Method and System for Obtaining GNSS Satellite Inter-Frequency Bias Based on LEO

Abstract

The present invention discloses a method and a system for obtaining the inter-frequency bias of GNSS satellites based on LEO. The method includes the following steps: a GNSS receiver is carried on an LEO satellite above the ionospheric height to obtain observation information; a ground gateway station downloads the stored observation information from the LEO satellite and sends the observation information to a data center through a ground communication network; the data center calculates and obtains the inter-frequency bias of GNSS satellites and the inter-frequency bias of GNSS receivers based on the observation information and in combination with the least squares method. By carrying a GNSS receiver on an LEO satellite above the ionospheric height, the GNSS observation values are not affected by the ionosphere. When solving the inter-frequency bias of GNSS satellites and the inter-frequency bias of GNSS receivers, it is not necessary to model the ionosphere, eliminating the solution error caused by the difficulty in accurately quantifying the ionospheric model.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation, and specifically to a method and system for obtaining the inter-frequency bias of GNSS satellites based on LEO. Background Art

[0002] The Global Navigation Satellite System (GNSS) is also known as the Global Navigation Satellite System. It is a space-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 Earth's surface or in near-Earth space. The ionosphere, as an important part of the Earth's space atmosphere, has a serious impact on radio navigation signals and has become one of the most difficult error sources in the data processing of the Global Navigation Satellite System (GNSS).

[0003] The existing estimation of the inter-frequency bias of GNSS satellites generally adopts the method of continuous observation by ground monitoring stations. In order to ensure that all satellites in the constellation are observed, either long-term observation by a single regional station (such as 24 hours) or short-term synchronous observation by multiple global stations (such as 2 hours) can meet the conditions. The above-mentioned method of continuous observation by ground monitoring stations uses the dual-frequency pseudorange differences P1 - P2, P1 - P5 observed by the monitoring stations, and combines the ionospheric polynomial model and additional constraint conditions to solve the polynomial coefficients, the receiver inter-frequency bias, and the GNSS satellite inter-frequency bias.

[0004] However, the above-mentioned scheme has the following defects: (1) The time required for regional observation is relatively long, and it can only be processed retrospectively, which is not suitable for real-time applications. Due to permission issues, it is also difficult to obtain the observation data of multiple global stations. (2) The real ionospheric delay changes complexly, and it is not easy to accurately quantify the ionospheric model, which will affect the accuracy of the inter-frequency bias estimation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing estimation of the inter-frequency bias of GNSS satellites has the problems that the time required for regional observation is relatively long, the ionospheric delay changes complexly, and it is not easy to accurately quantify the ionospheric model, which will affect the accuracy of the inter-frequency bias estimation. The purpose is to provide a method and system for obtaining the inter-frequency bias of GNSS satellites based on LEO to solve the above problems.

[0006] The present invention is achieved by the following technical solutions:

[0007] A method for obtaining the inter-frequency bias of GNSS satellites based on LEO, comprising the following steps:

[0008] Mount a GNSS receiver on a LEO satellite above the ionospheric altitude to obtain observation information;

[0009] The ground gateway station downloads the stored observation information from the LEO satellites and sends the observation information to the data center through the ground communication network;

[0010] The data center calculates the GNSS satellite inter-frequency bias and the GNSS receiver inter-frequency bias based on the observation information and in combination with the least squares method.

[0011] The working principle of the present invention: Since the real ionospheric delay changes complexly and the ionospheric model is not easy to accurately quantify, which is likely to affect the accuracy of the GNSS satellite inter-frequency bias estimation. Therefore, the present invention changes the traditional method of continuous observation through ground monitoring stations to obtaining observation information by carrying a GNSS receiver on a LEO satellite above the ionospheric height, so that the observation information is not affected by the ionosphere. The present invention enables the elimination of the solution error caused by the difficulty in accurately quantifying the ionospheric model when solving the GNSS satellite inter-frequency bias and the GNSS receiver inter-frequency bias without the need to model the ionosphere.

[0012] Further, the method includes carrying an on-board GNSS receiver on a single LEO satellite, and the specific steps are as follows:

[0013] Carry an on-board GNSS receiver on a single LEO satellite above the ionosphere;

[0014] The on-board GNSS receiver stores the observation information in real time;

[0015] The ground gateway station downloads the stored observation information from the LEO satellite and sends the observation information to the data center through the ground communication network;

[0016] The data center calculates the GNSS satellite inter-frequency bias and the GNSS receiver inter-frequency bias based on the observation information and in combination with the least squares method.

[0017] Further, the method further includes carrying on-board GNSS receivers on multiple LEO satellites, and the specific steps are as follows:

[0018] Carry an on-board GNSS receiver on each LEO satellite above the ionosphere;

[0019] The on-board GNSS receivers store the observation information in real time;

[0020] The LEO satellites outside the country send the stored observation information to the LEO satellites within the country through the LEO inter-satellite link for aggregation to obtain aggregated observation information;

[0021] The ground gateway station downloads the aggregated observation information from the LEO satellites within the country and sends the aggregated observation information to the data center through the ground communication network;

[0022] The data center obtains the GNSS satellite inter-frequency bias and GNSS receiver inter-frequency bias based on the aggregated observation information and combined with the least squares method.

[0023] Furthermore, the observation information includes receiver position, pseudorange, CN0, GNSS satellite ephemeris, and elevation angle.

[0024] Furthermore, the ionosphere altitude includes the Earth orbit altitude between 1000km and 2000km.

[0025] Since the ionosphere is distributed below 1000km above the Earth's orbit, we carry GNSS receivers on LEO satellites above 1000km in orbit, and their observations can be considered unaffected by ionospheric delays, which eliminates the errors caused by the difficulty in accurately quantifying the ionospheric model. In addition, LEO satellites move quickly, and observations of all satellites in the GNSS constellation can be completed in about 2 hours. After multiple LEO satellites are networked, the observation time will be shorter, and the real-time performance will be stronger than ground observations.

[0026] Furthermore, the data center obtains the GNSS satellite inter-frequency deviation and the GNSS receiver inter-frequency deviation based on the aggregated observation information and in combination with the least squares method, including:

[0027] Step S1, calculate the pseudo-range frequency difference P3 of each GNSS satellite i within the time period when the elevation angle is greater than 10° i and P4 i ;

[0028] Step S2, based on the pseudorange frequency difference P3 i and P4 i Calculate the median value and The middle value and From the pseudorange frequency difference P3 i and P4 i After deducting, the absolute value is ε3 i , ε4 i ;

[0029] Step S3, calculate ε3 i , ε4 i The median value Find ε3 i More than 3 times time period, P3 of this period i Eliminate Find ε4 i More than 3 times time period, and P4 i Eliminate

[0030] Step S4, calculate the mean value of and the mean value of

[0031] Step S5, based on the mean value and the mean value simultaneously establish equations, write the equations in matrix form, and use the least squares method to calculate and obtain the inter-frequency bias DCB12 u and DCB15 u of the on-board GNSS receiver and the inter-frequency biases (i = 1, 2,..., M) of all GNSS satellites.

[0032] Furthermore, in Step S1, the calculation of the inter-frequency difference P3 i and P4 i of each GNSS satellite i has the following calculation expressions:

[0033] P3 i = P1 i - P2 i (1)

[0034] P4 i = P1 i - P5 i (2)

[0035] where P1 is the pseudo-range observation of the first frequency L1, P2 is the pseudo-range observation of the second frequency L2, and P5 is the pseudo-range observation of the third frequency L5.

[0036] Furthermore, in Step S2, the calculation expressions of i ε3 i and ε4

[0037]

[0038]

[0039] are as follows: where i is the intermediate value of the inter-frequency difference P3 of the pseudo-range, and i is the intermediate value of the inter-frequency difference P4

[0040] Furthermore, in Step S5, the equations should satisfy:

[0041]

[0042]

[0043] Among them, DCB12 u is the L1-L2 inter-frequency bias of the spaceborne GNSS receiver, and DCB15 u is the L1-L5 inter-frequency bias of the spaceborne GNSS receiver. is the L1-L2 inter-frequency bias of GNSS satellite i, is the L1-L5 inter-frequency bias of GNSS satellite i, and M is the total number of satellites in the GNSS constellation.

[0044] A system for obtaining the inter-frequency bias of GNSS satellites based on LEO includes:

[0045] A creation module for carrying a GNSS receiver on a LEO satellite above the ionospheric altitude to obtain observation information;

[0046] A data acquisition module for downloading the stored observation information from the LEO satellite and sending the observation information to the data center through a ground communication network;

[0047] A data analysis module for calculating and obtaining the inter-frequency bias of GNSS satellites and the inter-frequency bias of GNSS receivers based on the observation information and in combination with the least squares method.

[0048] The present invention changes the traditional method of continuous observation through ground monitoring stations to receiving observation information by carrying a GNSS receiver on a LEO satellite at an altitude above 1000 km of the earth's orbit. Since the ionosphere is distributed below an altitude of 1000 km of the earth's orbit, the observation information is not affected by the ionosphere. When solving the inter-frequency bias of GNSS satellites and the inter-frequency bias of GNSS receivers, it is not necessary to model the ionosphere, eliminating the solution error caused by the difficulty in accurately quantifying the ionosphere model.

[0049] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0050] 1. The method and system for obtaining the inter-frequency bias of GNSS satellites based on LEO provided by the present invention carry a GNSS receiver on a LEO satellite above the ionospheric altitude. The observation information is not affected by the ionosphere. When solving the inter-frequency bias of GNSS satellites and the inter-frequency bias of GNSS receivers, it is not necessary to model the ionosphere, eliminating the solution error caused by the difficulty in accurately quantifying the ionosphere model.

[0051] 2. The method and system for obtaining the inter-frequency bias of GNSS satellites based on LEO provided by the present invention have a fast moving speed of the LEO satellite. It can complete the observation of all satellites in the GNSS constellation in about 2 hours. After multiple LEOs are networked, the observation time will be shorter, and the real-time performance is stronger than that of ground observation.

[0052] 3. For the method and system for obtaining the GNSS satellite inter-frequency bias based on LEO provided by the present invention, due to permission issues, it is difficult to obtain the observation data of multiple ground stations globally. However, there is no such problem when using LEO satellite observations. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0054] Figure 1 Schematic diagram of the LEO orbit altitude of the present invention;

[0055] Figure 2 Schematic diagram of the flow of the observation data of the present invention;

[0056] Figure 3 Overall flowchart of the method for obtaining the GNSS satellite inter-frequency bias based on LEO satellites of the present invention;

[0057] Figure 4 Flowchart of the method for obtaining the GNSS satellite inter-frequency bias based on a single LEO satellite in Embodiment 1 of the present invention;

[0058] Figure 5 Flowchart of the method for obtaining the GNSS satellite inter-frequency bias based on multiple LEO satellites in Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] GNSS navigation satellites broadcast navigation signals of multiple frequencies. The satellite and the receiver transmit and receive these navigation signals of different frequencies through different channels, and the time delays generated when these navigation signals pass through different channels are not exactly the same. The difference between the time delays of different frequency signals generated thereby is called the inter-frequency bias. The inter-frequency bias includes satellite DCB, receiver DCB, and ionospheric delay.

[0060] In the prior art, the relative method and the absolute method are generally used to estimate the DCB. The relative method selects a receiver b with a known DCB to estimate the DCB of another receiver r. However, this method can only estimate the DCB of the receiver and cannot estimate the DCB of the satellite. The absolute method estimates the DCB of the receiver and the satellite together, and the absolute method is divided into two implementation methods: the known ionosphere method and the undetermined ionosphere coefficient method. The known ionosphere method is limited by the accuracy of the ionosphere data product, and the accuracy of the estimated DCB is not high. Since the ionosphere changes extremely slowly, the undetermined ionosphere coefficient method generally requires a long observation time (usually one day) to converge. In addition, the real ionosphere is relatively complex and it is difficult to represent it with an accurate model, so it can only be approximated. Therefore, the solved DCB is affected by the refinement degree of the ionosphere model. The finer the ionosphere model, the greater the corresponding calculation amount, and the more undetermined coefficients, which will bring stability problems to the solution.

[0061] The present invention changes the traditional continuous observation method through ground monitoring stations to receiving observation information by a GNSS receiver carried on a LEO satellite at an altitude of more than 1000 km above the earth's orbit. Since the ionosphere is distributed below an altitude of 1000 km above the earth's orbit, the observation information is not affected by the ionosphere. The present invention enables the solution of the inter-frequency bias of GNSS satellites and the inter-frequency bias of GNSS receivers without having to model the ionosphere, eliminating the solution error caused by the difficulty of accurately quantifying the ionosphere model. The LEO satellite moves at a high speed and can complete the observation of all satellites within the GNSS constellation in about 2 hours. After multiple LEOs are networked, the observation time will be shorter and the real-time performance will be stronger than that of ground observation.

[0062] To make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and the accompanying drawings. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and do not limit the present invention.

[0063] In the accompanying drawings, Figure 1 shows the schematic diagram of the LEO orbit altitude of the embodiment; Figure 2 shows the schematic diagram of the observation data flow of the embodiment; Figure 3 shows the overall flowchart of the method for obtaining the inter-frequency bias of GNSS satellites based on LEO satellites; Figure 4 shows the overall flowchart of the method for obtaining the inter-frequency bias of GNSS satellites based on a single LEO satellite in this embodiment; Figure 5 shows the overall flowchart of the method for obtaining the inter-frequency bias of GNSS satellites based on multiple LEO satellites in this embodiment.

[0064] Embodiment 1

[0065] This Embodiment 1 uses a single LEO for observation and distance description. As Figure 4As shown, the following steps are included:

[0066] A satellite-borne GNSS receiver is carried on a single LEO satellite above the ionosphere;

[0067] The onboard GNSS receiver stores observation information in real time, including receiver position, pseudorange, CN0, GNSS satellite ephemeris, and elevation angle;

[0068] The ground gateway downloads the stored observation information from the LEO satellite and sends the observation information to the data center through the ground communication network;

[0069] The data center obtains the GNSS satellite inter-frequency bias and GNSS receiver inter-frequency bias based on the observation information and the least squares method.

[0070] Preferably, the data center obtains the GNSS satellite inter-frequency deviation and the GNSS receiver inter-frequency deviation based on the observation information and in combination with the least squares method, comprising the following steps:

[0071] Step S1, deleting the observation information with elevation angle less than 10° or CN0 less than 40dB / Hz;

[0072] Step S2, calculating the pseudorange residual of each GNSS satellite according to the onboard receiver position, GNSS satellite ephemeris, and pseudorange;

[0073] Step S3, deleting the observation information with pseudorange residual greater than 10 meters;

[0074] Step S4, for each GNSS satellite: select the common observation period of the L1 and L2 frequency points, and calculate the pseudorange difference P3;

[0075] Step S5, calculate the median value of the P3 sequence From P3, the intermediate value After deducting, the absolute value of the obtained sequence is obtained to obtain ε3 i sequence;

[0076] Step S6, calculate ε3 i The middle value of the sequence From the median Find the value greater than three times the middle value period and will be greater than three times the median value The period is deleted from the P3 series and the mean of the remaining data is calculated

[0077] Step S7: Observation values of all GNSS satellites Combine them to form a system of equations, and add a constraint equation: the sum of the DCBs of all GNSS satellites is zero;

[0078] Step S8: Rewrite the system of equations in matrix form and use the least squares method to solve for the receiver DCB and GNSS satellite DCB.

[0079] Specifically, referring to Figure 1-2 , Figure 4 , a method for obtaining the GNSS satellite inter-frequency bias based on LEO provided in this embodiment has the following specific steps and calculation processes:

[0080] 1. Install a GNSS receiver on an LEO satellite above the ionospheric height;

[0081] 2. When the LEO satellite transits, the ground gateway station within the territory downloads multi-frequency pseudorange observation data (P1, P2, P5) from the LEO satellite through a feeder link and sends it to the data analysis center through the ground network;

[0082] 3. Calculate the pseudorange inter-frequency difference P3 i , P4 i of each GNSS satellite i during the period when the elevation angle is greater than 10°:

[0083] P3 i = P1 i - P2 i (1)

[0084] P4 i = P1 i - P5 i (2)

[0085] 4. Calculate the median of the pseudorange inter-frequency differences P3 i , P4 i ; Subtract the median of the pseudorange inter-frequency differences from the pseudorange inter-frequency differences P3 i , P4 i respectively, and then take the absolute value to obtain ε3 i , ε4 i ;

[0086]

[0087]

[0088]

[0089]

[0090] 5. Calculate the median of ε3 i , ε4 i ; Find the values in ε3 i that are greater than 3 times time period, and P3 i Eliminate Find ε4 i More than 3 times time period, and P4 i Eliminate

[0091]

[0092]

[0093] 6. Calculation The mean The mean

[0094]

[0095]

[0096] 7. After all satellites are calculated, additional constraints are added: the sum of the inter-frequency deviations of all GNSS satellites is zero, and the simultaneous equations are:

[0097]

[0098]

[0099] Among them, DCB12 u is the L1 and L2 frequency deviation of the satellite-borne GNSS receiver, DCB15 u is the L1 and L5 inter-frequency deviation of the satellite-borne GNSS receiver, is the L1 and L2 inter-frequency deviation of GNSS satellite i, is the L1 and L5 inter-frequency bias of GNSS satellite i, and M is the total number of satellites.

[0100] 8. Write the equations in matrix form and use the least squares method to solve the inter-frequency deviation DCB12 of the satellite-borne GNSS receiver u 、DCB15 u Inter-frequency deviations of all GNSS satellites (i=1,2,…M).

[0101] The normal matrix H is:

[0102]

[0103]

[0104]

[0105]

[0106]

[0107] Embodiment 2:

[0108] In this Embodiment 2, N LEOs are used for observation and distance description, where N is an integer greater than 1, such as Figure 5 shown, and it includes the following steps:

[0109] A method for obtaining the inter-frequency bias of GNSS satellites based on LEO, as Figure 5 shown, includes the following steps:

[0110] On each LEO satellite above the ionosphere, an on-board GNSS receiver is carried;

[0111] The on-board GNSS receiver stores the observation information in real time;

[0112] The LEO satellites outside the country send the stored observation information to the LEO satellites inside the country through the LEO inter-satellite link for aggregation to obtain aggregated observation information;

[0113] The ground gateway station downloads the aggregated observation information from the LEO satellites inside the country and sends the aggregated observation information to the data center through the ground communication network;

[0114] The data center calculates the inter-frequency bias of GNSS satellites and the inter-frequency bias of GNSS receivers based on the aggregated observation information and in combination with the least squares method.

[0115] Preferably, the data center calculates the inter-frequency bias of GNSS satellites and the inter-frequency bias of GNSS receivers based on the aggregated observation information and in combination with the least squares method, including the following steps:

[0116] Step S1, delete the observation information with an elevation angle less than 10° or CN0 less than 40 dB / Hz;

[0117] Step S2, calculate the pseudorange residual of each GNSS satellite according to the position of the on-board receiver, the ephemeris of the GNSS satellite, and the pseudorange;

[0118] Step S3, delete the observation information with a pseudorange residual greater than 10 meters;

[0119] Step S4, for each GNSS satellite: select the common observation period of the L1 and L2 frequency points and calculate the pseudorange difference P3;

[0120] Step S5, calculate the median of the P3 sequence Subtract the median from P3 After deduction, the obtained sequence is taken the absolute value to obtain the ε3 i sequence;

[0121] Step S6, calculate ε3 i The middle value of the sequence From the median Find the value greater than three times the middle value period and will be greater than three times the median value The period is deleted from the P3 series and the mean of the remaining data is calculated

[0122] Step S7: Observation values of all GNSS satellites Combine them to form a system of equations;

[0123] Step S8, the equations of each satellite receiver are combined to form a large equation set, and a constraint equation is added; the sum of the DCBs of all GNSS satellites is zero;

[0124] Step S9, rewrite the equations into a matrix form, and use the least square method to solve the DCB of each receiver and the DCB of the GNSS satellite.

[0125] refer to Figure 1-2 , Figure 5 This embodiment provides a method for obtaining GNSS satellite inter-frequency deviation based on LEO, and the specific steps and calculation process are as follows:

[0126] 1. A GNSS receiver is mounted on a LEO satellite above the ionosphere, and the LEO satellite outside the country transmits the observation data to the LEO satellite inside the country through an intersatellite link;

[0127] 2. The ground gateway in the territory downloads the multi-frequency pseudo-range observation data (P1, P2, P5) from the LEO satellite passing through the feeder link, and sends it to the data analysis center through the ground network. For each satellite i in the GNSS receiver, perform steps 3 to 6;

[0128] 3. Calculate the pseudo-range frequency difference P3 of each GNSS satellite i during the period when the elevation angle is greater than 10° i 、P4 i :

[0129] P3 i =P1 i -P2 i (1)

[0130] P4 i =P1 i -P5 i (2)

[0131] 4. Calculate the pseudorange frequency difference P3 i 、P4 i The median value The median value of the pseudorange inter-frequency difference is subtracted from the pseudorange inter-frequency differences P3 i and P4 i respectively, and the absolute values are taken to obtain ε3 i and ε4 i ;

[0132]

[0133]

[0134]

[0135]

[0136] 5. Calculate the median value of ε3 i and ε4 i ; Find the time periods in ε3 i that are greater than 3 times . Exclude P3 i for these time periods to obtain Find the time periods in ε4 i that are greater than 3 times . Exclude P4 i for these time periods to obtain

[0137]

[0138]

[0139] 6. Calculate the mean value of and the mean value of ;

[0140]

[0141]

[0142] 7. Assume that the number of satellites observed by N receivers are M1, M2, … M N , and the satellite numbers observed are For each GNSS receiver m, establish equations:

[0143]

[0144] where DCB12 u m is the L1 and L2 inter-frequency bias of the m-th spaceborne GNSS receiver, is the L1 and L2 frequency deviation of GNSS satellite i, M m is the total number of satellites of the mth onboard GNSS receiver;

[0145] 8. Combine the equations of all N receivers, with the additional constraint that the sum of the inter-frequency deviations of all GNSS satellites is zero, and use the least squares method to solve the inter-frequency deviation DCB12 of all onboard GNSS receivers u m Inter-frequency deviations of all GNSS satellites The solution for L1 and L5 inter-frequency deviation is similar to that for L1 and L2.

[0146] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for obtaining the inter-frequency bias of GNSS satellites based on LEO, characterized in that It includes the following steps: On multiple LEO satellites above the ionospheric altitude, on-board GNSS receivers are carried to acquire and store observation information; The LEO satellites outside the country send the stored observation information to the LEO satellites inside the country through the LEO inter-satellite link for summarization to obtain summarized observation information; The ground gateway station downloads the summarized observation information from the LEO satellites inside the country and sends the summarized observation information to the data center through the ground communication network; The data center calculates the GNSS satellite inter-frequency bias and the GNSS receiver inter-frequency bias based on the summarized observation information and in combination with the least squares method; Among them, the ground gateway station downloads the summarized observation information from the LEO satellites inside the country and sends the summarized observation information to the data center, including: Step S1, within the time period when the elevation angle is greater than 10°, calculate the pseudo-range frequency difference of each GNSS satellite i and ; Step S2, based on the pseudo-range frequency difference and calculate the intermediate value . After subtracting the intermediate value from the pseudo-range frequency difference respectively and taking the absolute value, obtain ; Step S3, calculate the median value of ; find out the time periods in that are greater than three times and remove the in these time periods to obtain ; find out the time periods in that are greater than three times and remove the in these time periods to obtain Step S4, calculate the mean value of and the mean value of ; Step S5, based on the mean value and the mean value Simultaneously solve the equations and write the equations in matrix form, and calculate the inter-frequency bias of the spaceborne GNSS receiver using the least squares method and the inter-frequency biases of all GNSS satellites .

2. The method for obtaining the inter-frequency bias of GNSS satellites based on LEO according to claim 1, wherein The method includes carrying an on-board GNSS receiver on a single LEO satellite, and the specific steps are as follows: Carry an on-board GNSS receiver on a single LEO satellite above the ionosphere; The on-board GNSS receiver stores the observation information in real time; The ground gateway station downloads the stored observation information from the LEO satellite and sends the observation information to the data center through the ground communication network; The data center calculates the GNSS satellite inter-frequency bias and the GNSS receiver inter-frequency bias based on the observation information and in combination with the least squares method.

3. The method for obtaining the inter-frequency bias of GNSS satellites based on LEO according to any one of claims 1-2, characterized in that The observation information includes receiver position, pseudorange, CN0, GNSS satellite ephemeris, and elevation angle.

4. The method for obtaining the inter-frequency bias of GNSS satellites based on LEO according to any one of claims 1-2, characterized in that, Above the ionospheric altitude includes between 1000 km and 2000 km of the Earth's orbital altitude.

5. The method for obtaining the inter-frequency bias of GNSS satellites based on LEO according to claim 1, wherein In step S1, calculating the pseudo-range inter-frequency difference of each GNSS satellite i and , the calculation expression is as follows: (1) (2) Among them, is the pseudorange observation of the first frequency L1, is the pseudorange observation of the second frequency L2, is the pseudorange observation of the third frequency L5.

6. The method for obtaining the inter-frequency bias of GNSS satellites based on LEO according to claim 1, wherein In step S2, the has the following calculation expression: (5) (6) Among them, is the median value of the pseudorange frequency difference, is the median value of the pseudorange frequency difference.

7. The method for obtaining the inter-frequency bias of GNSS satellites based on LEO according to claim 1, wherein In step S5, the system of equations should satisfy: （11） Among them, is the L1-L2 inter-frequency bias of the spaceborne GNSS receiver, is the L1-L5 inter-frequency bias of the spaceborne GNSS receiver, is the L1-L2 inter-frequency bias of GNSS satellite i, is the L1-L5 inter-frequency bias of GNSS satellite i, and M is the total number of satellites in the GNSS constellation.

8. A system for obtaining the inter-frequency bias of GNSS satellites based on LEO, characterized in that, It includes: A creation module for carrying a GNSS receiver on a LEO satellite above the ionospheric altitude to acquire observation information; The LEO satellites outside the country send the stored observation information to the LEO satellites inside the country through the LEO inter-satellite link for summarization to obtain summarized observation information; A data acquisition module for downloading the stored observation information from the LEO satellite and sending the observation information to the data center, including: Step S1, within the time period when the elevation angle is greater than 10°, calculate the pseudo-range frequency difference between each GNSS satellite i and ; Step S2, based on the pseudo-range frequency difference and calculate the intermediate value . After subtracting the intermediate value from the pseudo-range frequency difference respectively, take the absolute value to obtain ; Step S3, calculate the intermediate value of ; find out the time periods in which are greater than three times , and remove the of these time periods to obtain ; find out the time periods in which are greater than three times , and remove the of these time periods to obtain ; Step S4, calculate the mean value of and the mean value of ; Step S5, based on the mean value and the mean value Simultaneously solve the equations and write the equations in matrix form, and use the least squares method to calculate the inter-frequency bias of the spaceborne GNSS receiver and the inter-frequency biases of all GNSS satellites ; A data analysis module for calculating the GNSS satellite inter-frequency bias and the GNSS receiver inter-frequency bias based on the observation information and in combination with the least squares method.

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