On-orbit collision avoidance method and device for constellation system

Abstract

The invention relates to the field of satellite operation, and discloses an in-orbit collision avoidance method and device for a constellation system, and the method comprises the steps: enabling a ground system to obtain the ephemeris information of a constellation satellite and space debris; the ground system evaluates the first collision risk of the satellite in the first period time in the future according to the ephemeris information of the constellation satellite and the space debris; when the first collision risk is greater than a first threshold value, the ground system uploads ephemeris information of the space debris to a satellite; the satellite updates a second collision risk in a second period time in the future in real time based on the received space debris ephemeris information and the satellite positioning information; when the second collision risk is greater than a second threshold value, the satellite formulates a corresponding collision avoidance strategy, and orbital maneuver is carried out according to the collision avoidance strategy; and after the avoidance is completed, the satellite actively maneuvers and returns to a nominal position corresponding to satellite ephemeris information, and the connection with the ground system is recovered. According to the invention, the accuracy of collision risk assessment is improved, and the implementability is improved.

Description

Technical Field

[0001] The present application relates to the field of satellite operation, and in particular to an on-orbit collision avoidance technology for a constellation system. Background Art

[0002] This section is intended to provide a background or context to the embodiments of the present application as recited in the claims. The description herein is not admitted to be prior art as disclosed by virtue of its inclusion in this section.

[0003] There are two types of conventional satellite on-orbit collision avoidance strategies.

[0004] Simply relying on ground-based on-orbit collision avoidance strategy: The ground system receives real-time satellite orbit information, makes orbit predictions, and generates satellite ephemeris information for a period of time in the future. The collision risk is assessed with the ephemeris information of other satellites and space debris provided by the NORAD website. When the collision risk between the satellite and a certain space target is greater than the safety threshold, the ground generates a collision avoidance maneuver strategy, which is uploaded to the satellite through remote control commands to implement orbital maneuvers. Due to the periodic upload of ground information, there are certain errors in the calculation based on the long-period orbit prediction data of the satellite, and the reliability of the analysis results is low. For example, in the collision between the US Iridium 33 and the Russian Cosmos 2251 in 2009, the collision risk of Iridium 33 and Cosmos 2251 was never ranked in the top ten in the risk analysis report before the collision. It can be seen that the method of relying solely on ground-based calculation to upload the avoidance strategy has large calculation errors. In addition, the space segment of a large constellation system includes thousands or even tens of thousands of satellites, while the number of ground stations is limited. Simply relying on ground-based calculation to upload the project is labor-intensive. Moreover, when the satellite measurement and control system fails, the satellite cannot receive collision avoidance instructions issued by the ground during the period when it loses contact with the ground, resulting in the inability to guarantee the safety of the satellite during the failure.

[0005] Relying solely on the satellite's autonomous collision avoidance strategy on orbit: The traditional method is that the ground station periodically injects the acquired space debris information into the satellite, and the satellite calculates the collision probability based on the real-time position information. The biggest drawback of this method is that the amount of debris information data is huge, and relying entirely on the satellite's autonomous calculation occupies a large amount of satellite resources. To improve this, some related studies have used satellites to carry additional on-board radar / laser detection equipment, and calculated the collision path of debris from anywhere in the sphere around the satellite based on the satellite's own orbital data obtained by the onboard sensor, reducing the amount of space debris calculation. If the collision probability is large, the satellite collision avoidance system formulates a collision avoidance orbit maneuver strategy and generates execution instructions to control the ignition of the thrusters to raise or lower the orbit. However, this solution requires additional orbital debris tracking tools, one or more radar or laser equipment, and the detection range of the two types of detection equipment is limited. It is mainly used for close-range avoidance. If the two celestial bodies are running at a relatively fast speed, the time left for the satellite to formulate an avoidance strategy and execute the avoidance action is extremely limited, mostly from a dozen seconds to tens of seconds, and the feasibility is poor. Summary of the invention

[0006] The purpose of this application is to provide an on-orbit collision avoidance method for a constellation system, which combines ground remote control and on-board autonomous calculation to formulate a collision avoidance strategy, thereby improving the accuracy of collision risk assessment and improving feasibility.

[0007] The present application discloses an on-orbit collision avoidance method for a constellation system, comprising:

[0008] The ground system obtains ephemeris information of constellation satellites and space debris;

[0009] The ground system evaluates the first collision risk of the satellite within a first future period according to the ephemeris information of the constellation satellites and the space debris;

[0010] When the first collision risk is greater than a first threshold, the ground system injects the ephemeris information of the space debris into the satellite;

[0011] The satellite updates the second collision risk in the second future period in real time based on the received space debris ephemeris information and own satellite positioning information;

[0012] When the second collision risk is greater than a second threshold, the satellite formulates a corresponding collision avoidance strategy and performs orbital maneuvers according to the collision avoidance strategy;

[0013] After the avoidance is completed, the satellite actively maneuvers to return to the nominal position corresponding to the satellite ephemeris information and restores the connection with the ground system.

[0014] In a preferred example, the step of the ground system evaluating the first collision risk of the satellite within a first future period further includes:

[0015] A regional method is selected, and the minimum spatial safety distance between the satellite and the space debris is used as the basis for the first collision risk assessment.

[0016] In a preferred example, the first cycle time is 5 to 7 days.

[0017] In a preferred example, the criterion for determining that the first collision risk is greater than a first threshold value specifically includes:

[0018] When the space debris enters the distance threshold range of the satellite, it is determined that the first collision risk is greater than a first threshold value, and the space debris is identified as a dangerous target.

[0019] In a preferred example, the step of the satellite updating the second collision risk in real time within the second future period based on the received space debris ephemeris information and own satellite positioning information also includes:

[0020] A collision probability assessment method is selected to determine the collision time and collision probability of the satellite when the second collision risk is greater than a second threshold.

[0021] In a preferred example, the second cycle time is within 6 hours.

[0022] In a preferred example, the criterion for determining that the second collision risk is greater than the second threshold value specifically includes:

[0023] Based on the position, velocity and position covariance matrix of the space debris and the satellite in the inertial system at the moment of closest approach, the probability of the space debris entering the satellite collision circle on the intersection plane is calculated, and when the probability is higher than a second threshold, it is judged that the second collision risk is greater than the second threshold.

[0024] In a preferred example, performing orbital maneuvers according to the collision avoidance strategy further includes:

[0025] The thrusters perform orbital maneuvers under the control of the satellite's onboard computer to raise or lower the orbit and complete the avoidance.

[0026] The present application also discloses an on-orbit collision avoidance device for a constellation system, comprising:

[0027] a memory for storing computer executable instructions; and,

[0028] A processor, coupled to the memory, is configured to implement the steps in the method described above when executing the computer executable instructions.

[0029] The present application also discloses a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, the steps in the method described above are implemented.

[0030] In the implementation mode of the present application, the "false alarm" problem in the collision warning is effectively reduced, and the accuracy of the collision risk assessment is improved;

[0031] Furthermore, the requirements for satellite data storage and on-orbit computing power are reduced, and feasibility is improved;

[0032] Furthermore, it reduces the satellite fuel consumption and interruption of communication missions due to orbital maneuvers, and also ensures that the satellite can effectively identify collision risks and implement orbital maneuvers within the limited failure period when it loses contact with the ground system.

[0033] The specification of the present application records a large number of technical features, which are distributed in various technical solutions. If all possible combinations of technical features of the present application (i.e., technical solutions) are to be listed, the specification will be too long. In order to avoid this problem, the various technical features disclosed in the above-mentioned invention content of the present application, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the accompanying drawings can be freely combined with each other to form various new technical solutions (these technical solutions should all be regarded as having been recorded in this specification), unless the combination of such technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed, and features C and D are equivalent technical means that play the same role. Technically, only one can be used, and it is impossible to use them at the same time. Feature E can be combined with feature C technically. Then, the solution of A+B+C+D should not be regarded as having been recorded because it is technically infeasible, and the solution of A+B+C+E should be regarded as having been recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart according to an embodiment of the present application;

[0035] Figure 2 is a schematic diagram of a calculation method for a first collision risk according to an embodiment of the present application. DETAILED DESCRIPTION

[0036] In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0037] Description of some concepts:

[0038] Space debris: refers to the products of human space activities, including rocket bodies and satellite bodies that have completed their missions, rocket ejecta, discarded objects during space missions, fragments produced by collisions between space objects, etc. It is the main source of pollution to the space environment.

[0039] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below in conjunction with the accompanying drawings.

[0040] An embodiment of the present application relates to an on-orbit collision avoidance method for a constellation system, the process of which is as follows: Figure 1 As shown, the method comprises the following steps:

[0041] Step 101, the ground system obtains ephemeris information of constellation satellites and space debris;

[0042] The ground system receives satellite positioning orbit information, performs orbit extrapolation to generate satellite ephemeris information for a period of time, and obtains space debris ephemeris information from NORAD.

[0043] Step 102, the ground system evaluates the first collision risk of the satellite within the first future period according to the ephemeris information of the constellation satellites and the space debris;

[0044] In one embodiment, the step of evaluating the first collision risk of the satellite in the first future cycle time by the ground system further includes: selecting a regional method (BOX method) and taking the minimum space safety distance between the satellite and the space debris as the basis for evaluating the first collision risk. In one embodiment, the first cycle time includes 5 to 7 days.

[0045] The BOX method follows the following principle: the minimum distance between two intersecting space targets in one of the space targets UNW coordinate system is used as the criterion. The definition of the UNW coordinate system is: the U direction is the direction of the satellite velocity vector of this system, the N direction is perpendicular to the U direction and points to the direction of the outer normal of the orbit, and the W direction and the UN direction form a right-handed system, such as Figure 2 shown.

[0046] The BOX method takes into account the position and orbit prediction errors of the two space targets. The first threshold is higher than the threshold set in the conventional ground remote control avoidance strategy. The ground segment of the present invention selects a higher threshold to screen space debris with collision risks, which can effectively avoid the "missed alarm" problem and greatly reduce the space debris orbit data injected into the satellite, reducing the demand for satellite platform storage space and computing power.

[0047] Step 103: When the first collision risk is greater than a first threshold, the ground system injects the ephemeris information of the space debris into the satellite;

[0048] In one embodiment, the criterion for the first collision risk being greater than the first threshold specifically includes: when the space debris enters the distance threshold range of the satellite, it is determined that the first collision risk is greater than the first threshold, and the space debris is determined as a dangerous target. Since there are certain errors in the determination and prediction of the orbits of space debris and constellation satellites, it is impossible to determine absolutely through orbit prediction, and only an area where a collision is very likely to occur can be determined.

[0049] Step 104, the satellite updates the second collision risk in the second future period in real time based on the received space debris ephemeris information and own satellite positioning information;

[0050] In one embodiment, the step of the satellite updating the second collision risk in real time within the future second period based on the received space debris ephemeris information and own satellite positioning information also includes:

[0051] A collision probability assessment method is selected to determine the collision time and collision probability of the satellite when the second collision risk is greater than the second threshold. In one embodiment, the second cycle time includes 6 hours.

[0052] That is, the satellite extrapolates the orbit based on the real-time positioning information of the satellite to obtain the ephemeris information of the satellite within 6 hours, combines the received space debris ephemeris information and time information to conduct a collision risk assessment, and uses the collision probability risk assessment method to determine the satellite's high warning collision time and collision probability.

[0053] Step 105: When the second collision risk is greater than the second threshold, the satellite formulates a corresponding collision avoidance strategy and performs orbital maneuvers according to the collision avoidance strategy;

[0054] In one embodiment, the criterion for determining whether the second collision risk is greater than the second threshold value specifically includes:

[0055] Based on the position, velocity and position covariance matrix of the space debris and the satellite in the inertial system at the moment of closest approach, the probability of the space debris entering the satellite collision circle on the intersection plane is calculated. When the probability is higher than the second threshold, it is judged that the second collision risk is greater than the second threshold.

[0056] The collision probability calculation method is usually based on the following assumptions: the position, velocity and position covariance matrix of the space debris and the system satellite in the inertial system at the time of closest approach can be obtained; both targets can be equivalent to spheres with known radius; the motion of both targets during the rendezvous is linear motion with no velocity uncertainty; the position uncertainty of both targets obeys a three-dimensional normal distribution and can be described by the distribution center and the position error covariance matrix, and the position error covariance matrices of the two targets are unrelated.

[0057] The intersection coordinate system is established, with the mass center of the constellation satellite as the coordinate origin, the z-axis pointing to the relative velocity direction when passing the closest point, the x-axis pointing to the main axis direction of the composite position error ellipsoid projected on the intersection plane (the plane perpendicular to the relative velocity vector), and the y-axis determined by the right-hand rule. The collision probability is defined as the probability that space debris enters the collision circle of the system satellite on the intersection plane.

[0058] The collision probability not only takes into account the orbital prediction error, but also the orbital characteristics of the space rendezvous objects, the distance between the two sides at the rendezvous moment, the relative speed at the rendezvous moment and other parameters. It can obtain a more reasonable geometric relative relationship, reduce the "false alarm" problem in the collision warning, and reduce the satellite fuel consumption and communication mission interruption caused by orbital maneuvers. Similarly, on-board autonomous computing also ensures that the satellite can autonomously calculate the collision probability and formulate avoidance strategies for high-risk points during the period of loss of ground control.

[0059] In one embodiment, performing orbital maneuvers according to the collision avoidance strategy further includes: the thrusters perform orbital maneuvers under the control of the satellite's satellite service computer to raise or lower the orbit to complete the avoidance.

[0060] Step 106, after the avoidance is completed, the satellite actively maneuvers to return to the nominal position corresponding to the satellite ephemeris information and restores the connection with the ground system.

[0061] During the period when the satellite loses contact, it performs active maneuvers, and the ground loses control of the satellite position. In addition, since the antenna of the tracking and control station is a large-gain spot beam, taking a certain model as an example, the beam diameter is only 7km, and the time cost of re-scanning and link building is relatively high. Therefore, the present invention proposes that after the satellite autonomously maneuvers to avoid collision objects, after ensuring that there is no collision risk, it autonomously maneuvers to the position of the original orbit corresponding to time t1 (the satellite arrives at this position at time t1), and this position is the ground-annotated extrapolated orbit information stored by the satellite. At the same time, the antenna of the ground tracking and control station points the beam to the theoretical orbital position of the satellite at time t1.

[0062] It should be noted that those skilled in the art should understand that the implementation functions of each module shown in the implementation of the on-orbit collision avoidance device of the above-mentioned constellation system can be understood by referring to the relevant description of the on-orbit collision avoidance method of the above-mentioned constellation system. The functions of each module shown in the implementation of the on-orbit collision avoidance method of the above-mentioned constellation system can be implemented by a program (executable instruction) running on a processor, or by a specific logic circuit. If the on-orbit collision avoidance method of the above-mentioned constellation system in the embodiment of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read Only Memory), disk or optical disk and other media that can store program code. In this way, the embodiment of the present application is not limited to any specific combination of hardware and software.

[0063] Accordingly, the present application also provides a computer-readable storage medium in which computer executable instructions are stored, and when the computer executable instructions are executed by the processor, the various method embodiments of the present application are implemented. Computer-readable storage media include permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be a computer-readable instruction, a data structure, a module of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable storage media do not include temporary computer-readable media (transitory media), such as modulated data signals and carriers.

[0064] In addition, the embodiments of the present application also provide an on-orbit collision avoidance method for a constellation system, which includes a memory for storing computer executable instructions, and a processor; the processor is used to implement the steps in the above-mentioned method implementation methods when executing the computer executable instructions in the memory. Among them, the processor can be a central processing unit (Central Processing Unit, referred to as "CPU"), or other general-purpose processors, digital signal processors (Digital Signal Processor, referred to as "DSP"), Application Specific Integrated Circuit (Application Specific Integrated Circuit, referred to as "ASIC"), etc. The aforementioned memory can be a read-only memory (read-only memory, referred to as "ROM"), a random access memory (random access memory, referred to as "RAM"), a flash memory (Flash), a hard disk or a solid-state hard disk, etc. The steps of the method disclosed in each embodiment of the present invention can be directly embodied as being executed by a hardware processor, or executed by a combination of hardware and software modules in the processor.

[0065] It should be noted that in the application documents of this patent, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one" do not exclude the existence of other identical elements in the process, method, article or device including the elements. In the application documents of this patent, if it is mentioned that an action is performed according to an element, it means that the action is performed at least according to the element, which includes two situations: performing the action only according to the element, and performing the action according to the element and other elements. Expressions such as multiple, multiple, and multiple include 2, 2 times, 2 kinds, and more than 2, more than 2 times, and more than 2 kinds.

[0066] All documents mentioned in this specification are considered to be included in the disclosure of this application as a whole, so that they can be used as a basis for modification when necessary. In addition, it should be understood that the above is only a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this specification should be included in the scope of protection of one or more embodiments of this specification.

[0067] In some cases, the actions or steps described in the claims may be performed in a different order than in the embodiments and still achieve the desired results. In addition, the processes depicted in the drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. An on-orbit collision avoidance method for a constellation system, characterized in that: include: The ground system obtains ephemeris information of constellation satellites and space debris; The ground system evaluates the first collision risk of the satellite within a first future period according to the ephemeris information of the constellation satellites and the space debris; When the first collision risk is greater than a first threshold, the ground system injects the ephemeris information of the space debris into the satellite; The satellite updates the second collision risk in the second future period in real time based on the received space debris ephemeris information and own satellite positioning information; When the second collision risk is greater than a second threshold, the satellite formulates a corresponding collision avoidance strategy and performs orbital maneuvers according to the collision avoidance strategy; After the avoidance is completed, the satellite actively maneuvers to return to the nominal position corresponding to the satellite ephemeris information and restores the connection with the ground system.

2. The on-orbit collision avoidance method for a constellation system according to claim 1, characterized in that: The step of the ground system evaluating the first collision risk of the satellite within a first future period also includes: A regional method is selected, and the minimum spatial safety distance between the satellite and the space debris is used as the basis for the first collision risk assessment.

3. The on-orbit collision avoidance method for a constellation system according to claim 1, characterized in that: The first cycle time comprises 5 to 7 days.

4. The on-orbit collision avoidance method for a constellation system according to claim 1, characterized in that: The criterion for determining that the first collision risk is greater than a first threshold value specifically includes: When the space debris enters the distance threshold range of the satellite, it is determined that the first collision risk is greater than a first threshold value, and the space debris is identified as a dangerous target.

5. The on-orbit collision avoidance method for a constellation system according to claim 1, characterized in that: The step of the satellite updating the second collision risk in real time within a future second period based on the received space debris ephemeris information and own satellite positioning information also includes: A collision probability assessment method is selected to determine the collision time and collision probability of the satellite when the second collision risk is greater than a second threshold.

6. The on-orbit collision avoidance method for a constellation system according to claim 1, characterized in that: The second cycle time is included within 6 hours.

7. The on-orbit collision avoidance method for a constellation system according to claim 1, characterized in that: The criterion for determining whether the second collision risk is greater than a second threshold value specifically includes: Based on the position, velocity and position covariance matrix of the space debris and the satellite in the inertial system at the moment of closest approach, the probability of the space debris entering the satellite collision circle on the intersection plane is calculated, and when the probability is higher than a second threshold, it is judged that the second collision risk is greater than the second threshold.

8. The on-orbit collision avoidance method for a constellation system according to claim 1, characterized in that: The performing orbital maneuvers according to the collision avoidance strategy further includes: The thrusters perform orbital maneuvers under the control of the satellite's onboard computer to raise or lower the orbit and complete the avoidance.

9. An on-orbit collision avoidance device for a constellation system, characterized in that: include: A memory for storing computer executable instructions; as well as, A processor, coupled to the memory, configured to implement the steps of the method according to any one of claims 1 to 8 when executing the computer executable instructions.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, the steps in the method according to any one of claims 1 to 8 are implemented.

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