A method for constructing integrity model of medium and high orbit navigation satellites based on low orbit satellites

Abstract

The present invention relates to a method for constructing an integrity model of medium- and high-orbit navigation satellites based on low-orbit satellites, and is mainly used in the field of satellite navigation integrity monitoring. In view of the existing problems of spatiotemporal benchmark uncertainty and conservative estimation of integrity models in low-orbit satellite integrity monitoring, the present invention proposes a method for constructing an integrity model of medium- and high-orbit navigation satellites based on low-orbit satellites, including the construction of a one-way benchmark-related integrity monitoring network model and a benchmark-independent integrity monitoring network model. The present invention can provide a high-precision risk value estimation capability in real time according to the satellite geometric configuration, effectively improve the system integrity level, and has the characteristics of accurate monitoring, high real-time performance, and easy implementation.

Description

Technical Field

[0001] The invention relates to a method for constructing an integrity model of a medium-orbit and high-orbit navigation satellite based on a low-orbit satellite, and belongs to the field of integrity monitoring of satellite navigation. Background Art

[0002] Based on the global coverage of low-orbit satellite monitoring, medium-orbit satellites and high-orbit satellites are the technical direction of satellite navigation integrity monitoring. However, unlike ground stations, low-orbit satellites are in motion, and their time and space references have certain uncertainties. In addition, the existing integrity model is a static conservative estimate, which fails to provide high-precision risk value estimation capabilities in real time based on the geometric configuration of the monitoring model.

[0003] Therefore, constructing a real-time integrity model construction method for medium and high orbit navigation satellites based on low orbit satellites has important research value and engineering significance. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of uncertain spatiotemporal reference and inaccurate existing integrity models in future low-orbit integrity monitoring, and to propose a method for constructing a real-time integrity model of medium- and high-orbit navigation satellites based on low-orbit satellites.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for constructing an integrity model of a medium- and high-orbit navigation satellite based on a low-orbit satellite is based on a ground monitoring station and a low-orbit satellite monitoring network. The ground monitoring station is equipped with a GNSS monitoring receiver, and the low-orbit satellite is equipped with a GNSS monitoring receiver and a GNSS navigation signal transmission payload; the method comprises the following steps:

[0007] (1) The integrity risks of medium and high orbit satellites are generally divided into benchmark-related integrity risks and benchmark-independent integrity risks. The benchmark-related integrity risks include satellite orbit anomalies and satellite clock anomalies, while the benchmark-independent integrity risks include low power, signal distortion, and ephemeris data anomalies.

[0008] (2) Construct the network vector topology relationship between ground monitoring stations, low-orbit satellites, and medium- and high-orbit satellites. Based on the set principle, the two low-orbit satellites that have a bidirectional relationship between transmission and monitoring reception in the network topology are changed into a unidirectional relationship, forming a unidirectional benchmark-related integrity monitoring network model from the ground monitoring station through the low-orbit satellite monitoring network to the medium- and high-orbit satellites. The theoretical risk value of the satellite benchmark-related integrity model is estimated in real time based on the unidirectional network relationship.

[0009] (3) Considering only the integrity constraints of single-satellite connection relationships, the network vector topology relationship between ground monitoring stations, low-orbit satellites, and medium- and high-orbit satellites is constructed to form a benchmark-independent integrity monitoring network model from ground monitoring stations through low-orbit satellite monitoring networks to medium- and high-orbit satellites, and the theoretical risk value of the satellite benchmark-independent integrity model is calculated;

[0010] (4) The theoretical risk value of the satellite benchmark-dependent integrity model is summed with the theoretical risk value of the satellite benchmark-independent integrity model to obtain the total integrity model risk value of the satellite.

[0011] Furthermore, the specific method of step (2) is:

[0012] Based on the ground monitoring station as an absolute reference, calculate the number of ground monitoring stations REC_LEO_N receiving low-orbit satellite i i Average carrier-to-noise ratio of low-orbit satellites received by all ground monitoring stations REC_LEO_CN i , i represents the low-orbit satellite number;

[0013] Construct the network vector topology relationship between ground monitoring stations, low-orbit satellites and medium- and high-orbit satellites. For two low-orbit satellites in the network topology that have a bidirectional relationship between transmission and monitoring reception, “REC_LEO_N i A large low-orbit satellite is determined as the monitoring receiver. If REC_LEO_N i If they are the same, REC_LEO_CN i Based on the principle of "determining large low-orbit satellites as monitoring receivers", all bidirectional relationships in the network topology are changed into unidirectional relationships, forming a unidirectional integrity monitoring network model from ground monitoring stations to medium and high-orbit satellites through the low-orbit satellite monitoring network, and the theoretical risk value P_corr of the satellite benchmark correlation integrity model is estimated in real time according to the unidirectional network relationships. sat，i :

[0014]

[0015] In the above formula, S c represents the set of integrity monitoring scenarios that lead to monitoring risks; B represents a certain integrity monitoring scenario in S that leads to monitoring risks; Mt_c i represents the set of low-orbit satellites and ground monitoring stations that can monitor and receive satellite i in the one-way integrity monitoring network model; k represents Mt i A ground monitoring station or low-orbit satellite in the k represents the risk probability value corresponding to the ground monitoring station or low-orbit satellite numbered k in scenario B, and its calculation method is:

[0016] If k is assumed to be normal in the scene, then:

[0017] P_monitoring k =1-P_corr k

[0018] otherwise:

[0019] P_monitoring k =P_corr k

[0020] P_corr k represents the theoretical risk value of the integrity model corresponding to the ground monitoring station numbered k or the low-orbit satellite. For the ground monitoring station P_corr k is a priori statistical known value, for low-orbit satellites and medium- and high-orbit satellites P_corr k =P_corr sat，i , P_corr sat，i The calculation is iterated sequentially according to the above method.

[0021] Furthermore, the specific method of step (3) is:

[0022] The network vector topological relationship between ground monitoring stations, low-orbit satellites and medium- and high-orbit satellites is constructed to form a benchmark-independent integrity monitoring network model from ground monitoring stations through low-orbit satellite monitoring networks to medium- and high-orbit satellites. For low-orbit satellites or medium- and high-orbit satellites i, all monitoring stations and low-orbit satellites that can receive their signals are counted to calculate the theoretical risk value P_ncorr of the satellite benchmark-independent integrity model sat，i :

[0023]

[0024] In the above formula, S n_c represents the set of integrity monitoring scenarios that lead to monitoring risks; B represents a possible integrity monitoring scenario that leads to monitoring risks in S; Mt_nc i represents the set of low-orbit satellites and ground monitoring stations that can receive satellite i; k represents Mt_nc i A ground monitoring station or low-orbit satellite in the k represents the risk probability value corresponding to the ground monitoring station or low-orbit satellite numbered k in scenario B, and the calculation method is:

[0025] If k is assumed to be normal in the scene, then:

[0026] P_ncorr_monitoring k =1-P_fault k

[0027] otherwise:

[0028] P_ncorr_monitoring k =P_fault k

[0029] P_fault k represents the corresponding benchmark-independent failure probability in the ground monitoring station numbered k or the low-orbit satellite, both of which are a priori statistically known values.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This patent proposes a method for constructing an integrity model of medium- and high-orbit navigation satellites based on low-orbit satellites. Based on low-orbit satellites, the invention constructs a real-time one-way monitoring network model, which solves the integrity monitoring problem under uncertain future space-time benchmarks and the inaccurate risk value problem caused by conservative estimates of the current integrity model. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a flow chart of a method for constructing an integrity model of medium- and high-orbit navigation satellites based on low-orbit satellites. DETAILED DESCRIPTION

[0033] In order to better illustrate the purpose and advantages of the present invention, the following Figure 1 The technical scheme of the present invention is further illustrated with embodiments.

[0034] In order to facilitate the description of the algorithm and further reduce the scale of the problem, this article assumes that: there are 3 ground monitoring stations, numbered 1, 2, and 3; there are 3 low-orbit satellites, numbered a, b, and c; there is 1 medium- and high-orbit satellite, numbered d. The specific relationship between signal transmission and monitoring reception is as follows:

[0035] Table 1 Relationship between signal transmission and monitoring reception

[0036] Monitoring Receiver Number of satellites that can be received 1 a,b,c 2 a,b 3 a,c,d a b,c,d b a,c,d c a,b,d

[0037] The reduction of the problem scale does not affect the demonstration process of this example. The specific implementation process of the present invention is:

[0038] A method for constructing an integrity model of medium and high orbit navigation satellites based on low-orbit satellites is based on a small number of ground monitoring stations and a low-orbit satellite monitoring network. The ground monitoring stations are equipped with GNSS monitoring receivers, and the low-orbit satellites are equipped with GNSS monitoring receivers and GNSS navigation signal transmission payloads, that is, the low-orbit satellites have both GNSS signal monitoring reception and transmission functions. Figure 1 The specific steps include:

[0039] (1) The integrity risks of medium and high orbit satellites are generally divided into benchmark-related integrity risks and benchmark-independent integrity risks. The benchmark-related integrity risks include satellite orbit anomalies and satellite clock anomalies, while the benchmark-independent integrity risks include low power, signal distortion, and ephemeris data anomalies.

[0040] (2) Construct the network vector topology relationship between ground monitoring stations, low-orbit satellites, and medium- and high-orbit satellites, and change the two low-orbit satellites that have a bidirectional relationship between transmission and monitoring reception in the network topology into a unidirectional relationship according to the set principle, forming a unidirectional benchmark-related integrity monitoring network model from the ground monitoring station through the low-orbit satellite monitoring network to the medium- and high-orbit satellites, and estimate the theoretical risk value of the satellite benchmark-related integrity model in real time based on the network unidirectional relationship. The specific method is:

[0041] Based on a small number of ground monitoring stations as an absolute reference, calculate the number of ground monitoring stations REC_LEO_N receiving low-orbit satellite i i 、The average carrier-to-noise ratio of all ground monitoring stations receiving low-orbit satellites REC_LEO_CN i , i represents the low-orbit satellite number; then the number of receivers corresponding to all low-orbit satellites and the average carrier-to-noise ratio are as follows:

[0042] Table 2 Reference table for low-orbit satellite sorting

[0043]

[0044] Construct the network vector topology relationship between ground monitoring stations, low-orbit satellites and medium- and high-orbit satellites. For two low-orbit satellites in the network topology that have a bidirectional relationship between transmission and monitoring reception, “REC_LEO_N i Large low-orbit satellites are determined as monitoring receivers; if REC_LEO_N i If they are the same, REC_LEO_CN i The principle of "large low-orbit satellites are determined as monitoring receivers" is to change all the bidirectional relationships in the vector topology relationship between the navigation signal transmission and the monitoring reception network into unidirectional relationships, forming a unidirectional integrity monitoring network model from the ground monitoring station through the low-orbit satellite monitoring network to the medium- and high-orbit satellites. The specific unidirectional monitoring network model refers to Table 3:

[0045] Table 3 Relationship between signal transmission and monitoring reception

[0046]

[0047] According to the one-way relationship of the network, the theoretical risk value P_corr of the satellite benchmark correlation integrity model is estimated in real time. sat，i :

[0048]

[0049] In the above formula, S c represents the set of integrity monitoring scenarios that lead to monitoring risks; B represents a certain integrity monitoring scenario in S that leads to monitoring risks; Mt_c i represents the set of low-orbit satellites and ground monitoring stations that can monitor and receive satellite i in the one-way integrity monitoring network model; k represents Mt i A ground monitoring station or low-orbit satellite in the k represents the risk probability value corresponding to the ground monitoring station or low-orbit satellite numbered k in scenario B,

[0050] If k is assumed to be normal in the scene, then:

[0051] P_monitoring k =1-P_corr k

[0052] otherwise:

[0053] P_monitoring k =P_corr k

[0054] Taking low-orbit satellite b as an example, assuming that the abnormality judgment rule is that if two or more integrity channels are abnormal, then it is judged to be abnormal. Then Mt_c i For the set {1, 2, a}, S c For the set {{1 monitoring is normal, 2 monitoring is normal, a monitoring is normal}, {1 monitoring is normal, 2 monitoring is normal, a monitoring is abnormal}, {1 monitoring is normal, 2 monitoring is abnormal, a monitoring is normal}, {1 monitoring is abnormal, 2 monitoring is normal, a monitoring is normal}}, in S c None of the scenarios in the collection can determine that the low-orbit satellite b is abnormal, and there is an integrity risk. The above formula includes all risks.

[0055] (3) Only considering the integrity constraints of single-satellite connection relationships, the network vector topology relationship between ground monitoring stations, low-orbit satellites, and medium- and high-orbit satellites is constructed to form a benchmark-independent integrity monitoring network model from ground monitoring stations through low-orbit satellite monitoring networks to medium- and high-orbit satellites, and the theoretical risk value of the satellite benchmark-independent integrity model is calculated. The specific method is:

[0056] The network vector topological relationship between ground monitoring stations, low-orbit satellites and medium- and high-orbit satellites is constructed to form a benchmark-independent integrity monitoring network model from ground monitoring stations through low-orbit satellite monitoring networks to medium- and high-orbit satellites. For low-orbit satellites or medium- and high-orbit satellites i, all monitoring stations and low-orbit satellites that can receive their signals are counted to calculate the theoretical risk value P_ncorr of the satellite benchmark-independent integrity model sat，i :

[0057]

[0058] In the above formula, S n_c represents the set of integrity monitoring scenarios that lead to monitoring risks; B represents a possible integrity monitoring scenario that leads to monitoring risks in S; Mt_nc i represents the set of low-orbit satellites and ground monitoring stations that can receive satellite i; k represents Mt_nc i A ground monitoring station or low-orbit satellite in the k represents the risk probability value corresponding to the ground monitoring station or low-orbit satellite numbered k in scenario B, and the calculation method is:

[0059] If k is assumed to be normal in the scene, then:

[0060] P_ncorr_monitoring k =1-P_fault k

[0061] otherwise:

[0062] P_ncorr_monitoring k =P_fault k

[0063] P_fault k The theoretical risk value of the benchmark-independent integrity model corresponding to the ground monitoring station numbered k or the low-orbit satellite is a priori statistically known. At this point, the method for constructing a real-time integrity model of a medium- and high-orbit navigation satellite based on a low-orbit satellite is completed.

[0064] (4) Sum the benchmark-dependent integrity model risk value and the benchmark-independent integrity model risk value to obtain the total integrity model risk value.

[0065] In order to specifically analyze the advantages of a method for constructing a real-time integrity model of medium and high-orbit navigation satellites based on low-orbit satellites, taking the above example, this patent has three advantages: (1) Seamless coverage of high-orbit satellite monitoring. In the example, due to the layout of the ground station, the high-orbit satellite d cannot be monitored by the ground station, but can be monitored by the low-orbit satellite; (2) The uncertainty problem of the time and space reference is solved. In the example, the time and space reference of the low-orbit satellite is monitored by the ground station, and then the time and space reference of the high-orbit satellite is monitored. In this process, one-way monitoring of the low-orbit satellite is achieved based on the monitoring model, avoiding the cross-correlation problem caused by two-way monitoring; (3) Real-time quantification of integrity risk. In the example, the integrity risk can be accurately calculated in real time based on the geometric configuration and the a priori known value, avoiding the problem of service degradation caused by conservative estimation in the existing integrity allocation.

[0066] The method of the present invention is not limited to the scenario of monitoring medium and high orbit satellites based on low orbit satellites, but is applicable to any monitoring and evaluation method in the GNSS field with uncertain spatiotemporal reference using similar methods.

[0067] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, it is apparent to those skilled in the art that several modifications and improvements may be made without departing from the principles of the present invention, and these modifications and improvements should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for constructing an integrity model of a medium-orbit and high-orbit navigation satellite based on a low-orbit satellite, which is based on a ground monitoring station and a low-orbit satellite monitoring network. The ground monitoring station is equipped with a GNSS monitoring receiver, and the low-orbit satellite is equipped with a GNSS monitoring receiver and a GNSS navigation signal transmission payload; characterized in that: The following steps are involved: (1) The integrity risks of medium and high orbit satellites are generally divided into benchmark-related integrity risks and benchmark-independent integrity risks. The benchmark-related integrity risks include satellite orbit anomalies and satellite clock anomalies, while the benchmark-independent integrity risks include low power, signal distortion, and ephemeris data anomalies. (2) Construct the network vector topology relationship between ground monitoring stations, low-orbit satellites, and medium- and high-orbit satellites. Based on the set principle, the two low-orbit satellites that have a bidirectional relationship between transmission and monitoring reception in the network topology are changed into a unidirectional relationship, forming a unidirectional benchmark-related integrity monitoring network model from the ground monitoring station through the low-orbit satellite monitoring network to the medium- and high-orbit satellites. The theoretical risk value of the satellite benchmark-related integrity model is estimated in real time based on the unidirectional network relationship. (3) Considering only the integrity constraints of single-satellite connection relationships, the network vector topology relationship between ground monitoring stations, low-orbit satellites, and medium- and high-orbit satellites is constructed to form a benchmark-independent integrity monitoring network model from ground monitoring stations through low-orbit satellite monitoring networks to medium- and high-orbit satellites, and the theoretical risk value of the satellite benchmark-independent integrity model is calculated; (4) The theoretical risk value of the satellite benchmark-dependent integrity model is summed with the theoretical risk value of the satellite benchmark-independent integrity model to obtain the total integrity model risk value of the satellite.

2. According to claim 1, a method for constructing a medium- and high-orbit navigation satellite integrity model based on a low-orbit satellite is characterized in that: The specific method of step (2) is: Based on the ground monitoring station as an absolute reference, calculate the number of ground monitoring stations REC_LEO_N receiving low-orbit satellite i i Average carrier-to-noise ratio of low-orbit satellites received by all ground monitoring stations REC_LEO_CN i , i represents the low-orbit satellite number; Construct the network vector topology relationship between ground monitoring stations, low-orbit satellites and medium- and high-orbit satellites. For two low-orbit satellites in the network topology that have both transmission and monitoring reception bidirectional relationships, "REC_LEO_N i A large low-orbit satellite is determined as the monitoring receiver. If REC_LEO_N i If they are the same, REC_LEO_CN i Based on the principle of "determining large low-orbit satellites as monitoring receivers", all bidirectional relationships in the network topology are changed into unidirectional relationships, forming a unidirectional integrity monitoring network model from ground monitoring stations to medium and high-orbit satellites through the low-orbit satellite monitoring network, and the theoretical risk value P_corr of the satellite benchmark correlation integrity model is estimated in real time according to the unidirectional network relationships. sat，i : In the above formula, S c represents the set of integrity monitoring scenarios that lead to monitoring risks; B represents a certain integrity monitoring scenario in S that leads to monitoring risks; Mt_c i represents the set of low-orbit satellites and ground monitoring stations that can monitor and receive satellite i in the one-way integrity monitoring network model; k represents Mt i A ground monitoring station or low-orbit satellite in the k represents the risk probability value corresponding to the ground monitoring station or low-orbit satellite numbered k in scenario B, and its calculation method is: If k is assumed to be normal in the scene, then: P_monitoring k =1-P_corr k otherwise: P_monitoring k =P_corr k P_corr k represents the theoretical risk value of the integrity model corresponding to the ground monitoring station numbered k or the low-orbit satellite. For the ground monitoring station P_corr k is a priori statistical known value, for low-orbit satellites and medium- and high-orbit satellites P_corr k =P_corr sat，i , P_corr sat，i The calculation is iterated sequentially according to the above method.

3. According to claim 1, a method for constructing a medium- and high-orbit navigation satellite integrity model based on a low-orbit satellite is characterized in that: The specific method of step (3) is: The network vector topological relationship between ground monitoring stations, low-orbit satellites and medium- and high-orbit satellites is constructed to form a benchmark-independent integrity monitoring network model from ground monitoring stations through low-orbit satellite monitoring networks to medium- and high-orbit satellites. For low-orbit satellites or medium- and high-orbit satellites i, all monitoring stations and low-orbit satellites that can receive their signals are counted to calculate the theoretical risk value P_ncorr of the satellite benchmark-independent integrity model sat，i : In the above formula, S n_c represents the set of integrity monitoring scenarios that lead to monitoring risks; B represents a possible integrity monitoring scenario in S that leads to monitoring risks; Mt_nc i represents the set of low-orbit satellites and ground monitoring stations that can receive satellite i; k represents Mt_nc i A ground monitoring station or low-orbit satellite in the k represents the risk probability value corresponding to the ground monitoring station or low-orbit satellite numbered k in scenario B, and the calculation method is: If k is assumed to be normal in the scene, then: P_ncorr_monitoring k =1-P_fault k otherwise: P_ncorr_monitoring k =P_fault k P_fault k represents the corresponding benchmark-independent failure probability in the ground monitoring station numbered k or the low-orbit satellite, both of which are a priori statistically known values.

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