High- and low-orbit satellite constellation link collaborative maintenance system and method

Abstract

The present invention provides a system and method for collaborative maintenance of high and low orbit star clusters, which can improve the robustness of high and low orbit star cluster communication links, improve their ability to resist node loss, and enhance the autonomous maintenance capabilities of high and low orbit satellite links. The present invention solves the problems of low robustness of high and low orbit satellite interactions and strong dependence on the ground in existing remote sensing satellite clusters during space-based detection. The method of the present invention includes high and low orbit data interaction agreements and link maintenance methods. In the high and low orbit data interaction agreements, in order to maintain a certain degree of redundancy on unreliable links and ensure that high and low orbits have self-recovery capabilities against node loss most of the time, the link maintenance method includes link initialization process, communication satellite routine update method, backup satellite update method and communication satellite abnormal update method link maintenance, and good link maintenance is achieved through these specific methods.

Description

Technical Field

[0001] The present invention relates to the technical field of remote sensing satellite maintenance, and in particular to a system and method for collaborative maintenance of high-orbit and low-orbit satellite cluster links. Background Art

[0002] With the promotion of space multi-task exploration, ground-to-air multi-target observation and other applications, networking between satellites and other spacecraft has become a trend. The distributed star cluster organized by satellites has a flexible working mode. Through collaboration and information sharing, it can complete tasks such as moving target information collection and observation that cannot be completed by a single satellite, such as stereoscopic observation. In order to rationally utilize the resources on the satellite, enhance the ability of the star cluster to manage itself, and reduce dependence on the ground, the high-low ground star cluster communication link technology has received widespread attention from the global industry and academia. At present, the high-orbit inter-satellite links mostly use the method assigned by the ground system to enable communication between high-orbit satellites and low-orbit satellites. The satellite's participation in link maintenance is low, and the satellite cannot fully play the role of inter-satellite communication. Summary of the invention

[0003] In view of this, the present invention provides a high- and low-orbit satellite cluster collaborative maintenance system and method, which can improve the robustness of high- and low-orbit satellite cluster communication links, improve their ability to resist node loss, and enhance the autonomous maintenance capabilities of high- and low-orbit satellite links.

[0004] To achieve the above purpose, the technical solution of the present invention is as follows:

[0005] A high-orbit and low-orbit satellite cluster collaborative maintenance system of the present invention comprises a high-orbit network, a low-orbit network and a ground center; wherein the high-orbit network comprises a plurality of high-orbit satellites, and each high-orbit satellite needs to receive the heartbeat information of a low-orbit communication satellite; the low-orbit network comprises a plurality of low-orbit satellites, and at least one of the satellites has an antenna pointing to the high-orbit satellite, which is called a low-orbit network interface satellite; the low-orbit network interface satellite comprises a low-orbit communication satellite and a low-orbit backup satellite, wherein the low-orbit communication satellite is a satellite currently communicating with a certain high-orbit satellite, and is responsible for feeding back heartbeat information to the high-orbit satellite and supervising the status information of the low-orbit backup satellite, and the low-orbit backup satellite is a satellite maintaining the redundancy of the high-orbit and low-orbit communication link, and is responsible for sending its own heartbeat information to the high-orbit satellite; the ground center is the designator of the satellite initial state, allocates communication links to any high-orbit and low-orbit satellites, and is responsible for designating the initial state of the communication link for the high-orbit and low-orbit satellites when the constellation is initially established and the constellation link is disconnected.

[0006] Among them, ordinary low-orbit satellites become communication satellites or backup satellites after receiving ground designation; if communication satellites and backup satellites leave the communication range of high-orbit satellites, they become ordinary low-orbit satellites; after the high-orbit satellite switches the antenna direction, the communication satellite becomes an ordinary low-orbit satellite, and the backup satellite being pointed to becomes the new communication satellite; after an ordinary low-orbit satellite receives the delegation of a communication satellite, it becomes a backup satellite.

[0007] Among them, the working status of the high-orbit and low-orbit satellite communication link includes the normal link state, the link switching state and the abnormal link state; specifically, the normal link state refers to the steady state in which the communication link between the high-orbit and low-orbit satellites is unobstructed and the high-orbit and low-orbit satellites can exchange information through the link; the link switching state refers to the transient state of the system when the role of the node in the communication link between the high-orbit and low-orbit satellites changes, or when the link is rebuilt due to certain reasons; the abnormal link state refers to the transient state in which the communication link between the high-orbit and low-orbit satellites is disconnected and the high-orbit and low-orbit satellites cannot communicate with each other;

[0008] After the satellite enters the network and the communication link is initialized, the communication link is in normal working state; in the link switching state, after a series of steps, after the link update is completed, it enters the normal link state; in the normal link state, if the communication satellite and the backup satellite are about to leave the satellite link establishment range, it enters the link switching state; in the abnormal link state, after the high-orbit satellite detects the abnormality, it initiates the abnormal link switching and enters the link switching state; if the link is abnormally disconnected and the data interaction is abnormal, it enters the abnormal link state.

[0009] The system adopts the heartbeat data packet mode, and the satellite that needs to send the heartbeat will broadcast the satellite's ID and satellite time at the heartbeat frequency v.

[0010] A method for collaborative maintenance of high-orbit and low-orbit satellite constellation links of the present invention adopts the system of the present invention to implement collaborative maintenance, comprising the following steps:

[0011] Step 1, link initialization: After the high-orbit or low-orbit satellite initially enters the network, the ground center sends instructions to the high-orbit or low-orbit satellite to allocate links. The high-orbit or low-orbit satellite executes the command, obtains the link role, and starts normal operation;

[0012] Step 2: Maintenance of the coordinated status of the high-orbit and low-orbit links: The low-orbit communication satellite and the low-orbit backup satellite continuously obtain the orbit information of the high-orbit satellite, obtain the position and speed of the high-orbit satellite by extrapolation, continuously adjust the direction of their own antennas, point the antennas at the high-orbit satellites, and send heartbeat data packets to the high-orbit satellites at a fixed frequency; the high-orbit satellite adjusts its own antenna direction according to the pointing table of the low-orbit communication satellite or the ground center, and points the antenna at the low-orbit communication satellite; the low-orbit backup satellite sends heartbeat data packets to the communication satellite at a fixed frequency; the high-orbit satellite checks whether it has received the heartbeat data packet of the low-orbit communication satellite, and the low-orbit communication satellite needs to check whether it has received the heartbeat data packet of the low-orbit backup satellite;

[0013] Step 3, regular update of communication satellite: In step 2, the high-orbit satellite determines that the communication time of the low-orbit communication satellite is less than a certain time, performs regular update of the communication satellite, switches to the pointing table of the backup satellite with the longest communication time, and establishes a link with the backup satellite; the new communication satellite broadcasts the communication satellite change information in the low-orbit star group, and elects a new communication satellite; when the high-orbit satellite normally receives the heartbeat data packet of the new low-orbit communication satellite, the low-orbit backup satellite sends the heartbeat to the new communication satellite, and the link redundancy meets the predetermined value, the link returns to normal working state;

[0014] Step 4, backup satellite update: In step 2, the communication satellite checks the backup satellite heartbeat. If it is determined that there is a flag bit in the backup satellite heartbeat data packet, or if a backup satellite heartbeat data packet cannot be received for more than a period of time, the backup satellite update is executed; the communication satellite selects a satellite in the constellation that can communicate with the high-orbit satellite for the longest time as the backup satellite to meet the link redundancy requirements;

[0015] Step 5, abnormal update of communication satellite: In step 2, the high-orbit satellite checks the heartbeat of the communication satellite. If the heartbeat data packet of the communication satellite is not received for a period of time, the abnormal update of the communication satellite is executed. The high-orbit satellite traverses the backup satellite and tries to receive the heartbeat data packet. If it is received, the backup satellite pointing table is executed; otherwise, the high-orbit satellite needs to send information to the ground center, and the ground center will reinitialize the link for the high and low-orbit satellites.

[0016] Beneficial effects:

[0017] 1. The high-orbit and low-orbit satellite cluster collaborative maintenance system of the present invention solves the problems of low robustness of high-orbit and low-orbit satellite interaction and strong dependence on the ground in the existing remote sensing satellite cluster during space-based detection. According to the above content, the implementation of the present invention can improve the robustness of the high-orbit and low-orbit satellite cluster communication link, improve its ability to resist node loss, and enhance the autonomous maintenance capability of the high-orbit and low-orbit satellite link.

[0018] 2. The method of the present invention includes high-orbit and low-orbit data interaction agreements and link maintenance methods. In the high-orbit and low-orbit data interaction agreements, in order to maintain a certain degree of redundancy on unreliable links and ensure that the high-orbit and low-orbit have the self-recovery ability to resist node loss most of the time, the link maintenance method includes link initialization process, communication satellite regular update method, backup satellite update method and communication satellite abnormal update method link maintenance, and good link maintenance is achieved through these specific methods.

[0019] 3. The present invention adopts the heartbeat data packet method. The satellite that needs to send a heartbeat will broadcast the ID and satellite time of the satellite at the heartbeat frequency v, maintain a certain redundancy on the unreliable link, and ensure that the high and low orbits have the self-recovery ability to resist node loss most of the time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of the high-low-ground integrated intersatellite link network of the present invention.

[0021] Figure 2 This is a schematic diagram of the low-orbit satellite link state switching of the present invention.

[0022] Figure 3 It is a schematic diagram of the state switching of the inter-satellite link of high and low orbit satellites of the present invention.

[0023] Figure 4 The present invention provides a maintenance flow chart for collaboratively constructing intersatellite links between high and low orbit satellites.

[0024] Figure 5 This is a flow chart of initializing the high-orbit and low-orbit communication links of the present invention.

[0025] Figure 6 This is a flow chart of the conventional update method for a low-orbit communication satellite of the present invention.

[0026] Figure 7 This is a flow chart of the backup star updating method of the present invention.

[0027] Figure 8 This is a flow chart of the communication satellite abnormality update method of the present invention. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0029] The present invention provides a high- and low-orbit satellite cluster collaborative maintenance system to solve the problems of low high- and low-orbit satellite interaction robustness and strong dependence on the ground in existing remote sensing satellite clusters during space-based detection.

[0030] The high-low-ground integrated intersatellite link network structure of the present invention is as follows Figure 1 As shown, it includes three major types of communication sub-networks, namely high-orbit network, low-orbit network and ground center.

[0031] Among them, the high-orbit network includes multiple high-orbit satellites, and each high-orbit satellite needs to receive the heartbeat information of a low-orbit communication satellite.

[0032] The low-orbit network includes multiple low-orbit satellites, some of which have the possibility of communicating with a high-orbit satellite at the current moment, that is, they have at least one antenna pointing to the high-orbit satellite, and are called low-orbit network interface satellites. Among the low-orbit network interface satellites, there are two roles: low-orbit communication satellites and low-orbit backup satellites. A low-orbit communication satellite is a satellite that is currently communicating with a high-orbit satellite, and is responsible for feeding back heartbeat information to the high-orbit satellite and supervising the status information of the low-orbit backup satellite. A low-orbit backup satellite is a satellite that maintains the redundancy of the high-orbit and low-orbit communication links, and is responsible for sending its own heartbeat information to the high-orbit satellite.

[0033] The ground center is the specifier of the satellite's initial state and can allocate communication links to any high-orbit or low-orbit satellite. It is responsible for specifying the initial state of the communication link for high-orbit or low-orbit satellites when the constellation is initially established and the constellation link is disconnected.

[0034] The present invention low-orbit satellite link role switching is as follows Figure 2 As shown, the details are as follows:

[0035] After receiving ground designation, an ordinary low-orbit satellite can become a communication satellite or a backup satellite; if a communication satellite and a backup satellite leave the communication range of a high-orbit satellite, they will become ordinary low-orbit satellites; after a high-orbit satellite switches the antenna direction, the communication satellite will become an ordinary low-orbit satellite, and the backup satellite being pointed to will become the new communication satellite; after an ordinary low-orbit satellite receives the delegation of a communication satellite, it will become a backup satellite.

[0036] The working states of the high-orbit satellite communication link provided by the present invention include a normal link state, a link switching state, and an abnormal link state. The state switching between the three states is as follows: Figure 3 As shown. Specifically, the normal link state refers to the steady state in which the communication link between high-orbit and low-orbit satellites is unobstructed and the high-orbit and low-orbit satellites can exchange information through the link. After the satellite enters the network and the communication link is initialized, the communication link is in a normal working state; in the link switching state, after a series of steps, the link update is completed and the link enters the normal link state. The link switching state refers to the transient state of the system when the node role in the communication link between high-orbit and low-orbit satellites changes, such as when the communication satellite and the backup satellite are handed over, or when the link is rebuilt for some reason. In the normal link state, if the communication satellite and the backup satellite are about to leave the satellite link building range, the link switching state is entered; in the abnormal link state, after the high-orbit satellite detects the abnormality, the abnormal link switching is initiated and the link switching state is entered. The abnormal link state refers to the transient state in which the communication link between high-orbit and low-orbit satellites is disconnected and the high-orbit and low-orbit satellites cannot communicate. If the link is abnormally disconnected and the data exchange is abnormal, the link abnormal state is entered.

[0037] In summary, the high- and low-orbit satellite cluster collaborative maintenance system of the present invention solves the problems of low robustness of high- and low-orbit satellite interaction and strong dependence on the ground in existing remote sensing satellite clusters during space-based detection. Based on the above content, the implementation of the present invention can improve the robustness of the high- and low-orbit satellite cluster communication link, improve its ability to resist node loss, and enhance the autonomous maintenance capability of the high- and low-orbit satellite link.

[0038] The present invention also provides a method for collaborative maintenance of high- and low-orbit constellation links, which implements collaborative maintenance based on the system of the present invention, including high- and low-orbit data interaction agreements and link maintenance methods.

[0039] The specific agreement on high and low orbit data interaction is as follows:

[0040] Satellites often communicate with each other by broadcasting. To ensure the timeliness of observation information and feedback information, the communication protocol between satellites often uses a stateless link layer, that is, the sender and receiver cannot feel each other's existence, and there is no reliability guarantee for data delivery. In the scenario of establishing links between high and low orbits, the field of view of high-orbit satellites is wider, and low-orbit satellites include some satellites that can communicate with high-orbit satellites. In order to maintain a certain degree of redundancy on unreliable links and ensure that high and low orbits have the ability to self-recover from node loss most of the time, this system uses a heartbeat data packet method to broadcast the satellite ID and satellite time to the satellite that needs to send a heartbeat at the heartbeat frequency v. The specific interaction method is as follows:

[0041] 1) Low-orbit communication satellite -> high-orbit satellite:

[0042] While the high-orbit satellite is transmitting information to the low-orbit satellite, it also needs to receive heartbeat data packets sent by the low-orbit satellite to the high-orbit satellite to ensure that the low-orbit satellite is still working properly.

[0043] 2) Low-orbit backup satellite -> low-orbit communication satellite:

[0044] In order to communicate with low-orbit satellites and reduce the burden on high-orbit satellites, low-orbit communication satellites need to maintain the status of low-orbit backup satellites by themselves, and backup satellites need to broadcast heartbeat data packets to communication satellites to ensure that the backup satellites are still working properly. If the backup satellite and the high-orbit satellite can communicate for less than the communication satellite switching threshold t0, the heartbeat data packet should contain a flag bit so that the communication satellite can select a new backup satellite in the low-orbit constellation.

[0045] 3) Low orbit backup satellite -> high orbit satellite:

[0046] In order to ensure that the high-orbit satellite can sense the existence of the backup satellite when switching links and ensure the success of the link switching, the backup satellite also needs to broadcast a heartbeat data packet to the high-orbit satellite. However, the high-orbit satellite will only receive the heartbeat packet after the link is switched to the backup satellite. At other times, the high-orbit satellite will not receive the heartbeat packet sent by the backup satellite.

[0047] Based on the heartbeat data packet mechanism, high-orbit and low-orbit satellites can maintain link stability with the least amount of data possible.

[0048] According to the system redundancy setting, the high-orbit satellite maintains an antenna pointing table for each currently communicable satellite, referred to as the pointing table. The table is updated in real time as time goes by. The pointing table of a satellite at a certain moment maintains a series of antenna center point directions and the start and end times of the directions. When the high-orbit satellite communicates with a low-orbit satellite, it adjusts the antenna pointing according to the pointing table and the current time. When switching communication satellites, it directly switches to the corresponding pointing table. An example of the pointing table is shown in Table 1.

[0049] Table 1 Antenna pointing table of a high-orbit satellite to a low-orbit satellite

[0050] Antenna center pointing Communication start time Communication end time 100°E, 60°N 2015.1.1 12:00:00 2015.1.1 13:00:00 102°E,61°N 2015.1.1 12:55:00 2015.1.1 13:40:00 … … …

[0051] After the communication satellite is changed, the new communication satellite needs to inform the entire low-orbit satellite group of this information. After receiving this information, the backup satellite will send a heartbeat data packet to the new communication satellite. This data includes the current timestamp and the ID of the new communication satellite.

[0052] The link maintenance method is as follows:

[0053] (1) Link initialization process

[0054] When the link is initialized, the ground center first selects a communicable satellite for each high-orbit satellite. Among the communicable satellites, the low-orbit satellite with the longest communicable time is selected as the communication satellite. Then, according to the system redundancy, several satellites with the second longest communicable time are selected as backup communication satellites. For example, if the system redundancy is 3, after selecting the communication satellite, two communicable satellites need to be selected as backup communication satellites. After the ground selects the communication satellite and backup satellite list, the orbital position information of the high-orbit satellite is injected into the target low-orbit satellite. The low-orbit satellite automatically extrapolates the position of the high-orbit satellite and always points the antenna to the high-orbit satellite during the agreed communicable period. At the same time, the ground center sends the pointing table of the selected low-orbit satellite to the high-orbit satellite. The high-orbit satellite adjusts the antenna pointing according to the pointing table of the communication satellite and communicates with the low-orbit satellite. At this point, the link initialization is completed. Let the set of low-orbit satellites that can currently communicate with the high-orbit satellite be S, and the remaining time that the i-th low-orbit satellite can communicate with the high-orbit satellite from the beginning of the link establishment is t i , then the necessary and sufficient condition for selecting the i-th satellite as the communication satellite is

[0055]

[0056] (2) Conventional update method for communication satellite

[0057] This process is triggered when the communication satellite is about to leave the communication range of the high-orbit satellite. When the high-orbit satellite adjusts the antenna pointing according to the pointing table, if it finds that the current pointing is the antenna pointing of the last element in the pointing table, it will point the antenna to the backup satellite with the longest communication time in advance according to the communication end time of the last item in the table, based on the communication satellite switching threshold t0. The typical value of t0 is 10s. After receiving the broadcast from the high-orbit satellite, the backup satellite immediately becomes a new communication satellite and broadcasts the communication satellite change information to the low-orbit star cluster. Select another satellite in the star cluster that can communicate with the high-orbit satellite and has the longest communication time as the new backup satellite. The new communication satellite needs to send the new backup satellite pointing table to the high-orbit satellite. After receiving the new pointing table, the high-orbit satellite updates the pointing table and removes the pointing table of the expired communication satellite. At this point, the regular link switching is completed.

[0058] (3) Backup star update method

[0059] There are two main situations in which the backup satellite status changes. One is that the backup satellite will no longer have the conditions to establish a link with the high-orbit satellite and will fly out of the high-orbit satellite link establishment range. The other is that due to unexpected events such as satellite failures, the backup satellite can no longer communicate with the high-orbit satellite and no longer send heartbeat information to the communication satellite. If the low-orbit communication satellite cannot receive the heartbeat information of the low-orbit backup satellite within a certain heartbeat cycle, it will select a satellite that can communicate with the high-orbit satellite and has the longest communication time as the backup satellite. The typical value of the heartbeat cycle for the high-orbit satellite to switch to the backup satellite is 3. The communication satellite needs to send the new backup satellite information to the high-orbit satellite, and the backup satellite status update is completed.

[0060] (4) Communication satellite abnormality update method

[0061] Taking into account satellite anomalies and other situations, the high-orbit satellite needs to sense the working status of the communication satellite and decide whether to switch to the backup satellite. When the status of the communication satellite changes and the link is interrupted, the high-orbit satellite can no longer sense the heartbeat information of the communication satellite. When the high-orbit satellite cannot receive the heartbeat information of the low-orbit satellite within a certain heartbeat cycle, the high-orbit satellite determines that the communication link is disconnected. This number of cycles is called the heartbeat maintenance cycle, and the typical value is 3. After the high-orbit satellite determines that the communication link is disconnected, it will sort from long to short according to the current time and the pointing table of each backup satellite, traverse each backup satellite, point the antenna to the position of each backup satellite and stay for a period of time, and try to receive the heartbeat information of the backup satellite. This time is called the heartbeat detection time, and the typical value is the time interval of 2 heartbeat cycles. If the high-orbit satellite receives the heartbeat information of the backup satellite, the backup satellite is selected as the communication satellite. At the same time, after the communication satellite receives the heartbeat of the high-orbit satellite, it will immediately broadcast the change information of the communication satellite to the entire network, and the other backup satellites will immediately send heartbeat information to the new communication satellite. The new communication satellite waits for a period of time to confirm the current number of backup satellites and ID information. This time is called the low-orbit communication satellite confirmation time, and the typical value is 3 heartbeat cycle time intervals. According to the current number of backup satellites, a certain number of new backup satellites are selected to meet the system redundancy. For example, if the system redundancy is set to 3, and the new communication satellite only receives the heartbeat of 1 backup satellite, it is necessary to select another backup satellite. After the above information is confirmed, the new communication satellite sends the new backup satellite pointing table to the high-orbit satellite. If the high-orbit traverses the backup satellite position and cannot receive the backup satellite heartbeat, the high-orbit satellite needs to send a link initialization request to the ground command and control center, and the ground center reinitializes the link.

[0062] The collaborative construction and maintenance process of the intersatellite links between high and low orbit satellites of the present invention is as follows: Figure 4As shown in the figure, it includes the steps of link initialization, high-orbit link coordinated status maintenance, communication satellite routine update, communication satellite abnormal update and backup satellite update, which are the replacement methods of high-orbit communication link participants in specific scenarios, and the detailed communication information format is designed, as follows:

[0063] Step 1, link initialization: After the high-orbit or low-orbit satellite initially enters the network, the ground center sends instructions to the high-orbit and low-orbit satellites to allocate links. The high-orbit and low-orbit satellites execute the commands, obtain link roles, and start normal operation.

[0064] Step 2, maintenance of the coordinated status of the high-orbit and low-orbit links: The low-orbit communication satellite and the low-orbit backup satellite continuously obtain the orbit information of the high-orbit satellite, rely on extrapolation to obtain the position and speed of the high-orbit satellite, continuously adjust the direction of their own antennas, point the antennas at the high-orbit satellites, and send heartbeat packets to the high-orbit satellites at a fixed frequency. The high-orbit satellite needs to adjust its own antenna direction according to the pointing table noted on the low-orbit communication satellite or the ground center, and point the antenna at the low-orbit communication satellite. In addition, the low-orbit backup satellite sends heartbeat packets to the communication satellite at a fixed frequency. The high-orbit satellite needs to check whether it has received the heartbeat packet from the low-orbit communication satellite, and the low-orbit communication satellite needs to check whether it has received the heartbeat packet from the low-orbit backup satellite.

[0065] Step 3, regular update of communication satellite: In step 2, the high-orbit satellite determines that the communication time of the low-orbit communication satellite is less than a certain time, performs regular update of the communication satellite, switches to the pointing table of the backup satellite with the longest communication time, and establishes a link with the backup satellite. The new communication satellite needs to broadcast the communication satellite change information within the low-orbit star cluster and elect a new communication satellite. When the high-orbit satellite can normally receive the heartbeat data packet of the new low-orbit communication satellite, the low-orbit backup satellite sends the heartbeat to the new communication satellite, and the link redundancy meets the predetermined value, the link returns to normal working state.

[0066] Step 4, backup satellite update: In step 2, the communication satellite checks the backup satellite heartbeat. If it is determined that there is a flag bit in the backup satellite heartbeat data packet, or if a backup satellite heartbeat data packet is not received for a period of time, the backup satellite update is executed. The communication satellite selects a satellite in the constellation that can communicate with the high-orbit satellite for the longest time as the backup satellite to meet the link redundancy requirements.

[0067] Step 5, abnormal update of communication satellite: In step 2, the high-orbit satellite checks the heartbeat of the communication satellite. If the heartbeat data packet of the communication satellite is not received for a period of time, the abnormal update of the communication satellite is executed. The high-orbit satellite traverses the backup satellite and tries to receive the heartbeat data packet. If it is received, the backup satellite pointing table is executed; otherwise, the high-orbit satellite needs to send information to the ground center, and the ground center will reinitialize the link for the high and low-orbit satellites.

[0068] Among them, the technical routes adopted for initialization of high and low orbit communication links are as follows: Figure 5As shown, the following steps are included:

[0069] The ground center selects the low-orbit satellite with the longest communication time as the communication satellite for the high-orbit satellite; based on the link redundancy, the ground center selects (redundancy - 1) satellites as backup satellites for the high-orbit satellite; each satellite adjusts the antenna direction and sends heartbeat information based on the scheduling information from the ground center.

[0070] Conventional update methods for low-orbit communication satellites are as follows: Figure 6 As shown, the following steps are included:

[0071] The high-orbit satellite selects the backup satellite with the longest communication time from the backup satellite list as the new communication satellite, switches the antenna pointing, and removes the expired communication satellite pointing table; the new communication satellite broadcasts the communication satellite change information in the low-orbit star cluster, and the backup satellite sends the heartbeat to the new communication satellite; the new communication satellite then selects a non-backup satellite that can communicate with the high-orbit satellite for the longest time as the new backup satellite, and notes its pointing table to the high-orbit satellite.

[0072] Backup star update method is as follows Figure 7 As shown, the following steps are included:

[0073] The low-orbit communication satellite selects a non-backup satellite that can communicate with the high-orbit satellite for the longest time as the new backup satellite; the communication satellite points the new backup satellite to the high-orbit satellite marked on the table.

[0074] Communication satellite abnormal update method Figure 8 As shown, the following steps are included:

[0075] The high-orbit satellite traverses the backup satellite list from large to small according to the link establishment time. It stays on each backup satellite for a period of time and tries to receive heartbeat data packets. If a backup satellite heartbeat data packet is received, a link is established with the backup satellite. The backup satellite broadcasts the communication satellite change information, selects a certain number of backup satellites to meet the link redundancy, and notes the new backup satellite pointing table to the high-orbit satellite. If the backup satellite heartbeat data packet cannot be received, a request is sent to the ground center, and the ground center executes the link initialization process.

[0076] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-orbit and low-orbit satellite constellation link collaborative maintenance system, characterized in that: It includes a high-orbit network, a low-orbit network and a ground center; the high-orbit network includes multiple high-orbit satellites, each of which needs to receive the heartbeat information of a low-orbit communication satellite; the low-orbit network includes multiple low-orbit satellites, among which there is at least one antenna pointing to the high-orbit satellite, which is called a low-orbit network interface satellite; the low-orbit network interface satellite includes low-orbit communication satellites and low-orbit backup satellites. The low-orbit communication satellite is a satellite that is currently communicating with a high-orbit satellite and is responsible for feeding back heartbeat information to the high-orbit satellite and supervising the status information of the low-orbit backup satellite. The low-orbit backup satellite is a satellite that maintains the redundancy of the high-orbit and low-orbit communication links and is responsible for sending its own heartbeat information to the high-orbit satellite; the ground center is the designator of the satellite's initial state, allocating communication links to any high-orbit and low-orbit satellites, and is responsible for specifying the initial state of the communication link for the high-orbit and low-orbit satellites when the constellation is initially established and the constellation link is disconnected; After receiving ground designation, ordinary low-orbit satellites become communication satellites or backup satellites; if communication satellites and backup satellites leave the communication range of high-orbit satellites, they become ordinary low-orbit satellites; after the high-orbit satellite switches the antenna direction, the communication satellite becomes an ordinary low-orbit satellite, and the backup satellite pointed to becomes the new communication satellite; after receiving the designation of the communication satellite, the ordinary low-orbit satellite becomes a backup satellite; The working status of the high-orbit and low-orbit satellite communication link includes the normal link state, the link switching state and the abnormal link state. Specifically, the normal link state refers to the steady state in which the communication link between the high-orbit and low-orbit satellites is unobstructed and the high-orbit and low-orbit satellites can exchange information through the link. The link switching state refers to the transient state of the system when the role of the node in the communication link between the high-orbit and low-orbit satellites changes, or when the link is rebuilt due to some reasons. The abnormal link state refers to the transient state in which the communication link between high-orbit and low-orbit satellites is disconnected and the high-orbit and low-orbit satellites cannot communicate with each other; After the satellite is connected to the network and the communication link is initialized, the communication link is in normal working state; in the link switching state, after a series of steps, the link update is completed and the link enters the normal state; When the link is in normal state, if the communication satellite and backup satellite are about to leave the satellite link range, the link switching state will be entered; In the link abnormality state, after the high-orbit satellite detects the abnormality, it initiates link abnormality switching and enters the link switching state; If the link is disconnected abnormally and data exchange is abnormal, the link enters abnormal state.

2. The system according to claim 1, characterized in that The system adopts the heartbeat data packet mode, and the satellite that needs to send the heartbeat will broadcast the satellite's ID and satellite time at the heartbeat frequency v.

3. A method for collaborative maintenance of high and low orbit satellite constellation links, characterized in that: The collaborative maintenance is realized by using the system as claimed in any one of claims 1 to 2, comprising the following steps: Step 1, link initialization: After the high-orbit or low-orbit satellite initially enters the network, the ground center sends instructions to the high-orbit or low-orbit satellite to allocate links. The high-orbit or low-orbit satellite executes the command, obtains the link role, and starts normal operation; Step 2: Maintenance of the coordinated status of the high-orbit and low-orbit links: The low-orbit communication satellite and the low-orbit backup satellite continuously obtain the orbit information of the high-orbit satellite, obtain the position and speed of the high-orbit satellite through extrapolation, continuously adjust the direction of their own antennas, point the antennas at the high-orbit satellites, and send heartbeat data packets to the high-orbit satellites at a fixed frequency; the high-orbit satellite adjusts the direction of its own antenna according to the pointing table of the low-orbit communication satellite or the ground center, and points the antennas at the low-orbit communication satellite; The low-orbit backup satellite sends heartbeat data packets to the communication satellite at a fixed frequency; The high-orbit satellite checks whether it has received the heartbeat data packet from the low-orbit communication satellite, and the low-orbit communication satellite needs to check whether it has received the heartbeat data packet from the low-orbit backup satellite; Step 3, regular update of communication satellite: In step 2, the high-orbit satellite determines that the communication time of the low-orbit communication satellite is less than a certain time, performs regular update of the communication satellite, switches to the pointing table of the backup satellite with the longest communication time, and establishes a link with the backup satellite; the new communication satellite broadcasts the communication satellite change information in the low-orbit star group, and elects a new communication satellite; when the high-orbit satellite normally receives the heartbeat data packet of the new low-orbit communication satellite, the low-orbit backup satellite sends the heartbeat to the new communication satellite, and the link redundancy meets the predetermined value, the link returns to normal working state; Step 4, backup star update: In step 2, the communication star checks the backup star heartbeat. If it is determined that there is a flag bit in the backup star heartbeat data packet, or a backup star heartbeat data packet is not received for more than a period of time, the backup star update is executed; The communication satellite selects a satellite in the constellation that can communicate with the high-orbit satellite for the longest time as a backup satellite to meet the link redundancy requirements; Step 5, abnormal update of communication satellite: in step 2, the high-orbit satellite checks the heartbeat of the communication satellite. If the heartbeat data packet of the communication satellite is not received for a period of time, the abnormal update of the communication satellite is executed. The high-orbit satellite traverses the backup satellite and tries to receive the heartbeat data packet. If it is received, the backup satellite pointing table is executed; Otherwise, the high-orbit satellite needs to send information to the ground center, and the ground center will reinitialize the links for the high-orbit and low-orbit satellites.

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