Low-orbit navigation satellite clock error solving method and device, electronic equipment and storage medium

Abstract

The embodiment of the application discloses a low-orbit navigation satellite clock error solving method and device, electronic equipment and a storage medium, the method comprises the following steps: through the satellite orbit parameter and the clock error product of the medium-high orbit GNSS satellite, the ionosphere-free combination precise orbit determination of the observation data received by the LEO is carried out, the satellite orbit parameter and the signal receiving end clock error of the LEO are obtained; based on the dual-frequency mixed observation data, the signal transmitting end clock error of the LEO in the ground visible arc segment is solved jointly; the mathematical model of the signal receiving end clock error of the LEO and the signal transmitting end clock error of the LEO in the ground visible arc segment is established respectively, and the clock error model difference is extracted; according to the clock error model difference, the signal receiving end clock error of the LEO is converted into the full-arc segment signal transmitting end clock error of the LEO.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of GNSS data processing, and particularly relates to a low-orbit navigation satellite clock error solving method and device, an electronic device and a storage medium. BACKGROUND

[0002] Global Navigation Satellite System (GNSS) is widely used in many fields such as earthquake monitoring and intelligent driving due to its advantages such as all-weather, simple operation, fast and accurate positioning, covering global and regional systems such as GPS and Beidou. However, the existing medium and high orbit satellite signal loss is large, and the positioning effect is limited in complex environment. Low-orbit satellites can optimize positioning and enhance anti-interference capability due to strong signal landing power. China plans to build a hybrid constellation of medium, high and low orbits for the next generation of Beidou.

[0003] Satellite clock error is a key navigation service. Medium and high orbit satellites achieve clock error estimation through continuous observation of global ground stations, and the technology is mature. However, low-orbit satellites are difficult to track continuously by ground stations due to their high speed and small field of view. When the distribution is sparse, the observation may be missed, which affects the service performance.

[0004] Therefore, it is urgent to solve the problem of accurately determining the precise clock error of low-orbit navigation satellites in the whole arc segment. SUMMARY

[0005] The embodiments of the application provide a low-orbit navigation satellite clock error solving method, device, electronic device and storage medium, which can solve the problem of accurately determining the precise clock error of low-orbit navigation satellites in the whole arc segment.

[0006] In a first aspect, the embodiments of the application provide a low-orbit navigation satellite clock error solving method, which comprises:

[0007] Obtaining observation data of medium and high orbit GNSS satellites received by a low-orbit navigation satellite (LEO), double-frequency mixed observation data containing LEO and medium and high orbit satellites received by a ground station, and satellite orbit parameters and clock error products of the medium and high orbit GNSS satellites. The clock error product is the deviation between the time displayed by the satellite atomic clock and the real time.

[0008] Performing ionosphere-free combination precise orbit determination on the observation data received by the LEO based on the satellite orbit parameters and clock error products of the medium and high orbit GNSS satellites, to obtain satellite orbit parameters and signal receiving end clock error of the LEO.

[0009] Based on the double-frequency mixed observation data, jointly solving the signal transmitting end clock error of the LEO in the ground visible arc segment.

[0010] respectively, a mathematical model of the signal receiving end clock difference of the LEO and a mathematical model of the signal transmitting end clock difference of the LEO in the ground visible arc segment, and extract a clock difference model difference, the clock difference model difference being a difference between the receiving end clock difference model and the transmitting end clock difference model;

[0011] According to the clock difference model difference, the signal receiving end clock difference of the LEO is converted into the signal transmitting end clock difference of the LEO in the full-arc segment.

[0012] In a second aspect, an embodiment of the present application provides a low-orbit navigation satellite clock difference solving device, the low-orbit navigation satellite clock difference solving device comprising:

[0013] The obtaining module is configured to obtain middle-high-orbit GNSS satellite observation data received by a low-orbit navigation satellite LEO, double-frequency mixed observation data received by a ground station and containing the LEO and a middle-high-orbit navigation satellite, and satellite orbit parameters and clock difference products of the middle-high-orbit GNSS satellite, the clock difference products being a deviation between a satellite atomic clock display time and a real time;

[0014] The orbit determination module is configured to perform ionosphere-free combination precise orbit determination on the observation data received by the LEO based on the satellite orbit parameters and the clock difference products of the middle-high-orbit GNSS satellite, to obtain satellite orbit parameters and a signal receiving end clock difference of the LEO.

[0015] The solving module is configured to jointly solve a signal transmitting end clock difference of the LEO in the ground visible arc segment based on the double-frequency mixed observation data.

[0016] The extracting module is configured to respectively establish a mathematical model of the signal receiving end clock difference of the LEO and a mathematical model of the signal transmitting end clock difference of the LEO in the ground visible arc segment, and extract a clock difference model difference, the clock difference model difference being a difference between the receiving end clock difference model and the transmitting end clock difference model.

[0017] The converting module is configured to convert, according to the clock difference model difference, the signal receiving end clock difference of the LEO into the signal transmitting end clock difference of the LEO in the full-arc segment.

[0018] In a third aspect, an embodiment of the present application provides an electronic device, the device comprising a processor and a memory storing computer program instructions; when the processor executes the computer program instructions, the method in the first aspect or any possible implementation manner of the first aspect is implemented.

[0019] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium, the computer readable storage medium storing computer program instructions, and the computer program instructions are executed by a processor to implement the method in the first aspect or any possible implementation manner of the first aspect.

[0020] In the embodiment of the present application, the low earth orbit navigation satellite LEO receives the medium-high orbit GNSS satellite observation data, the ground station receives the double-frequency mixed observation data containing LEO and medium-high orbit satellite, and the satellite orbit parameters and clock difference products of the medium-high orbit GNSS satellite. The clock difference product is the deviation between the satellite atomic clock display time and the real time. The satellite orbit parameters and signal receiving end clock difference of LEO are obtained by precise orbit determination of the observation data received by LEO without ionosphere combination based on the satellite orbit parameters and clock difference products of the medium-high orbit GNSS satellite. The orbit and receiving end clock difference of LEO are accurately obtained by using the medium-high orbit satellite resources and double-frequency observation technology to eliminate the interference of ionosphere and other interference. The signal transmitting end clock difference of LEO in the ground visible arc segment is jointly solved based on the double-frequency mixed observation data. The transmitting end time error data of LEO in the ground visible area is filled. Mathematical models of the signal receiving end clock difference of LEO and the signal transmitting end clock difference of LEO in the ground visible arc segment are established, and the clock difference model difference is extracted, which is the difference between the receiving end clock difference model and the transmitting end clock difference model. The local transmitting end clock difference is solved by the ground station data, which is extended to the full orbit combined with the model difference, solving the clock difference missing problem in the ground observation blind area. According to the clock difference model difference, the signal receiving end clock difference of LEO is converted into the full-arc segment signal transmitting end clock difference of LEO, realizing the dynamic prediction and accurate compensation of LEO clock difference, and finally improving the time synchronization accuracy and positioning reliability of the low earth orbit navigation system. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. For those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0022] Figure 1 is a flow chart of a low earth orbit navigation satellite clock difference solving method provided by the embodiments of the present application;

[0023] Figure 2 is a flow chart of a low earth orbit navigation satellite clock difference solving method provided by the embodiments of the present application;

[0024] Figure 3 is a structural schematic diagram of a low earth orbit navigation satellite clock difference solving device provided by the embodiments of the present application;

[0025] Figure 4 is a hardware structural schematic diagram of an electronic device provided by the embodiments of the present application. DETAILED DESCRIPTION

[0026] The features and exemplary embodiments of various aspects of the present application will be described below in detail, in order to make the purposes, technical solutions and advantages of the present application more clear and apparent, the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present application, and are not configured to limit the present application. The present application can be implemented without some of these specific details for those skilled in the art. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0027] It should be noted that, in this paper, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the elements defined by the statement "include" do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0028] The technical terms involved in the present application are briefly introduced as follows.

[0029] Low Earth Orbit Navigation Satellite (LEO): Navigation satellite with an orbital height of 200-2000 km, with the characteristics of short orbital period and dynamic signal coverage area, commonly used to enhance Global Navigation Satellite System (GNSS) or build independent navigation system. Provides high-precision positioning services to make up for the lack of coverage of medium-high orbit satellites in certain areas.

[0030] Medium-high orbit GNSS satellite: Global navigation satellite with an orbital height higher than 20000 km, such as GPS and Beidou medium circular orbit satellites, which are the core components of traditional GNSS, with high orbital stability and wide coverage.

[0031] Satellite orbit parameters: Parameters describing the satellite motion trajectory, such as orbital semi-major axis, inclination, ascending node right ascension, etc., used to determine the real-time position of the satellite.

[0032] Clock difference product: The deviation data between satellite atomic clock time and real time, reflecting the clock accuracy, is a key error source affecting navigation and positioning accuracy.

[0033] Dual-frequency hybrid observation data: This refers to dual-frequency (e.g., L1 / L2 band) observation data simultaneously received by ground stations from LEO satellites and medium-to-high orbit GNSS satellites, including pseudorange, carrier phase, and other observations. Utilizing dual-frequency data can eliminate ionospheric delay errors and improve the accuracy of joint calculations.

[0034] Ionospherically-free combined precise orbit determination: This technique involves linearly combining dual-frequency observation data, such as combinations that eliminate the influence of the first-order ionospheric term, to remove ionospheric errors. Then, using the known orbital parameters and clock errors of medium- and high-orbit satellites, it precisely determines the orbit of LEO satellites. It utilizes the ionospheric delay differences in dual-frequency data to construct ionospherically-free combined observations, and then solves for the LEO orbital parameters using dynamic models or geometric methods. Figure 1 This is a flowchart of a low-orbit navigation satellite clock bias calculation method provided in an embodiment of this application.

[0035] like Figure 1 As shown, the low-Earth orbit navigation satellite clock bias calculation method may include steps 110-150. This method is applied to a low-Earth orbit navigation satellite clock bias calculation device, as detailed below:

[0036] Step 110: Obtain observation data from medium and high orbit GNSS satellites received by the low orbit navigation satellite (LEO), dual-frequency hybrid observation data containing LEO and medium and high orbit satellites received by the ground station, and satellite orbit parameters and clock bias products of the medium and high orbit GNSS satellites. The clock bias products are the deviation between the time displayed by the satellite atomic clock and the actual time.

[0037] Step 120: Using the satellite orbit parameters and clock bias products of medium- and high-orbit GNSS satellites, perform ionospherically-free combined precise orbit determination on the observation data received by LEO to obtain the satellite orbit parameters and signal receiver clock bias of LEO.

[0038] Step 130: Based on the dual-frequency hybrid observation data, jointly calculate the clock difference of the signal transmitter of LEO within the visible arc of the ground;

[0039] Step 140: Establish mathematical models for the clock bias at the signal receiver of LEO and the clock bias at the signal transmitter of LEO within the visible arc of the ground, respectively, and extract the difference between the clock bias models. The difference between the clock bias models is the difference between the clock bias model at the receiver and the clock bias model at the transmitter.

[0040] Step 150: Based on the clock difference model, convert the clock difference of the LEO signal receiver into the clock difference of the LEO full-segment signal transmitter.

[0041] In the embodiments of the present application, firstly, the clock difference information of the low-orbit navigation satellite receiving end and the clock difference information of the low-orbit navigation satellite signal transmitting end in the ground visible arc segment are solved, and then the clock difference of the low-orbit navigation satellite receiving end and the clock difference of the signal transmitting end are respectively modeled; the difference between the two models can convert the clock difference of the low-orbit navigation satellite receiving end into the clock difference of the signal transmitting end. Since the LEO satellite-borne receiver can receive the observed GNSS satellite signal all day long, the continuous clock difference sequence of the low-orbit navigation satellite receiving end can be obtained by using the LEO precise orbit determination technology; by the embodiments of the present application, the precise clock difference information of the low-orbit navigation satellite in the whole arc segment can be obtained, and the precise clock difference solution of the low-orbit navigation satellite in the whole arc segment can be realized, which is beneficial to the GNSS time and space reference maintenance accuracy, autonomous operation ability, and LEO enhanced precise position service.

[0042] The following will explain each step in turn:

[0043] Step 110:

[0044] The LEO satellite receives the middle-high-orbit GNSS satellite signal to obtain the observation data; the ground station synchronously receives the dual-frequency mixed observation data of the LEO and middle-high-orbit satellites, which is used for subsequent joint solution; and the official or third-party published middle-high-orbit satellite orbit parameters and clock difference products are collected. The multi-source observation data and reference parameters are provided for subsequent orbit determination and clock difference solution, and the integrity of the data chain is ensured.

[0045] The BDS dual-frequency pseudorange and carrier phase observation values received by the low-orbit navigation satellite are used to form ionosphere-free combined observation equations, as shown below:

[0046]

[0047] Among them:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055] In the formula: BDS satellite and LEO receiver are represented respectively;

[0056] , respectively represent the ionosphere-free combined coefficient;

[0057] , represent the equivalent wavelength after ionosphere-free combination;

[0058] , represent the integer ambiguity after ionosphere-free combination;

[0059] , respectively represent the noise term after ionosphere-free combination of pseudorange and carrier phase;

[0060] represents the geometric distance between BDS satellite and observation station;

[0061] and respectively represent the light speed, clock error and clock error containing differential code bias;

[0062] represents the pseudorange and phase hardware delay;

[0063] represents the ambiguity parameter;

[0064] represents the pseudorange and phase IF combination noise;

[0065] represents the pseudorange observation value;

[0066] represents the carrier phase observation value;

[0067] refers to the pseudorange observation value of the i-th frequency point of LEO to r;

[0068] : represents the pseudorange ionosphere-free combined observation value of LEO receiver to BDS satellite;

[0069] : represents the carrier phase ionosphere-free combined observation value of LEO receiver to BDS satellite;

[0070] P right upper is the signal transmitting end, which can be a GNSS medium-high orbit satellite or a LEO navigation satellite; P right lower is the signal receiving end, which can be a ground receiver or a receiver on LEO.

[0071] The precise orbit and clock error of BDS medium-high orbit satellite are used for LEO precise orbit determination, and thus the precise orbit of BDS low orbit navigation satellite and the BDS clock error result of signal receiving end can be obtained .

[0072] Step 120:

[0073] With the known orbits and clock errors of the medium-high orbit satellites, the ionosphere delay is eliminated by ionosphere-free combination, and the LEO orbit error and the receiving end clock error are reserved. Based on the dynamic model or kinematic method, the orbit parameters of the LEO and the signal receiving end clock error, i.e. the clock deviation of the LEO satellite when receiving the signal, are solved by simultaneous equations.

[0074] Thus, the precise orbit parameters of the LEO satellite and the receiving end clock error are obtained, which lays a foundation for subsequent clock error solving.

[0075] The BDS dual-frequency pseudo-range and carrier phase observation values received by the low-orbit navigation satellite are used to form ionosphere-free combination observation equations as follows:

[0076]

[0077] Among them:

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085] In the formula: BDS satellite and LEO receiver are respectively represented;

[0086] The geometric distance between the BDS satellite and the observation station is represented;

[0087] And The speed of light, clock error and clock error containing differential code bias are respectively represented;

[0088] The pseudo-range and phase hardware delay are represented;

[0089] The ambiguity parameter is represented;

[0090] The pseudo-range and phase IF combination noise are represented.

[0091] : represents the ionosphere-free combined pseudorange observation of the LEO receiver to the BDS satellite;

[0092] : represents the ionosphere-free combined carrier phase observation of the LEO receiver to the BDS satellite;

[0093] The BDS low-orbit navigation satellite precise orbit and the BDS clock bias at the signal receiving end are obtained by using the BDS medium-orbit and high-orbit satellite precise orbit and clock bias for LEO precise orbit determination processing .

[0094] Step 130:

[0095] A joint equation set containing the LEO signal transmitting end clock bias, the medium-orbit and high-orbit satellite clock bias, and the receiver clock bias is established by using the dual-frequency mixed observation data of the ground station, and the LEO transmitting end clock bias in the ground visible arc segment is solved by a least square method and other optimization algorithms. The LEO orbit parameters are taken as known quantities to constrain the solving of the transmitting end clock bias.

[0096] The LEO transmitting end clock bias in the ground station visible period is obtained, and the problem that the transmitting end clock bias cannot be directly solved by only using the LEO observation is solved.

[0097] The BDS dual-frequency pseudorange and carrier phase observations containing low-orbit, medium-orbit and high-orbit satellites received by the globally distributed ground stations are ionosphere-free combined, and a clock bias solving equation set is established:

[0098]

[0099]

[0100] The matrix form corresponding to each parameter form in the formula is as follows:

[0101]

[0102] In the formula:

[0103]

[0104]

[0105]

[0106] And represents the troposphere mapping function;

[0107] represents the zenith troposphere delay of the ground station;

[0108] 、 、 、 respectively represent noise terms of different observation data;

[0109] The matrix H represents a coefficient matrix;

[0110] Solving the above matrix, the clock difference result of the signal transmitting end of the Beidou low earth orbit navigation satellite in the visible arc segment is obtained .

[0111] Step 140:

[0112] The mathematical model of the receiving end clock difference and the transmitting end clock difference in the visible arc segment is fitted respectively, and the law of its change with time is described. The difference between the receiving end clock difference model and the transmitting end clock difference model is obtained by operation, which reflects the difference between the two kinds of clock differences in time continuity and physical mechanism. The space-time characteristics of the clock difference are converted into mathematical expressions, which provides a theoretical basis for the full-arc clock difference conversion.

[0113] The clock difference is decomposed into a polynomial trend item and a periodic item, and the model is described as follows:

[0114]

[0115] In the formula: represents the clock difference value at time t, are the orders of the polynomial and the periodicity respectively, are the amplitude, frequency component and phase of the periodic disturbance respectively, represents random noise. represents the coefficient of the polynomial trend item;

[0116] : represents the j-th power of the time variable t, j is the order of the polynomial item, which is used to describe the polynomial trend component in the signal;

[0117] : represents time t.

[0118] 1) Model the low earth orbit navigation satellite receiving end clock difference obtained by S2:

[0119]

[0120] represents the random noise term in the model;

[0121] 2) Model the signal transmitting end clock difference in the visible arc segment obtained by S3:

[0122]

[0123] represents the random noise term in the model;

[0124] 3) Obtain the difference between the two clock error models:

[0125]

[0126] Step 150:

[0127] Using the clock bias model difference obtained in step 140, the receiver clock bias calculated in step 120 based on medium- and high-orbit satellite observations is converted into the transmitter clock bias of LEO satellites across the entire orbital arc through a model mapping relationship. The clock bias model difference is continuous in time and can achieve full arc coverage through mathematical extrapolation or interpolation.

[0128] Clock bias of BeiDou low-orbit navigation satellite signal receiver obtained based on observation data from high-orbit satellites in the BeiDou system received by low-orbit navigation satellites ( ), based on S4 model difference It can obtain the clock bias of the BeiDou low-orbit navigation satellite signal transmitter, that is, the precise clock bias information of the BeiDou low-orbit navigation satellite. ):

[0129]

[0130] The embodiments of this application are not limited to the precise clock bias calculation of low-orbit navigation satellites applied to the BeiDou navigation system, but can also be used for GPS, GALILEO, GLONASS and other navigation systems; the clock bias sequence used for modeling in the embodiments of this application can be derived from the product of post-calculation, and the clock bias model difference can be used for high-frequency calculation and prediction of precise clock bias of low-orbit navigation satellites under different time-sensitivity conditions, namely post-calculation mode and real-time mode.

[0131] This allows for the filling of clock bias gaps at the transmitter during periods when ground stations are not visible, achieving clock bias uniformity across the entire orbital cycle of LEO satellites and improving the continuity and reliability of the navigation system.

[0132] In one possible embodiment, the medium-to-high orbit GNSS satellite observation data received by LEO includes:

[0133] Dual-frequency pseudorange observations and carrier phase observations are used to eliminate the error in clock error calculation caused by ionospheric delay.

[0134] Dual-frequency pseudorange observations: These refer to the "pseudo-range" data calculated by measuring the propagation time difference of signals from medium- and high-orbit GNSS satellites to the LEO satellite, which are received by a low-Earth orbit (LEO) navigation satellite from signals transmitted on two different frequencies. The "pseudorange" is the raw distance observation value without correction for errors such as clock errors and atmospheric delays.

[0135] Carrier phase observation: refers to the data obtained by measuring the phase change of the signal carrier when the LEO receives the signal of the medium-high orbit GNSS satellite. The carrier phase observation can be used for more accurate distance calculation, but there is a problem of solving the integer ambiguity.

[0136] Ionospheric delay: refers to the delay error caused by the influence of free electrons and ions in the ionosphere on the signal propagation speed when the radio signal passes through the ionosphere of the earth. The ionospheric delay is related to the signal frequency, and the higher the frequency, the smaller the delay.

[0137] High-frequency signals (such as L2 frequency band) are less affected by ionospheric delay, while low-frequency signals (such as L1 frequency band) are more affected. The delay of both is inversely proportional to the square of the frequency. By simultaneously using the dual-frequency pseudorange or carrier phase observation of the same satellite, the ionospheric delay terms are offset by weighted combination of the two sets of data, so that the "pure" observation data containing almost no ionospheric error is obtained, which is used for subsequent clock difference calculation.

[0138] Therefore, the difference in frequency dependence of ionospheric delay can be used to offset the influence of this error on clock difference calculation, and after eliminating the ionospheric error, the pseudorange and carrier phase observation can more truly reflect the signal propagation time between the satellite and the LEO, so as to accurately calculate the signal receiving end clock difference of the LEO. The high resolution characteristic of the carrier phase observation further improves the accuracy of the clock difference calculation, and lays a foundation for subsequent joint ground station data calculation of the launch end clock difference.

[0139] In one possible embodiment, step 120 can specifically include the following steps:

[0140] Constructing an ionosphere-free combined observation equation, which eliminates the ionospheric delay term by weighted combination of dual-frequency observations;

[0141] Solving the ionosphere-free combined observation equation to obtain the satellite orbit parameters and signal receiving end clock difference of the LEO.

[0142] Ionosphere-free combined observation equation: refers to an observation equation constructed by specific weighted combination of dual-frequency observations of medium-high orbit GNSS satellites received by low-orbit navigation satellites (LEO). Its core characteristic is to eliminate the systematic influence of ionospheric delay on observation data, so that the equation no longer contains ionosphere-related error terms.

[0143] Dual-frequency observation: refers to the observation data formed after the navigation satellite simultaneously transmits signals at two different frequencies (such as L1 and L2) and the signals are received by the LEO. Since the delay of the ionosphere to signals of different frequencies is inversely proportional to the square of the frequency, the difference between dual-frequency data can offset the ionospheric error.

[0144] High-frequency signals (such as L2) are less affected by ionospheric delay, while low-frequency signals (such as L1) are more affected. By combining the dual-frequency observations with appropriate weights, the ionospheric delay terms of the two can be canceled out, resulting in a pure observation equation that only contains satellite orbit errors, clock errors, noise, and other factors.

[0145] Based on the constructed ionosphere-free combined observation equation, the unknown parameters in the equation are fitted and solved with known medium-high orbit GNSS satellite orbit parameters and clock difference products using data processing algorithms such as least squares. Through iterative calculation, the real values are gradually approached, and finally the orbit parameters of LEO and the clock difference at the receiving end are obtained. By combining dual-frequency to eliminate the systematic interference of ionosphere on observation data, the deviation caused by orbit calculation and clock difference calculation is avoided, and the data accuracy is improved.

[0146] Orbit parameters: including three-dimensional position, velocity, etc. of LEO, providing a basis for subsequent orbit determination and time synchronization.

[0147] Signal receiving end clock difference: the deviation of the LEO satellite's own clock from the true time when receiving signals, which is a key parameter for achieving high-precision time synchronization.

[0148] Through this step, high-precision LEO orbit information and receiving end time reference can be obtained, laying a foundation for subsequent joint resolution of launch end clock difference using mixed observation data from ground stations.

[0149] In one possible embodiment, step 130 can specifically include the following steps:

[0150] Using the dual-frequency observation data of LEO and medium-high orbit satellites received by the ground station, a linear equation set containing the ground station clock difference, LEO launch end clock difference, and tropospheric delay is constructed;

[0151] The linear equation set is solved by the least squares method to obtain the signal launch end clock difference of LEO within the visible arc segment of the ground station.

[0152] Ground station clock difference: refers to the deviation between the time displayed by the clock of the ground observation station and the true time. When the ground station receives satellite signals, its own clock error will directly affect the time reference of the observation data, which needs to be involved in the calculation as an unknown parameter.

[0153] LEO launch end clock difference: refers to the deviation between the time displayed by the satellite atomic clock and the true time when the low-orbit navigation satellite (LEO) launches signals. This parameter is the core target of time synchronization and needs to be obtained by solving the observation data.

[0154] Tropospheric delay: The delay error caused by the influence of water vapor, carbon dioxide and other gases in the atmosphere on the signal propagation speed when the radio signal passes through the Earth's troposphere. Tropospheric delay is related to signal propagation path and weather conditions, which needs to be corrected in the model or as an error term in the solution.

[0155] Linear equation set: A set of equations composed of multiple linear equations, each describing the linear relationship between observed data and unknown parameters. By solving the equation set simultaneously, the values of multiple unknown parameters can be determined.

[0156] Through the dual-frequency observation data of LEO and medium-high orbit satellites by ground stations, a mathematical model of multiple parameter correlation is established, and statistical methods are used to eliminate errors and solve target parameters. The signals received by the ground station contain observation data of LEO and medium-high orbit satellites, and each observation value is affected by factors such as ground station clock error, LEO launch end clock error, and tropospheric delay.

[0157] Based on the time relationship of signal propagation, each observation value is expressed as a linear combination of unknown parameters. For example:

[0158] Observation value = true geometric distance + ground station clock error influence + LEO launch end clock error influence + tropospheric delay + other noise error + ionospheric delay;

[0159] Through the combination of dual-frequency observation values, the equation is further simplified, and the unknown parameters only include the ground station clock error, the LEO launch end clock error and the tropospheric delay.

[0160] Due to random noise in the observation data, direct solution of the equation set may have multiple solutions or deviations. The least squares method finds the parameter combination closest to the true value by minimizing the sum of the squares of all observation errors.

[0161] By simultaneously solving the ground station clock error, LEO launch end clock error and tropospheric delay with the same set of observation data, the interference of other errors in single parameter solution is avoided. For example: the ground station clock error can be known or partially constrained by long-term calibration or comparison with medium-high orbit satellite clock error, so as to separate the independent solution of LEO launch end clock error.

[0162] Ground visible arc segment refers to the time period when LEO satellite is within the line of sight of ground station. During this period, the ground station can continuously receive LEO signals, providing sufficient observation data for solution. With the fixed position of the ground station and high-precision observation equipment, combined with the known orbit and clock error products of medium-high orbit satellites, the solution error can be greatly reduced. Dual-frequency data eliminates ionospheric delay, least squares method suppresses random noise, so that the LEO launch end clock error accuracy reaches nanosecond level or higher, meeting the stringent requirements of navigation system for time synchronization.

[0163] In one possible embodiment, step 140 can specifically include the following steps:

[0164] Establishing a receiving-end clock difference model and a transmitting-end clock difference model, the receiving-end clock difference model being used to characterize the change rule of the receiving-end clock difference over time, and the transmitting-end clock difference model being used to characterize the change rule of the transmitting-end clock difference over time.

[0165] Extracting the clock difference model difference between the receiving-end clock difference model and the transmitting-end clock difference model in the trend item and the periodic disturbance item.

[0166] Clock difference model: a mathematical expression describing the change rule of the clock difference over time. By analyzing the historical data of the clock difference, a model that can reflect its long-term trend and short-term fluctuation is fitted, which is used to predict or correct the clock difference at different times.

[0167] Trend item: the part of the clock difference model reflecting the long-term change rule, which usually shows a monotonic increase, decrease or polynomial change over time. For example, the drift of a satellite atomic clock will cause the clock difference to show an approximately linear trend change.

[0168] Periodic disturbance item: the part of the clock difference model with periodic fluctuation characteristics, such as daily or semidiurnal periodic errors. Such errors may be caused by factors such as satellite orbit motion, Earth rotation, temperature changes on the clock body, etc.

[0169] By analyzing the time variation characteristics of the receiving-end and transmitting-end clock differences, the systematic differences between the two are separated, providing a basis for cross-period clock difference conversion. Based on the LEO satellite orbit parameters and signal receiving-end clock difference data solved in step 120, the change rule of the clock difference over time is fitted. For example, if the receiving-end clock difference approximately linearly increases over a long period of time.

[0170] Based on the LEO signal transmitting-end clock difference data in the ground visible arc segment solved in step 130, the change rule of the clock difference over time is fitted. Since the data in the visible period is more intensive and contains ground station observation constraints, the transmitting-end clock difference model may more accurately reflect the short-term fluctuation of the true clock difference.

[0171] The two models are decomposed into two parts: trend item and periodic disturbance item.

[0172] Trend item comparison: analyze whether the long-term change rates of the two are consistent.

[0173] Periodic disturbance item comparison: check whether there are fluctuations of the same period in the two, but the amplitude or phase may be different.

[0174] The model difference essentially reflects the inconsistency of the clock difference between the receiving end and the transmitting end in the time characteristics. For example: the clock difference at the receiving end may accumulate more trend errors due to the lack of ground constraints during the non- visible period of the LEO satellite; the clock difference at the transmitting end is corrected by ground station observation during the visible period, and the periodic disturbance is closer to the true value.

[0175] By comparing the trend items, the long-term drift difference of the clock difference between the receiving end and the transmitting end can be identified, which may be caused by satellite payload or solution conditions. By comparing the periodic disturbance items, the regularity of the two being affected by the same physical factors can be found, while the disturbance amplitude difference caused by different observation environments can be found.

[0176] Step 150 needs to convert the clock difference at the receiving end to the clock difference at the transmitting end. At this time, the model difference can be used as a "correction factor": if the trend item difference is "2 nanoseconds per day faster at the receiving end than at the transmitting end", the trend difference needs to be deducted from the clock difference at the receiving end when converting the entire arc segment; if the periodic disturbance item difference is "there is an additional 12-hour period error of ± 2 nanoseconds at the receiving end", the disturbance needs to be offset when converting.

[0177] By analyzing the source of the model difference, the clock difference modeling method can be optimized, for example, a compensation term for error accumulation during the non- visible period can be added to the receiving end model. By constructing the clock difference model and extracting the difference, the time characteristic difference between the clock difference at the receiving end and the clock difference at the transmitting end is converted into a quantifiable correction parameter, providing a theoretical basis for subsequent clock difference conversion of the entire arc segment, ensuring the consistency of the time reference of the LEO satellite during the entire operation period.

[0178] Among the above-mentioned steps of establishing the clock difference model at the receiving end and the clock difference model at the transmitting end, the specific steps can include the following steps:

[0179] A trend item model is constructed based on the physical characteristics of the atomic clock, and the trend item model is used to describe the long-term drift characteristics of the clock difference;

[0180] The clock difference sequence is analyzed by Fourier transform or wavelet transform to extract the periodic disturbance items related to the orbit, and a periodic item model is formed;

[0181] According to the trend item model and the periodic item model, the clock difference model at the receiving end and the clock difference model at the transmitting end are obtained.

[0182] Atomic clocks use the stable frequency of atomic energy level transitions to generate time references, and their physical characteristics include long-term frequency drift and short-term stability. These characteristics determine the long-term trend and random noise characteristics of the clock difference.

[0183] Fourier transform: a mathematical method for decomposing clock difference sequences into different frequency sine waves superimposed, used to identify the periodic components and their amplitudes and phases hidden in the signal.

[0184] Wavelet transform: Similar to Fourier transform, but better at analyzing non-stationary signals, can locate both the frequency and the time of occurrence of periodic disturbances.

[0185] Spectral analysis: Convert the clock difference series from "time domain" to "frequency domain" by Fourier or wavelet transform, analyze the energy distribution of different frequency components, and identify the periodic disturbances related to satellite orbit period, Earth rotation period, etc.

[0186] Combine the physical laws of atomic clocks and signal processing techniques to separate the long-term trend and periodic fluctuations of clock differences, and build models that conform to actual physical phenomena. The long-term drift of atomic clocks is usually approximated as a linear or low-order polynomial law. For example: if the atomic clock frequency is 1 × 10⁻¹² per day, the clock difference trend item model can be expressed as "initial deviation + drift rate × time". By analyzing the long-term trend of historical clock difference data, a trend item consistent with the physical characteristics of the atomic clock is fitted, and the interference of random noise is removed.

[0187] During satellite operation, clock differences may be affected by periodic factors related to the orbit, such as:

[0188] Orbit period: LEO satellites complete one orbit around the Earth, and their relative geometric relationship with medium-high orbit satellites or ground stations repeats once, which may cause 90-minute periodic disturbances in clock differences;

[0189] Earth rotation period: The observation range of the ground station changes with the Earth's rotation within 24 hours, which may introduce 24-hour or 12-hour periodic disturbances.

[0190] Fourier or wavelet transform can separate the frequency components of these periodic fluctuations in the clock difference series, for example: Fourier transform shows that a certain frequency component has significant energy, then the corresponding periodic item model is "sinusoidal wave (amplitude × sin (2π × time / period + phase))"; wavelet transform can further analyze whether the periodic disturbance only occurs at a specific orbit stage, thereby more accurately modeling.

[0191] The actual clock difference can be considered as the superposition of long-term trend and periodic fluctuations. For example: the trend item model describes the long-term change of "atomic clock drifts 50 nanoseconds per day"; the periodic item model describes "±10 nanosecond fluctuations every 12 hours". Adding them together, we get the complete clock difference model: clock difference = trend item + periodic item + random noise.

[0192] The trend item model is based on the physical characteristics of atomic clocks, avoiding non-physical deviations that may be introduced by pure data fitting, making the model more consistent with the clock operation law.

[0193] The periodic term model locks the disturbance related to physical phenomena such as orbits and the rotation of the earth through spectral analysis, avoids missing errors caused by actual operating environments, and improves the ability of the model to depict real clock errors.

[0194] Trend term errors can be improved through long-term calibration or replacement of high-stability clocks; periodic disturbance term errors can be corrected by pre-compensating fluctuations of the corresponding period in the model. For example, if the periodic term model shows that there is a ±8 nanosecond disturbance of 90 minutes, the periodic error can be directly deducted when solving the clock error, thereby improving the accuracy of the time reference.

[0195] The receiver clock error model and the transmitter clock error model are both based on the same trend term and periodic term modeling logic, ensuring that the differences between the two are only due to observation conditions and not the model structure. By comparing the trend term differences and the periodic term differences between the two in subsequent steps, the error characteristics under different observation scenarios can be directly reflected, providing a clear correction direction for clock error conversion.

[0196] By combining the physical laws of atomic clocks and signal spectrum analysis, the clock error is decomposed into trend terms and periodic terms that conform to the actual physical meaning, enabling the model to describe the long-term drift characteristics of atomic clocks and capture periodic disturbances caused by orbit operation, thereby laying a foundation for high-precision clock error modeling and cross-scene time reference unification.

[0197] In the embodiments of the present application, the observation data of the medium-high orbit GNSS satellite received by the low orbit navigation satellite LEO, the dual-frequency mixed observation data containing LEO and medium-high orbit satellites received by the ground station, and the satellite orbit parameters and clock error products of the medium-high orbit GNSS satellite are obtained. The clock error product is the deviation between the time displayed by the satellite atomic clock and the real time; the observation data received by the LEO is precisely orbited without ionosphere combination based on the satellite orbit parameters and clock error products of the medium-high orbit GNSS satellite, to obtain the satellite orbit parameters and signal receiving end clock error of the LEO; the signal transmitting end clock error of the LEO in the ground visible arc segment is jointly solved based on the dual-frequency mixed observation data; and the transmitting end time error data of the LEO in the ground visible area is filled.

[0198] A mathematical model is established for the signal receiving end clock difference of LEO and the signal transmitting end clock difference of LEO in the ground visible arc segment, and a clock difference model difference is extracted, which is the difference between the receiving end clock difference model and the transmitting end clock difference model; the local transmitting end clock difference is solved through the ground station data, and is extended to the full orbit in combination with the model difference, solving the clock difference missing problem of the ground observation blind area; according to the clock difference model difference, the signal receiving end clock difference of LEO is converted into the full arc segment signal transmitting end clock difference of LEO, realizing the dynamic prediction and accurate compensation of the LEO clock difference, and finally improving the time synchronization accuracy and positioning reliability of the low-orbit navigation system.

[0199] The low-orbit navigation satellite clock difference solving method is described below Figure 2 The embodiments of the present application are described as follows:

[0200] The input data layer is related to:

[0201] The low-orbit satellite (LEO) receives the signals of the medium-orbit / high-orbit satellite (such as the medium-orbit / high-orbit satellite of GPS and Beidou) itself to obtain the original observation data for subsequent calculation. The medium-orbit / high-orbit satellite has mature precise orbit and clock difference products, which are used as known references to provide a “reference standard” for the low-orbit satellite orbit determination and clock difference solving. The ground station receives the signals of the low-orbit, medium-orbit and high-orbit satellites to form mixed observation data for constraining the clock difference of the low-orbit satellite from the ground perspective.

[0202] The intermediate solving layer is related to:

[0203] The “low-orbit received medium-orbit / high-orbit data” and the “medium-orbit / high-orbit precise orbit / clock difference” are used to calculate the precise orbit of the low-orbit satellite through ionosphere-free combination orbit determination, and the clock difference of the low-orbit satellite when receiving signals. The “ground received mixed observation data” is used to solve the clock difference of the low-orbit satellite when transmitting signals in combination with the known information of the ground station. However, due to the limitation of the visible range of the ground station, only the “period when the ground can see the low-orbit satellite” is covered, which is not the full orbit. The trend item model is established by using the physical characteristics of the atomic clock for the “receiving end clock difference” and the “transmitting end clock difference”. The periodic item model is found by using the Fourier / wavelet transform. The differences of the trend item and the periodic item are found by comparing the “receiving end clock difference model” and the “transmitting end clock difference model”.

[0204] The output result layer is related to:

[0205] The difference between the receiving end clock difference and the clock difference model is used to extend the transmitting end clock difference covering only the visible arc segment to the full orbit of the low-orbit satellite. Finally, the precise clock difference of the low-orbit satellite in the full operation period and the full orbit is obtained, which supports the time synchronization and positioning accuracy improvement of the navigation system.

[0206] Based on the above Figure 1The low-orbit navigation satellite clock error solving method and the low-orbit navigation satellite clock error solving device are provided. Figure 3 The low-orbit navigation satellite clock error solving device 300 can include:

[0207] The acquisition module 310 is configured to acquire the middle-high-orbit GNSS satellite observation data received by the low-orbit navigation satellite LEO, the double-frequency mixed observation data containing the LEO and the middle-high-orbit satellite received by the ground station, and the satellite orbit parameter and the clock error product of the middle-high-orbit GNSS satellite, wherein the clock error product is the deviation between the time displayed by the satellite atomic clock and the real time.

[0208] The orbit determination module 320 is configured to perform ionosphere-free combination precise orbit determination on the observation data received by the LEO based on the satellite orbit parameter and the clock error product of the middle-high-orbit GNSS satellite, to obtain the satellite orbit parameter and the signal receiving end clock error of the LEO.

[0209] The solving module 330 is configured to jointly solve the signal transmitting end clock error of the LEO in the ground visible arc segment based on the double-frequency mixed observation data.

[0210] The extraction module 340 is configured to respectively establish mathematical models for the signal receiving end clock error of the LEO and the signal transmitting end clock error of the LEO in the ground visible arc segment, and extract the clock error model difference, wherein the clock error model difference is the difference between the receiving end clock error model and the transmitting end clock error model.

[0211] The conversion module 350 is configured to convert the signal receiving end clock error of the LEO into the full-arc-segment signal transmitting end clock error of the LEO according to the clock error model difference.

[0212] In a possible embodiment, the middle-high-orbit GNSS satellite observation data received by the LEO includes:

[0213] Double-frequency pseudo-range observation values and carrier phase observation values, wherein the double-frequency observation values are used to eliminate the error of the clock error solving caused by the ionospheric delay.

[0214] In a possible embodiment, the orbit determination module 320 is specifically configured to:

[0215] Construct an ionosphere-free combination observation equation, wherein the ionosphere-free combination observation equation eliminates the ionospheric delay term by weighting the double-frequency observation values.

[0216] Solve the ionosphere-free combination observation equation to obtain the satellite orbit parameter and the signal receiving end clock error of the LEO.

[0217] In a possible embodiment, the solving module 330 is specifically configured to:

[0218] A linear equation set containing the ground station clock error, the LEO launch end clock error and the troposphere delay is constructed by using the LEO and medium-high orbit satellite dual-frequency observation data received by the ground station;

[0219] The linear equation set is solved by the least square method to obtain the signal launch end clock error of the LEO in the ground visible arc segment.

[0220] In a possible embodiment, the extraction module 340 is specifically configured to:

[0221] The launch end clock error model is used to represent the variation law of the launch end clock error with time.

[0222] The clock error model difference between the receiving end clock error model and the launch end clock error model on the trend term and the periodic disturbance term is extracted.

[0223] In a possible embodiment, the extraction module 340 is specifically configured to:

[0224] The trend term model is constructed based on the physical characteristics of the atomic clock, and is used to describe the long-term drift characteristics of the clock error.

[0225] The clock error sequence is analyzed by the Fourier transform or the wavelet transform to extract the periodic disturbance term related to the orbit and form the periodic term model.

[0226] The receiving end clock error model and the launch end clock error model are obtained according to the trend term model and the periodic term model.

[0227] In the embodiments of the present application, the observation data of the medium-high orbit GNSS satellite received by the low orbit navigation satellite LEO and the double-frequency mixed observation data containing the LEO and the medium-high orbit satellite received by the ground station, and the satellite orbit parameters and clock difference products of the medium-high orbit GNSS satellite are acquired, the clock difference product is the deviation between the time displayed by the satellite atomic clock and the real time; the observation data received by the LEO is precisely tracked without ionosphere combination through the satellite orbit parameters and clock difference products of the medium-high orbit GNSS satellite, and the satellite orbit parameters and signal receiving end clock difference of the LEO are obtained; the orbit and receiving end clock difference of the LEO are accurately acquired by using the medium-high orbit satellite resources and double-frequency observation technology to eliminate the interference of ionosphere and the like; the signal transmitting end clock difference of the LEO in the ground visible arc segment is jointly solved based on the double-frequency mixed observation data; and the transmitting end time error data of the LEO in the ground visible area is filled. The mathematical models of the signal receiving end clock difference of the LEO and the signal transmitting end clock difference of the LEO in the ground visible arc segment are respectively established, the clock difference model difference is extracted, the clock difference model difference is the difference between the receiving end clock difference model and the transmitting end clock difference model; the local transmitting end clock difference is solved through the ground station data, and is extended to the full orbit in combination with the model difference, so that the clock difference missing problem of the ground observation blind area is solved, the signal receiving end clock difference of the LEO is converted into the full-arc segment signal transmitting end clock difference of the LEO according to the clock difference model difference, the dynamic prediction and accurate compensation of the LEO clock difference are realized, and finally the time synchronization accuracy and positioning reliability of the low orbit navigation system are improved.

[0228] Figure 4 A hardware structure schematic diagram of an electronic device provided by the embodiments of the present application is shown.

[0229] The electronic device can include a processor 401 and a memory 402 having computer program instructions stored therein.

[0230] Specifically, the processor 401 can include a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0231] The memory 402 can include mass storage for data or instructions. By way of example, and not limitation, the memory 402 can include a hard disk drive (HDD), floppy disk drive, flash memory, compact disk, digital versatile disk, optical disk, tape, or universal serial bus (USB) drive or combinations of two or more of these. The memory 402 can be removable and / or non-removable (or fixed) as appropriate. The memory 402 can be internal or external as appropriate. In certain embodiments, the memory 402 is non-volatile solid-state memory. In certain embodiments, the memory 402 includes read-only memory (ROM). The ROM can be mask programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory, or combinations of two or more of these, as appropriate.

[0232] The processor 401 implements any of the low earth orbit navigation satellite clock error solving methods in the embodiments shown in the figures by reading and executing computer program instructions stored in the memory 402.

[0233] In one example, the electronic device can further include a communication interface 404 and a bus 410. As shown, the processor 401, the memory 402, and the communication interface 404 are connected through the bus 410 and complete communication with each other. Figure 4

[0234] The communication interface 404 is mainly used to realize the communication between the modules, devices, units, and / or equipment in the embodiments of the present application.

[0235] The bus 410 includes hardware, software, or both, that couples components of the electronic device to each other. By way of example, and not limitation, the bus can include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), a HyperTransport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an InfiniBand (IB) interconnect, a Low Pin Count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local (VLB) bus, or another suitable bus or interconnect, or combinations of two or more of these. The bus 410 can include one or more buses, as appropriate. Although the present application describes and illustrates a particular bus, the present application contemplates any suitable bus or interconnect.

[0236] ​The electronic device can execute the low-orbit navigation satellite clock error solving method in the embodiments of the present application, so as to realize the low-orbit navigation satellite clock error solving method combined with Figure 2 The low-orbit navigation satellite clock error solving method is described.

[0237] In addition, in combination with the low-orbit navigation satellite clock error solving method in the above embodiments, the embodiments of the present application can provide a computer readable storage medium to realize. The computer readable storage medium has computer program instructions stored thereon; the computer program instructions are executed by a processor to realize the low-orbit navigation satellite clock error solving method. Figure 1

[0238] It should be noted that the present application is not limited to the specific configurations and processes described above and shown in the drawings. For the sake of brevity, detailed descriptions of well-known methods are omitted herein. In the above embodiments, several specific steps are described and shown as examples. However, the method processes of the present application are not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between steps, after understanding the spirit of the present application.

[0239] The functional blocks shown in the structural block diagrams described above can be implemented as hardware, software, firmware or a combination thereof. When implemented in hardware, it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a functional card, etc. When implemented in software, the elements of the present application are program or code segments used to perform the required tasks. The program or code segments can be stored in a machine readable medium or transmitted through a data signal carried in a carrier wave over a transmission medium or communication link. The "machine readable medium" can include any medium capable of storing or transmitting information. Examples of machine readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, optical fiber media, radio frequency (RF) links, etc. The code segments can be downloaded via a computer network such as the Internet, an intranet, etc.

[0240] It should also be noted that the exemplary embodiments mentioned in the present application describe some methods or systems based on a series of steps or devices. However, the present application is not limited to the order of the above steps, that is, the steps can be executed in the order mentioned in the embodiments, or in an order different from the embodiments, or several steps can be executed simultaneously.

[0241] ​The above merely describes a specific implementation of the present application. Those skilled in the art can clearly understand the specific working processes of the system, modules and units described above for the convenience and brevity of description, and can refer to the corresponding processes in the foregoing method embodiments, which will not be described herein again. It should be understood that the protection scope of the present application is not limited to this, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application.

Claims

1. A method for calculating the clock bias of low-Earth orbit navigation satellites, characterized in that, The method includes: Acquire observation data from medium and high orbit GNSS satellites received by low orbit navigation satellites (LEO), dual-frequency hybrid observation data containing LEO and medium and high orbit satellites received by ground stations, and satellite orbit parameters and clock bias products of medium and high orbit GNSS satellites. Clock bias products are the deviation between the time displayed by the satellite atomic clock and the actual time. By using the satellite orbit parameters and clock bias products of medium and high orbit GNSS satellites, ionospherically-free combined precise orbit determination is performed on the observation data received by LEO, and the satellite orbit parameters and signal receiver clock bias of LEO are obtained. Based on dual-frequency hybrid observation data, the clock difference of the signal transmitter in the LEO within the visible arc of the ground is jointly calculated; Mathematical models were established for the clock bias at the receiver of the LEO and the clock bias at the transmitter of the LEO within the visible arc of the ground. The difference between the clock bias models was extracted, which is the difference between the receiver clock bias model and the transmitter clock bias model. The difference between the clock bias models is obtained by decomposing the receiver clock bias and the transmitter clock bias into polynomial trend terms and periodic terms, respectively, establishing receiver clock bias models and transmitter clock bias models, and calculating the difference between the receiver clock bias model and the transmitter clock bias model. Based on the clock difference model, the clock difference at the signal receiver of LEO is converted into the clock difference at the full-segment signal transmitter of LEO.

2. The method according to claim 1, characterized in that, The LEO-received medium- and high-orbit GNSS satellite observation data includes: Dual-frequency pseudorange observations and carrier phase observations are used to eliminate the error in clock error calculation caused by ionospheric delay.

3. The method according to claim 1, characterized in that, The method involves using the satellite orbit parameters and clock bias products of medium- and high-orbit GNSS satellites to perform ionospherically-free combined precise orbit determination on the observation data received by LEO, obtaining the LEO satellite orbit parameters and signal receiver clock bias, including: An ionospheric-free combined observation equation is constructed, which eliminates the ionospheric delay term by weighting dual-frequency observations. Solve the combined observation equations without ionosphere to obtain the satellite orbital parameters and signal receiver clock errors of LEO.

4. The method according to claim 1, characterized in that, The method of jointly calculating the clock bias of the signal transmitter of LEO within the visible arc of the ground based on dual-frequency hybrid observation data includes: Using dual-frequency observation data from LEO and medium-high orbit satellites received by the ground station, a system of linear equations was constructed, including the clock bias of the ground station, the clock bias of the LEO transmitter, and the tropospheric delay. The clock bias of the signal transmitter in the LEO within the visible arc segment on the ground is obtained by solving the linear equations using the least squares method.

5. The method according to claim 1, characterized in that, The process involves establishing mathematical models for the clock bias at the LEO signal receiver and the clock bias at the LEO signal transmitter within the visible arc of the ground, and extracting the differences in the clock bias models, including: Establish a receiver clock bias model and a transmitter clock bias model. The receiver clock bias model is used to characterize the variation of the receiver clock bias with time, and the transmitter clock bias model is used to characterize the variation of the transmitter clock bias with time. Extract the differences in clock bias models between the receiver and transmitter in terms of trend and periodic disturbance terms.

6. The method according to claim 5, characterized in that, The establishment of the receiver clock bias model and the transmitter clock bias model includes: A trend term model is constructed based on the physical properties of atomic clocks. The trend term model is used to describe the long-term drift characteristics of clock bias. Spectral analysis of clock error sequences is performed using Fourier transform or wavelet transform to extract orbit-related periodic perturbation terms and form a periodic term model. Based on the trend term model and the period term model, the receiver clock bias model and the transmitter clock bias model are obtained.

7. A low-orbit navigation satellite clock bias calculation device, characterized in that, The device includes: The acquisition module is used to acquire observation data from medium and high orbit GNSS satellites received by the low orbit navigation satellite (LEO), dual-frequency mixed observation data containing LEO and medium and high orbit satellites received by the ground station, and satellite orbit parameters and clock bias products of medium and high orbit GNSS satellites. The clock bias products are the deviation between the time displayed by the satellite atomic clock and the actual time. The orbit determination module is used to perform ionospherically-free combined precise orbit determination on the observation data received by LEO using the satellite orbit parameters and clock error products of medium and high orbit GNSS satellites, so as to obtain the satellite orbit parameters and signal receiver clock error of LEO. The calculation module is used to jointly calculate the clock difference of the signal transmitter of LEO within the visible arc of the ground based on dual-frequency hybrid observation data; The extraction module is used to establish mathematical models for the clock bias at the signal receiver of the LEO and the clock bias at the signal transmitter of the LEO within the visible arc of the ground, and to extract the difference between the clock bias models. The difference between the clock bias models is the difference between the receiver clock bias model and the transmitter clock bias model. The difference between the clock bias models is obtained by decomposing the signal receiver clock bias and the signal transmitter clock bias into polynomial trend terms and periodic terms, respectively, establishing receiver clock bias models and transmitter clock bias models, and calculating the difference between the receiver clock bias model and the transmitter clock bias model. The conversion module is used to convert the clock difference at the signal receiver of the LEO into the clock difference at the full-segment signal transmitter of the LEO based on the clock difference model difference.

8. The apparatus according to claim 7, characterized in that, The extraction module is specifically used for: Establish a receiver clock bias model and a transmitter clock bias model. The receiver clock bias model is used to characterize the variation of the receiver clock bias with time, and the transmitter clock bias model is used to characterize the variation of the transmitter clock bias with time. Extract the differences in clock bias models between the receiver and transmitter in terms of trend and periodic disturbance terms.

9. An electronic device, characterized in that, The electronic device includes: a processor and a memory storing computer program instructions; when the processor executes the computer program instructions, it implements the low-orbit navigation satellite clock bias calculation method as described in any one of claims 1-6.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer program instructions, which, when executed by a processor, implement the low-orbit navigation satellite clock bias calculation method as described in any one of claims 1-6.

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