A method for transferring time based on common view of multiple GEO satellites

Abstract

The application provides a multi-GEO satellite-based common view time transfer method, which comprises the following steps: selecting multiple GEO satellites in the visible range of two tracking stations, respectively using each GEO satellite to perform common view time transfer, and obtaining common view time transfer results of the GEO satellites; preprocessing the common view time transfer results of the GEO satellites to obtain preprocessed common view time transfer results; traversing the GEO satellites, analyzing the stability of the link of the current GEO satellite, and simultaneously referring to broadcast ephemeris to determine whether the current GEO satellite is in an orbit maneuvering state; if not, assigning a weight to the GEO satellite based on a static adaptive weight distribution method, or assigning a weight to the GEO satellite based on a dynamic adaptive weight distribution method; and based on the weights assigned to the GEO satellites, performing weighted average processing on the preprocessed common view time transfer results to finally obtain multi-GEO satellite common view time transfer results.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of satellite navigation technology, in particular to a common view time transfer method based on multiple GEO satellites. BACKGROUND

[0002] Time transfer generally refers to the process of obtaining the clock difference of two clocks located at different places through measurement and calculation. Time transfer is generally for the sending end, i.e., the sending end transfers time to the receiving end. Satellite time transfer refers to the realization of time transfer between two or more stations through satellites. Due to its global coverage advantage, satellite time transfer is widely used in scientific observation and research, positioning and navigation services, communication, power grid, transportation, finance, emergency rescue, environmental resource management, etc., and is still expanding. At the same time, precise time and frequency transfer technology is also one of the core supports for the establishment and maintenance of international standard time Coordinated Universal Time (UTC). The actual performance bottleneck of UTC is not the clock, but the realization of time and frequency transfer performance indicators between two places.

[0003] The Beidou Navigation Satellite System (BDS, hereinafter referred to as Beidou system) is a global satellite navigation system independently constructed and operated by China. The Beidou system can provide all-weather, all-day, high-precision positioning, navigation and timing services for global users. The Beidou system adopts a hybrid constellation of geostationary orbit (GEO), inclined geo synchronous orbit (IGSO) and medium earth orbit (MEO). Among them, the GEO satellite is a characteristic component of the Beidou system, including 5 GEO satellites (C01 to C05) of BDS-2 and 3 GEO satellites (C59 to C61) of BDS-3. The Quasi-Zenith Satellite System (QZSS) is a regional augmentation system that relies on the Global Positioning System (GPS) service, and has completed the deployment of 4 satellites, consisting of GEO satellites and IGSO satellites. Among them, QZS-3 (J07) is a geostationary satellite located at 55 degrees east longitude, which provides sufficient satellite resources for satellite time transfer.

[0004] There are two traditional time transfer methods, one is precise point positioning (PPP) method, and the other is Beidou common view time transfer method.

[0005] PPP time transfer is a high-precision time transfer technology based on Beidou / GNSS (Global Navigation Satellite System). The technology uses the pseudorange and carrier phase observation values of Beidou satellites received by a single station, and uses precise products to solve PPP to obtain the deviation (station clock error) of the station receiver clock and the Beidou / GNSS system time. Then, the station clock errors of two or more stations are subtracted to obtain the time transfer result of two or more stations.

[0006] Beidou common view time transfer is a high-precision time transfer method realized by two receivers synchronously observing the same satellite or multiple satellites. The relative clock error of two stations is directly obtained by performing single difference on the pseudorange or carrier phase observation of two or more stations.

[0007] In addition, some researchers have proposed a method of precise common view time transfer based on a single GEO satellite. Two stations use Beidou / GNSS receivers to synchronously observe the same GEO satellite to form a single difference observation between stations. The station clock error is obtained by using satellite orbit, station coordinate and other information and processing the common view data.

[0008] However, although PPP time transfer has the advantages of high precision and flexibility, it still has some obvious limitations in practical application. It relies on satellite precise ephemeris and clock error products, which need to be obtained from the outside, and has the problems of complex processing model, jump at the connection between the sky and the ground, etc. Common view time transfer has been widely used in recent decades because of its simple method and easy implementation. At the beginning of the development of this technology, MEO satellites of GPS were used. Because the MEO satellite has an orbital height of about 21500 kilometers, the distance between two stations for common view time transfer is limited. In addition, this method uses pseudorange observation values, and the time transfer precision is limited. When using a single GEO satellite for time transfer, the GEO satellite needs to be maneuvered once every two weeks to maintain its orbit. During the maneuvering period, satellite orbit and clock error products are unavailable, which seriously affects the continuity and precision of time transfer. SUMMARY

[0009] To solve the above technical problems, the embodiments of the present application propose a common view time transfer method based on multiple GEO satellites, which aims to use multiple GEO satellites for common view time transfer, effectively improving the stability of GEO satellite time transfer, and realizing continuous and high-precision common view time transfer.

[0010] To achieve the above object, embodiments of the present application propose a multi-GEO satellite based common view time transfer method, the method comprising: selecting multiple GEO satellites within the visual range of two tracking stations, respectively using each GEO satellite for common view time transfer, and obtaining the common view time transfer result of each GEO satellite; performing preprocessing on the common view time transfer result of each GEO satellite, including height angle threshold filtering and 3sigma rule for removing clock difference abnormal values, to obtain the preprocessed common view time transfer result of each GEO satellite; traversing each GEO satellite, analyzing the link stability of the current GEO satellite based on the preprocessed common view time transfer result, and simultaneously referring to broadcast ephemeris to determine whether the current GEO satellite is in an orbit maneuvering state; if the current GEO satellite is not in the orbit maneuvering state, using a static adaptive weight distribution method based on Allan variance to distribute weights for the GEO satellite, otherwise, using a dynamic adaptive weight distribution method based on Allan variance to distribute weights for the GEO satellite; based on the weights distributed for each GEO satellite, performing weighted average processing on each preprocessed common view time transfer result to obtain the common view time transfer result of the multi-GEO satellite.

[0011] To achieve the above object, embodiments of the present application also propose a multi-GEO satellite based common view time transfer system, the system comprising: a single satellite common view module for selecting multiple GEO satellites within the visual range of two tracking stations, respectively using each GEO satellite for common view time transfer, and obtaining the common view time transfer result of each GEO satellite; a preprocessing module for performing preprocessing on the common view time transfer result of each GEO satellite, including height angle threshold filtering and 3sigma rule for removing clock difference abnormal values, to obtain the preprocessed common view time transfer result of each GEO satellite; a state discrimination module for traversing each GEO satellite, analyzing the link stability of the current GEO satellite based on the preprocessed common view time transfer result, and simultaneously referring to broadcast ephemeris to determine whether the current GEO satellite is in an orbit maneuvering state; a weight distribution module for, when the current GEO satellite is not in the orbit maneuvering state, using a static adaptive weight distribution method based on Allan variance to distribute weights for the GEO satellite, and when the current GEO satellite is in the orbit maneuvering state, using a dynamic adaptive weight distribution method based on Allan variance to distribute weights for the GEO satellite; a weighted fusion module for, based on the weights distributed for each GEO satellite, performing weighted average processing on each preprocessed common view time transfer result to obtain the common view time transfer result of the multi-GEO satellite.

[0012] To achieve the above objectives, embodiments of this application also propose an electronic device, including: a processor and a memory, wherein the memory stores instructions executable by the processor, and the processor is configured to execute the instructions such that the electronic device can implement a common-view time transfer method based on multiple GEO satellites as described above.

[0013] To achieve the above objectives, embodiments of this application also propose a computer-readable storage medium storing a computer program that, when executed by a processor, enables a common-view time transfer method based on multiple GEO satellites as described above.

[0014] Optionally, the number of selected GEO satellites is , The integer is greater than 1. Observations are made on the selected GEO satellite through the first and second tracking stations. The digit is denoted as _____. Each GEO satellite is represented as , , The co-view time transfer result is expressed by the formula:

[0015] ;

[0016] in, express The result of co-visual time transmission, Indicates the first tracking station and The time difference between them, Indicates the second tracking station and The time difference between them, For the calendar year, , and All are about the calendar. sequence.

[0017] Optionally, the common-view time transfer results of each GEO satellite are preprocessed, including elevation angle threshold filtering and clock difference inconsistency removal using the 3sigma rule, to obtain the preprocessed common-view time transfer results of each GEO satellite, including:

[0018] Traverse all GEO satellites, and denote the current GEO satellite as... ,Sure The first altitude angle and the second altitude angle relative to the first tracking station;

[0019] If the first or second elevation angle is less than the preset elevation angle threshold, it will be discarded directly. ;

[0020] If both the first elevation angle and the second elevation angle are not less than the preset elevation angle threshold, the 3sigma rule is used to remove clock difference outliers, that is, values outside the 3sigma range in the clock difference are removed, thereby obtaining the pretreated common view time transfer result of the GEO satellite . Finally, the pretreated common view time transfer result of each GEO satellite is obtained.

[0021] Optionally, the current GEO satellite is denoted as , and based on the pretreated common view time transfer result, the link stability of the current GEO satellite is analyzed, and whether the current GEO satellite is in an orbit maneuvering state is determined by referring to the broadcast ephemeris, including:

[0022] Curve fitting is performed based on to generate a common view time transfer result sequence diagram corresponding to , and mutation analysis including step and drift is performed on the common view time transfer result sequence diagram, and each epoch is traversed while referring to the broadcast ephemeris, if no mutation occurs in the current epoch and the broadcast ephemeris is healthy, it is determined that is not in an orbit maneuvering state, otherwise, it is determined that is in an orbit maneuvering state.

[0023] Optionally, if the current GEO satellite is not in an orbit maneuvering state, a static adaptive weight distribution method based on Allan variance is used to distribute weights for the GEO satellite, including:

[0024] The Allan variance corresponding to is calculated by the following formula:

[0025] ;

[0026] Wherein, denotes the total number of epochs, that is, the total number of samples obtained, also known as the data period, denotes the Allan variance corresponding to .

[0027] Based on the initial weight of and the Allan variance corresponding to each GEO satellite, static adaptive weight distribution is performed by the following formula to obtain the weight corresponding to :

[0028] , , ;

[0029] Wherein, is​​ The inverse proportional function, express The corresponding weights.

[0030] Optionally, if the current GEO satellite is in an orbital maneuver, then... The period is divided into the pre-maneuver phase based on the epoch in which the orbital maneuver occurs. During the maneuvering period and the period after maneuver ,correspond , and ;

[0031] Pre-maneuver period and the period after maneuver The weights are still allocated using a static adaptive weight allocation method based on Allan variance to obtain... and ;

[0032] During the maneuvering period ,Will The weights are reduced to zero, while the weights of other GEO satellites not in orbital maneuvering state are increased, and the sum of the weights of other GEO satellites not in orbital maneuvering state is guaranteed to be 1, so as to achieve dynamic adaptive weight allocation based on Allan variance.

[0033] Optionally, based on the weights assigned to each GEO satellite, a weighted average is performed on the preprocessed common-view time transfer results to obtain the common-view time transfer results for multiple GEO satellites, which is achieved through the following formula:

[0034] ;

[0035] in, This indicates the common-view time transfer result of multiple GEO satellites.

[0036] This application proposes a common-view time transfer method based on multiple GEO satellites, which selects multiple visible GEO satellites to form a multi-satellite common-view framework. Compared with the traditional single-satellite common-view method, it has at least the following advantages.

[0037] First, it significantly improves the continuity of time transfer. This application effectively solves the problem of time transfer interruption caused by orbital maneuvers of a single GEO satellite. Traditional methods rely on a single GEO satellite, during which orbital and clock products are unavailable, causing time transfer interruptions. This application, however, utilizes multiple GEO satellites working together, so that even if one GEO satellite is in orbital maneuver, time transfer can continue using other GEO satellites, avoiding service interruptions.

[0038] Second, the stability and accuracy of time transfer are significantly improved. The application performs preprocessing on the common view time transfer results of each GEO satellite, including height angle threshold filtering and 3sigma rule to remove clock difference abnormal values, so as to remove abnormal values that may be detrimental to the final results. Based on the preprocessed common view time transfer results, the link stability of the GEO satellite is analyzed, and reference is made to the broadcast ephemeris to determine whether the GEO satellite is in an orbit maneuvering state. The static adaptive weight distribution based on the Allan variance is performed on the GEO satellite not in the orbit maneuvering state, and the dynamic adaptive weight distribution based on the Allan variance is performed on the GEO satellite in the orbit maneuvering state, so as to avoid the multi-satellite common view being deviated by the unstable GEO satellite, and thus the accuracy, long-term stability and anti-interference ability of the multi-GEO satellite common view time transfer result are effectively improved.

[0039] Third, good practicability and compatibility are provided. The multi-satellite common view framework designed in the application makes full use of the existing GEO satellite resources, does not need to add new hardware, and does not need to modify the GEO satellite and the tracking station, so the design cost and implementation cost are very low, and the application can be widely promoted and applied. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the application or the related art, the following will briefly introduce the drawings needed to be used in the embodiments of the application or the related art description. Obviously, the following drawings are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings. The drawings described herein are only used to explain the application, and are not used to limit the application.

[0041] Figure 1 is a flowchart of a multi-GEO satellite based common view time transfer method provided in an embodiment of the application;

[0042] Figure 2 is a schematic diagram of a multi-satellite common view framework provided in an embodiment of the application;

[0043] Figure 3 is a detailed schematic diagram of a multi-GEO satellite based common view time transfer method provided in an embodiment of the application;

[0044] Figure 4 is a common view time transfer result sequence diagram provided in an embodiment of the application;

[0045] Figure 5 is a schematic diagram of phase observation values of single-satellite common view and multi-satellite common view in an orbit maneuvering state provided in an embodiment of the application;

[0046] Figure 6 is a schematic diagram of phase-smoothed pseudorange and pseudorange of single-satellite common view and multi-satellite common view in orbit maneuvering state provided in an embodiment of the present application;

[0047] Figure 7 is a comparison diagram of single-satellite common view time transfer result and multi-satellite common view time transfer result in orbit maneuvering state provided in an embodiment of the present application;

[0048] Figure 8 is a comparison diagram of PPP time transfer result and multi-GEO satellite common view time transfer result provided in an embodiment of the present application;

[0049] Figure 9 is a schematic diagram of pseudorange observation value of single-satellite common view and multi-satellite common view in orbit maneuvering state provided in an embodiment of the present application;

[0050] Figure 10 is a schematic diagram of phase observation value of single-satellite common view and multi-satellite common view in orbit maneuvering state provided in an embodiment of the present application;

[0051] Figure 11 is a schematic diagram of effectiveness verification of dynamic adaptive weight distribution method based on Allan variance provided in an embodiment of the present application;

[0052] Figure 12 is a structural schematic diagram of a multi-GEO satellite based common view time transfer system provided in another embodiment of the present application;

[0053] Figure 13 is a structural schematic diagram of an electronic device provided in another embodiment of the present application. DETAILED DESCRIPTION

[0054] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. Those skilled in the art can understand that, in the embodiments of the present application, many technical details are proposed in order to make the readers better understand. However, the technical solutions claimed by the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The following embodiments are classified for the convenience of description, and should not constitute any limitation on the specific implementation of the present application. The following embodiments can be combined and referenced with each other without contradiction.

[0055] One embodiment of the present application proposes a multi-GEO satellite based common view time transfer method. The following will specifically describe the implementation details of the multi-GEO satellite based common view time transfer method proposed in the embodiment, and the following implementation details are provided for the convenience of understanding, and are not necessary for implementing the present application.

[0056] The specific process of the multi-GEO satellite based common view time transfer method proposed in the embodiment can be as shown in Figure 1 , which includes the following steps.

[0057] In step 101, multiple GEO satellites in the visible range of two tracking stations are selected, and each GEO satellite is used for common view time transfer to obtain the common view time transfer result of each GEO satellite.

[0058] In a specific implementation, when performing multi-satellite common view, first, multiple GEO satellites in the visible range of two tracking stations (visible means that they can be observed by the tracking station) are selected, and then each GEO satellite is used for common view time transfer (that is, single-satellite common view is performed first), so as to obtain the common view time transfer result of each GEO satellite.

[0059] The GEO satellite is located about 36000 kilometers above the equator, and the use of the GEO satellite for time transfer has very obvious advantages. First, the downlink signal coverage of the GEO satellite is very wide, and 3 GEO satellites can achieve global coverage. Second, the sub-satellite point longitude of the GEO satellite is fixed, and it is continuously visible to the tracking station (station), so that continuous time transfer can be achieved.

[0060] However, when using a single GEO satellite for time transfer, the GEO satellite needs to be maneuvered once every two weeks to maintain the orbit, and the satellite orbit and clock difference products are not available during the maneuvering period, which will seriously affect the continuity and accuracy of the time transfer.

[0061] To solve this problem, the present embodiment selects multi-satellite common view, that is, multiple GEO satellites are used for common view time transfer at the same time, which can effectively improve the stability of the GEO satellite time transfer and completely solve the problem that a single GEO satellite cannot be used during the maneuvering period, causing the time transfer to be interrupted and the accuracy to be deteriorated.

[0062] The detailed information of the GEO satellite that can be selected is shown in Table 1.

[0063] Table 1: Detailed information of GEO satellite

[0064]

[0065] In one example, the multi-satellite common view framework is as shown in Figure 2 Figure 2 ​(Showing 4 visible GEO satellites), details of the multi-satellite simultaneous viewing implementation are as follows: Figure 3 As shown.

[0066] Let the number of selected GEO satellites be... , For integers greater than 1 (for Figure 2 , ), through the first tracking station ( Figure 2 Tracking station A (10MHz, 1pps) and the second tracking station ( Figure 2 Tracking station B (10MHz, 1pps) observed the selected GEO satellite, recording the observations at the first station. Each GEO satellite is represented as , , The co-view time transfer result is expressed by the formula:

[0067] ;

[0068] in, express The result of co-visual time transmission, Indicates the first tracking station and The time difference between them, Indicates the second tracking station and The time difference between them, For the calendar year, , and All are about the calendar. sequence.

[0069] Step 102: Perform preprocessing on the common-view time transfer results of each GEO satellite, including elevation angle threshold filtering and clock difference deviance removal using the 3sigma rule, to obtain the preprocessed common-view time transfer results of each GEO satellite.

[0070] In practice, to ensure the accuracy of multi-satellite co-view, we need to preprocess the co-view time transfer results of each GEO satellite, including elevation angle threshold filtering and clock difference constant removal using the 3sigma rule, so as to obtain the preprocessed co-view time transfer results of each GEO satellite.

[0071] In one example, during preprocessing, it is necessary to iterate through all GEO satellites, and denote the current GEO satellite as... The first step in preprocessing is to determine The system determines whether the first elevation angle relative to the first tracking station and the second elevation angle relative to the second tracking station are less than a preset elevation angle threshold (usually set to 10 degrees). If either the first or second elevation angle is less than the preset threshold, it needs to be discarded. If both the first and second elevation angles are not less than the preset elevation angle threshold, then the 3sigma rule is used to... Perform clock difference constant removal, that is Values ​​outside the 3sigma range are removed, thus obtaining... Preprocessed co-view time transfer results Finally, the preprocessed common-view time transfer results of each GEO satellite are obtained.

[0072] Step 103: Traverse each GEO satellite, analyze the link stability of the current GEO satellite based on the preprocessed common-view time transmission results, and at the same time refer to the broadcast ephemeris to determine whether the current GEO satellite is in an orbital maneuvering state.

[0073] In practice, after completing the preprocessing operation, the orbital maneuver status can be determined. This involves traversing each GEO satellite, analyzing the link stability of the current GEO satellite based on the preprocessed common-view time transmission results, and referring to the broadcast ephemeris to determine whether the current GEO satellite is in an orbital maneuver state.

[0074] In one example, let the current GEO satellite be denoted as ,based on Perform curve fitting to generate The corresponding sequence diagram of co-view time transfer results (e.g.) Figure 4 As shown), a mutation analysis, including step and drift, is performed on the sequence diagram of the common-view time transfer result. This is done by traversing each epoch and referencing the broadcast ephemeris. If no mutation occurs in the current epoch and the broadcast ephemeris is healthy, then the sequence is determined to be... It is not currently in a state of orbital maneuvering; otherwise, confirm. It is currently in a state of orbital maneuvering.

[0075] High-precision common-view time transfer relies on known, precise satellite positions (precise orbit products). When satellites (especially GEO satellites requiring frequent position-keeping) perform orbital maneuvers, precise orbit determination mechanisms (such as IGS) cannot provide effective precise ephemeris during the maneuver. If the "normal orbit" before and after the maneuver is forcibly used for interpolation to fill the orbital gaps during the maneuver, systematic errors will occur in the calculated "pseudo-distances" because the interpolation model is significantly inconsistent with the satellite's actual controlled motion. These systematic errors can cause step or drift in common-view clock bias and increase the Allan variance of the clock bias sequence (see...). Figure 4), so the common view clock error time series of a single GEO satellite can be used as a means to monitor whether the satellite has performed orbit maneuver.

[0076] In step 104, if the current GEO satellite is not in the orbit maneuver state, a static adaptive weight distribution method based on Allan variance is used to distribute weights for it, otherwise, a dynamic adaptive weight distribution method based on Allan variance is used to distribute weights for it.

[0077] In a specific implementation, if the current GEO satellite is not in the orbit maneuver state, a static adaptive weight distribution method based on Allan variance is used to distribute weights for it, otherwise, a dynamic adaptive weight distribution method based on Allan variance is used to distribute weights for it. That is, the adaptive weight distribution of the embodiment is based on Allan variance. Allan variance is a clock stability standard recommended by IEEE (Institute of Electrical and Electronics Engineers), which is specially used to measure the stability of a clock or signal. Using Allan variance to measure the stability of a satellite signal is more scientific than simply using standard deviation. In addition, Allan variance uses second-order difference calculation, which can automatically eliminate the linear drift of the data clock, so it can be used as an analysis tool to measure the stability of the common view clock error results of each single GEO satellite.

[0078] In one example, when the static adaptive weight distribution method based on Allan variance is used to distribute weights for it, the following formula is used to calculate the corresponding Allan variance:

[0079] ;

[0080] wherein, indicates the total number of epochs, that is, the total number of samples obtained by sampling, also known as the data period, indicates the corresponding Allan variance. The data period (sampling period) of the embodiment is sampled at an interval of 30s.

[0081] Next, based on the initial weight of and the corresponding Allan variance of each GEO satellite, static adaptive weight distribution is performed to obtain the corresponding weight:

[0082] , , ;

[0083] wherein,​ is an inverse function of represents the corresponding weight.

[0084] In one example, when a GEO satellite occurs a maneuver within the whole data cycle , the precise orbit product of the maneuver GEO satellite on the same day will be unavailable, in order to reduce the influence on the subsequent multi-GEO satellite common view time transfer after the orbit maneuver, we will divide the epoch of the orbit maneuver into the pre-manipulation period , the manipulation period and the post-manipulation period , corresponding to , and . In the pre-manipulation period and the post-manipulation period , the static adaptive weight distribution method based on Allan variance is still used to distribute weights to obtain and . In the manipulation period , it is necessary to reduce to zero, while increasing the weights of other GEO satellites which are not in the orbit maneuver state, and ensuring that the sum of the weights of other GEO satellites which are not in the orbit maneuver state is 1, to realize the dynamic adaptive weight distribution based on Allan variance.

[0085] Step 105, based on the weights allocated to each GEO satellite, weighted average processing is performed on each pre-processed common view time transfer result to obtain the multi-GEO satellite common view time transfer result.

[0086] In a specific implementation, after the weights of each GEO satellite are allocated, weighted average processing can be performed on each pre-processed common view time transfer result to obtain the multi-GEO satellite common view time transfer result.

[0087] In one example, based on the weights allocated to each GEO satellite, weighted average processing is performed on each pre-processed common view time transfer result to obtain the multi-GEO satellite common view time transfer result, which can be realized by the following formula:

[0088] ;

[0089] Wherein, represents the multi-GEO satellite common view time transfer result.

[0090] The embodiment proposes a multi-GEO satellite-based common view time transfer method. Compared with the traditional single-satellite common view, the method has at least the following advantages.

[0091] First, the continuity of time transfer is significantly improved. The embodiment effectively solves the problem of time transfer interruption caused by the orbit maneuver of a single GEO satellite. The traditional method relies on a single GEO satellite, and during its two-week orbit maneuver, the orbit and clock difference products are unavailable, which will cause time transfer interruption. However, the embodiment uses multiple GEO satellites for coordinated common view. Even if a GEO satellite is in an orbit maneuver state, time transfer can still be carried out using other GEO satellites to avoid service interruption.

[0092] Second, the stability and accuracy of time transfer are significantly improved. The embodiment performs preprocessing on the common view time transfer results of each GEO satellite, including height angle threshold filtering and 3sigma rule for removing clock difference outliers. The abnormal values that may be detrimental to the final result are removed. Based on the preprocessed common view time transfer results, the link stability of the GEO satellite is analyzed, and the broadcast ephemeris is referred to determine whether the GEO satellite is in an orbit maneuver state. For GEO satellites not in an orbit maneuver state, static adaptive weight distribution based on Allan variance is performed, and for GEO satellites in an orbit maneuver state, dynamic adaptive weight distribution based on Allan variance is performed. This avoids the multi-satellite common view being biased by unstable GEO satellites, thereby effectively improving the accuracy, long-term stability, and anti-interference ability of the multi-GEO satellite common view time transfer results.

[0093] Third, it has good practicability and compatibility. The multi-satellite common view framework designed in the embodiment fully utilizes existing GEO satellite resources, without the need for additional hardware or modification of GEO satellites and tracking stations. The design and implementation costs are very low, and it can be widely applied.

[0094] The above method steps are only for a clear description of the technical solution. In specific implementation, they can be combined into one step or some steps can be divided into multiple steps, as long as the same logical relationship is included, and they are within the protection scope of the present application. Any insignificant modification or introduction of insignificant design in the algorithm or flowchart, as long as it does not change the core of the algorithm and flowchart, is within the protection scope of the present application.

[0095] In one embodiment, in order to verify the superiority of the multi-GEO satellite-based common view time transfer method proposed in the present application, two simulation experiments are performed.

[0096] The two simulation experiments are described in detail below.

[0097] Simulation Experiment One.

[0098] The simulation experiment selects two tracking stations PARK and TID1 in Australia, uses the pseudorange and carrier phase observation data from February 17 to 18, 2023 (mjd: 59992 to 59993), sets the sampling interval to 30s, and carries out the research on multi-GEO satellite common view time transfer (non-orbit maneuver). The detailed information of the two tracking stations is shown in Table 2. There are 4 Beidou GEO satellites observed by the two stations at the same time, the baseline length is 275km, and the external clock is a high-precision hydrogen atomic clock. The common view time transfer experiment based on 4 visible GEO satellites is carried out, and the experimental results are shown in Figure 5 、 Figure 6 .

[0099] Table 2: Basic information of tracking stations

[0100]

[0101] Figure 5 、 Figure 6 The two-station common view clock difference results of C01, C03, C04, J07 single satellite and multi-GEO satellite in the same time period from February 17 to 18, 2023 are given, and the vertical coordinate is the inter-station clock difference (nanoseconds). The title of the single GEO satellite common view result figure shows the proportion of each satellite in the multi-satellite common view result. Since the biases of each visible satellite are not calibrated, the clock difference solution is a relative value. From the figure, it can be seen that the common view results of single / multi-satellite have good consistency. The weights of each satellite based on phase and pseudorange observations are inconsistent. The weights of the four satellites based on phase observations are relatively balanced, which are 0.2509, 0.2483, 0.2500 and 0.2508 respectively. The weight distribution of each visible GEO satellite based on pseudorange observation is quite different. The proportion of Japanese GEO satellite J07 is as high as 0.4942, close to 50%. This is because the Allan variance of the two-station clock difference result of J07 based on pseudorange observation is 0.3565930, which is much smaller than that of other single GEO satellites. The adaptive weight distribution method based on Allan variance used in this simulation experiment takes the Allan variance of single satellite common view clock difference result as the index, and does not depend on the factors of the satellite itself (elevation angle, signal-to-noise ratio, etc.), so different observation data of the same satellite have different weight distribution.

[0102] Table 3: Comparison of standard deviations of single GEO satellite and multi-GEO satellite common view results

[0103]

[0104] As can be seen from Table 3, the standard deviations of the multi-GEO satellite co-view results are all smaller than those of the single-GEO satellite co-view results. We only compared the Allan variance and standard deviation of the single-satellite and multi-satellite co-view results based on pseudorange observations. Figure 7 As shown, the Allan variance and standard deviation of the multi-GEO satellite co-view results are lower than those of the single-GEO satellite co-view results. Compared with the results of the best satellite J07, the stability of the multi-GEO satellite co-view results based on carrier phase is improved by 76.8%, and the stability of pseudorange observations is improved by 49.5%. This demonstrates the effectiveness of the adaptive weight allocation method based on clock difference results, and also shows that co-viewing based on multiple GEO satellites can further improve the stability of time transfer.

[0105] The comparison between PPP time transfer results and multi-GEO satellite co-view time transfer results can be seen as follows: Figure 8 As shown, both multi-GEO satellite co-view and PPP time transfer can reflect the clock difference between two stations, therefore the results obtained from the two should be consistent, and the difference is mainly manifested as systematic bias. The calculation results show that the standard deviation of the bias between the multi-GEO satellite co-view and PPP time transfer results is 0.564 ns, indicating that the two have a high degree of agreement and good consistency. Therefore, multi-GEO satellite co-view can be used as an alternative or supplementary solution with comparable accuracy to PPP and greater efficiency and robustness in regional applications.

[0106] Simulation Experiment 2.

[0107] This simulation experiment uses two tracking stations in Australia, PARK and TID1, and employs three days of pseudorange and carrier phase observation data from July 26th to 29th, 2023 (mjd: 60151 to 60157) to conduct an experimental study on the common-view time transfer of multiple GEO satellites. The BeiDou Navigation Satellite System constellation contains eight GEO satellites. To maintain its geosynchronous characteristics, frequent orbital adjustments are required. According to statistics, GEO satellites may perform orbital maneuvers approximately every two weeks. Orbital maneuvers can cause step shifts or drifts in the common-view clock bias, leading to an increase in the Allan variance of the clock bias sequence. In a single GEO satellite common-view time transfer experiment, an anomaly was found in the clock bias sequence of C03. Reviewing the broadcast ephemeris file brdm2080.23p revealed that the satellite status of C03 was unhealthy at 9:00 AM, and this state persisted until 2:00 PM. Therefore, it can be concluded that satellite C03 underwent an orbital maneuver during this period, and the weight of the clock bias result for that maneuvering satellite C03 on that day was reduced to zero. Considering the impact of orbital maneuvers on common-view time propagation, a dynamic adaptive weight allocation method was adopted for weight allocation during the maneuver. This involved dividing the entire experimental cycle into three phases: pre-maneuver, mid-maneuver, and post-maneuver. Weights were assigned to each visible satellite in each phase, ensuring that the sum of the weights of the visible satellites in each phase was 1. Specific allocation results are detailed below. Figure 9 , Figure 10.

[0108] Due to the maneuver of C03 in this period, the C03 during the maneuver cannot carry out common view based on precise orbit product, and the orbit solved by interpolation before and after the maneuver will cause the common view clock error to appear step or drift ( Figure 4 ). As can be seen from Figure 8 、 Figure 9 , the common view time transfer result based on C03 in this period is not continuous, so we reduce the weight of this day to zero and recalculate the weight of other visible satellites. The multi-GEO satellite result in this period is calculated according to the three different weight results before and after the maneuver, and the specific values are shown in the top left legend of Figure 9 、 Figure 10 . In addition, it can be seen from the single-satellite common view time transfer sequence that there is a discontinuity at the day boundary, which may be caused by the orbit file in units of days or the discontinuity between days caused by the orbit maneuver. As can be seen from Figure 9 、 Figure 10 , the common view time transfer result of multi-GEO satellite has certain improvement on this phenomenon.

[0109] As shown in Figure 11 , compared with the optimal satellite J07, the Allan variance of the multi-GEO satellite clock error is lower, and the stability of each observation is improved by more than 50%, which can show that the application is suitable for multi-GEO satellite common view time transfer under the condition of maneuver.

[0110] Another embodiment of the application provides a multi-GEO satellite based common view time transfer system. Details of the multi-GEO satellite based common view time transfer system provided in the embodiment are described below. The following content is only provided for the implementation details for easy understanding, and is not necessary for implementing the scheme. Figure 12 is a structural schematic diagram of the multi-GEO satellite based common view time transfer system provided in the embodiment, which comprises a single-satellite common view module 201, a preprocessing module 202, a state discrimination module 203, a weight distribution module 204 and a weighted fusion module 205.

[0111] The single-satellite common view module 201 is configured to select multiple GEO satellites in the visible range of two tracking stations, and perform common view time transfer using each GEO satellite to obtain common view time transfer results of each GEO satellite.

[0112] The preprocessing module 202 is configured to preprocess the common view time transfer results of each GEO satellite, including height angle threshold filtering and 3sigma rule to remove clock error outliers, to obtain the preprocessed common view time transfer results of each GEO satellite.

[0113] The state determination module 203 is used to traverse each GEO satellite, analyze the link stability of the current GEO satellite based on the preprocessed common-view time transmission results, and at the same time refer to the broadcast ephemeris to determine whether the current GEO satellite is in an orbital maneuver state.

[0114] The weight allocation module 204 is used to allocate weights to the GEO satellite when it is not in an orbital maneuvering state using a static adaptive weight allocation method based on Allan variance, and to allocate weights to the GEO satellite when it is in an orbital maneuvering state using a dynamic adaptive weight allocation method based on Allan variance.

[0115] The weighted fusion module 205 is used to perform weighted averaging on the preprocessed common-view time transfer results based on the weights assigned to each GEO satellite, so as to obtain the common-view time transfer results of multiple GEO satellites.

[0116] It is worth noting that all modules involved in this embodiment are logical modules. In practical applications, a logical module can be a physical module, a part of a physical module, or an organic combination of multiple physical modules. Furthermore, to highlight the innovative aspects of this application, this embodiment does not introduce modules that are not closely related to solving the technical problems proposed in this application. However, this does not mean that other modules are absent from this embodiment.

[0117] It is not difficult to see that this embodiment is a system embodiment corresponding to the above method embodiments, and this embodiment can be implemented in conjunction with the above method embodiments. The relevant technical details and technical effects mentioned in the above method embodiments are still valid in this embodiment, and will not be repeated here to reduce repetition. Accordingly, the relevant technical details mentioned in this embodiment can also be applied to the above method embodiments.

[0118] Another embodiment of this application provides an electronic device, such as Figure 13 As shown, it includes a processor 301 and a memory 302. The memory 302 stores instructions that the processor 301 can execute. When the processor 301 is configured to execute the instructions, the electronic device can implement a common-view time transfer method based on multiple GEO satellites as described in the above method embodiment.

[0119] The bus includes any number of interconnecting buses and bridges, allowing for a variety of configurations supporting more processors, peripheral or I / O devices, or firmware or software caches. The bus also can include one or more buses implementing various bus architectures (e.g., an industry standard architecture, IBM® open firmware technology, or Intel® hub architecture). The bus interfaces allow for a variety of configurations connecting the processor, memory, and various peripherals. The bus interfaces couple the processor to various other circuits, including peripheral devices, voltage regulators, and power management circuitry, all of which are well known in the art and will not be described further. A bus interface provides an interface between the bus and a transceiver. The transceiver can be a single element or multiple elements, such as a plurality of receivers and transmitters, providing a means for communicating with various other apparatus over a transmission medium. Data processed by the processor is transmitted over a wireless medium via an antenna, and further, the antenna receives data and communicates the data to the processor.

[0120] The processor is responsible for managing the bus and general processing, and can also provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The memory can be used for storing data used by the processor while executing operations.

[0121] Another embodiment of the present application provides a computer readable storage medium, the computer readable storage medium stores a computer program, the computer program is executed by a processor to implement a multi-GEO satellite based common view time transfer method as described in the above method embodiments.

[0122] That is, those skilled in the art can understand that all or part of the steps of the above-mentioned method embodiments can be completed by programs instructing related hardware, and the programs are stored in a storage medium, including a plurality of instructions for causing an apparatus (such as a single-chip microcomputer, a chip, etc.) or a processor to execute all or part of the steps of the method described in the method embodiments of the present application. The foregoing storage medium includes a U disk, a mobile hard disk, a read-only memory, a random access memory, a magnetic disk or an optical disk, and various storage medium capable of storing program codes.

[0123] Those skilled in the art can understand that the above-mentioned embodiments are specific embodiments for implementing the present application, and in actual applications, various changes can be made in form and details without departing from the spirit and scope of the present application. Those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements are also considered within the protection scope of the present application.

Claims

1. A common-view time transfer method based on multiple GEO satellites, characterized in that, The method comprises the following steps: selecting multiple GEO satellites within the visual range of two tracking stations, respectively using each GEO satellite for common view time transfer, and obtaining common view time transfer results of each GEO satellite; performing preprocessing on the common view time transfer results of each GEO satellite, including height angle threshold filtering and 3sigma rule for removing clock difference abnormal values, to obtain the preprocessed common view time transfer results of each GEO satellite; iterating through each GEO satellite, analyzing the link stability of the current GEO satellite based on the preprocessed common view time transfer results, and judging whether the current GEO satellite is in an orbit maneuvering state by referring to broadcast ephemeris; if the current GEO satellite is not in the orbit maneuvering state, assigning a weight to the GEO satellite by using a static adaptive weight distribution method based on Allan variance, or assigning a weight to the GEO satellite by using a dynamic adaptive weight distribution method based on Allan variance if the GEO satellite is in the orbit maneuvering state; performing weighted average processing on the preprocessed common view time transfer results based on the weights assigned to each GEO satellite, to obtain the common view time transfer results of multiple GEO satellites.

2. The method of claim 1, wherein the method is based on a multi-GEO satellite. The number of selected GEO satellites is , is an integer greater than 1, observing the selected GEO satellites by the first tracking station and the second tracking station, denoting the th GEO satellite as , , The common view time transfer result of the th GEO satellite is expressed by the formula: ； wherein denotes the common view time transfer result, denotes the clock difference between the first tracking station and the second tracking station, denotes the clock difference between the second tracking station and the first tracking station, is the epoch, , and are sequences with respect to the epoch .

3. The method of claim 2, wherein the method is based on a multi-GEO satellite. The method comprises the following steps: traversing the GEO satellites, noting a current GEO satellite as , determining a first elevation angle relative to a first tracking station and a second elevation angle relative to a second tracking station; if the first elevation angle or the second elevation angle is less than a preset elevation angle threshold, directly discard ; If both the first and second elevation angles are not less than the preset elevation angle threshold, then the 3sigma rule is used to... To remove outliers from clocks, that is... Values ​​outside the 3sigma range are removed, thus obtaining... Preprocessed co-view time transfer results Finally, the preprocessed common-view time transfer results of each GEO satellite are obtained.

4. The method of claim 3, wherein the method is based on a multi-GEO satellite. The current GEO satellite is recorded as The link stability of the current GEO satellite is analyzed based on the preprocessed common view time transfer result, and whether the current GEO satellite is in an orbit maneuver state is judged by referring to broadcast ephemeris, including: Based on Curve fitting is performed to generate The corresponding sequence diagram of the common view time transfer result is analyzed for mutations including jumps and drifts, and each epoch is traversed while referring to the broadcast ephemeris. If no mutation occurs in the current epoch and the broadcast ephemeris is healthy, it is determined that At this time, the satellite is not in an orbit maneuvering state, otherwise, it is determined that At this time, the satellite is in an orbit maneuvering state.

5. The method of claim 4, wherein the method is based on a multi-GEO satellite. performing preprocessing on the common view time transfer results of each GEO satellite, including height angle threshold filtering and 3sigma rule for removing clock difference abnormal values, to obtain the preprocessed common view time transfer results of each GEO satellite, including: The following equation is used to calculate The corresponding Allan variance is: ； wherein, denotes the total number of epochs, i.e. the total number of samples obtained, also referred to as data period, denotes corresponding Allan variance; The static adaptive weight distribution is performed based on the initial weight of the GEO satellite and the Allan variance corresponding to each GEO satellite by the following formula: The weight corresponding to each GEO satellite is obtained: ​​ ， ， ； wherein is an inverse function of denotes the corresponding weight.

6. The method of claim 5, wherein the method is based on a multi-GEO satellite. If the current GEO satellite is in orbit maneuvering state, then According to the epoch of orbit maneuvering, it is divided into pre-maneuvering period , maneuvering period and post-maneuvering period , corresponding to , and ; Pre-maneuver period and post-maneuver period , still using the static adaptive weight allocation method based on Allan variance to allocate weights to obtain and ; During the maneuvering period ,Will The weights are reduced to zero, while the weights of other GEO satellites not in orbital maneuvering state are increased, and the sum of the weights of other GEO satellites not in orbital maneuvering state is guaranteed to be 1, so as to achieve dynamic adaptive weight allocation based on Allan variance.

7. The method of claim 6, wherein the method is based on a multi-GEO satellite. if the current GEO satellite is not in the orbit maneuvering state, assigning a weight to the GEO satellite by using a static adaptive weight distribution method based on Allan variance, including: ； wherein, represents the common view time transfer result of the multi-GEO satellites.

8. A multi-GEO satellite based common view time transfer system, characterized in that, performing weighted average processing on the preprocessed common view time transfer results based on the weights assigned to each GEO satellite, to obtain the common view time transfer results of multiple GEO satellites, which is realized by the following formula: The method comprises the following steps: a single-satellite common view module for selecting multiple GEO satellites within the visual range of two tracking stations, respectively using each GEO satellite for common view time transfer, and obtaining common view time transfer results of each GEO satellite; a preprocessing module for performing preprocessing on the common view time transfer results of each GEO satellite, including height angle threshold filtering and 3sigma rule for removing clock difference abnormal values, to obtain the preprocessed common view time transfer results of each GEO satellite; a state discrimination module for iterating through each GEO satellite, analyzing the link stability of the current GEO satellite based on the preprocessed common view time transfer results, and judging whether the current GEO satellite is in an orbit maneuvering state by referring to broadcast ephemeris; a weight distribution module for assigning a weight to the GEO satellite by using a static adaptive weight distribution method based on Allan variance if the current GEO satellite is not in the orbit maneuvering state, or assigning a weight to the GEO satellite by using a dynamic adaptive weight distribution method based on Allan variance if the GEO satellite is in the orbit maneuvering state; 9. An electronic device, comprising: a weighted fusion module for performing weighted average processing on the preprocessed common view time transfer results based on the weights assigned to each GEO satellite, to obtain the common view time transfer results of multiple GEO satellites. The method comprises the following steps: A processor and a memory having stored therein instructions executable by the processor, the processor being configured to execute the instructions to enable the electronic device to implement a multi-GEO satellite based common view time transfer method as claimed in any one of claims 1 to 7.

10. A computer readable storage medium storing a computer program, characterized in that, The computer program, when executed by a processor, is capable of implementing a multi-GEO satellite based common view time transfer method as claimed in any one of claims 1 to 7.

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