Satellite timing system and method, and application thereof

Abstract

A satellite timing system and method, an interstation time synchronization system, and a satellite positioning system. The satellite timing system comprises: a satellite (100), and a master operation control station (210) and a user station (220) which are separately communicatively connected to the satellite (100). A master transmission ranging signal is provided between the master operation control station (210) and the satellite (100), and a pseudorange uplink signal is broadcast to the satellite (100); the satellite (100) transmits the pseudorange uplink signal as a pseudorange downlink signal to form a long pseudorange ranging signal; and at the same time, a slave transmission ranging signal is provided between the user station (220) and the satellite (100). The master operation control station (210) obtains a master transmission ranging value by measuring the master transmission ranging signal, and the user station (220) obtains a long pseudorange ranging value and a slave transmission ranging value by measuring the long pseudorange ranging signal and the slave transmission ranging signal. On the basis of the long pseudorange ranging value, the master transmission ranging value, and the slave transmission ranging value, a computing device calculates a master ionospheric total electron content between the master operation control station (210) and the satellite (100), a slave ionospheric total electron content between the user station (220) and the satellite (100), and a user station (220) clock offset relative to a system time.

Description

A satellite timing system, method and its application

[0001] Cross-references

[0002] This disclosure claims priority to Chinese Patent Application No. 202411534140.7, filed on October 31, 2024, entitled “A Satellite Timing System, Method and Application Thereto,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention belongs to the field of space science and technology, and in particular relates to a satellite timing system, method and its application. Background Technology

[0004] Satellite time synchronization is currently the most widely used and cost-effective time synchronization method. The GPS system and the BeiDou Navigation Satellite System provide satellite time synchronization services. In addition, the China Dual-Satellite Positioning System and the China Area Positioning System (CAPS) also provide satellite time synchronization services. Among these, the time synchronization services provided by the BeiDou Navigation Satellite System and the China Dual-Satellite Positioning System are widely used.

[0005] China's dual-satellite positioning system was an early satellite navigation system in my country, providing active positioning and timing services with an accuracy of approximately 10ns-100ns. The BeiDou Navigation Satellite System (BDS) offers significantly improved timing service accuracy, ranging from approximately 1ns to 30ns. Therefore, the timing service provided by BDS has been widely adopted. The standard timing accuracy of BDS is approximately 30ns, but when using methods such as dual-frequency pseudorange, common-view method, SBAS, and PPP, the accuracy can reach approximately 2ns-10ns. Among various timing services, ionospheric delay is the primary source of error and a major factor contributing to satellite navigation and positioning errors.

[0006] Ionospheric delay is a major positioning error term in satellite navigation and positioning, and it also has a significant impact on satellite communication and satellite remote sensing. Currently, there are two main methods for obtaining satellite-to-ground ionospheric delay: obtaining it from third parties such as the IGS (International GPS Service); and obtaining real-time ionospheric delay directly from dual-frequency pseudorange. This method, which relies on third parties to provide the total number of ionospheric electrons, poses significant security risks. When using ionospheric data provided by third-party organizations such as IGS, users need to download the ionospheric delay for the corresponding time period from the IGS website, which involves time lag and may even result in the inability to obtain the data.

[0007] Therefore, overcoming ionospheric delay is a fundamental issue. Solving the ionospheric delay problem can not only improve the accuracy of satellite navigation, but also improve the accuracy of satellite timing.

[0008] The above content is only used to help understand the technical solution of this application and does not represent an admission that the above content is prior art. Summary of the Invention

[0009] To address the aforementioned problems, this application proposes an innovative satellite timing system and method. By using long pseudorange ranging signals and relayed ranging signals, it solves the problems of the total number of ionospheric electrons between the main control station and the satellite, and between the user station and the satellite. This enables the satellite timing system proposed in this application to overcome ionospheric delay, improve satellite timing accuracy, and eliminate the system's reliance on the total number of ionospheric electrons provided by a third party, thus making the system safe and reliable.

[0010] To address the aforementioned problems, this application provides a satellite timing system, comprising a satellite, a master control station, and user stations. The master control station and user stations are all communicatively connected to the satellite. The satellite communicates with the master control station via h primary relay ranging signals and with the user stations via r secondary relay ranging signals. The master control station, satellite, and user stations communicate with each other via m long pseudorange ranging signals. Where m, h, and r are all positive integers and m + h + r ≥ 5. The long pseudorange ranging signals consist of pseudorange uplink signals and pseudorange downlink signals. The master control station broadcasts the pseudorange uplink signals, and the satellite relays the pseudorange uplink signals to form the pseudorange downlink signals. The user station receives the pseudorange downlink signal; the primary relay ranging signal and the pseudorange uplink signal have at least three different carrier frequencies, and the secondary relay ranging signal and the pseudorange downlink signal have at least three different carrier frequencies; the primary relay ranging signal consists of a primary uplink signal and a primary downlink signal, the primary control station broadcasts the primary uplink signal and receives the primary downlink signal, and the satellite receives the primary uplink signal and forwards it to form the primary downlink signal; the secondary relay ranging signal consists of a secondary uplink signal and a secondary downlink signal, the user station broadcasts the secondary uplink signal and receives the secondary downlink signal, and the satellite receives the secondary uplink signal and forwards it to form the secondary downlink signal.

[0011] In addition, to solve the above problems, this application also provides an inter-station time synchronization system, including: the satellite timing system described in any embodiment of this application; wherein, when there are multiple user stations, the multiple user stations perform inter-station time synchronization with each other through data exchange.

[0012] In addition, to solve the above problems, this application also provides a satellite positioning system, including: a satellite timing system as described in any embodiment of this application, wherein the number of satellites is greater than or equal to 2; an orbit determination system; wherein the orbit determination system monitors the orbits of the satellites to obtain the orbital parameters of the satellites; the user station obtains the orbital parameters of the corresponding satellites based on the data transmission results with each satellite, and determines its own coordinate information based on the orbital parameters of each satellite and the space distance between itself and the satellites.

[0013] Furthermore, to address the aforementioned problems, this application also provides a satellite timing method, applied to the satellite timing system described in any embodiment of this application. The method is executed by a computing device and includes: communicating with a main control station to acquire h primary transponder ranging values, communicating with a user station to acquire m long pseudorange ranging values ​​and r secondary transponder ranging values, wherein the primary transponder ranging values ​​are obtained by the main control station measuring the primary transponder ranging signal, and the long pseudorange ranging values ​​and secondary transponder ranging values ​​are obtained by the user station measuring the long pseudorange ranging signal and the secondary transponder ranging signal respectively, where m, h, and r are all positive integers and m+h+r≥5; respectively using The long pseudorange ranging expression characterizes each of the long pseudorange ranging values, and the forwarding ranging expression characterizes each of the primary forwarding ranging values ​​and the secondary forwarding ranging values. Based on the long pseudorange ranging values ​​characterized by m expressions, the primary forwarding ranging values ​​characterized by h expressions, and the secondary forwarding ranging values ​​characterized by r expressions, the total number of primary ionospheric electrons, the total number of secondary ionospheric electrons, and the clock difference of the user station relative to the system time are determined. The total number of primary ionospheric electrons is the total number of ionospheric electrons on the ranging signal path between the primary control station and the satellite, and the total number of secondary ionospheric electrons is the total number of ionospheric electrons on the ranging signal path between the user station and the satellite.

[0014] The satellite timing system and method provided by this application creatively overcome ionospheric time delay errors, and can significantly improve positioning and timing accuracy compared with the Chinese regional positioning system and the Chinese dual-satellite positioning system. Attached Figure Description

[0015] Figures 1 to 6 are schematic diagrams of the satellite timing system provided in the embodiments of this application;

[0016] Figure 7 is a structural block diagram of a satellite timing system according to one embodiment of this application;

[0017] Figure 8 is a flowchart of a satellite timing method according to one embodiment of this application.

[0018] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] To address the aforementioned ionospheric time delay error problem, this application provides a satellite timing system and method. The parameters involved in the embodiments of this application are explained below:

[0021] ρ 1,a (n), ρ 2,a (n), ρ 3,a (n) represent the first, second, and third corrected long pseudorange measurements at time n, respectively, in meters; ρ1(n), ρ2(n), and ρ3(n) represent the first, second, and third long pseudorange measurements at time n, respectively, in meters; R true,pu,1 (n), R true,pu,2 (n), R true,pu,3 (n) represents the actual spatial distance traversed by the pseudorange uplink signals of the first, second, and third long pseudorange ranging signals at time n, respectively, in meters; pu,1 (n), I pu,2 (n), I pu,3 (n) represents the ionospheric delay of the pseudorange uplink signals of the first, second, and third long pseudorange ranging signals at time n, respectively, in meters (T). duiliu,pu,1 (n), T duiliu,pu,2 (n), T duiliu,pu,3 (n) represents the tropospheric delay of the pseudorange uplink signals of the first, second, and third long pseudorange ranging signals at time n, respectively, in meters;

[0022] R true,pd,1 (n), R true,pd,2 (n), R true,pd,3 (n) represents the actual spatial distance traversed by the pseudorange downlink signals of the first, second, and third long pseudorange ranging signals at time n, respectively, in meters; pd,1 (n), I pd,2 (n), I pd,3 (n) represents the ionospheric delay of the pseudorange downlink signals of the first, second, and third long pseudorange ranging signals at time n, respectively, in meters (T).duiliu,pd,1 (n), T duiliu,pd,2 (n), T duiliu,pd,3 (n) represents the tropospheric delay of the pseudorange downlink signals of the first, second, and third long pseudorange ranging signals at time n, respectively, in meters;

[0023] X1(n), X2(n), and X3(n) represent the hardware device delays of the first, second, and third long pseudorange ranging signals at time n, respectively, in meters. The hardware device delays of the long pseudorange ranging signals include the transmission delay of the pseudorange uplink signals of the first, second, and third long pseudorange ranging signals from the main control station, the forwarding delay of the pseudorange downlink signals generated by the satellite, and the reception delay of the pseudorange downlink signals of the first, second, and third long pseudorange ranging signals from the user station.

[0024] L z,1,a (n), L z,2,a (n) represents the corrected primary relay ranging value numbered 1 or 2 at time n, in meters; L z,1 (n), L z,2 (n) represents the main relay ranging value numbered 1 and 2 at time n, in meters; R true,zu,1 (n), R true,zu,2 (n) represents the actual spatial distance traversed by the primary uplink signal numbered 1 and 2 at time n, in meters; zu,1 (n), I zu,2 (n) represents the ionospheric delay of the main uplink signal numbered 1 and 2 at time n, in meters (T). duiliu,zu,1 (n), T duiliu,zu,2 (n) represents the tropospheric delay of the main uplink signal numbered 1 and 2 at time n, in meters; R true,zd,1 (n), R true,zd,2 (n) represents the actual spatial distance traversed by the main downlink signal numbered 1 and 2 at time n, in meters; zd,1 (n), I zd,2 (n) represents the ionospheric delay of the main downlink signal numbered 1 and 2 at time n, in meters (T). duiliu,zd,1 (n), T duiliu,zd,2 (n) represents the tropospheric delay of the main downlink signal numbered 1 and 2 at time n, in meters;

[0025] Y z,1 (n), Y z,2(n) represents the hardware device delay of the primary relay ranging signal numbered 1 and 2 at time n, in meters. The hardware device delay of the primary relay ranging signal includes the transmission delay of the primary uplink signal of the primary relay ranging signal numbered 1 and 2 by the main control station, the forwarding delay of the primary downlink signal of the primary relay ranging signal numbered 1 and 2 generated by the satellite, and the reception delay of the primary downlink signal of the primary relay ranging signal numbered 1 and 2 by the main control station.

[0026] L u,1,a (n), L u,2,a (n) represents the corrected relay ranging value numbered 1 and 2 at time n, in meters; L u,1 (n), L u,2 (n) represents the relay ranging value of the numbered 1 and 2 at time n, in meters;

[0027] R true,uu,1 (n), R true,uu,2 (n) represents the actual spatial distance traversed by the uplink signal at time n, where the signals are numbered 1 and 2, in meters; uu,1 (n), I uu,2 (n) represents the ionospheric delay of the uplink signal numbered 1 and 2 at time n, in meters (T). duiliu,uu,1 (n), T duiliu,uu,2 (n) represents the tropospheric delay of the uplink signal numbered 1 and 2 at time n, in meters; R true,ud,1 (n), R true,ud,2 (n) represents the actual spatial distance traversed by the downlink signal numbered 1 and 2 at time n, in meters; ud,1 (n), I ud,2 (n) represents the ionospheric delay of downlink signals numbered 1 and 2 at time n, in meters (T). duiliu,ud,1 (n), T duiliu,ud,2 (n) represents the tropospheric delay of downlink signals numbered 1 and 2 at time n, in meters;

[0028] Y u,1 (n), Y u,2 (n) represents the hardware device delay of the forwarded ranging signal numbered 1 and 2 at time n, in meters. The hardware device delay of the forwarded ranging signal includes the transmission delay of the user station for the uplink signal of the forwarded ranging signal numbered 1 and 2, the forwarding delay of the satellite generating the downlink signal of the forwarded ranging signal numbered 1 and 2, and the reception delay of the user station receiving the downlink signal of the forwarded ranging signal numbered 1 and 2.

[0029] Q ionThe ionospheric time delay coefficient is represented; TECz(n) represents the total number of electrons in the main ionosphere between the satellite and the main control station at time n, in electrons per square meter; TEC u (n) represents the total number of electrons from the ionosphere between the user station and the satellite at time n, in electrons per square meter;

[0030] f pu,1 (n), f pd,1 (n) represents the carrier frequencies of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered 1 at time n, respectively, in Hertz; f pu,2 (n), f pd,2 (n) represents the carrier frequencies of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered 2 at time n, respectively, in Hertz; f pu,3 (n), f pd,3 (n) represents the carrier frequencies of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered 3 at time n, respectively, in Hertz;

[0031] f zu,1 (n), f zd,1 (n) represents the carrier frequencies of the main uplink and main downlink signals of the main relay ranging signal numbered 1 at time n, respectively, in Hertz; f zu,2 (n), f zd,2 (n) represents the carrier frequencies of the main uplink and main downlink signals of the main relay ranging signal numbered 2 at time n, respectively, in Hertz; f uu,1 (n), f ud,1 (n) represents the carrier frequencies of the uplink and downlink signals of the slave relay ranging signal numbered 1 at time n, respectively, in Hertz; f uu,2 (n), f ud,2 (n) represents the carrier frequencies of the uplink and downlink signals of the forwarding ranging signal numbered 2 at time n, respectively, in Hertz;

[0032] It is worth noting, and specifically pointed out: Q ion The ionospheric time delay coefficient is published by certain international organizations. With in-depth research on ionospheric time delay, the coefficient has become increasingly accurate. Previously, the coefficient was 40.28, 40.30, and currently it is 40.309. More precise coefficients may be available in the future. This application does not impose any specific limitations on the ionospheric time delay coefficient and uses the latest published value. In this embodiment, the value is 40.309.

[0033] The satellite timing system provided in this application includes a satellite, a main control station, user stations, and computing equipment. The main control station and user stations are all connected to the satellite for communication, and the computing equipment is connected to the satellite, the main control station, and the user stations for communication.

[0034] The computing device can communicate with the main control station and the user station respectively to obtain long pseudorange ranging values, slave forwarding ranging values ​​and main forwarding ranging values, as well as device latency, etc.

[0035] After obtaining the long pseudorange ranging value, the primary relay ranging value, and the secondary relay ranging value, the computing device executes the method of this application to calculate the total number of primary ionospheric electrons on the ranging signal path between the satellite and the primary control station, the total number of primary ionospheric electrons on the ranging signal path between the satellite and the user, and the clock difference of the user station relative to the system time.

[0036] It is worth noting that in the embodiments of this application, the computing device may be integrated into the main operation and control station; or integrated into the user station; or it may be independent of the main operation and control station and the user station; or it may be distributed in the main operation and control station and the user station to perform computing separately; or it may be a separate device.

[0037] In actual use, the main control station and the user station each have corresponding devices with computing functions to perform different computing tasks.

[0038] Since the function of the computing device is to perform calculations based on long pseudorange ranging values, primary relay ranging values, and secondary relay ranging values, which is not the core function of this application, this application focuses on describing the satellite timing system and various calculation methods.

[0039] This application creatively proposes a satellite timing system that can overcome the ionospheric delay between the main control station and the satellite, as well as the ionospheric delay between the user station and the satellite, by organically integrating the relay ranging signal and the long pseudorange ranging signal.

[0040] Based on the satellite timing system, a satellite positioning system is also proposed. Compared to the existing BeiDou Navigation Satellite System, the most significant difference is that this system first obtains high-precision user station clock bias, and then calculates the three-dimensional coordinates of the user station using the spatial geometric distance between the user station and the satellite. This differs from the BeiDou system, which calculates both the three-dimensional coordinates and the user clock bias. The satellite positioning system provided in this application requires only a minimum of two satellites to achieve high-precision timing and positioning services, offering advantages such as low investment and superior performance.

[0041] The system time mentioned in this application refers to the time during which a system generates and maintains its operation, such as the system composed of satellites, main control station, user stations, and computing equipment described in this application. In practical applications, my country's BeiDou time is often used as the reference time and system time, and the clock difference of different devices is the clock difference of different devices relative to this BeiDou reference time.

[0042] In the satellite timing system proposed in this application, the number of long pseudorange ranging signals is m, the number of primary relay ranging signals is h, and the number of secondary relay ranging signals is r, where m+h+r≥5. There are multiple simplest satellite timing systems that meet this condition.

[0043] Before introducing the simplest system, let's first explain some basic signal structures.

[0044] The Y-type bifurcated long pseudorange ranging signal is: there is one pseudorange uplink signal and a pseudorange downlink signals with different carrier frequencies, where a is a positive integer greater than or equal to 2, denoted as Y(a).

[0045] The T-type converged long pseudorange ranging signal is defined as follows: there are at least b pseudorange uplink signals and b pseudorange downlink signals with different carrier frequencies, and all pseudorange downlink signals have the same carrier frequency, where b is a positive integer greater than or equal to 2, denoted as T(b).

[0046] The M-type comb-shaped long pseudorange ranging signal is: after at least x pseudorange uplink signals with different carrier frequencies arrive at the satellite, the satellite forwards the x pseudorange uplink signals into x pseudorange downlink signals with different carrier frequencies, where x is a positive integer greater than or equal to 2, denoted as M(x).

[0047] The following section provides an explanation of the simplest system, using the system architecture diagram as an example.

[0048] The first simplified system, as shown in Figure 1, has three long pseudorange ranging signals (m=3), one main relay ranging signal (h=1), and one slave relay ranging signal (r=1). The three long pseudorange ranging signals are transmitted by the main control station 210 as two pseudorange uplink signals with different carrier frequencies. After reaching satellite 100, these signals are relayed into three pseudorange downlink signals with two carrier frequencies. The pseudorange uplink signal with carrier frequency fpu,2 is relayed by the satellite into two pseudorange downlink signals with carrier frequencies fpd,2 and fpd,1, respectively. The total number of electrons in the primary ionosphere and the total number of electrons in the secondary ionosphere are calculated based on the three long pseudorange ranging values ​​corresponding to the three long pseudorange ranging signals.

[0049] The second simplest system, as shown in Figure 2, has one long pseudorange ranging signal (m=1), two main relay ranging signals (h=2), and two slave relay ranging signals (r=2). The pseudorange uplink signal transmitted by the main control station 210 is split into three after reaching satellite 100. One of them is used as a pseudorange downlink signal to reach user station 220, and the other two are used as main downlink signals to reach main control station 210. User station 220 transmits two slave uplink signals with different carrier frequencies. After being relayed by satellite 100, using carrier frequency multiplexing technology, the two slave downlink signals and the pseudorange downlink signal use the same carrier frequency fpd,1 to reach user station 220.

[0050] The third simplest system, as shown in Figure 3, has two long pseudorange ranging signals (m=2), two main relay ranging signals (h=2), and one slave relay ranging signal (r=1). The two long pseudorange ranging signals are Y(2) type bifurcated long pseudorange ranging signals. One pseudorange uplink signal transmitted by the main control station 210 is split into four after reaching satellite 100. Two pseudorange downlink signals with different carrier frequencies fpd,1 and fpd,2 reach user station 220, and the other two main downlink signals with different carrier frequencies fzd,1 and fzd,2 reach main control station 210. User station 220 transmits a slave uplink signal, which is relayed by satellite 100 as a slave downlink signal. The carrier frequency of the slave downlink signal is the same as the carrier frequency of any pseudorange downlink signal of the Y type bifurcated long pseudorange ranging signal. In this figure, the carrier frequency is reused with the pseudorange downlink signal with carrier frequency fpd,2.

[0051] The fourth simplest system, as shown in Figure 4, has two long pseudorange ranging signals (m=2), one main forwarding ranging signal (h=1), and two slave forwarding ranging signals (r=2). The two long pseudorange ranging signals are T(2) type converged long pseudorange ranging signals. Any one of the pseudorange uplink signals of the two T-type converged long pseudorange ranging signals is split into two after reaching satellite 100. One of them is forwarded to user station 220 as a pseudorange downlink signal, and the other is sent to the main control station 210 as a main downlink signal. In this figure, the pseudorange uplink with carrier frequency fpu,2 is split into two. User station 220 transmits two slave uplink signals with different carrier frequencies, which are forwarded by satellite 100 into two slave downlink signals with the same carrier frequency. The carrier frequency is the same as the carrier frequency of the pseudorange downlink signal of the T-type converged long pseudorange ranging signal.

[0052] The fifth, simplest system, as shown in Figure 5, has two long pseudorange ranging signals (m=2), one main relay ranging signal (h=1), and two secondary relay ranging signals (r=2). The two long pseudorange ranging signals are M-type comb-shaped long pseudorange ranging signals. Any one of the pseudorange uplink signals from the two M-type comb-shaped long pseudorange ranging signals is relayed by satellite 100 as a main downlink signal, forming one main relay ranging signal. In this figure, the pseudorange uplink signal with carrier frequency fpu,2 is relayed as the main downlink signal. User station 220 transmits one secondary uplink signal, which is relayed by satellite 100 into two secondary downlink signals. The carrier frequencies of the two secondary downlink signals correspond one-to-one with the carrier frequencies of the pseudorange downlink signals of the two M-type comb-shaped long pseudorange ranging signals.

[0053] The sixth simplified system, as shown in Figure 6, has two long pseudorange ranging signals (m=2), two main relay ranging signals (h=2), and one slave relay ranging signal (r=1). The two long pseudorange ranging signals are M-type comb-shaped long pseudorange ranging signals. The two pseudorange uplink signals with different carrier frequencies of the two M-type comb-shaped long pseudorange ranging signals are relayed by satellite 100 into two main downlink signals with the same carrier frequency, fzd,1, forming two main relay ranging signals. User station 220 transmits one slave uplink signal, which is relayed by satellite 100 into one slave downlink signal. The carrier frequency of the slave downlink signal is the same as the carrier frequency of any one of the pseudorange downlink signals of the two M-type comb-shaped long pseudorange ranging signals. In this figure, the pseudorange downlink signal with a carrier frequency of fpd,2 and the slave downlink signal have their carrier frequencies multiplexed.

[0054] In Figure 5, both pseudorange uplink signals can be forwarded by the satellite as main downlink signals with the same carrier frequency fzd,1, forming two main forwarding ranging signals. There are still three different carrier frequencies between the satellite and the main control station. However, at this time, the total number of long pseudorange ranging signals, main forwarding ranging signals, and slave forwarding ranging signals is six. The purpose of this application can still be achieved, but it is not the simplest system.

[0055] In Figure 6, one uplink signal can be relayed by the satellite into two downlink signals with carrier frequencies fpd,1 and fpd,2, forming two relay ranging signals. There are still three different carrier frequencies between the satellite and the user station. However, the total number of long pseudorange ranging signals, main relay ranging signals, and slave relay ranging signals is six. This can still achieve the purpose of this application, but it is not the simplest system.

[0056] The satellite timing system and method provided in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0057] In the exemplary embodiment shown in Figure 1, the satellite timing system includes a master control station 210, a satellite 100, a user station 220, and a computing device (not shown in the figure). A long pseudorange ranging signal exists between the master control station 210, the satellite 100, and the user station 220. This long pseudorange ranging signal consists of a pseudorange uplink signal and a pseudorange downlink signal. The master control station 210 broadcasts the pseudorange uplink signal, the satellite 100 forwards the pseudorange uplink signal to form the pseudorange downlink signal, and the user station 220 receives the pseudorange downlink signal.

[0058] Figure 1 shows three long pseudorange ranging signals. Satellite 100 is used to forward three pseudorange downlink signals with only two different carrier frequencies to user station 220 based on the two received pseudorange uplink signals with different carrier frequencies and pseudocodes. Among them, the pseudorange uplink signal with carrier frequency fpu,2 is converted into two signals after being forwarded by satellite 100, namely pseudorange downlink signals with carrier frequencies fpd,1 and fpd,2, respectively. The pseudorange uplink signal with carrier frequency fpu,1 is converted into one signal after being forwarded by satellite 100, which is forwarded as a pseudorange downlink signal with carrier frequency fpd,1.

[0059] User station 220 receives and measures three long pseudorange ranging signals, obtains three long pseudorange ranging values, and communicates with computing equipment. The computing equipment uses the long pseudorange ranging formula to express the long pseudorange ranging values, and determines the total number of primary ionospheric electrons between satellite 100 and main control station 210, and the total number of secondary ionospheric electrons between satellite 100 and user station 220 based on the three long pseudorange ranging values.

[0060] In Figure 1, the three long pseudorange ranging signals include three signal structures: two Y-shaped bifurcation long pseudorange ranging signals, two T-shaped convergence long pseudorange ranging signals, and two M-shaped comb-shaped long pseudorange ranging signals.

[0061] Among them, the two Y-shaped bifurcation long pseudorange ranging signals are: the pseudorange uplink signal with carrier frequency fpu,2 is forwarded by satellite 100 and becomes two pseudorange downlink signals with carrier frequencies fpd,1 and fpd,2, respectively, thus forming two Y-shaped bifurcation long pseudorange ranging signals. The user station 220 measures the two Y-shaped bifurcation long pseudorange ranging signals to obtain two Y-shaped bifurcation long pseudorange ranging values.

[0062] The two T-type converged long pseudorange ranging signals are: the two pseudorange uplink signals with carrier frequencies of fpu,1 and fpu,2 are forwarded by satellite 100 and become two pseudorange downlink signals with carrier frequency of fpd,1, thus forming two T-type converged long pseudorange ranging signals. The user station 220 measures the two T-type converged long pseudorange ranging signals to obtain two T-type converged long pseudorange ranging values.

[0063] The two M-type comb-shaped long pseudorange ranging signals are: the two pseudorange uplink signals with carrier frequencies of fpu,1 and fpu,2 are forwarded by satellite 100 and become two pseudorange downlink signals with carrier frequencies of fpd,1 and fpd,2, which constitute two M-type comb-shaped long pseudorange ranging signals, and two M-type comb-shaped long pseudorange ranging values ​​are obtained accordingly.

[0064] In the exemplary embodiment shown in Figure 1, there is also a main relay ranging signal between the main control station 210 and the satellite 100. The pseudorange uplink signal with a carrier frequency of fpu,2 serves as the main relay ranging signal. After being relayed by the satellite 100, it forms a main downlink signal with a carrier frequency of fzd,1. There is also a slave relay ranging signal between the user station 220 and the satellite 100. The user station 220 transmits a slave uplink signal with a carrier frequency of fuu,1, which is relayed by the satellite 100 as a slave downlink signal with a carrier frequency of fud,1. The carrier frequencies of the slave uplink signal and the pseudorange downlink signal with a carrier frequency of fpd,2 are reused, and the following relationships exist: fpu,2 = fzu,1, fpd,2 = fud,1.

[0065] It should be noted that the long pseudorange ranging signal, primary relay ranging signal, and secondary relay ranging signal described in this exemplary embodiment all refer to signals obtained by modulating a ranging code signal onto a carrier signal. In some specific embodiments, the ranging code can be a pseudocode, a Weil code, an M code, etc., and this application does not make any special limitation on which ranging code is specifically selected. Furthermore, it should be understood that all long pseudorange ranging signals, primary relay ranging signals, and secondary relay ranging signals described in the embodiments of this application are spread spectrum signals. When multiple spread spectrum signals are transmitted and received, the relationship between the carrier frequency and the ranging code is processed according to spread spectrum communication technology and code division multiple access communication technology, which will not be elaborated here.

[0066] Since long pseudorange ranging signals, main relay ranging signals, and slave relay ranging signals are all spread spectrum signals, they are collectively referred to as ranging signals for the sake of simplicity and convenience.

[0067] The specific structures of the satellite 100, main control station 210, and user station 220 in this exemplary embodiment will be further described below with reference to the accompanying drawings.

[0068] The satellite timing system provided in this application embodiment is used to provide timing services to user station 220, which may be a base station or the like in the field of mobile communication.

[0069] Figure 7 is a structural block diagram of a satellite timing system according to an embodiment of this application. As shown in Figure 7, in an exemplary embodiment, the satellite 100 may include a transponder 101 and a satellite time and frequency device 103. The satellite time and frequency device 103 can provide time and frequency signals to the transponder 101. The transponder 101 can forward several pseudorange downlink signals to the user station 220 based on several received pseudorange uplink signals. It can forward the main uplink signal of the main forwarding ranging signal to the main downlink signal of the main forwarding ranging signal, and it can also forward the secondary uplink signal of the secondary forwarding ranging signal to the secondary downlink signal of the secondary forwarding ranging signal.

[0070] The repeater 101 can perform frequency conversion and power amplification on the acquired pseudorange uplink signal before forwarding it. In this embodiment, the repeater 101 performs frequency conversion and power amplification on the uplink signal in each long pseudorange ranging signal and forwards the corresponding pseudorange downlink signal to the user station 220.

[0071] Furthermore, the repeater 101 performs frequency conversion and power amplification on the acquired uplink signal before forwarding the downlink signal to the user station 220. Similarly, the repeater 101 performs frequency conversion and power amplification on the acquired main uplink signal before forwarding the main downlink signal to the main operation and control station 210.

[0072] It should be understood that the transponder 101 and the satellite time and frequency device 103 described in the embodiments of this application can be set independently or integrated into a hardware device, that is, implemented through an integrated hardware device, and these are all within the protection scope of this application.

[0073] Referring again to Figure 7, the main control station 210 may include a main time-frequency device 213 and a main forwarding ranging device 211 that establish a communication connection with each other. The main forwarding ranging device 211 is used to broadcast pseudorange uplink signals and main uplink signals. The main time-frequency device 213 can provide time-frequency signals to the main forwarding ranging device 211.

[0074] The main relay ranging device 211 broadcasts the main uplink signal and receives the main downlink signal, and measures the received main downlink signal to obtain the main relay ranging value.

[0075] In practice, in order to reduce system costs and save frequency resources, the uplink signals of pseudorange uplink signals and main relay ranging signals can be the same. That is, part of the main uplink signal broadcast by the main relay ranging device 211 is relayed by satellite 100 into a main downlink signal and received by the main relay ranging device 211, and part of it is relayed into a pseudorange downlink signal and received by the user station 220.

[0076] In addition, it should be noted that the main time and frequency equipment 213 and the main relay ranging equipment 211 included in the main operation and control station 210 can be set up independently or integrated, and these are all within the protection scope of this application.

[0077] Referring again to Figure 7, user station 220 may include a time-frequency device 223, a pseudorange ranging device 222, and a relay ranging device 221.

[0078] The pseudorange measuring device 222 is used to receive and measure long pseudorange ranging signals to obtain long pseudorange ranging values.

[0079] The relay ranging device 221 transmits uplink signals and receives downlink signals to measure and obtain the relay ranging value.

[0080] Time-frequency signal is provided from time-frequency device 223 to pseudorange ranging device 222 and from repeater ranging device 221.

[0081] Furthermore, it should be noted that the pseudorange ranging device 222, the time-frequency device 223, and the relay ranging device 221 included in the user station 220 can be set up independently or integrated, and these all fall within the protection scope of this application.

[0082] The pseudorange ranging device 222 includes a receiving antenna and a receiver. The receiving antenna receives long pseudorange ranging signals and performs measurements.

[0083] The primary relay ranging device 211 and the secondary relay ranging device 221 may include a modulator, a mixer, a demodulator, an antenna, a data acquisition unit, etc. The modulator generates an intermediate frequency spread spectrum signal; the mixer mixes the intermediate frequency spread spectrum signal to a radio frequency signal; the antenna transmits the radio frequency signal to the satellite 100 and receives the radio frequency signal relayed by the satellite 100; the antenna receives the radio frequency signal and mixes it to an intermediate frequency signal by the mixer; the demodulator demodulates the intermediate frequency signal and obtains the relay ranging value through ranging code correlation calculation; the data acquisition unit records and stores the relay ranging value.

[0084] The computing device is communicatively connected to the pseudorange ranging device 222 and the slave relay ranging device 221 to obtain long pseudorange ranging values ​​and slave relay ranging values. The computing device also communicates with the main control station 210 to obtain the main relay ranging value and executes the method of this application to obtain the total number of primary ionospheric electrons between the main control station 210 and the satellite 100, the total number of secondary ionospheric electrons between the satellite 100 and the user station 220, and the clock difference of the user station 220 relative to the system time.

[0085] In this exemplary embodiment, the pseudorange ranging device 222 and the slave-forward ranging device 221 are set to zero baseline.

[0086] It is worth noting that the zero baseline setting mentioned in this application does not mean that the distance between the pseudorange ranging device 222 and the relay ranging device 221 is zero. Rather, it means that the distance between them is set to ensure that the pseudorange downlink signal and the relay ranging signal of each long pseudorange ranging signal traverse approximately the same spatial path. For example, as the distance between the pseudorange ranging device 222 and the relay ranging device 221 becomes smaller and smaller, and they can be integrated into one device, the approximation gradually becomes identical, with the same satellite-to-ground space distance, the same tropospheric time delay, and the same total number of ionospheric electrons.

[0087] In an exemplary embodiment, the pseudorange ranging device 222 and the slave ranging device 221 use at least one time-frequency device. One time-frequency device provides a time-frequency signal to the pseudorange ranging device 222, while the remaining time-frequency devices provide time-frequency signals to the slave ranging device 221. In practical use, the pseudorange ranging device 222 and the slave ranging device 221 perform ranging measurements at a preset time interval, which can be set to, for example, 1 second. The pseudorange ranging device 222 performs synchronous measurements on the rising or falling edge of its own 1PPS (1 Pulse Per Second) signal. The slave ranging device 221 operates under its own time-frequency signal. Preferably, it is generally recommended to use a single clock, i.e., the slave ranging device 221 and the pseudorange ranging device 222 use a common time-frequency signal for measurement.

[0088] The main relay ranging device 211 broadcasts both the pseudorange uplink signal of the long pseudorange ranging signal and generates the main relay ranging signal, which is the pseudorange uplink signal of the long pseudorange ranging signal. The main relay ranging signal follows the same spatial path, so it is naturally equivalent to a zero baseline configuration.

[0089] The transponder of satellite 100 generates a forwarding delay when forwarding signals. The forwarding delay includes the forwarding delay generated when satellite 100 forwards the main uplink signal after receiving the main uplink signal sent by the main control station 210 to form the main downlink signal, and the forwarding delay generated when the main uplink signal is forwarded as a pseudorange uplink signal of long pseudorange ranging signal to form a pseudorange downlink signal. It also includes the forwarding delay from the forwarded ranging signal to the satellite 100, where the uplink signal reaches the satellite 100 and is forwarded by the satellite 100 as a downlink signal.

[0090] Furthermore, in this exemplary embodiment, the main relay ranging device 211 in the main control station 210 has a relay signal transmission delay, a relay signal reception delay, and a pseudorange signal transmission delay.

[0091] The pseudorange ranging device 222 of user station 220 has a receiving delay, and the relay ranging device 221 has a transmitting delay and a receiving delay;

[0092] The aforementioned forwarding delay, transmission delay, and reception delay are collectively referred to as device delay.

[0093] It is worth noting that, in this exemplary embodiment, during communication between the main control station 210 and the satellite 100, the satellite 100 can first transmit all forwarding delays to the main control station 210 by adding a communication signal. Thus, the main control station 210 can obtain the various forwarding delays of the satellite 100, and the computing device communicates with the main control station 210 to obtain the device delay. Of course, the computing device can also directly communicate with the satellite 100 to obtain the various forwarding delays.

[0094] In this exemplary embodiment, the carrier frequencies of all long pseudorange ranging signals, all main relay ranging signals, and all slave relay ranging signals are frequency-hopped on the time axis according to a preset frequency hopping pattern, which can improve the anti-interference capability and anti-interception capability of the signals.

[0095] Of course, the carrier frequency of each signal in all long pseudorange ranging signals, all master relay ranging signals, and all slave relay ranging signals can remain unchanged for a long time, that is, the time interval between two frequency hopping is infinite.

[0096] In an exemplary embodiment, the satellite timing system provided in this application also has a satellite-to-ground communication function. The satellite 100 uses an additional communication signal to interact with the main control station 210. The additional communication signal can be a remote control and telemetry signal.

[0097] When the main control station 210 and the user station 220 communicate, they can establish a direct communication connection. For example, in a city, the main control station 210 and the user station 220 can communicate directly via a 4G or 5G network. Alternatively, as shown in Figure 1, the main control station 210 can also communicate with the user station 220 via satellite 100. For example, at sea or in a desert, both the main control station 210 and the user station 220 can communicate directly with satellite 100, thus achieving communication between them through satellite 100.

[0098] In this embodiment, the user station 220 can be a base station, radar, or a satellite telescope. Furthermore, there can be multiple user stations 220. For example, a telecommunications operator can build a communication network based on this satellite timing system. In this case, the user station 220 can be a communication base station. The telecommunications operator controls each communication base station through the main control station 210 and obtains relevant information about each communication base station based on the communication results between the main control station 210 and the communication base stations.

[0099] It should be understood that in this exemplary embodiment, the master control station 210 communicates with the user station 220 to obtain the user station 220's operating parameters and control the user station 220 to perform corresponding actions. Typically, an Internet of Things (IoT) system can be built based on the satellite timing system provided in this application embodiment. The specific content of the operating parameters can be determined according to the user's needs. For example, the operating parameters may include the clock difference of the user station 220 relative to the system time, the location information of the user station 220, the current temperature information of the location of the user station 220, etc.

[0100] It should be noted that in this embodiment of the application, the corresponding Sagnac effect delay needs to be obtained when calculating the clock bias of user station 220. When calculating the clock bias of user station 220, the Sagnac effect delay requires the coordinates of master control station 210, user station 220 and satellite 100. The coordinates of satellite 100 can be obtained through the known ephemeris of satellite 100. The coordinates of master control station 210 and user station 220 can be obtained through existing positioning methods. In this way, the coordinate information required by the method of this embodiment of the application is obtained, and then the Sagnac effect delay is obtained.

[0101] When using the forwarding ranging expression to characterize the master and slave forwarding ranging values, the Sagnac effect delay is not included in the expression because the signs of the uplink and downlink Sagnac effect delays are opposite, and their absolute values ​​differ very little. Therefore, these two Sagnac effect delays can be approximately canceled out, and thus the Sagnac effect delay term is not reflected in the forwarding ranging expression. Of course, in other embodiments of this application, the Sagnac effect delay can also be considered, i.e., the uplink and downlink Sagnac effect delays can be added to the forwarding ranging expression to achieve better measurement accuracy of the forwarding ranging value. These are all within the scope of protection of this application.

[0102] Furthermore, the main control station 210 communicates with the satellite 100 based on the added communication signal. The main control station 210 obtains the forwarding delay of the satellite 100 based on the communication result. The forwarding delay of the satellite 100 includes the forwarding delay of the satellite 100 for the main forwarding ranging signal, the forwarding delay for the slave forwarding ranging signal, and the forwarding delay for forwarding the pseudorange uplink signal into the pseudorange downlink signal.

[0103] The main control station 210 can transmit relevant parameters to the user station 220 using the long pseudorange ranging signal. These parameters include the main relay ranging value, the carrier frequency of each signal in the long pseudorange ranging signal, the relay delay of satellite 100, the transmission delay and reception delay of the main relay ranging signal, the transmission delay of the pseudorange uplink signal, and the orbital parameters of satellite 100.

[0104] It should be noted that, unless otherwise specified, this application uses the time of the master control station 210 as the system time. When the time of the master control station 210 is standard time or UTC time, the pseudorange uplink signal broadcast by the master control station 210 is the transmitted standard time. User station 220 receives the pseudorange downlink signal relayed by satellite 100, and user station 220 can obtain its own clock difference relative to standard time, thus realizing the time synchronization function.

[0105] Clock difference δt of main control station 210 relative to system time z(n) is a known quantity Δt. The goal is to find the clock difference of user station 220 relative to the system time. For ease of explanation, we assume the clock difference δt of the main control station 210 relative to the system time is assumed. z When (n) is zero, Δt = 0, therefore equation (z18) holds: δt z (n)=Δt=0(z18);

[0106] Even when Δt is not equal to 0, the clock difference of user station 220 relative to the system can still be calculated according to the method of this application.

[0107] Specifically, when the clock difference δt between the master control station and the system time... z When (n) is unknown, the computing device calculates the clock difference between the user station and the main control station, which can still achieve time synchronization between the user station and the main control station.

[0108] The pseudorange uplink signal and the main relay ranging signal traverse the exact same atmospheric path, and the total number of electrons in the ionosphere traversed by the ranging signal is exactly the same. The ionosphere is a diffuse medium, meaning that the time delay produced by the ionosphere for radio frequency signals of different carrier frequencies varies depending on the carrier frequency. In contrast, the troposphere is a non-diffuse medium, meaning that the troposphere produces the same time delay for radio frequency signals of different carrier frequencies.

[0109] Because the primary relay ranging device 211 broadcasts both the pseudorange uplink signal of the long pseudorange ranging signal and generates the primary relay ranging signal (i.e., the pseudorange uplink signal of the long pseudorange ranging signal), the primary relay ranging signal traverses the same spatial path, which is equivalent to a zero baseline configuration. The pseudorange uplink signal and the primary uplink signal traverse the same spatial path, but the moment the primary uplink signal crosses the ionosphere differs from the moment the primary downlink signal, relayed by satellite 100, crosses the ionosphere, resulting in a certain time difference. Within a relatively short time (e.g., a few seconds), the ionosphere is stable, and the total number of electrons in the ionosphere remains almost unchanged. It can be calculated that the round-trip time of radio frequency signals between almost all spacecraft and ground stations currently does not exceed a few seconds, fully meeting the conditions. Combining the spatial relationship of the zero baseline setting and the very short time difference, the spatial paths traversed by the primary relay ranging signal and the pseudorange uplink signal are exactly the same. Therefore, the following equations (u50) and (u51) exist: R true,pu,1 (n)=R true,pu,2 (n)=R zu,1 (n)=R zd,1 (n)=R zu,2 (n)=R zd,2 (n) (u50); T duiliu,pu,1 (n)=T duiliu,pu,2 (n)=T duiliu,zu,1 (n)=T duiliu,zd,1 (n)=T duiliu,zu,2 (n)=T duiliu,zd,2(n) (u51);

[0110] In this embodiment, the pseudorange ranging device 222 and the slave relay ranging device 221 are set to zero baseline. The pseudorange downlink signal, the slave relay ranging signal's uplink signal, and the slave downlink signal also have similar spatial path relationships as described above, hence the following equation applies: R true,pd,1 (n)=R true,pd,2 (n)=R uu,1 (n)=R ud,1 (n)=R uu,2 (n)=R ud,2 (n) (u52); T duiliu,pd,1 (n)=T duiliu,pd,2 (n)=T duiliu,uu,1 (n)=T duiliu,ud,1 (n)=T duiliu,uu,2 (n)=T duiliu,ud,2 (n) (u53);

[0111] Based on the above description, the interaction process between the main control station and the satellite in this exemplary embodiment can be summarized as follows:

[0112] Transmit the main uplink signal that relays the ranging signal;

[0113] Receive the h-channel main relay ranging signal relayed back by the satellite;

[0114] The main relay ranging signals are measured synchronously to obtain h main relay ranging values, where h is a positive integer.

[0115] Similarly, the interaction process between the user station and the satellite can be summarized as follows:

[0116] Transmit at least one uplink signal to the satellite;

[0117] The satellite acquires at least one downlink signal based on at least one uplink signal relayed from the uplink signal, wherein at least one uplink signal and at least one downlink signal constitute r relayed ranging signals;

[0118] Acquire m-channel pseudorange ranging signals;

[0119] By synchronously measuring each slave relay ranging signal and each long pseudorange ranging signal, r slave relay ranging values ​​and m long pseudorange ranging values ​​are obtained;

[0120] Where m+h+r≥5, and m, h, and r are all positive integers.

[0121] Based on the above embodiments, this application also provides a satellite timing method, applied to the satellite timing system described in any of the above embodiments, the method being executed by a computing device.

[0122] Figure 8 is a flowchart of a satellite timing method according to an embodiment of the present application. As shown in Figure 8, the satellite timing method may include the following steps:

[0123] S200: Communicate with the main control station to obtain h main forwarding ranging values, and communicate with the user station to obtain m long pseudorange ranging values ​​and r secondary forwarding ranging values. The main forwarding ranging values ​​are obtained by the main control station measuring the main forwarding ranging signal. The long pseudorange ranging values ​​and the secondary forwarding ranging values ​​are obtained by the user station measuring the long pseudorange ranging signal and the secondary forwarding ranging signal respectively. m, h, and r are all positive integers and m+h+r≥5.

[0124] S210. Each of the long pseudorange ranging values ​​is represented by a long pseudorange ranging expression, and each of the master forwarding ranging value and the slave forwarding ranging value is represented by a forwarding ranging expression.

[0125] S220. Based on the long pseudorange ranging values ​​represented by m long pseudorange ranging expressions, the primary relay ranging values ​​represented by h relay ranging expressions, and the secondary relay ranging values ​​represented by r relay ranging expressions, determine the total number of primary ionospheric electrons, the total number of secondary ionospheric electrons, and the clock difference of the user station relative to the system time. The total number of primary ionospheric electrons is the total number of ionospheric electrons along the ranging signal path between the primary control station and the satellite, and the total number of secondary ionospheric electrons is the total number of ionospheric electrons along the ranging signal path between the user station and the satellite.

[0126] The satellite timing system provided in this application has six simplified systems that can achieve high-precision timing services. The corresponding master control station and user station measure the following six simplified system's long pseudorange ranging values, master relay ranging values, and slave relay ranging values.

[0127] The first simplest system: m=3, h=1, r=1; the three long pseudorange ranging signals are transmitted by the main operation and control station. Two pseudorange uplink signals with different carrier frequencies are transmitted to the satellite and then forwarded into three pseudorange downlink signals with two different carrier frequencies.

[0128] The second simplest system: m=1, h=2, r=2; the system has one long pseudorange ranging signal, two main relay ranging signals and two slave relay ranging signals;

[0129] The third simplest system: m=2, h=2, r=1, has a Y-shaped bifurcation long pseudorange ranging signal;

[0130] The fourth simplest system: m=2, h=1, r=2, has T-type convergent long pseudorange ranging signal;

[0131] The fifth simplest system: m=2, h=1, r=2, has two long pseudorange ranging signals, which are M-type comb-shaped long pseudorange ranging signals, and also has two slave relay ranging signals and one master relay ranging signal;

[0132] The sixth simplest system: m=2, h=2, r=1, has an M-type comb-shaped long pseudorange ranging signal, and also has one slave relay ranging signal and two master relay ranging signals;

[0133] The maximum envelope of the six simplest systems mentioned above consists of three long pseudorange ranging values ​​+ two primary relay ranging values ​​+ two secondary relay ranging values. The calculations are explained based on the required measurement values ​​for each of the six simplest systems.

[0134] In S210, the computing device can characterize the primary relay ranging value using the following formula (z1), the long pseudorange ranging value using the following formula (u1), and the secondary relay ranging value using the following formula (u2): L z,j (n)=R true,zu,j (n)+R true,zd,j (n)+I zu,j (n)+I zd,j (n)+T duiliu,zu,j (n)+T duiliu,zd,j (n)+Y z,j (n) (z1); L u,k (n)=R true,uu,k (n)+R true,ud,k (n)+I uu,k (n)+I ud,k (n)+T duiliu,uu,k (n)+T duiliu,ud,k (n)+Y u,k (n) (u2);

[0135] As analyzed above, the maximum envelope of the system consists of three long pseudorange ranging values ​​+ two primary forwarding ranging values ​​+ two secondary forwarding ranging values. Therefore, the computing device further obtains the specific first, second, and third long pseudorange ranging values ​​based on formula (u1), as shown in formulas (u1-1), (u1-2), and (u1-3):

[0136] Similarly, the computing device obtains the specific first primary forwarding ranging value and the second primary forwarding ranging value according to formula (z1), as shown in formulas (z1-1) and (z1-2); L z,1 (n)=R true,zu,1 (n)+R true,zd,1 (n)+I zu,1 (n)+I zd,1 (n)+Tduiliu,zu,1 (n)+T duiliu,zd,1 (n)+Y z,1 (n) (z1-1); L z,2 (n)=R true,zu,2 (n)+R true,zd,2 (n)+I zu,2 (n)+I zd,2 (n)+T duiliu,zu,2 (n)+T duiliu,zd,2 (n)+Y z,2 (n) (z1-2);

[0137] The computing device obtains the specific first and second slave forwarding ranging values ​​according to formula (u2), as shown in formulas (u2-1) and (u2-2): L u,1 (n)=R true,uu,1 (n)+R true,ud,1 (n)+I uu,1 (n)+I ud,1 (n)+T duiliu,uu,1 (n)+T duiliu,ud,1 (n)+Y u,1 (n) (u2-1); L u,2 (n)=R true,uu,2 (n)+R true,ud,2 (n)+I uu,2 (n)+I ud,2 (n)+T duiliu,uu,2 (n)+T duiliu,ud,2 (n)+Y u,2 (n) (u2-2);

[0138] In an exemplary embodiment, step S220 specifically includes the following process:

[0139] S2201. The m long pseudorange ranging values ​​represented by the long pseudorange ranging expression are corrected to obtain m corrected long pseudorange ranging values; the h primary forwarding ranging values ​​and r secondary forwarding ranging values ​​represented by the forwarding ranging expression are corrected to obtain h corrected primary forwarding ranging values ​​and r corrected secondary forwarding ranging values.

[0140] S2202. Based on the m corrected long pseudorange ranging values, the h corrected primary relay ranging values, and the r corrected secondary relay ranging values, a simultaneous equation is formed to determine the total number of electrons in the primary ionosphere, the total number of electrons in the secondary ionosphere, and the clock difference of the user station relative to the system time.

[0141] Alternatively, the total number of electrons in the primary ionosphere and the total number of electrons in the secondary ionosphere can be determined using the m corrected long pseudorange ranging values, the h corrected primary relay ranging values, and the r corrected secondary relay ranging values. The clock difference of the user station relative to the system time can then be determined using the total number of electrons in the primary ionosphere, the total number of electrons in the secondary ionosphere, and any corrected long pseudorange ranging value, any corrected primary relay ranging value, and any corrected secondary relay ranging value.

[0142] Specifically, in step S2201, the computing device corrects the aforementioned long pseudorange ranging value, primary forwarding ranging value, and secondary forwarding ranging value to obtain the corrected long pseudorange ranging value, corrected primary forwarding ranging value, and corrected secondary forwarding ranging value as follows:

[0143] Step S2202 indicates that this application provides two methods to determine the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, and the clock difference of the user station relative to the system time. The first method uses a matrix approach to jointly solve for the three unknowns; the second method first calculates the total number of electrons in the secondary ionosphere between the user station and the satellite, and the total number of electrons in the main ionosphere between the main control station and the satellite, and then calculates the clock difference of the user station relative to the system time. These two calculation methods are explained in detail below.

[0144] In the matrix method, the computing device utilizes the zero-baseline setting relationship between the slave relay ranging device and the pseudorange ranging device in the user station, and processes the m corrected long pseudorange ranging values, the h corrected main relay ranging values, and the r corrected slave relay ranging values ​​to form a matrix equation as shown in formula (u3):

[0145] Solving the matrix equation (u3), we obtain the clock difference of the user station relative to the system time, the total number of electrons in the main ionosphere between the master control station and the satellite, and the total number of electrons in the secondary ionosphere between the user station and the satellite, as shown in the following formula (u4):

[0146] Wherein: matrix G has at least 3 rows and 3 columns, with the first column consisting entirely of 1s; matrix b has at least 3 rows and 1 column;

[0147] The computing device obtains the corresponding matrices G and b for each of the six simplest systems, and then substitutes these matrices into formula (u4) to solve for the unknowns. The calculation process for each of the six simplest systems is described below.

[0148] The first simplified system (Figure 1): The master control station transmits two pseudorange uplink signals with different carrier frequencies. After reaching the satellite, these are relayed into three pseudorange downlink signals with two carrier frequencies each. At this point, the carrier frequency of the third long pseudorange ranging signal is divided into f...pu,3 (n),f pd,3 (n), related to: f pu,3 (n)=f pu,2 (n), f pd,3 (n)=f pd,1 (n), f zu,1 (n)=f pu,2 (n), f ud,1 (n)=f pd,2 (n). Obtain matrix G and matrix b.

[0149] The second simplest system (Figure 2): The system has one long pseudorange ranging signal (m=1), two main relay ranging signals (h=2), and two slave relay ranging signals (r=2). The pseudorange uplink signal transmitted by the main control station is split into three after reaching the satellite. One of them is used as a pseudorange downlink signal to reach the user station, and the other two are used as main downlink signals to reach the main control station. The user station transmits two slave uplink signals with different carrier frequencies. After being relayed by the satellite, the two slave downlink signals and the pseudorange downlink signal use the same carrier frequency to reach the user station.

[0150] At this time, f zu,1 (n)=f zu,2 (n)=f pu,1 (n), f ud,1 (n)=f ud,2 (n)=f pd,1 (n). The matrices G and b are obtained as follows:

[0151] The third simplest system (Figure 3): The system has two long pseudorange ranging signals (m=2), two main relay ranging signals (h=2), and one slave relay ranging signal (r=1). The two long pseudorange ranging signals are Y-type bifurcated long pseudorange ranging signals. The Y-type bifurcated long pseudorange ranging signal is a pseudorange uplink signal that reaches the satellite and is relayed by the satellite into at least two pseudorange downlink signals with different carrier frequencies. The pseudorange uplink signal transmitted by the main control station is split into three after reaching the satellite. One of them is used as a pseudorange downlink signal to reach the user station, and the other two are main downlink signals with different carrier frequencies to reach the main control station. The user station transmits a slave uplink signal, which is relayed by the satellite into a slave downlink signal. The carrier frequency of the slave downlink signal is the same as the carrier frequency of any one of the pseudorange downlink signals of the Y-type bifurcated long pseudorange ranging signal.

[0152] At this time, f zu,1 (n)=f zu,2 (n)=f pu,1 (n), f ud,1 (n)=f pd,2(n). The matrices G and b are obtained as follows:

[0153] The fourth simplified system (Figure 4): The system has two long pseudorange ranging signals (m=2), one main relay ranging signal (h=1), and two slave relay ranging signals (r=2). The two long pseudorange ranging signals are T-type converged long pseudorange ranging signals. The T-type converged long pseudorange ranging signals are formed when at least two pseudorange uplink signals with different carrier frequencies arrive at the satellite and are then relayed by the satellite into at least two pseudorange downlink signals with the same carrier frequency. After any one of the two T-type converged long pseudorange ranging signals arrives at the satellite, it is split into two. One of them is relayed to the user station as a pseudorange downlink signal, and the other is relayed to the main control station as a main downlink signal. The user station transmits two slave uplink signals with different carrier frequencies, which are relayed by the satellite into two slave downlink signals with the same carrier frequency. The carrier frequency of these slave downlink signals is the same as the carrier frequency of the pseudorange downlink signal of the T-type converged long pseudorange ranging signal.

[0154] At this time, f pu,2 (n)=f zu,1 (n), f ud,1 (n)=f ud,2 (n)=f pd,2 (n)=f pd,1 (n). The matrices G and b are obtained as follows:

[0155] The fifth simplest system (Figure 5): The system has two long pseudorange ranging signals (m=2), one main relay ranging signal (h=1), and two slave relay ranging signals (r=2); the two long pseudorange ranging signals are M-type comb-shaped long pseudorange ranging signals, where the M-type comb-shaped long pseudorange ranging signals are formed when two pseudorange uplink signals with different carrier frequencies arrive at the satellite, and the satellite forwards the pseudorange uplink signals into two pseudorange downlink signals with the same carrier frequency;

[0156] Either of the two M-type comb-shaped long pseudorange ranging signals is forwarded by the satellite as the main downlink signal, forming a main forwarding ranging signal;

[0157] The user station transmits one uplink signal, which is relayed by the satellite into two downlink signals. The carrier frequencies of the two downlink signals correspond one-to-one with the carrier frequencies of the pseudorange downlink signals of the two M-type comb-shaped long pseudorange ranging signals.

[0158] At this time, f zu,1 (n)=f pu,2 (n), f ud,1 (n)=f pd,1 (n),f ud,2 (n)=f pd,2(n). The matrices G and b are obtained as follows:

[0159] The sixth simplest system (Figure 6): The system has two long pseudorange ranging signals (m=2), two main relay ranging signals (h=2), and one slave relay ranging signal (r=1); the two long pseudorange ranging signals are M-type comb-shaped long pseudorange ranging signals, where the M-type comb-shaped long pseudorange ranging signals are formed when two pseudorange uplink signals with different carrier frequencies arrive at the satellite, and the satellite forwards the pseudorange uplink signals into two pseudorange downlink signals with the same carrier frequency;

[0160] The two pseudorange uplink signals with different carrier frequencies of the two M-type comb-shaped long pseudorange ranging signals are forwarded by the satellite into two main downlink signals with the same carrier frequency, forming two main forwarding ranging signals;

[0161] The user station transmits one uplink signal, which is relayed by the satellite as one downlink signal. The carrier frequency of the downlink signal is the same as the carrier frequency of either of the two M-type comb-shaped long pseudorange ranging signals.

[0162] At this time, f pu,1 (n)=f zu,1 (n),f pu,2 (n)=f zu,2 (n), f pd,2 (n)=f ud,1 (n). The matrices G and b are obtained as follows:

[0163] The second method is explained below. This method involves the computing equipment first calculating the total number of electrons in the ionosphere between the user station and the satellite, and the total number of electrons in the main ionosphere between the main control station and the satellite. Then, using the total number of electrons in the main ionosphere and the total number of electrons in the ionosphere, the clock difference between the user station and the system time is calculated. This will still be explained for the six simplest systems:

[0164] The first simplest system: The main control station transmits two pseudorange uplink signals with different carrier frequencies, which are then forwarded by the satellite into three pseudorange downlink signals with two carrier frequencies.

[0165] At this time, the carrier frequency of the third long pseudorange ranging signal is divided into f pu,3 (n),f pd,3 (n), related to: f pu,3 (n)=f pu,2 (n), f pd,3 (n)=f pd,1 (n).

[0166] A matrix equation is constructed using three long pseudorange ranging values ​​to calculate the total number of electrons in the primary ionosphere and the total number of electrons in the secondary ionosphere. Then, the clock difference between the user station and the system time is determined using the total number of electrons in the primary and secondary ionospheres, any corrected long pseudorange ranging value, any corrected primary relay ranging value, and any corrected secondary relay ranging value.

[0167] Construct a matrix equation (u7) for the unknowns, which represents the total number of electrons in the main ionosphere and the total number of electrons in the secondary ionosphere.

[0168] The solution to matrix equation (u7) is given by formula (u8).

[0169] in,

[0170] The second simplest system: The system has one long pseudorange ranging signal (m=1), two main relay ranging signals (h=2), and two slave relay ranging signals (r=2). The pseudorange uplink signal transmitted by the main control station is split into three after reaching the satellite. One of them is used as a pseudorange downlink signal to reach the user station, and the other two are used as main downlink signals to reach the main control station. The user station transmits two slave uplink signals with different carrier frequencies. After being relayed by the satellite, the two slave downlink signals and the pseudorange downlink signal use the same carrier frequency to reach the user station.

[0171] The total number of electrons in the main ionosphere is calculated using two primary relay ranging values, and the total number of electrons in the secondary ionosphere is calculated using two secondary relay ranging values. Then, the clock difference between the user station and the system time is determined using the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, any corrected long pseudorange ranging value, any corrected primary relay ranging value, and any corrected secondary relay ranging value.

[0172] The total number of electrons in the main ionosphere is calculated based on the two main relay ranging values ​​and the following formula.

[0173] The total number of electrons from the ionosphere is calculated based on two forward ranging values ​​and the following formula.

[0174] The third simplest system: The total number of electrons in the main ionosphere is calculated using two main forwarding ranging values, and the total number of electrons in the secondary ionosphere is calculated using two Y-shaped bifurcation long pseudorange ranging values. Then, the clock difference of the user station relative to the system time is determined using the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, any corrected long pseudorange ranging value, any corrected main forwarding ranging value, and any corrected secondary forwarding ranging value.

[0175] The total number of electrons from the ionosphere is calculated based on two Y-shaped bifurcation pseudorange measurements and the following formula:

[0176] The fourth simplest system: The total number of electrons in the main ionosphere is calculated using two T-shaped convergent pseudorange ranging values, and the total number of electrons in the secondary ionosphere is calculated using two secondary relay ranging values. Then, the clock difference of the user station relative to the system time is determined using the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, any corrected pseudorange ranging value, any corrected main relay ranging value, and any corrected secondary relay ranging value.

[0177] The total number of electrons from the ionosphere is calculated based on two Y-shaped bifurcation pseudorange measurements and the following formula:

[0178] The fifth simplest system: First, the total number of electrons in the ionosphere is calculated using two slave-to-spindle ranging values. Then, the total number of electrons in the main ionosphere is calculated using the known total number of electrons in the ionosphere and two M-type comb-shaped long pseudorange ranging values. Finally, the clock difference between the user station and the system time is determined using the total number of electrons in the main ionosphere, the total number of electrons in the ionosphere, any corrected long pseudorange ranging value, any corrected main-topin ranging value, and any corrected slave-topin ranging value.

[0179] The sixth simplest system: First, the total number of electrons in the main ionosphere is calculated using two main transponder ranging values. Then, the total number of electrons in the secondary ionosphere is calculated using the known total number of electrons in the main ionosphere and two M-type comb-shaped long pseudorange ranging values. Finally, the clock difference of the user station relative to the system time is determined using the total number of electrons in the main ionosphere and the total number of electrons in the secondary ionosphere, any corrected long pseudorange ranging value, any corrected main transponder ranging value, and any corrected secondary transponder ranging value.

[0180] dρ(n) represents the difference between the second corrected long pseudorange measurement value and the first corrected long pseudorange measurement value.

[0181] The total number of electrons in the main ionosphere is determined using the total number of electrons in the ionosphere and the corrected long pseudorange distance difference, resulting in either the total number of electrons in the main ionosphere shown in formula (z13-1) or the total number of electrons in the ionosphere shown in formula (u13-1):

[0182] For the above situations, after obtaining the total number of electrons in the primary ionosphere and the total number of electrons in the secondary ionosphere, the clock difference between the user station and the system time is calculated using any corrected long pseudorange ranging value, any corrected primary relay ranging value, and any corrected secondary relay ranging value, according to formula (u5):

[0183] Where i = 1, 2, ..., m, j = 1, 2, ..., h, k = 1, 2, ..., r;

[0184] In a specific embodiment, the clock difference between the user station and the system time, as shown in formula (u5-1), is calculated by taking the specific first corrected long pseudorange ranging value, the first corrected main relay ranging value, and the first corrected secondary relay ranging value, as well as the known total number of electrons in the main ionosphere and the total number of electrons in the secondary ionosphere.

[0185] In summary, it can be seen that the satellite timing system and method provided in this application, compared with traditional satellite timing systems, can eliminate both the primary ionospheric delay between the satellite and the main control station, and the secondary ionospheric delay between the satellite and the user station, thus improving timing accuracy. The satellite timing system and method provided in this application have the following characteristics:

[0186] 1. This application can independently obtain the total number of ionospheric electrons along the ranging signal path without requiring the total number of ionospheric electrons data provided by a third party. It has the advantages of high real-time performance and independence from third-party total number of ionospheric electrons data.

[0187] 2. This system can provide users with sub-nanosecond timing services, while significantly reducing the accuracy requirements of satellite ephemeris and user position accuracy, which is very important for reducing system operating costs.

[0188] 3. User stations can leverage existing BeiDou industry resources by simply adding a relay ranging signal to achieve high-precision time synchronization, thus shortening the R&D cycle and reducing user costs.

[0189] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A satellite timing system, characterized in that, It includes a satellite, a main operation and control station, and user stations, all of which are communicatively connected to the satellite. There are m long pseudorange ranging signals between the main control station, the satellite, and the user station; The satellite has h primary relay ranging signals between itself and the main control station, and r secondary relay ranging signals between itself and the user station; Where m, h, and r are all positive integers and m+h+r≥5; The primary forwarding ranging signal and the pseudorange uplink signal have at least three different carrier frequencies, and the secondary forwarding ranging signal and the pseudorange downlink signal have at least three different carrier frequencies. The long pseudorange ranging signal consists of a pseudorange uplink signal and a pseudorange downlink signal. The main control station broadcasts the pseudorange uplink signal, the satellite forwards the pseudorange uplink signal to form the pseudorange downlink signal, and the user station receives the pseudorange downlink signal. The main relay ranging signal consists of a main uplink signal and a main downlink signal. The main operation and control station broadcasts the main uplink signal and receives the main downlink signal. The satellite receives the main uplink signal and forwards it to form the main downlink signal. The ranging signal is composed of an uplink signal and a downlink signal. The user station broadcasts the uplink signal and receives the downlink signal. The satellite receives the uplink signal and forwards it to form the downlink signal.

2. The satellite timing system according to claim 1, characterized in that, The satellites include: The repeater forwards the main downlink signal to the main control station based on the received main uplink signal, forwards the secondary downlink signal to the user station based on the received secondary uplink signal, and forwards the pseudorange downlink signal to the user based on the received pseudorange uplink signal. Satellite time and frequency equipment provides time and frequency signals to the transponder; The main operation and control station includes: The main forwarding ranging device is used to generate and broadcast the main uplink signal and the pseudorange uplink signal, and to receive the main downlink signal to obtain the main forwarding ranging value; At least one primary time-frequency device is used to provide time-frequency signals to the primary relay ranging device; The user station includes: A pseudorange ranging device is used to receive and measure the long pseudorange ranging signal to obtain the long pseudorange ranging value; The forwarding ranging device is used to generate and broadcast the forwarding uplink signal, receive and measure the forwarding downlink signal to obtain the forwarding ranging value; At least one time-frequency device is used to provide time-frequency signals to the pseudorange ranging device and the repeater ranging device.

3. The satellite timing system according to claim 1, characterized in that, The pseudorange ranging device and the slave ranging device are set to zero baseline.

4. The satellite timing system according to claim 1, further comprising: The computing device is communicatively connected to the main control station and the user station, respectively. The computing device receives the main relay ranging value, the slave relay ranging value and the long pseudorange ranging value, and determines the total number of primary ionospheric electrons between the main control station and the satellite, the total number of slave ionospheric electrons between the user station and the satellite, and the clock difference of the user station relative to the system time based on the main relay ranging value, the slave relay ranging value and the long pseudorange ranging value. Wherein, the sum of the number of the primary forwarding ranging value, the secondary forwarding ranging value, and the long pseudorange ranging value is greater than or equal to 5; The main control station measures the main relay ranging signal to obtain the main relay ranging value, and the user station measures the slave relay ranging signal and the long pseudorange ranging signal to obtain the slave relay ranging value and the long pseudorange ranging value.

5. An inter-station time synchronization system, characterized in that, include: The satellite timing system according to any one of claims 1-4; When there are multiple user stations, they achieve inter-station time synchronization through data exchange.

6. A satellite positioning system, characterized in that, include: The satellite timing system according to any one of claims 1-4, wherein the number of satellites is greater than or equal to 2; An orbit determination system monitors the satellite's orbit and obtains the satellite's orbital parameters. The user station obtains the orbital parameters of the corresponding satellites based on the data transmission results with each satellite, and determines its own coordinate information based on the orbital parameters of each satellite and the space distance between itself and the satellite.

7. A satellite timing method, characterized in that, Applied to the satellite timing system according to any one of claims 1-4, the method is executed by a computing device, and the method includes: The system communicates with the main control station to obtain h primary forwarding ranging values, and communicates with the user station to obtain m long pseudorange ranging values ​​and r secondary forwarding ranging values. The primary forwarding ranging values ​​are obtained by the main control station measuring the primary forwarding ranging signal. The long pseudorange ranging values ​​and the secondary forwarding ranging values ​​are obtained by the user station measuring the long pseudorange ranging signal and the secondary forwarding ranging signal respectively. m, h, and r are all positive integers and m+h+r≥5. The m long pseudorange ranging values ​​are represented by the long pseudorange ranging expression, and the h primary forwarding ranging values ​​and r secondary forwarding ranging values ​​are represented by the forwarding ranging expression. Based on the long pseudorange ranging values ​​represented by m long pseudorange ranging expressions, the primary relay ranging values ​​represented by h relay ranging expressions, and the secondary relay ranging values ​​represented by r relay ranging expressions, the total number of primary ionospheric electrons, the total number of secondary ionospheric electrons, and the clock difference of the user station relative to the system time are determined. The total number of primary ionospheric electrons is the total number of ionospheric electrons along the ranging signal path between the primary control station and the satellite, and the total number of secondary ionospheric electrons is the total number of ionospheric electrons along the ranging signal path between the user station and the satellite.

8. The satellite timing method according to claim 7, characterized in that, The process of characterizing each of the long pseudorange ranging values ​​using a long pseudorange ranging expression and characterizing each of the primary forwarding ranging values ​​and the secondary forwarding ranging values ​​using a forwarding ranging expression includes: Each of the long pseudorange values ​​is characterized by the long pseudorange ranging expression shown in the following formula (u1): Where i = 1, 2, ..., m, i and m are positive integers; Each of the primary forwarding ranging values ​​is characterized by the forwarding ranging expression shown in the following formula (z1): L z,j (n)=R true,zu,j (n)+R true,zd,j (n)+I zu,j (n)+I zd,j (n)+T duiliu,zu,j (n)+T duiliu,zd,j (n)+Y z,j (n)(z1); Where j = 1, 2, ..., h, j and h are positive integers; Furthermore, each of the aforementioned forwarding ranging values ​​is characterized using the forwarding ranging expression shown in the following formula (u2): L u,k (n)=R true,uu,k (n) + R true,ud,k (n)+I uu,k (n)+I ud,k (n) + T duiliu,uu,k (n) + T duiliu,ud,k (n)+Y u,k (n)(u2); Where k = 1, 2, ..., r, and k and r are positive integers; In the formula: ρ i (n) represents the long pseudorange distance measured at time n, with the number i, in meters; R true,pu,i (n), R true,pd,i (n) represents the actual spatial distance traversed by the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters; pu,i (n), I pd,i (n) represents the ionospheric delay of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters (T). duiliu,pu,i (n), T duiliu,pd,i (n) represents the tropospheric delay of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters; c represents the speed of light, in meters per second; δt z (n) represents the clock difference between the master control station and the system time at time n, in seconds; δt u (n) represents the clock difference between the user station and the system time at time n, in seconds; sagnac zz (n), sagnac uu (n) represents the Sagnac effect delay of the pseudorange uplink and pseudorange downlink signals at time n, in meters; X i (n) represents the hardware delay of the long pseudorange ranging signal numbered i at time n, in meters. The hardware delay of the long pseudorange ranging signal includes the transmission delay of the pseudorange uplink signal of the long pseudorange ranging signal numbered i by the main control station, the forwarding delay of the pseudorange downlink signal numbered i generated by the satellite, and the reception delay of the pseudorange downlink signal of the long pseudorange ranging signal numbered i by the user station. L z,j (n) represents the primary relay ranging value numbered j at time n, in meters; R true,zu,j (n), R true,zd,j (n) represents the actual spatial distance traversed by the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters; zu,j (n), I zd,j (n) represents the ionospheric delay of the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters (T). duiliu,zu,j (n), T duiliu,zd,j (n) represents the tropospheric delay of the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters; Y z,j (n) represents the hardware device delay of the primary relay ranging signal numbered j at time n, in meters. The hardware device delay of the primary relay ranging signal includes the transmission delay of the primary uplink signal of the primary relay ranging signal numbered j by the main control station, the forwarding delay of the primary downlink signal of the primary relay ranging signal numbered j generated by the satellite, and the reception delay of the primary downlink signal of the primary relay ranging signal numbered j by the main control station. L u,k (n) represents the ranging value of the slave relay with ID k at time n, in meters; R true,uu,k (n), R true,ud,k (n) represents the actual spatial distance traversed by the uplink and downlink signals numbered k at time n, in meters; uu,k (n), I ud,k (n) represents the ionospheric delay of the uplink and downlink signals numbered k at time n, in meters (T). duiliu,uu,k (n), T duiliu,ud,k (n) represents the tropospheric delay of the uplink and downlink signals numbered k at time n, in meters; Y u,k (n) represents the hardware device delay of the k-th slave ranging signal at time n, in meters. The hardware device delay of the slave ranging signal includes the transmission delay of the slave ranging device for the k-th slave uplink signal, the forwarding delay of the satellite generating the k-th slave downlink signal, and the reception delay of the slave ranging device receiving the k-th slave downlink signal.

9. The satellite timing method according to claim 7, characterized in that, The determination of the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, and the clock difference between the user station and the system time, based on the long pseudorange ranging values ​​represented by m long pseudorange ranging expressions, the primary relay ranging values ​​represented by h relay ranging expressions, and the secondary relay ranging values ​​represented by r relay ranging expressions, includes: The long pseudorange ranging values ​​represented by m long pseudorange ranging expressions, the master forwarding ranging values ​​represented by h forwarding ranging expressions, and the slave forwarding ranging values ​​represented by r forwarding ranging expressions are corrected to obtain m corrected long pseudorange ranging values, h corrected master forwarding ranging values, and r corrected slave forwarding ranging values. The total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, and the clock difference of the user station relative to the system time are determined based on the m corrected long pseudorange ranging values, the h corrected main forwarding ranging values, and the r corrected secondary forwarding ranging values. Alternatively, the total number of electrons in the primary ionosphere and the total number of electrons in the secondary ionosphere can be determined using the m corrected long pseudorange ranging values, h corrected primary relay ranging values, and r corrected secondary relay ranging values. The clock difference of the user station relative to the system time can then be determined using the total number of electrons in the primary ionosphere, the total number of electrons in the secondary ionosphere, any of the corrected long pseudorange ranging values, any of the corrected primary relay ranging values, and any of the corrected secondary relay ranging values.

10. The satellite timing method according to claim 8, characterized in that, The process of correcting the long pseudorange ranging values ​​represented by m long pseudorange ranging expressions, the primary forwarding ranging values ​​represented by h forwarding ranging expressions, and the secondary forwarding ranging values ​​represented by r forwarding ranging expressions to obtain m corrected long pseudorange ranging values, h corrected primary forwarding ranging values, and r corrected secondary forwarding ranging values ​​includes: The long pseudorange value numbered i, represented by the long pseudorange ranging expression shown in formula (u1), is corrected to obtain the corrected long pseudorange value numbered i: Where i = 1, 2, ..., m, i is a positive integer; The primary forwarding ranging value with number j, represented by the forwarding ranging expression shown in formula (z1), is corrected to obtain the corrected primary forwarding ranging value with number j: L z,j (n)=R true,zu,j (n)+R true,zd,j (n)+I zu,j (n)+I zd,j (n)+T duiliu,zu,j (n)+T duiliu,zd,j (n)+Y z,j (n)(z1); Where j = 1, 2, ..., h, j and h are positive integers; Furthermore, the modified slave ranging value k, represented by the forwarding ranging expression shown in formula (u2), is obtained by correcting the slave forwarding ranging value k: L u,k (n)=R true,uu,k (n) + R true,ud,k (n)+I uu,k (n)+I ud,k (n) + T duiliu,uu,k (n) + T duiliu,ud,k (n)+Y u,k (n)(u2); Where k = 1, 2, ..., r, and k and r are positive integers; In the formula: ρ i,a (n) represents the corrected long pseudorange measurement value numbered i at time n, in meters; ρ i (n) represents the long pseudorange distance measured at time n, with the number i, in meters; R true,pu,i (n), R true,pd,i (n) represents the actual spatial distance traversed by the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters; pu,i (n), I pd,i (n) represents the ionospheric delay of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters (T). duiliu,pu,i (n), T duiliu,pd,i (n) represents the tropospheric delay of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters; c represents the speed of light, in meters per second; δt z (n) represents the clock difference between the master control station and the system time at time n, in seconds; δt u (n) represents the clock difference between the user station and the system time at time n, in seconds; sagnac zz (n), sagnac uu (n) represents the Sagnac effect delay of the pseudorange uplink and pseudorange downlink signals at time n, in meters; X i (n) represents the hardware delay of the long pseudorange ranging signal numbered i at time n, in meters. The hardware delay of the long pseudorange ranging signal includes the transmission delay of the pseudorange uplink signal of the long pseudorange ranging signal numbered i by the main control station, the forwarding delay of the pseudorange downlink signal numbered i generated by the satellite, and the reception delay of the pseudorange downlink signal of the long pseudorange ranging signal numbered i by the user station. L z,j,a (n) represents the corrected primary relay ranging value with number j at time n, in meters; L z,j (n) represents the primary relay ranging value numbered j at time n, in meters; R true,zu,j (n), R true,zd,j (n) represents the actual spatial distance traversed by the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters; zu,j (n), I zd,j (n) represents the ionospheric delay of the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters (T). duiliu,zu,j (n), T duiliu,zd,j (n) represents the tropospheric delay of the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters; Y z,j (n) represents the hardware device delay of the primary relay ranging signal numbered j at time n, in meters. The hardware device delay of the primary relay ranging signal includes the transmission delay of the primary uplink signal of the primary relay ranging signal numbered j by the main control station, the forwarding delay of the primary downlink signal of the primary relay ranging signal numbered j generated by the satellite, and the reception delay of the primary downlink signal of the primary relay ranging signal numbered j by the main control station. L u,k,a (n) represents the corrected relay ranging value with number k at time n, in meters; L u,k (n) represents the ranging value of the slave relay with ID k at time n, in meters; R true,uu,k (n), R true,ud,k (n) represents the actual spatial distance traversed by the uplink and downlink signals numbered k at time n, in meters; uu,k (n), I ud,k (n) represents the ionospheric delay of the uplink and downlink signals numbered k at time n, in meters (T). duiliu,uu,k (n), T duiliu,ud,k (n) represents the tropospheric delay of the uplink and downlink signals numbered k at time n, in meters; Y u,k (n) represents the hardware device delay of the k-th slave ranging signal at time n, in meters. The hardware device delay of the slave ranging signal includes the transmission delay of the slave ranging device for the k-th slave uplink signal, the forwarding delay of the satellite generating the k-th slave downlink signal, and the reception delay of the slave ranging device receiving the k-th slave downlink signal.

11. The satellite timing method according to claim 9, characterized in that, The determination of the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, and the clock difference of the user station relative to the system time based on the m corrected long pseudorange ranging values, the h corrected primary relay ranging values, and the r corrected secondary relay ranging values ​​includes: The m corrected long pseudorange ranging values ​​as shown in formula (u1'), h corrected primary relay ranging values ​​as shown in formula (z1'), and r corrected secondary relay ranging values ​​as shown in formula (u2') are processed to construct a matrix equation (u3) with the total number of electrons in the primary ionosphere, the total number of electrons in the secondary ionosphere, and the clock difference of the user station relative to the system time as unknowns. Solving the matrix equation (u3) yields the following formula (u4): the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, and the clock difference of the user station relative to the system time. In this matrix, G has 3 columns and at least 3 rows; and matrix b has 1 column and at least 3 rows. In the formula: ρ i,a (n) represents the corrected long pseudorange measurement value numbered i at time n, in meters; ρ i (n) represents the long pseudorange distance measured at time n, with the number i, in meters; R true,pu,i (n), R true,pd,i (n) represents the actual spatial distance traversed by the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters; pu,i (n), I pd,i (n) represents the ionospheric delay of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters (T). duiliu,pu,i (n), T duiliu,pd,i (n) represents the tropospheric delay of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, in meters; c represents the speed of light, in meters per second; δt z (n) represents the clock difference between the master control station and the system time at time n, in seconds; δt u (n) represents the clock difference between the user station and the system time at time n, in seconds; sagnac zz (n), sagnac uu (n) represents the Sagnac effect delay of the pseudorange uplink and pseudorange downlink signals at time n, in meters; X i (n) represents the hardware delay of the long pseudorange ranging signal numbered i at time n, in meters. The hardware delay of the long pseudorange ranging signal includes the transmission delay of the pseudorange uplink signal of the long pseudorange ranging signal numbered i by the main control station, the forwarding delay of the pseudorange downlink signal numbered i generated by the satellite, and the reception delay of the pseudorange downlink signal of the long pseudorange ranging signal numbered i by the user station. L z,j,a (n) represents the corrected primary relay ranging value with number j at time n, in meters; L z,j (n) represents the primary relay ranging value numbered j at time n, in meters; R true,zu,j (n), R true,zd,j (n) represents the actual spatial distance traversed by the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters; zu,j (n), I zd,j (n) represents the ionospheric delay of the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters (T). duiliu,zu,j (n), T duiliu,zd,j (n) represents the tropospheric delay of the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, in meters; Y z,j (n) represents the hardware device delay of the primary relay ranging signal numbered j at time n, in meters. The hardware device delay of the primary relay ranging signal includes the transmission delay of the primary uplink signal of the primary relay ranging signal numbered j by the main control station, the forwarding delay of the primary downlink signal of the primary relay ranging signal numbered j generated by the satellite, and the reception delay of the primary downlink signal of the primary relay ranging signal numbered j by the main control station. L u,k,a (n) represents the corrected relay ranging value with number k at time n, in meters; L u,k (n) represents the ranging value of the slave relay with ID k at time n, in meters; R true,uu,k (n), R true,ud,k (n) represents the actual spatial distance traversed by the uplink and downlink signals numbered k at time n, in meters; uu,k (n), I ud,k (n) represents the ionospheric delay of the uplink and downlink signals numbered k at time n, in meters (T). duiliu,uu,k (n), T duiliu,ud,k (n) represents the tropospheric delay of the uplink and downlink signals numbered k at time n, in meters; Y u,k (n) represents the hardware device delay of the k-th slave ranging signal at time n, in meters. The hardware device delay of the slave ranging signal includes the transmission delay of the slave ranging device for the k-th slave uplink signal, the forwarding delay of the satellite generating the k-th slave downlink signal, and the reception delay of the slave ranging device receiving the k-th slave downlink signal; Q ion Indicates the ionospheric time delay factor; TEC z (n) represents the total number of electrons in the main ionosphere between the satellite and the main control station at time n, in electrons per square meter; TEC u (n) represents the total number of electrons from the ionosphere between the user station and the satellite at time n, in electrons per square meter.

12. The satellite timing method according to claim 9, characterized in that, The method of determining the clock difference of the user station relative to the system time using the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, any of the corrected long pseudorange ranging values, any of the corrected main relay ranging values, and any of the corrected secondary relay ranging values ​​includes: Using the zero-baseline setting relationship between the slave relay ranging device and the pseudorange ranging device in the user station, and based on the total number of electrons in the main ionosphere, the total number of electrons in the slave ionosphere, any of the corrected long pseudorange ranging values, any of the corrected main relay ranging values, and any of the corrected slave relay ranging values, the clock difference of the user station relative to the system time, as shown in formula (u5), is obtained: Where i = 1, 2, ..., m, j = 1, 2, ..., h, k = 1, 2, ..., r; Alternatively, the averaged clock difference of the user station relative to the system time can be obtained by averaging the clock differences of multiple user station relative to the system time determined based on the total number of electrons in the main ionosphere, the total number of electrons in the secondary ionosphere, multiple corrected long pseudorange ranging values, multiple corrected main relay ranging values, and multiple corrected secondary relay ranging values. In the formula: ρ i,a (n) represents the corrected long pseudorange distance value numbered i at time n, in meters; L z,j,a (n) represents the corrected primary relay ranging value with number j at time n, in meters; L u,k,a (n) represents the corrected relay ranging value with number k at time n, in meters; c represents the speed of light, in meters per second; δt z (n) represents the clock difference between the master control station and the system time at time n, in seconds; δt u (n) represents the clock difference between the user station and the system time at time n, in seconds; Q ion Indicates the ionospheric time delay factor; TEC z (n) represents the total number of electrons in the main ionosphere between the satellite and the main control station at time n, in electrons per square meter; TEC u (n) represents the total number of electrons from the ionosphere between the user station and the satellite at time n, in electrons per square meter; f pu,i (n), f pd,i (n) represents the carrier frequencies of the pseudorange uplink and pseudorange downlink signals of the long pseudorange ranging signal numbered i at time n, respectively, in Hertz; f zu,j (n), f zd,j (n) represents the carrier frequencies of the main uplink and main downlink signals of the main relay ranging signal numbered j at time n, respectively, in Hertz; f uu,k (n), f ud,k (n) represents the carrier frequencies of the uplink and downlink signals of the slave relay ranging signal numbered k at time n, respectively, in Hertz.

13. The satellite timing method according to claim 9, characterized in that, The determination of the total number of electrons in the main ionosphere and the total number of electrons in the secondary ionosphere using the m corrected long pseudorange ranging values, h corrected main relay ranging values, and r corrected secondary relay ranging values ​​includes: When m≥3, h≥1, and r≥1, at least three long pseudorange ranging signals are transmitted by the main control station. At least two pseudorange uplink signals with different carrier frequencies are transmitted to the satellite and then forwarded into at least three pseudorange downlink signals with two different carrier frequencies. The total number of electrons in the main ionosphere and the total number of electrons in the secondary ionosphere are calculated based on at least three long pseudorange ranging values ​​corresponding to the at least three long pseudorange ranging signals. When m≥1, h≥2, and r≥2, the total number of electrons in the main ionosphere is determined using at least two corrected main forwarding ranging values, and the total number of electrons in the secondary ionosphere is determined using at least two corrected secondary forwarding ranging values. When m≥2, h≥2, r≥1, and the m corrected long pseudorange ranging values ​​include at least two Y-shaped bifurcation corrected long pseudorange ranging values, the total number of electrons in the main ionosphere is determined using at least two main forward ranging values, and the total number of electrons in the secondary ionosphere is determined using two Y-shaped bifurcation corrected long pseudorange ranging values. When m≥2, h≥1, r≥2, and the m corrected long pseudorange ranging values ​​include at least two T-type convergence corrected long pseudorange ranging values, the total number of electrons in the ionosphere is determined by using at least two forward ranging values, and the total number of electrons in the main ionosphere is determined by using two T-type convergence corrected long pseudorange ranging values. When m≥2, h≥2, r≥1, and the m corrected long pseudorange ranging values ​​include at least two M-type comb corrected long pseudorange ranging values, the total number of electrons in the main ionosphere is determined using at least two main forward ranging values, and the total number of electrons in the secondary ionosphere is determined using the total number of electrons in the main ionosphere and the two M-type comb corrected long pseudorange ranging values. When m≥2, h≥1, r≥2, and the m corrected long pseudorange ranging values ​​include at least two M-type comb corrected long pseudorange ranging values, the total number of electrons in the ionosphere is determined by using at least two slave-to-spinning ranging values, and the total number of electrons in the main ionosphere is determined by using the total number of electrons in the ionosphere and the two M-type comb corrected long pseudorange ranging values. Wherein, the Y-type bifurcation corrected long pseudorange ranging value is the corrected long pseudorange ranging value obtained by measuring the Y-type bifurcation long pseudorange ranging signal; the T-type convergence corrected long pseudorange ranging value is the corrected long pseudorange ranging value obtained by measuring the T-type convergence long pseudorange ranging signal; and the M-type comb corrected long pseudorange ranging value is the corrected long pseudorange ranging value obtained by measuring the M-type comb long pseudorange ranging signal.

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