclosure may be implemented as a device that uses any appropriate hardware, firmware, software, or any combination thereof to perform a desired configuration, and the device may include: electronic devices such as terminal devices and servers (clusters). Figure 5 An exemplary apparatus 1100 that can be used to implement various embodiments described in this application is schematically shown.

[0152] For one embodiment, Figure 5 An exemplary apparatus 1100 is shown having one or more processors 1102, a control module (chip set) 1104 coupled to at least one of the processor(s) 1102, a memory 1106 coupled to the control module 1104, a non-volatile memory / storage device 1108 coupled to the control module 1104, one or more input / output devices 1110 coupled to the control module 1104, and a network interface 1112 coupled to the control module 1104.

[0153] The processor 1102 may include one or more single-core or multi-core processors, and the processor 1102 may include any combination of general-purpose processors or special-purpose processors (such as graphics processors, application processors, baseband processors, etc.). In some embodiments, the device 1100 can be used as a terminal device, server (cluster), etc. described in the embodiments of the present application.

[0154] In some embodiments, the apparatus 1100 may include one or more computer-readable media (e.g., memory 1106 or non-volatile memory / storage device 1108) having instructions 1114 and one or more processors 1102 combined with the one or more computer-readable media and configured to execute the instructions 1114 to implement a module to perform the actions described in the present disclosure.

[0155] For one embodiment, the control module 1104 may include any suitable interface controller to provide any suitable interface to at least one of the processor(s) 1102 and / or any suitable device or component in communication with the control module 1104 .

[0156] The control module 1104 may include a memory controller module to provide an interface to the memory 1106. The memory controller module may be a hardware module, a software module, and / or a firmware module.

[0157] The memory 1106 may be used, for example, to load and store data and / or instructions 1114 for the device 1100. For one embodiment, the memory 1106 may include any suitable volatile memory, such as a suitable DRAM (Dynamic Random Access Memory). In some embodiments, the memory 1106 may include a double data rate type four synchronous dynamic random access memory.

[0158] For one embodiment, the control module 1104 may include one or more input / output controllers to provide an interface to the non-volatile memory / storage device 1108 and the input / output device(s) 1110 .

[0159] For example, non-volatile memory / storage 1108 may be used to store data and / or instructions 1114. Non-volatile memory / storage 1108 may include any suitable non-volatile memory (e.g., flash memory) and / or may include any suitable non-volatile storage device(s) (e.g., one or more hard disk drives, one or more optical disk drives, and / or one or more digital versatile optical disk drives).

[0160] The non-volatile memory / storage device 1108 may include storage resources that are physically part of the device on which the apparatus 1100 is installed, or it may be accessible to the device without being part of the device. For example, the non-volatile memory / storage device 1108 may be accessed via (one or more) input / output devices 1110 over a network.

[0161] The input / output device(s) 1110 may provide an interface for the apparatus 1100 to communicate with any other appropriate device, and the input / output device 1110 may include a communication component, an audio component, a sensor component, etc. The network interface 1112 may provide an interface for the apparatus 1100 to communicate through one or more networks, and the apparatus 1100 may wirelessly communicate with one or more components of a wireless network according to any of one or more wireless network standards and / or protocols, for example, accessing a wireless network based on a communication standard, such as WiFi (Wireless Fidelity), 2G (2nd Generation Wireless Telephone Technology), 3G (3rd Generation Wireless Telephone Technology), 4G (4th Generation Wireless Telephone Technology), 5G (5th Generation Wireless Telephone Technology), etc., or a combination thereof for wireless communication.

[0162] For one embodiment, at least one of the processor(s) 1102 may be packaged together with the logic of one or more controllers (e.g., a memory controller module) of the control module 1104. For one embodiment, at least one of the processor(s) 1102 may be packaged together with the logic of one or more controllers of the control module 1104 to form a system-in-package. For one embodiment, at least one of the processor(s) 1102 may be integrated on the same die with the logic of one or more controllers of the control module 1104. For one embodiment, at least one of the processor(s) 1102 may be integrated on the same die with the logic of one or more controllers of the control module 1104 to form a system-on-chip.

[0163] In various embodiments, the device 1100 may be, but is not limited to, a terminal device such as a server, a desktop computing device, or a mobile computing device (e.g., a laptop computing device, a handheld computing device, a touch screen device, a netbook, etc.). In various embodiments, the device 1100 may have more or fewer components and / or a different architecture. For example, in some embodiments, the device 1100 includes one or more cameras, a keyboard, a liquid crystal display screen (including a touch screen display), a non-volatile memory port, multiple antennas, a graphics chip, a dedicated integrated circuit, and a speaker.

[0164] Among them, the main control chip can be used as a processor or control module in the detection device, sensor data, location information, etc. are stored in a memory or non-volatile memory / storage device, the sensor group can be used as an input / output device, and the communication interface may include a network interface.

[0165] As for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0166] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0167] The present application embodiment is described with reference to the flowchart and / or block diagram of the method, terminal device (system) and computer program product according to the embodiment of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, and the combination of the process and / or box in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing terminal device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device produce a device for implementing the function specified in one process or multiple processes in the flowchart and / or one box or multiple boxes in the block diagram.

[0168] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0169] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device so that a series of operating steps are executed on the computer or other programmable terminal device to produce computer-implemented processing, so that the instructions executed on the computer or other programmable terminal device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0170] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0171] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0172] The above is a detailed introduction to an ionospheric electron density inversion method, device and system, an electronic device and a machine-readable medium provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation methods and application sets. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for inverting ionospheric electron density, characterized in that: The method comprises: Determine the target area for electron density inversion; Acquire observation data corresponding to signal links in the target area; the signal links include: a first signal link from a GNSS satellite to a ground station, a second signal link from a GNSS satellite to a low-orbit satellite, and a third signal link from a low-orbit satellite to a ground station; Determining the oblique total electron content corresponding to the signal link according to the observation data corresponding to the signal link; According to the oblique total electron content corresponding to the signal link, the ionospheric tomography function is solved to obtain the electron density value of the grid in the target area; the ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

2. The method according to claim 1, characterized in that The observation data includes: first signal link observation data, second signal link observation data and third signal link observation data; The first signal link observation data includes: first pseudorange observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite, and first carrier phase observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite; The second signal link observation data includes: second pseudorange observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite, and second carrier phase observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite; The third signal link observation data includes: the third pseudo-range observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite And the third carrier phase observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite.

3. The method according to claim 2, characterized in that The obtaining of observation data corresponding to the signal link in the target area includes: Determine the first pseudorange observation value of frequency i and frequency j received by the ground station receiver from the GNSS satellite according to the geometric distance between the ground station receiver and the GNSS satellite, the clock error of the ground station receiver, the clock error of the GNSS satellite, the first tropospheric layer mapping function, the tropospheric zenith delay, the ionospheric delay of the GNSS satellite, the pseudorange hardware delay of the ground station receiver at frequency i and frequency j, the pseudorange hardware delay of the GNSS satellite at frequency i and frequency j, and the first pseudorange observation noise corresponding to the GNSS satellite; The first carrier phase observation value of frequency i and frequency j from the GNSS satellite received by the ground station receiver is determined based on the geometric distance between the ground station receiver and the GNSS satellite, the clock error of the ground station receiver, the clock error of the GNSS, the first stratus mapping function, the tropospheric zenith delay, the ionospheric delay, the phase hardware delay of the ground station receiver at frequency i and frequency j, the phase hardware delay of the GNSS satellite at frequency i and frequency j, the wavelength of the GNSS satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the first signal link, and the first phase observation noise corresponding to the GNSS satellite.

4. The method according to claim 2, characterized in that: The obtaining of observation data corresponding to the signal link in the target area includes: Determine the second pseudorange observation value of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite according to the geometric distance between the low-orbit satellite and the GNSS satellite, the clock error of the low-orbit satellite, the clock error of the GNSS satellite, the ionospheric delay of the GNSS satellite, the pseudorange hardware delay of the low-orbit satellite at frequency i and frequency j, the pseudorange hardware delay of the GNSS satellite at frequency i and frequency j, and the second pseudorange observation noise corresponding to the GNSS satellite; Based on the geometric distance between the low-orbit satellite and the GNSS satellite, the clock error of the low-orbit satellite, the clock error of the GNSS, the ionospheric delay of the GNSS satellite, the phase hardware delay of the low-orbit satellite at frequency i and frequency j, the phase hardware delay of the GNSS satellite at frequency i and frequency j, the wavelength of the GNSS satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the second signal link, and the second phase observation noise corresponding to the GNSS satellite, the second carrier phase observation value of frequency i and frequency j from the GNSS satellite received by the ground station receiver is determined.

5. The method according to claim 2, characterized in that: The obtaining of observation data corresponding to the signal link in the target area includes: Determine the third pseudorange observation value of frequency i and frequency j from the low-orbit satellite received by the ground station receiver according to the geometric distance between the ground station receiver and the low-orbit satellite, the clock error of the ground station receiver, the clock error of the low-orbit satellite, the second tropospheric mapping function, the tropospheric zenith delay, the ionospheric delay of the low-orbit satellite, the pseudorange hardware delay of the ground station receiver at frequency i and frequency j, the pseudorange hardware delay of the low-orbit satellite at frequency i and frequency j, and the third pseudorange observation noise corresponding to the low-orbit satellite; According to the geometric distance between the ground station receiver and the low-orbit satellite, the clock error of the ground station receiver, the clock error of the low-orbit satellite, the second tropospheric mapping function, the tropospheric zenith delay, the ionospheric delay of the low-orbit satellite, the phase hardware delay of the ground station receiver at frequency i and frequency j, the phase hardware delay of the low-orbit satellite at frequency i and frequency j, the wavelength of the low-orbit satellite at frequency i and frequency j, the ambiguity of frequency i and frequency j on the third signal link, and the third phase observation noise corresponding to the low-orbit satellite, the third carrier phase observation value of frequency i and frequency j from the low-orbit satellite received by the ground station receiver is determined.

6. The method according to claim 1, characterized in that The observation data includes: pseudorange observation values ​​and carrier phase observation values; and determining the oblique total electron content corresponding to the signal link according to the observation data corresponding to the signal link includes: Determine, according to the pseudorange observation values ​​and carrier phase observation values ​​corresponding to the signal link at different frequencies, a first geometry-independent combination corresponding to the pseudorange observation values ​​and a second geometry-independent combination corresponding to the carrier phase observation values; According to the first geometrically independent combination and the second geometrically independent combination at different epochs, the oblique total electron content corresponding to the signal link is determined by using a phase smoothing pseudorange method.

7. The method according to claim 6, characterized in that Determining the oblique total electron content corresponding to the signal link by using a phase smoothing pseudorange method according to the first geometrically independent combination and the second geometrically independent combination at different epochs includes: Determine the phase smoothed pseudoranges at different epoch times according to the first geometry-independent combination and the second geometry-independent combination at different epoch times; According to the phase smoothed pseudorange corresponding to different epochs, and the corresponding relationship between the phase smoothed pseudorange and the ionospheric parameters of the slant path and the differential code deviations at both ends of the transmission, the ionospheric parameters of the slant path and the differential code deviations at both ends of the transmission are solved; The total oblique electron content of the signal link at the preset epoch time is determined according to the phase smoothed pseudorange corresponding to the preset epoch time and the differential code deviation at both ends of the transmission.

8. The method according to claim 7, characterized in that The phase smoothed pseudorange corresponding to epoch time k+1 is: Wherein, k is a positive integer; represents the phase smoothed pseudorange at the k+1th epoch; represents the first geometrically independent combination; represents the second geometrically independent combination; represents the average of the differences between the first geometrically independent and second geometrically independent combinations over the first k epochs; represents the ionospheric coefficient; represents the slant path ionospheric parameters; Indicates the differential code deviation at the receiving end; Indicates the differential code deviation at the transmitting end.

9. The method according to claim 7, characterized in that: Determining the oblique total electron content of the signal link at the preset epoch time according to the phase smoothed pseudorange at the preset epoch time and the differential code deviation at both ends of the transmission includes: The phase smoothed pseudorange corresponding to the preset epoch time is subtracted from the differential code deviation at both ends of the transmission to obtain the total oblique electron content of the signal link at the preset epoch time.

10. The method according to claim 6, characterized in that The first geometrically independent combination corresponding to the pseudorange observation value is equal to the difference between the pseudorange observation values ​​of different frequencies; the first geometrically independent combination corresponding to the pseudorange observation value is also equal to the product of the ionospheric coefficient and the slant path ionospheric parameter minus the differential code deviation at both ends of the transmission; The second geometrically independent combination corresponding to the carrier phase observation value is equal to the difference between the carrier phase observation values ​​of different frequencies; the second geometrically independent combination corresponding to the carrier phase observation value is also equal to the product of the wavelength and the ambiguity of the geometrically independent combination minus the product of the ionospheric coefficient and the slant path ionospheric parameter.

11. The method according to any one of claims 1 to 10, characterized in that: The specific ionospheric tomography function is: Where m is the total number of signal links, n is the total number of grids, The column vector formed by the total diagonal electron content of the signal link; Represents the column vector corresponding to the electron density value to be solved; Represents the intercept of the signal link passing inside the grid.

12. The method according to claim 11, characterized in that The process of determining the intercept of the first signal link passing through the inside of the grid includes: Determine the position of the GNSS satellite based on the broadcast ephemeris information of the GNSS satellite; Determine the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the first signal link according to the position of the GNSS satellite and the position of the ground station; According to the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the first signal link, the intercept of the first signal link passing through the inside of the grid is determined.

13. The method according to claim 11, characterized in that The process of determining the intercept of the second signal link passing through the inside of the grid includes: Determine the position of the GNSS satellite based on the broadcast ephemeris information of the GNSS satellite; Determine the position of the low-orbit satellite based on the broadcast ephemeris information of the low-orbit satellite; Determine the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the second signal link according to the position of the GNSS satellite and the position of the low-orbit satellite; According to the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the second signal link, the intercept of the second signal link passing through the inside of the grid is determined.

14. The method according to claim 11, characterized in that The process of determining the intercept of the third signal link passing through the inside of the grid includes: Determine the position of the low-orbit satellite based on the broadcast ephemeris information of the low-orbit satellite; Determine the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the third signal link according to the position of the low-orbit satellite and the position of the ground station; According to the altitude angle, azimuth angle and ionospheric puncture point coordinates corresponding to the third signal link, the intercept of the third signal link passing through the inside of the grid is determined.

15. An ionospheric electron density inversion system, characterized in that: include: GNSS satellites, low-orbit satellites, ground stations and data centers; The GNSS satellite transmits a satellite signal to the ground station using a first signal link; the first signal link is a signal link from the GNSS satellite to the ground station; The GNSS satellite transmits a satellite signal to the low-orbit satellite using a second signal link; the second signal link is a signal link from the GNSS satellite to the low-orbit satellite; The low-orbit satellite transmits a satellite signal to the ground station using a third signal link; the third signal link is a signal link from the low-orbit satellite to the ground station; The data center determines a target area for electron density inversion; obtains observation data corresponding to a signal link in the target area; determines the oblique total electron content corresponding to the signal link based on the observation data corresponding to the signal link; solves an ionospheric tomography function based on the oblique total electron content corresponding to the signal link to obtain the electron density value of the grid in the target area; the ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

16. An ionospheric electron density inversion device, characterized in that: The device comprises: A region determination module, used to determine the target region for electron density inversion; An observation data acquisition module is used to acquire observation data corresponding to a signal link in a target area; the signal link includes: a first signal link from a GNSS satellite to a ground station, a second signal link from a GNSS satellite to a low-orbit satellite, and a third signal link from a low-orbit satellite to a ground station; A link electron content determination module, used to determine the oblique total electron content corresponding to the signal link according to the observation data corresponding to the signal link; The electron density solving module is used to solve the ionospheric tomography function according to the oblique total electron content corresponding to the signal link to obtain the electron density value of the grid in the target area; the ionospheric tomography function is used to characterize the mapping relationship between the oblique total electron content and the electron density value of the grid.

17. The device according to claim 16, characterized in that The observation data includes: first signal link observation data, second signal link observation data and third signal link observation data; The first signal link observation data includes: first pseudorange observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite, and first carrier phase observation values ​​of frequency i and frequency j received by the ground station receiver from the GNSS satellite; The second signal link observation data includes: second pseudorange observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite, and second carrier phase observation values ​​of frequency i and frequency j received by the low-orbit satellite from the GNSS satellite; The third signal link observation data includes: the third pseudo-range observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite And the third carrier phase observation values ​​of frequency i and frequency j received by the ground station receiver from the low-orbit satellite.

18. An electronic device, characterized in that: include: processor; and A memory having executable codes stored thereon, which, when executed, causes the processor to execute the method as claimed in any one of claims 1 to 14.

19. A machine-readable medium having executable codes stored thereon, which, when executed, causes a processor to execute the method according to any one of claims 1 to 14.

20. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the method described in any one of claims 1 to 14 is implemented.

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