Method for monitoring integrity of information domain of satellite navigation system

Abstract

The invention provides an integrity monitoring method for an information domain of a satellite navigation system, and belongs to the field of spaceflight measurement and control. The method comprises the following steps: acquiring pseudo-range data measured by an inter-satellite link and reducing the pseudo-range data to respectively obtain geometric distance data without satellite clock error information and relative clock error data without satellite orbit information; performing joint processing on the geometric distance data, and estimating satellite broadcast ephemeris errors; respectively obtaining a radial error, a tangential error and a normal error, and calculating a mean value and a standard deviation of Gaussian distribution of the three errors; setting an integrity risk probability, and respectively calculating upper limit thresholds and lower limit thresholds of the radial error, the tangential error and the normal error according to the mean value and the standard deviation; and when the radial error, the tangential error and the normal error respectively exceed respective threshold values, giving an alarm. According to the invention, the construction cost and the operation and maintenance cost of satellite monitoring are reduced, decoupling of satellite orbit errors and clock error errors is realized, and accurate positioning of faults and accurate monitoring of integrity are realized.

Description

Technical Field

[0001] The invention belongs to the field of aerospace measurement and control, and in particular relates to a method for monitoring the integrity of an information domain of a satellite navigation system. Background Art

[0002] Integrity is an important service attribute of satellite navigation system. The information tasks involved include two categories: one is to describe the accuracy of satellite broadcast ephemeris and clock error parameters broadcast by navigation satellites and inform users; the other is to issue timely warnings to users when there are abnormal integrity events such as the actual state of the satellite being significantly different from the broadcast satellite broadcast ephemeris and clock error parameters, which affect the satellite's inability to achieve the service performance indicators promised to the outside world, such as the failure of the satellite's onboard atomic clock, the failure of the downlink signal generation unit, the decline in the accuracy of satellite broadcast ephemeris, and the decline in the accuracy of clock error parameters. Among them, the abnormal integrity warning is a key factor in determining the integrity service capability of the satellite navigation system, but there is currently a lack of effective monitoring means, rapid fault detection and positioning means. The reasons are: first, there is a lack of sufficient integrity monitoring means to monitor the integrity status of satellites in all dimensions in real time; second, there is a lack of sufficient methods to achieve rapid fault location and adaptive fault severity judgment, and it is impossible to accurately eliminate false alarms and identify accurate real alarms.

[0003] In the prior art, there are several methods for monitoring the integrity of satellite navigation systems from different angles, but all of them have certain shortcomings.

[0004] For example, the Chinese patent with application number 202210268013.1 discloses a method for monitoring the integrity of a satellite navigation system, in which the satellite navigation system performs the following actions: receiving intersatellite link bidirectional measurement data and correcting errors, and using the predicted orbit and predicted clock error parameters to reduce the intersatellite link bidirectional observation data to determine the first intersatellite geometric distance and the first relative clock error; calculating the second intersatellite geometric distance and the second relative clock error according to the satellite navigation message; subtracting the second intersatellite geometric distance and the second relative clock error from the first intersatellite geometric distance and the first relative clock error to determine the geometric distance residual and the relative clock error residual; receiving the pseudo-range data and phase data of the satellite downlink navigation signal from the ground monitoring station and correcting the errors, and using the satellite navigation message to calculate the navigation satellite equivalent distance error; and judging the integrity of the satellite payload according to the geometric distance residual, the relative clock error residual and the navigation satellite equivalent distance error. However, the scheme does not provide quantitative criteria for fault discrimination. In the absence of ground station observation data, it is impossible to accurately locate the cause of satellite faults and abnormal integrity events, and there is a certain missed alarm rate and false alarm rate.

[0005] The Chinese patent application number is 201910673604.5, which discloses a device and method for monitoring the integrity risk of navigation satellites on orbit. The method is as follows: extract the characteristic value of the signal, calculate the abnormal monitoring thresholds of navigation signal power, pseudo code waveform distortion value, pseudo code / carrier consistency, carrier leakage, pseudo code carrier deviation, message consistency, carrier phase consistency, etc. Compare the characteristic value with the monitoring threshold. If the threshold is exceeded, an alarm signal is issued. The integrity of the navigation signal of the on-orbit navigation satellite is monitored, and accurate and timely alarms are provided to users. However, this method cannot determine the integrity status of information domain parameters such as satellite broadcast ephemeris and clock error parameters in real time, nor can it adaptively provide abnormal alarm information of information domain parameters such as satellite broadcast ephemeris and clock error parameters, and there is a certain blind spot in integrity monitoring.

[0006] Another example is the Chinese patent application number 202210776358.8, which discloses a method and device for monitoring the integrity of medium and high-orbit navigation satellites using low-orbit satellites. The low-orbit satellite-borne GNSS pseudo-range phase observation data is used as global observation data, and the satellite broadcast ephemeris and clock error parameters broadcast by the GNSS satellite are subtracted to monitor the integrity status of the GNSS satellite, and the integrity status of information domain parameters such as the GNSS satellite broadcast ephemeris and clock error parameters is achieved. However, this method cannot distinguish between the accuracy of the GNSS satellite broadcast ephemeris and the accuracy of the clock error parameters. More importantly, this method requires a low-orbit satellite constellation as input, which has a high construction cost, high data cost, and a high economic cost. Summary of the invention

[0007] In view of the above-mentioned defects or deficiencies in the prior art, the present invention aims to provide a method for monitoring the integrity of the information domain of a satellite navigation system, which utilizes inter-satellite link observations to monitor the accuracy and integrity status of information domain parameters such as satellite orbit, clock error, satellite broadcast ephemeris, and clock error parameters, and utilizes inter-satellite link observation data to achieve decoupling of satellite orbit accuracy and integrity status monitoring and satellite clock error accuracy and integrity status monitoring, and to achieve adaptive detection and positioning of satellite broadcast ephemeris anomalies and clock error parameter anomalies.

[0008] In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solution:

[0009] An embodiment of the present invention provides a method for monitoring the integrity of an information domain of a satellite navigation system, the method comprising the following steps:

[0010] Step S1, obtaining pseudo-range data of inter-satellite link measurements of all healthy satellites in the navigation system within a preset time period;

[0011] Step S2, calculating the pseudo-range data measured by the inter-satellite link to obtain geometric distance data without satellite clock error information and relative clock error data without satellite orbit information;

[0012] Step S3, jointly processing the geometric distance data of all satellites without satellite clock error information to estimate the satellite broadcast ephemeris error;

[0013] Step S4, respectively obtaining the radial error, tangential error and normal error of the satellite broadcast ephemeris according to the satellite broadcast ephemeris error, and calculating the mean and standard deviation of the Gaussian distribution of the radial, tangential and normal errors of the satellite broadcast ephemeris;

[0014] Step S5, setting the integrity risk probability, and calculating the upper and lower thresholds of the satellite orbit radial error, tangential error and normal error respectively according to the mean and standard deviation of the Gaussian distribution of the radial, tangential and normal errors of the satellite broadcast ephemeris;

[0015] Step S6, when the radial error of the satellite broadcast ephemeris of the satellite at the current moment is greater than the upper threshold of the satellite orbit radial error, or the radial error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit radial error, or the tangential error of the satellite broadcast ephemeris at the current moment is greater than the upper threshold of the satellite orbit tangential error, or the tangential error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit tangential error, or the normal error of the satellite broadcast ephemeris at the current moment is greater than the upper threshold of the satellite orbit normal error, or the normal error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit normal error, a warning is issued.

[0016] As a preferred embodiment of the present invention, the pseudo-range data measured by the inter-satellite link is expressed as:

[0017]

[0018] In equations (1) and (2), i and j represent two satellites, ρ ij (t1) is the pseudo-range data of the inter-satellite link measurement formed by the inter-satellite link measurement signal transmitted by satellite i and received by satellite j at time t1; and are the position of satellite j at the time of signal reception and the position of satellite i at the time of signal transmission, c is the speed of light, clk j (t1) and clk i (t1) are the clock differences between satellite j and satellite i at the time of signal reception, and are the transmission delay of satellite i’s intersatellite link payload and the reception delay of satellite j’s intersatellite link payload, respectively. is the error correction term that can be accurately modeled in the intersatellite link measurement raw data formed by the intersatellite link measurement signal transmitted by satellite i and received by satellite j at time t1; ρ ji(t2) is the pseudo-range data of the inter-satellite link measurement formed by the inter-satellite link measurement signal transmitted by satellite j and received by satellite i at time t2, and are the position of satellite i at the time of signal reception and the position of satellite j at the time of signal transmission, respectively. j (t2) and clk i (t2) are the clock differences between satellite j and satellite i at the time of signal reception, and are the transmission delay of satellite j intersatellite link payload and the receiving delay of satellite i intersatellite link payload, respectively. is the error correction term that can be accurately modeled in the raw data of intersatellite link measurement transmitted by satellite i and received by satellite j at time t2.

[0019] As a preferred embodiment of the present invention, the error correction items that can be accurately modeled in the intersatellite link measurement raw data include satellite antenna phase center and relativistic effects.

[0020] As a preferred embodiment of the present invention, obtaining geometric distance data without satellite clock error information and relative clock error data without satellite orbit information in step S2 includes the following steps:

[0021] Step S21, based on the pseudo-range data measured by the intersatellite link, the time-divided two-way pseudo-range data are converted to the same time using the predicted orbit and clock error, and the converted two-way pseudo-range data is obtained as follows:

[0022]

[0023] In formulas (3) and (4), t0 is the target calculation time; and are the positions of satellite j and satellite i at time t0, clk j (t0) and clk i (t0) are the clock differences of satellite j and satellite i at time t0;

[0024] Step S22, subtract the two-way pseudo-range data after the reduction to obtain relative clock error data without satellite orbit information as data for satellite clock error accuracy monitoring:

[0025]

[0026] In formula (5), is the satellite relative clock error data at time t0, and are the transmission and reception delay differences of satellite i and satellite j respectively;

[0027] The calculated two-way pseudo-range data are added together to obtain the geometric distance data without satellite clock error information, which is used as the data for satellite orbit accuracy monitoring:

[0028]

[0029] In formula (6), is the satellite geometric distance data at time t0, and are the transmission and reception delays of satellite i and satellite j respectively.

[0030] As a preferred embodiment of the present invention, the specific process of estimating the satellite broadcast ephemeris error in step S3 is as follows:

[0031] The observation equation is constructed based on the theoretical calculation formula of geometric distance data; among them, the theoretical formula of geometric distance data without satellite clock error information is:

[0032]

[0033] In formula (7), and are the theoretical positions of satellites j and i, respectively. and represent the positions of satellite i and satellite j respectively calculated using the broadcast ephemeris; and They represent the position error of satellite i and satellite j calculated by satellite broadcast ephemeris, respectively, and are parameters to be estimated; is the observation error;

[0034] by and Approximately 0 value for Taylor series expansion, construct the first observation equation as follows:

[0035]

[0036] In formula (8),

[0037] When estimating the satellite orbit error, the prior constraints of the satellite orbit error are introduced and the second observation equation is constructed as follows:

[0038]

[0039] In formula (9), is the variance of the orbit error prior value, obtained from the broadcast ephemeris residual calculated by intersatellite ranging, that is:

[0040]

[0041] In formula (10), N represents the number of geometric distance data;

[0042] The first observation equation (9) and the second observation equation (10) are combined to calculate the broadcast ephemeris errors of all satellites.

[0043] As a preferred embodiment of the present invention, the calculation of the broadcast ephemeris errors of all satellites adopts the least square method or the Kalman filtering method.

[0044] As a preferred embodiment of the present invention, in step S4, Gaussian distribution is used as a random model of the satellite radial, tangential and normal broadcast ephemeris error sequence, and the mean and standard deviation of the satellite radial, tangential and normal broadcast ephemeris error sequence are calculated. The formula is as follows:

[0045]

[0046] In formula (11), err R / A / C is the radial / tangential / normal error of satellite broadcast ephemeris, Q is the number of radial / tangential / normal errors of satellite broadcast ephemeris, mean Rorb / Aorb / Corb and std Rorb / Aorb / Corb are the mean and standard deviation of the Gaussian distribution of the satellite orbit radial / tangential / normal errors, respectively.

[0047] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0048] The satellite navigation system information domain integrity monitoring method provided in the embodiment of the present invention utilizes intersatellite link observation to monitor the accuracy and integrity status of information domain parameters such as satellite orbit, clock error, satellite broadcast ephemeris, clock error parameters, etc., and utilizes intersatellite link observation data to realize the decoupling of satellite orbit accuracy and integrity status monitoring, satellite clock error accuracy and integrity status monitoring, and realizes the adaptive detection and positioning of satellite broadcast ephemeris anomalies and clock error parameter anomalies. The present invention uses intersatellite link measurement data unique to the satellite navigation system to monitor information domain integrity anomalies, avoiding dependence on ground monitoring stations and low-orbit satellite-borne GNSS observation data, greatly reducing construction costs and operation and maintenance costs; realizes the decoupling of satellite orbit errors and clock error errors, and realizes accurate positioning of faults; models satellite orbit and clock error errors based on historical model data, and realizes accurate detection and identification of satellite broadcast ephemeris and clock error anomalies.

[0049] Of course, it is not necessary to achieve all of the advantages described above at the same time to implement any product or method of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 It is a flow chart of the method for monitoring the integrity of the information domain of the satellite navigation system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations. It should be noted that the embodiments of the present invention and the features in the embodiments can also be combined with each other without conflict.

[0053] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In the description of the present invention, the terms "first", "second", "third", "fourth", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0054] After the above in-depth analysis, an embodiment of the present invention provides a method for monitoring the integrity of the information domain of a satellite navigation system, and establishes a method for monitoring the accuracy and integrity status of information domain parameters such as satellite broadcast ephemeris and clock error parameters based on inter-satellite link observation data. It only relies on the inter-satellite link measurement data embedded in the satellite navigation system, and does not require the deployment of additional ground monitoring stations and low-orbit satellite constellations, thereby greatly reducing costs. At the same time, due to the geometric configuration limitation that the GNSS satellite is high above the ground and the satellite orbit and clock error parameters are strongly correlated and coupled, the accuracy and integrity status monitoring method of satellite broadcast ephemeris, clock error parameters and other information domain parameters based on ground station and low-orbit satellite constellation observation data cannot achieve the separation of GNSS satellite broadcast ephemeris anomalies and clock error parameter anomalies. The two are coupled to each other and cannot be separated. The embodiment of the present invention relies on the bidirectional measurement of the inter-satellite link, and can decouple the satellite orbit and clock error information through mutual calculation, and respectively construct the geometric distance measurement without satellite clock error and the relative clock error measurement without orbit information, which are used for satellite broadcast ephemeris accuracy and integrity status monitoring, satellite clock error parameter accuracy and integrity status monitoring, respectively. The two are separated from each other and do not affect each other, and the separation of GNSS satellite broadcast ephemeris anomalies and clock error parameter anomalies is achieved. In addition, the existing method qualitatively identifies and locates the anomalies of information domain parameters such as satellite broadcast ephemeris and satellite clock error parameters based on multi-dimensional observation data and empirical thresholds, and cannot achieve adaptive detection. This embodiment establishes a probability distribution model of errors in information domain parameters such as satellite broadcast ephemeris and satellite clock difference parameters based on historical data, identifies the over-limit errors in information domain parameters such as satellite broadcast ephemeris and clock difference parameters based on the integrity indicator design and the principle of limit error, locates the integrity status of information domain parameters such as satellite broadcast ephemeris and clock difference parameters, and realizes adaptive detection and positioning of satellite broadcast ephemeris anomalies and satellite clock difference parameter anomalies. The model is adaptively processed based on historical data and has the characteristics of high reliability and low error.

[0055] like Figure 1 As shown, the satellite navigation system information domain integrity monitoring method comprises the following steps:

[0056] Step S1, obtaining pseudo-range data of inter-satellite link measurements of any two healthy satellites in a navigation system within a preset time period.

[0057] In this step, the preset time period is generally at least six months.

[0058] The pseudo-range data measured by the intersatellite link is expressed as:

[0059]

[0060]

[0061] In equations (1) and (2), i and j represent two satellites, ρ ij(t1) is the pseudo-range data of the inter-satellite link measurement formed by the inter-satellite link measurement signal transmitted by satellite i and received by satellite j at time t1; and are the position of satellite j at the time of signal reception and the position of satellite i at the time of signal transmission, c is the speed of light, clk j (t1) and clk i (t1) are the clock differences between satellite j and satellite i at the time of signal reception, and are the transmission delay of satellite i’s intersatellite link payload and the reception delay of satellite j’s intersatellite link payload, respectively. is the error correction term that can be accurately modeled in the intersatellite link measurement raw data formed by the intersatellite link measurement signal transmitted by satellite i and received by satellite j at time t1; ρ ji (t2) is the pseudo-range data of the inter-satellite link measurement formed by the inter-satellite link measurement signal transmitted by satellite j and received by satellite i at time t2, and are the position of satellite i at the time of signal reception and the position of satellite j at the time of signal transmission, respectively. j (t2) and clk i (t2) are the clock differences between satellite j and satellite i at the time of signal reception, and are the transmission delay of satellite j intersatellite link payload and the receiving delay of satellite i intersatellite link payload, respectively. is the error correction term that can be accurately modeled in the intersatellite link measurement raw data transmitted by satellite i and received by satellite j at time t2. The error correction term that can be accurately modeled in the intersatellite link measurement raw data includes the satellite antenna phase center and the relativistic effect.

[0062] Step S2, the pseudo-range data measured by the inter-satellite link is reduced to obtain geometric distance data without satellite clock error information and relative clock error data without satellite orbit information.

[0063] In this step, the geometric distance data without satellite clock error information and the relative clock error data without satellite orbit information are obtained, specifically including the following steps:

[0064] Step S21, based on the pseudo-range data measured by the intersatellite link, the time-divided two-way pseudo-range data are converted to the same time using the predicted orbit and clock error, and the converted two-way pseudo-range data is obtained as follows:

[0065]

[0066] In formulas (3) and (4), t0 is the target calculation time; and are the positions of satellite j and satellite i at time t0, clk j (t0) and clk i (t0) are the clock differences of satellite j and satellite i at time t0 respectively.

[0067] Step S22, subtract the two-way pseudo-range data after the reduction to obtain relative clock error data without satellite orbit information as data for satellite clock error accuracy monitoring:

[0068]

[0069] In formula (5), is the satellite relative clock error data at time t0, and are the transmission and reception delay differences of satellite i and satellite j respectively;

[0070] The calculated two-way pseudo-range data are added together to obtain the geometric distance data without satellite clock error information, which is used as the data for satellite orbit accuracy monitoring:

[0071]

[0072] In formula (6), is the satellite geometric distance data at time t0, and are the transmission and reception delays of satellite i and satellite j respectively.

[0073] Through the above process, the satellite orbit parameters and clock error parameters are decoupled by using the raw data measured by the intersatellite link.

[0074] Step S3, jointly processing the geometric distance data of all satellites without satellite clock error information to estimate the satellite broadcast ephemeris error.

[0075] In this step, when the geometric distance data is jointly processed, the observation equation is constructed based on the theoretical calculation formula of the geometric distance data. Among them, the theoretical formula of the geometric distance data without satellite clock error information is:

[0076]

[0077] In formula (7), and are the theoretical positions of satellites j and i, respectively. and represent the positions of satellite i and satellite j respectively calculated using the broadcast ephemeris; and They represent the position error of satellite i and satellite j calculated by satellite broadcast ephemeris, respectively, and are parameters to be estimated; is the observation error.

[0078] by and Approximately 0 value for Taylor series expansion, construct the first observation equation as follows:

[0079]

[0080] In formula (8),

[0081] When estimating the satellite orbit error, the prior constraints of the satellite orbit error are introduced to construct the second observation equation, as shown in the following formula:

[0082]

[0083] In formula (9), is the variance of the orbit error prior value, obtained from the broadcast ephemeris residual calculated by intersatellite ranging, that is:

[0084]

[0085] In formula (10), N represents the number of geometric distance data.

[0086] By combining the first observation equation (9) and the second observation equation (10), the broadcast ephemeris errors of all satellites can be calculated. The broadcast ephemeris errors of all satellites are calculated by using the least square method or Kalman filter method.

[0087] Step S4, obtaining the radial error, tangential error and normal error of the satellite broadcast ephemeris respectively according to the satellite broadcast ephemeris error, and calculating the mean and standard deviation of the Gaussian distribution of the radial, tangential and normal errors of the satellite broadcast ephemeris.

[0088] In this step, Gaussian distribution is used as the random model of the satellite radial, tangential and normal broadcast ephemeris error sequence, and the mean and standard deviation of the satellite radial, tangential and normal broadcast ephemeris error sequence are statistically calculated.

[0089] The statistical values ​​of the mean and standard deviation of the satellite radial broadcast ephemeris error are as follows:

[0090]

[0091] In formula (11), err R / A / C is the radial / tangential / normal error of satellite broadcast ephemeris, Q is the number of radial / tangential / normal errors of satellite broadcast ephemeris, mean Rorb / Aorb / Corb and std Rorb / Aorb / Corb are the mean and standard deviation of the Gaussian distribution of the satellite orbit radial / tangential / normal errors, respectively.

[0092] Step S5, setting the integrity risk probability, and calculating the upper and lower thresholds of the satellite orbit radial error, tangential error and normal error respectively according to the mean and standard deviation of the Gaussian distribution of the radial, tangential and normal errors of the satellite broadcast ephemeris.

[0093] Step S6, when the radial error of the satellite broadcast ephemeris of the satellite at the current moment is greater than the upper threshold of the satellite orbit radial error, or the radial error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit radial error, or the tangential error of the satellite broadcast ephemeris at the current moment is greater than the upper threshold of the satellite orbit tangential error, or the tangential error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit tangential error, or the normal error of the satellite broadcast ephemeris at the current moment is greater than the upper threshold of the satellite orbit normal error, or the normal error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit normal error, a warning is issued.

[0094] It can be seen from the above technical solutions that the integrity monitoring method of the information domain of the satellite navigation system provided by the embodiment of the present invention uses inter-satellite link observations to monitor the accuracy and integrity of information domain parameters such as satellite orbits, clock errors, satellite broadcast ephemeris, and clock error parameters, and at the same time uses inter-satellite link observation data to achieve the decoupling of satellite orbit accuracy and integrity status monitoring, and satellite clock error accuracy and integrity status monitoring, and achieves adaptive detection and positioning of satellite broadcast ephemeris anomalies and clock error parameter anomalies. The present invention uses inter-satellite link measurement data unique to the satellite navigation system to monitor information domain integrity anomalies, avoiding dependence on ground monitoring stations and low-orbit satellite-borne GNSS observation data, greatly reducing construction costs and operation and maintenance costs; achieving the decoupling of satellite orbit errors and clock error errors, and achieving accurate positioning of faults; based on historical model data, satellite orbit and clock error data are predicted to achieve accurate detection and identification of satellite broadcast ephemeris and clock error anomalies.

[0095] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. It is not intended to limit the scope of the invention claimed for protection, but only represents the preferred embodiment of the present invention. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

Claims

1. A method for monitoring the integrity of a satellite navigation system information domain, characterized in that: The method comprises the following steps: Step S1, obtaining pseudo-range data of inter-satellite link measurements of all healthy satellites in the navigation system within a preset time period; Step S2, calculating the pseudo-range data measured by the inter-satellite link to obtain geometric distance data without satellite clock error information and relative clock error data without satellite orbit information; Step S3, jointly processing the geometric distance data of all satellites without satellite clock error information to estimate the satellite broadcast ephemeris error; Step S4, respectively obtaining the radial error, tangential error and normal error of the satellite broadcast ephemeris according to the satellite broadcast ephemeris error, and calculating the mean and standard deviation of the Gaussian distribution of the radial, tangential and normal errors of the satellite broadcast ephemeris; Step S5, setting the integrity risk probability, and calculating the upper and lower thresholds of the satellite orbit radial error, tangential error and normal error respectively according to the mean and standard deviation of the Gaussian distribution of the radial, tangential and normal errors of the satellite broadcast ephemeris; Step S6, when the radial error of the satellite broadcast ephemeris of the satellite at the current moment is greater than the upper threshold of the satellite orbit radial error, or the radial error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit radial error, or the tangential error of the satellite broadcast ephemeris at the current moment is greater than the upper threshold of the satellite orbit tangential error, or the tangential error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit tangential error, or the normal error of the satellite broadcast ephemeris at the current moment is greater than the upper threshold of the satellite orbit normal error, or the normal error of the satellite broadcast ephemeris at the current moment is less than the lower threshold of the satellite orbit normal error, a warning is issued.

2. The method for monitoring the integrity of the satellite navigation system information domain according to claim 1, characterized in that: The pseudo-range data measured by the intersatellite link is expressed as: In equations (1) and (2), i and j represent two satellites, ρ ij (t1) is the pseudo-range data of the inter-satellite link measurement formed by the inter-satellite link measurement signal transmitted by satellite i and received by satellite j at time t1; and are the position of satellite j at the time of signal reception and the position of satellite i at the time of signal transmission, c is the speed of light, clk j (t1) and clk i (t1) are the clock differences between satellite j and satellite i at the time of signal reception, and are the transmission delay of satellite i’s intersatellite link payload and the reception delay of satellite j’s intersatellite link payload, respectively. is the error correction term that can be accurately modeled in the intersatellite link measurement raw data formed by the intersatellite link measurement signal transmitted by satellite i and received by satellite j at time t1; ρ ji (t2) is the pseudo-range data of the inter-satellite link measurement formed by the inter-satellite link measurement signal transmitted by satellite j and received by satellite i at time t2, and are the position of satellite i at the time of signal reception and the position of satellite j at the time of signal transmission, respectively. j (t2) and clk i (t2) are the clock differences between satellite j and satellite i at the time of signal reception, and are the transmission delay of satellite j intersatellite link payload and the receiving delay of satellite i intersatellite link payload, respectively. is the error correction term that can be accurately modeled in the raw data of intersatellite link measurement transmitted by satellite i and received by satellite j at time t2.

3. The method for monitoring the integrity of the satellite navigation system information domain according to claim 2, characterized in that: The error correction items that can be accurately modeled in the raw data of the intersatellite link measurement include satellite antenna phase center and relativistic effects.

4. The method for monitoring the integrity of the satellite navigation system information domain according to claim 2, characterized in that: The step S2 of obtaining geometric distance data without satellite clock error information and relative clock error data without satellite orbit information includes the following steps: Step S21, based on the pseudo-range data measured by the intersatellite link, the time-divided two-way pseudo-range data are converted to the same time using the predicted orbit and clock error, and the converted two-way pseudo-range data is obtained as follows: In formulas (3) and (4), t0 is the target calculation time; and are the positions of satellite j and satellite i at time t0, clk j (t0) and clk i (t0) are the clock differences of satellite j and satellite i at time t0; Step S22, subtract the two-way pseudo-range data after the reduction to obtain relative clock error data without satellite orbit information as data for satellite clock error accuracy monitoring: In formula (5), is the satellite relative clock error data at time t0, and are the transmission and reception delay differences of satellite i and satellite j respectively; The calculated two-way pseudo-range data are added together to obtain the geometric distance data without satellite clock error information, which is used as the data for satellite orbit accuracy monitoring: In formula (6), is the satellite geometric distance data at time t0, and are the transmission and reception delays of satellite i and satellite j respectively.

5. The method for monitoring the integrity of the satellite navigation system information domain according to claim 4, characterized in that: The specific process of estimating the satellite broadcast ephemeris error in step S3 is as follows: The observation equation is constructed based on the theoretical calculation formula of geometric distance data; among them, the theoretical formula of geometric distance data without satellite clock error information is: In formula (7), and are the theoretical positions of satellites j and i, respectively. and represent the positions of satellite i and satellite j respectively calculated using the broadcast ephemeris; and They represent the position error of satellite i and satellite j calculated by satellite broadcast ephemeris, respectively, and are parameters to be estimated; is the observation error; by and Approximately 0 value for Taylor series expansion, construct the first observation equation as follows: In formula (8), When estimating the satellite orbit error, the prior constraints of the satellite orbit error are introduced and the second observation equation is constructed as follows: In formula (9), is the variance of the orbit error prior value, obtained from the broadcast ephemeris residual calculated by intersatellite ranging, that is: In formula (10), N represents the number of geometric distance data; The first observation equation (9) and the second observation equation (10) are combined to calculate the broadcast ephemeris errors of all satellites.

6. The method for monitoring the integrity of the satellite navigation system information domain according to claim 5, characterized in that: The calculation of the broadcast ephemeris errors of all satellites adopts the least square method or the Kalman filter method.

7. The method for monitoring the integrity of the satellite navigation system information domain according to claim 4, characterized in that: In step S4, Gaussian distribution is used as the random model of the satellite radial, tangential and normal broadcast ephemeris error sequence, and the mean and standard deviation of the satellite radial, tangential and normal broadcast ephemeris error sequence are calculated. The formula is as follows: In formula (11), err R / A / C is the radial / tangential / normal error of satellite broadcast ephemeris, Q is the number of radial / tangential / normal errors of satellite broadcast ephemeris, mean Rorb / Aorb / Corb and std Rorb / Aorb / Corb are the mean and standard deviation of the Gaussian distribution of the satellite orbit radial / tangential / normal errors, respectively.

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