Method and system for laser inter-satellite link breakage reconstruction

Abstract

The application provides a laser intersatellite link breakage reconstruction method and a reconstruction system. The method comprises the following steps: two satellites establish laser intersatellite links according to ground planning link establishment tasks, wherein each of the two satellites is equipped with at least one laser terminal; the laser terminals on the two satellites perform one-way precise ranging by using laser signals respectively, and send one-way ranging values to each other; the two satellites respectively perform self-adaptive extrapolation according to two-way ranging values to obtain estimated autonomous orbit determination orbit data, wherein the two-way ranging values comprise a first ranging value measured by a satellite on another satellite and a second ranging value measured by the other satellite on the satellite; and when the laser intersatellite link is interrupted, the two satellites respectively select data satisfying laser terminal capture requirements from the first orbit data and the autonomous orbit determination orbit data as selected orbit data, and perform signal recapture by using the selected orbit data to complete reconstruction of the laser intersatellite link.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of inter-satellite links, and in particular to a laser inter-satellite link breakage reconstruction method and a reconstruction system. BACKGROUND

[0002] The operation management and performance of a satellite constellation require communication between satellites, so inter-satellite links are needed to connect each satellite and form a network, which is a necessary means for the operation of the constellation network. The Beidou-3 global system of China uses Ka-band inter-satellite links to achieve all-time connectivity between satellites and between satellites and ground stations in the constellation. However, microwave inter-satellite links have the disadvantages of low speed, susceptibility to interference, poor security, and the need to apply for frequencies.

[0003] Laser has high directivity in space and high frequency characteristics of optical signals, and laser inter-satellite links can support high-speed, high-bandwidth, high-security, and electromagnetic spectrum-free laser communication, which can meet the demand for high-quality satellite space communication. At the same time, laser inter-satellite links also naturally have high-performance ranging functions, with ranging accuracy generally reaching centimeter or even millimeter levels, providing the basic conditions for satellite autonomous orbit determination and time synchronization. Currently, the common method for building a link for laser inter-satellite links is as follows: before establishing a laser communication link, the satellite pre-injects the precise orbits of both parties, one satellite (the active party) calculates the pointing of the optical beam according to the orbit positions of both parties, and actively transmits an optical signal to illuminate the other satellite (the passive party); the passive party calculates the direction of the optical signal according to the orbit positions of both parties and points to the direction of the optical signal to detect it, and when the optical signal is detected, the signal acquisition is completed and the closed-loop feedback tracking is entered; when the link is interrupted, the above steps are repeated to complete the re-linking. However, due to the extremely narrow optical beam of laser, usually in the order of micro-radians, the orbit accuracy requirement is high, making it difficult to acquire the optical signal. Especially for satellites in medium and low orbits, the orbit determination accuracy is limited and the divergence speed is very fast, and the orbit extrapolation error cannot meet the requirements of laser terminal link building in a short time. Once the laser inter-satellite link is interrupted, it may not be able to complete the re-acquisition due to large orbit errors, causing long service interruption. Therefore, the ground needs to continuously perform "orbit determination - update orbit" operations, which will consume a large amount of ground observation stations, satellite-ground communication stations, and other resources for a satellite constellation consisting of dozens or even hundreds of satellites. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a laser inter-satellite link breakage reconstruction method and a reconstruction system that reduces ground dependence and shortens interruption time.

[0005] To solve the above technical problems, the application provides a laser intersatellite link breakage reconstruction method, which comprises the following steps: S11, two satellites establish laser intersatellite links according to ground planning link establishment tasks, wherein each of the two satellites is equipped with at least one laser terminal; S12, the laser terminals on the two satellites perform one-way precise ranging by using laser signals, and send one-way ranging values to each other, and the two satellites perform self-adaptive extrapolation according to two-way ranging values to obtain estimated autonomous orbit determination orbit data, wherein the two-way ranging values comprise a first ranging value of measuring the other satellite and a second ranging value of measuring the other satellite; and S13, when the laser intersatellite link is interrupted, each of the two satellites selects data meeting laser terminal capture requirements from ground injected first orbit data and the autonomous orbit determination orbit data as selected orbit data, and performs signal recapture by using the selected orbit data to complete reconstruction of the laser intersatellite link.

[0006] In an embodiment of the application, before the step S13, the method further comprises: a default link establishment data mode of each satellite is a ground injected orbit data mode; and each satellite continuously judges whether an autonomous selection orbit command injected by a ground control center is received, when the autonomous selection orbit command is received, the link establishment data mode of the satellite is changed to an autonomous selection orbit data mode, and the step S13 is executed; when the autonomous selection orbit command is not received, the satellite continuously judges whether a reference time of the first orbit data injected by the ground has expired, if not, the link establishment data mode of the satellite remains the ground injected orbit data mode, and if yes, the link establishment data mode of the satellite is changed to the autonomous selection orbit data mode, and the step S13 is executed.

[0007] In an embodiment of the application, the step that the two satellites select data meeting laser terminal capture requirements from ground injected first orbit data and the autonomous orbit determination orbit data as selected orbit data comprises: continuously performing error comparison on a first orbit calculated from the first orbit data and an autonomous orbit calculated from the autonomous orbit determination orbit data, when the error is less than a preset threshold, selecting the first orbit data as the selected orbit data, and when the error is greater than the preset threshold, selecting the autonomous orbit determination orbit data as the selected orbit data.

[0008] In an embodiment of the application, the preset threshold is a maximum error of an orbit corresponding to signal capture completed by the laser terminal.

[0009] In an embodiment of the present application, in step S12, the step of obtaining estimated autonomous orbit determination orbit data according to the bi-directional ranging values respectively by adaptive extrapolation includes: step S121: performing one-step prediction estimation of satellite position, velocity and clock error state variables according to ground station injected parameters, wherein the parameters include algorithm parameters and orbit parameters; step S122: accumulating the bi-directional ranging values to form orbit determination observations and time synchronization observations; step S123: performing autonomous orbit determination and time synchronization processing on the orbit determination observations and the time synchronization observations respectively by using a Kalman filter, obtaining optimal estimation of state variables by using multiple sets of bi-directional ranging values accumulated in each epoch, fitting the autonomous orbit determination orbit data by using the optimal estimation of state variables in different epochs, wherein the autonomous orbit determination orbit data includes satellite orbit parameters and clock errors.

[0010] In an embodiment of the present application, in step S123, the state variables in the current epoch are predicted by using one-step prediction of the optimal estimation in the previous epoch, gain matrix calculation is completed by combining the orbit determination observations and the time synchronization observations, and then the optimal estimation of state variables in the current epoch is completed.

[0011] In an embodiment of the present application, in step S123, the optimal estimation of state variables is obtained by using more than four sets of bi-directional ranging values accumulated in each epoch.

[0012] In an embodiment of the present application, in step S121, when the ground station re-injects the parameters, the adaptive extrapolation is performed by using the re-injected parameters.

[0013] The present application further proposes a laser inter-satellite link breakage reconstruction system to solve the above technical problems, which includes an adaptive extrapolation algorithm unit, an orbit autonomous selection logic unit and a control unit arranged on a satellite, wherein the adaptive extrapolation algorithm unit is configured to obtain estimated autonomous orbit determination orbit data according to bi-directional ranging values, wherein the bi-directional ranging values include a first ranging value measured by a satellite on another satellite and a second ranging value measured by the other satellite on the satellite, the satellite and the other satellite are each equipped with at least one laser terminal, and the satellite and the other satellite can establish a laser inter-satellite link according to a ground planned link building task; the orbit autonomous selection logic unit is configured to select data meeting laser terminal capture requirements as selected orbit data from ground injected first orbit data and the autonomous orbit determination orbit data when enabled; and the control unit is configured to control the satellite to perform signal recapture by using the selected orbit data to complete reconstruction of the laser inter-satellite link when the laser inter-satellite link is interrupted.

[0014] In one embodiment of this application, the satellite's default link establishment data mode is the ground-injected orbit data mode. The control unit is further configured to continuously determine whether it receives an autonomous orbit selection command from the ground control center. When the autonomous orbit selection command is received, the satellite's link establishment data mode is changed to the autonomous orbit selection data mode, and the autonomous orbit selection logic unit is activated. When the autonomous orbit selection command is not received, the satellite continuously determines whether the reference time of the ground-injected first orbit data has expired. If it has not expired, the satellite's link establishment data mode remains the ground-injected orbit data mode. If it has expired, the satellite's link establishment data mode is changed to the autonomous orbit selection data mode, and the autonomous orbit selection logic unit is activated.

[0015] In one embodiment of this application, the step of the orbit autonomous selection logic unit selecting data that meets the laser terminal capture requirements from the first orbit data injected on the ground and the autonomous orbit determination orbit data as the selected orbit data includes: continuously comparing the error between the first orbit calculated from the first orbit data and the estimated orbit calculated from the autonomous orbit determination orbit data; when the error is less than a preset threshold, selecting the first orbit data as the selected orbit data; when the error is greater than the preset threshold, selecting the autonomous orbit determination orbit data as the selected orbit data.

[0016] In one embodiment of this application, the preset threshold is the maximum track error corresponding to the signal capture capability of the laser terminal.

[0017] In one embodiment of this application, the step of the adaptive extrapolation algorithm unit obtaining estimated autonomous orbit determination data by adaptive extrapolation based on bidirectional ranging values ​​includes:

[0018] Step S121: Perform a one-step prediction and estimation of satellite position velocity and clock error state quantities based on the parameters injected by the ground station, wherein the parameters include algorithm parameters and orbital parameters;

[0019] Step S122: Accumulate the bidirectional ranging values ​​to form orbit determination observations and time synchronization observations;

[0020] Step S123: Use a Kalman filter to perform autonomous orbit determination and time synchronization processing on the orbit determination observations and time synchronization observations respectively. Use multiple sets of bidirectional ranging values ​​accumulated at each epoch to obtain the optimal estimate of the state variables. Use the optimal estimate of the state variables at different epochs to fit the autonomous orbit determination orbit data. The autonomous orbit determination orbit data includes the satellite orbit parameters and clock bias.

[0021] In one embodiment of this application, in step S123, the state variables of the current epoch are predicted one step by using the optimal estimate of the previous epoch, and the gain matrix is ​​calculated by combining the orbit determination observation and the time synchronization observation, thereby completing the optimal estimate of the state variables of the current epoch.

[0022] In one embodiment of this application, in step S123, the optimal estimate of the state variables is obtained by using the accumulated four or more sets of bidirectional ranging values ​​for each epoch.

[0023] In one embodiment of this application, in step S121, when the ground station re-injects the parameters, the re-injected parameters are used to perform the adaptive extrapolation.

[0024] According to the reconstruction method and system of this application, the satellite employs an adaptive orbit extrapolation algorithm to continuously calculate autonomous orbit data using the acquired two-way ranging values. Simultaneously, it selects the appropriate orbit data through an autonomous orbit selection logic unit. This ensures that even if the laser inter-satellite link is interrupted, orbit data for signal reacquisition can be quickly obtained, enabling rapid reconstruction of the laser inter-satellite link. The reconstruction method and system of this application significantly reduce ground resource consumption, decrease the satellite's dependence on ground control centers, shorten link interruption time, and improve the working efficiency of the laser inter-satellite link. Attached Figure Description

[0025] The accompanying drawings are included to provide a further understanding of this application; they are incorporated into and constitute a part of this application. The drawings illustrate embodiments of this application and, together with this specification, serve to explain the principles of the invention. In the drawings:

[0026] Figure 1 This is an exemplary flowchart of a laser inter-satellite link reconstruction method according to an embodiment of this application;

[0027] Figure 2 This is a block diagram of a laser inter-satellite link reconnection system according to an embodiment of this application;

[0028] Figure 3 This is an exemplary flowchart of an adaptive extrapolation algorithm according to an embodiment of this application;

[0029] Figure 4 This is a schematic diagram of the workflow of the track autonomous selection logic unit in the reconstruction system according to an embodiment of this application;

[0030] Figure 5 This is an exemplary flowchart of a laser inter-satellite link disconnection reconstruction method according to another embodiment of this application. Detailed Implementation

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this application. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0032] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0033] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0034] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. In addition, although the terminology used in this application is selected from commonly known and used terms, some terms mentioned in this application's specification may have been chosen by the applicant according to his or her judgment, and their detailed meanings are explained in the relevant sections of this description. Moreover, this application should be understood not only through the actual terms used, but also through the meaning implied by each term.

[0035] Flowcharts are used in this application to illustrate the operations performed by the system according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, various steps can be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more steps may be removed from these processes.

[0036] The laser inter-satellite link reconnection method and system of this application are applicable to any satellite that uses laser inter-satellite links for networking and to constellations that include such satellites. Preferably, the satellite is a BeiDou-3 satellite.

[0037] Figure 1 This is an exemplary flowchart of a laser inter-satellite link reconstruction method according to an embodiment of this application. In this embodiment, the reconstruction method includes the following steps:

[0038] Step S11: The two satellites establish laser inter-satellite links according to the ground-planned link establishment tasks, wherein each of the two satellites is equipped with at least one laser terminal;

[0039] Step S12: The laser terminals on both satellites perform unidirectional precise ranging using laser signals and send the unidirectional ranging values ​​to each other. The two satellites then adaptively extrapolate the bidirectional ranging values ​​to obtain estimated autonomous orbit determination data. The bidirectional ranging values ​​include the first ranging value measured by this satellite from the other satellite, and the second ranging value measured by the other satellite from this satellite.

[0040] Step S13: When the laser inter-satellite link is interrupted, the two satellites select data that meets the laser terminal acquisition requirements from the first orbit data and the autonomous orbit determination orbit data injected on the ground, respectively, and use the selected orbit data to reacquire the signal, thus completing the reconstruction of the laser inter-satellite link.

[0041] Figure 2 This is a block diagram of a laser inter-satellite link reconnection system according to an embodiment of this application. (Reference) Figure 2 As shown, the reconstruction system 200 includes an adaptive extrapolation algorithm unit 210, an orbit autonomous selection logic unit 220, and a control unit 230, all mounted on the satellite. The reconstruction system 200 of this application can be used to perform some or all of the steps in the above-described reconstruction method. The reconstruction method and reconstruction system 200 are described below with reference to the accompanying drawings.

[0042] In step S11, this application does not limit the number of satellites that can use the reconstruction method; within a satellite constellation, the reconstruction method can be used on multiple satellites. The laser inter-satellite link refers to the laser inter-satellite link formed between any two satellites. When a satellite is equipped with multiple laser terminals, these multiple laser terminals can be used to establish laser inter-satellite links with different other satellites.

[0043] In some embodiments, the step of establishing laser inter-satellite links between the two satellites in step S11 according to the ground-planned link establishment task includes:

[0044] Step S111: The ground control center uses methods such as two-way satellite-to-ground measurement to precisely determine the orbits of the two satellites and obtain orbital data that meets the requirements for laser terminal acquisition;

[0045] Step S112: Upload the orbital data that meets the laser terminal acquisition requirements to each satellite via the satellite-to-ground communication station;

[0046] Step S113: The local satellite (active party) calculates the direction of the light beam based on the orbital positions of both sides and actively transmits light signals to the other satellite (passive party);

[0047] Step S114: The other satellite probes the direction from which the light signal comes according to the orbital positions of both satellites. When the light signal is detected, the satellite completes the acquisition and enters closed-loop feedback tracking, thus establishing the laser inter-satellite link.

[0048] When the laser inter-satellite link is interrupted, continuous "orbit determination and update" operations are required on the ground to shorten the interruption time. For satellite constellations that now generally consist of dozens or even hundreds of satellites, this would consume a large amount of resources such as ground observation stations and satellite-to-ground communication stations. Therefore, the reconstruction method of this application continues to execute steps S12 and S13 to solve this problem.

[0049] like Figure 1 In step S12, each satellite can obtain two-way ranging values, namely, the first ranging value measured by the satellite from other satellites and the second ranging value measured by other satellites from the satellite itself, and can be obtained by... Figure 2 The adaptive extrapolation algorithm unit 210 in the middle performs the adaptive extrapolation algorithm, that is, calculates the autonomous orbit determination track data based on the two-way distance measurement value.

[0050] In some embodiments, each satellite is equipped with a set of Figure 2 The reconstruction system 200 shown.

[0051] In some embodiments, the step of obtaining estimated autonomous orbit determination data by adaptive extrapolation of the two satellites based on the two-way ranging values ​​in step S12 includes:

[0052] Step S121: Perform a one-step prediction and estimation of satellite position velocity and clock error state quantities based on the parameters injected by the ground station, wherein the parameters include algorithm parameters and orbital parameters;

[0053] Step S122: Accumulate the bidirectional ranging values ​​to form orbit determination observations and time synchronization observations;

[0054] Step S123: Use a Kalman filter to perform autonomous orbit determination and time synchronization processing on the orbit determination observations and time synchronization observations respectively. Use the multiple sets of bidirectional ranging values ​​accumulated at each epoch to obtain the optimal estimate of the state variables. Use the optimal estimate of the state variables at different epochs to fit the autonomous orbit determination orbit data. The autonomous orbit determination orbit data includes satellite orbit parameters and clock bias.

[0055] In step S121, the parameters recorded on the ground station include parameters involved in the adaptive extrapolation algorithm, such as startup parameters, adjustment parameters, error settings, filter order, etc., as well as orbital parameters, such as satellite position, commonly used orbital altitude, inclination, eccentricity, etc.

[0056] In step S121, a Kalman filter can also be used for one-step prediction estimation. Utilizing the state estimation characteristics of the Kalman filter, relevant state variables, including satellite position and velocity, clock bias, can be estimated. Those skilled in the art can execute step S121 based on this idea; this specification will not elaborate further.

[0057] In step S122, the more two-way ranging values ​​accumulated, the higher the reliability of the corresponding filtering results and the higher the fitting accuracy. Orbit determination observations and time synchronization observations are two types of observation matrices used in inter-satellite link communication processing, which are related to the satellite's real-time position, velocity, and clock error.

[0058] In step S123, a Kalman filter is used to perform autonomous orbit determination on the orbit determination observations and time synchronization processing on the time synchronization observations. An epoch represents a period, and multiple epochs are arranged consecutively in the time domain. This application does not limit the length of this period. Each epoch corresponds to a set of state variables. Since the clock zero points of different satellites may be different, obtaining the clock difference is for accurate orbit calculation. This application does not limit the process of state variable estimation using the Kalman filter; conventional processes in the art can be used. It should be noted that the state variables to be estimated using the Kalman filter in this application are specifically proposed to solve the technical problem addressed by this application.

[0059] In some embodiments, after step S122, the method further includes performing epoch reduction and outlier removal on the bidirectional ranging values ​​to form orbit determination observations and time synchronization observations.

[0060] In some embodiments, in step S123, the state variables of the current epoch are predicted one step by using the optimal estimate of the previous epoch, and the gain matrix is ​​calculated by combining the orbit determination observations and the time synchronization observations, thereby completing the optimal estimate of the state variables of the current epoch.

[0061] In other embodiments, in step S123, the optimal estimate of the state variables is derived using four or more sets of bidirectional ranging values ​​accumulated in each epoch. The more sets of bidirectional ranging values ​​accumulated in each epoch, the better the fitting accuracy.

[0062] Figure 3 This is an exemplary flowchart of an adaptive extrapolation algorithm according to an embodiment of this application. (Reference) Figure 3 As shown, the adaptive extrapolation algorithm of this embodiment includes the following steps:

[0063] Step S310: Inject initial orbit and algorithm startup parameters on the ground.

[0064] Step S311: State variable prediction.

[0065] Steps S310 and S311 can be performed in step S121 above. The state variables estimated in step S311 are one-step prediction estimates of the satellite position, velocity, and clock error state variables based on the initial orbit injected from the ground and the algorithm startup parameters.

[0066] Step S312: Measurement data update.

[0067] As the measurement progresses, the satellite acquires more and more sets of two-way ranging values, thereby updating the measurement data.

[0068] Step S313: Kalman filter calculation.

[0069] The Kalman filter calculation here involves performing steps S122 and S123 as described above.

[0070] Step S314: Generate satellite position velocity and clock bias.

[0071] After step S313, the estimated satellite position velocity and clock error can be obtained in step S314.

[0072] Step S315: The satellite calculates the laser terminal link establishment and acquisition parameters.

[0073] In step S315, the control unit 230 can transmit the autonomous orbit determination data obtained in step S314 to the laser terminal on the satellite to calculate the laser terminal link establishment and acquisition parameters.

[0074] Step S316: Establish a link at the laser terminal.

[0075] If the laser inter-satellite link between the two satellites is interrupted at this time, the link can be established in step S316. If it is not interrupted, the laser link parameters can be updated using the acquisition parameters in step S315.

[0076] Step S317: Obtain bidirectional ranging values.

[0077] Since the laser inter-satellite link between the two satellites is working normally at this time, it can continuously obtain two-way ranging values ​​and continue to execute step S312, using more and more two-way ranging values ​​to add to the calculation process of steps S312 to S315.

[0078] Step S318: Update the algorithm parameters and orbital parameters on the ground.

[0079] In some embodiments, if the ground station re-injects updated algorithm and orbit parameters, these updated parameters are used for adaptive extrapolation. It is generally assumed that the algorithm and orbit parameters injected on the ground are most accurate at the current moment; therefore, using these parameters for adaptive extrapolation also offsets any errors in the adaptive extrapolation.

[0080] according to Figure 3 It is clear that the adaptive extrapolation algorithm of this application is a loop-based method, and does not end after a single calculation.

[0081] refer to Figure 1 In some embodiments, before step S13, the reconstruction method of this application further includes: each satellite's default link establishment data mode is the ground-injected orbit data mode; and each satellite continuously determines whether it has received an autonomous orbit selection command from the ground control center. When an autonomous orbit selection command is received, the satellite's link establishment data mode is changed to the autonomous orbit selection data mode, and step S13 is executed; when no autonomous orbit selection command is received, the satellite continuously determines whether the reference time of the ground-injected first orbit data has expired. If it has not expired, the satellite's link establishment data mode remains the ground-injected orbit data mode; if it has expired, the satellite's link establishment data mode is changed to the autonomous orbit selection data mode, and step S13 is executed.

[0082] Figure 4 This is a schematic diagram illustrating the workflow of the track autonomous selection logic unit in a reconstruction system according to an embodiment of this application. (Reference) Figure 4 As shown, the workflow of the track autonomous selection logic unit 220 in this embodiment includes the following steps:

[0083] Step S410: Use the ground-injected orbit data mode. In this step, the satellite's link establishment data mode is set to the default ground-injected orbit data mode.

[0084] Step S411: Determine whether the satellite has received an autonomous orbit selection command from the ground control center. If yes, proceed to step S412; otherwise, proceed to step S430. This step can be executed by the control unit 230.

[0085] Step S412: The satellite's link establishment data mode is changed to autonomous orbit selection data mode. This step can be executed by the control unit 230, which changes the satellite's link establishment data mode and enables the autonomous orbit selection logic unit 220.

[0086] Step S413: In the autonomous orbit selection data mode, determine whether the error between the first orbit calculated from the first orbit data and the autonomous orbit determination calculated from the autonomous orbit determination data is greater than a preset threshold. If yes, proceed to step S414; otherwise, proceed to step S431. This step is executed by the orbit autonomous selection logic unit 220. It is generally believed that ground-injected orbits have higher accuracy in the short term, but after the ground orbit expires, the adaptively extrapolated orbit has higher accuracy. Therefore, the error between the two is used to determine which type of data to select as the orbit data.

[0087] In some embodiments, the preset threshold is the maximum trajectory error ΔP corresponding to the signal capture capability of the laser terminal. The preset threshold is determined by the characteristics of the laser terminal, and different laser terminals may have different preset thresholds.

[0088] In some embodiments, the preset threshold is the product of ΔP and a preset coefficient. This preset coefficient is an empirical value used to correct the preset threshold and improve its accuracy. The preset coefficient can be obtained experimentally.

[0089] Step S414: Select the autonomous orbit determination track data as the selected track data. This step is executed by the autonomous track selection logic unit 220. When the error exceeds a preset threshold, the track data has expired, indicating that the track data is no longer suitable for the current actual track conditions. Therefore, the autonomous orbit determination track data is used.

[0090] Step S415: Output the orbit result, i.e., output the selected orbit data. The selected orbit data can be transmitted to the satellite's laser terminal for calculating link establishment and acquisition parameters.

[0091] While the orbit autonomous selection logic unit 220 is operating, the adaptive extrapolation algorithm unit 210 also operates synchronously and relatively independently. When the satellite is in the autonomous orbit selection data mode, the adaptive extrapolation algorithm unit 210 runs the adaptive orbit extrapolation orbit determination algorithm in step S420 and obtains the satellite autonomous orbit determination result in step S421, which is the autonomous orbit determination calculated based on the autonomous orbit determination data. This autonomous orbit determination result is then sent to the orbit autonomous selection logic unit 220, which calculates the error between the first orbit and the autonomous orbit determination in step S413.

[0092] Step S430: Determine if the ground orbit data has expired. If yes, proceed to step S412 and subsequent steps; otherwise, proceed to step S431, select the ground orbit data as the selected orbit data, and output the corresponding orbit result in step S415. Simultaneously, continue executing step S411 to continuously determine whether the satellite has received the autonomous orbit selection command injected from the ground.

[0093] Figure 5 This is an exemplary flowchart of a laser inter-satellite link reconnection method according to another embodiment of this application. This embodiment... Figure 1 The illustrated embodiment has some added detailed steps; however, the entire process of this embodiment is as follows: Figure 1 Within the scope of the illustrated embodiment. Reference Figure 5 As shown, the reconstruction method of this embodiment includes the following steps:

[0094] Step S510: Ground-based precise orbit determination of the satellite. This step may include step S11. The satellites mentioned here include all satellites requiring laser inter-satellite link communication.

[0095] Step S511: The ground control center injects the initial precise orbital data of all satellites requiring link establishment into the satellite. This step may include step S11.

[0096] Step S512: The satellite completes laser terminal pointing using the initial precise orbit data. This step may include step S11. Completing laser terminal pointing means establishing a laser inter-satellite link between the two satellites.

[0097] Step S513: Establish inter-satellite laser links between satellites to obtain multiple sets of two-way ranging values. This step may include step S12, where after the two satellites establish inter-satellite laser links, they can perform two-way ranging through their respective laser terminals to obtain two-way ranging values ​​in real time.

[0098] Step S514: The satellite performs orbit calculations using an adaptive orbit extrapolation algorithm. This step may include step S12, which involves continuously performing orbit calculations based on the two-way ranging values.

[0099] Step S515: The laser inter-satellite link is interrupted. This application does not limit the cause of the link interruption.

[0100] Step S516: Perform signal reacquisition based on the track data. The track data used in this step is the selected track data selected in step S13.

[0101] Step S517: Complete the laser inter-satellite link reconstruction. Then continue to execute step S513, and repeat steps S513 to S517.

[0102] Step S520: The orbit autonomous selection logic unit 220 performs orbit data maintenance. This step may include step S13, specifically, the data maintenance process involves continuously comparing the error between the first orbit calculated from the first orbit data and the autonomous orbit determination calculated from the autonomous orbit determination orbit data.

[0103] Step S521: Select orbital data that meets the requirements.

[0104] In this step, the qualified orbital data may be selected orbital data obtained based on error comparison results, or it may be first orbital data injected from the ground that has not yet expired. The orbital data used in step S516 is the qualified orbital data obtained in this step.

[0105] according to Figure 5 It is clear that in the reconstruction method of this application, the satellite, on the one hand, continuously calculates autonomous orbit data using the acquired two-way ranging values ​​using an adaptive orbit extrapolation algorithm; on the other hand, it selects the orbit data to be used through the orbit autonomous selection logic unit 220. This ensures that even if the laser inter-satellite link is interrupted, orbit data for signal reacquisition can be quickly obtained, enabling the laser inter-satellite link to be quickly rebuilt. The reconstruction method of this application is particularly suitable for satellites with low uploading frequencies, such as once a week. Using the reconstruction method of this application can greatly save ground resource consumption, reduce the satellite's dependence on the ground control center, reduce the link interruption time, and improve the working efficiency of the laser inter-satellite link. Similarly, the reconstruction system 200 of this application can achieve the same technical effects, which will not be elaborated further.

[0106] The basic concepts have been described above. Obviously, for those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0107] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0108] Some aspects of this application can be executed entirely by hardware, entirely by software (including firmware, resident software, microcode, etc.), or by a combination of hardware and software. The aforementioned hardware or software may be referred to as a "data block," "module," "engine," "unit," "component," or "system." The processor may be one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DAPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or combinations thereof. Furthermore, aspects of this application may manifest as computer products residing in one or more computer-readable media, including computer-readable program code. For example, computer-readable media may include, but are not limited to, magnetic storage devices (e.g., hard disks, floppy disks, magnetic tapes, etc.), optical discs (e.g., compressed CDs, digital multifunction DVDs, etc.), smart cards, and flash memory devices (e.g., cards, sticks, key drives, etc.).

[0109] A computer-readable medium may contain a propagated data signal containing computer program code, for example, on baseband or as part of a carrier wave. This propagated signal may take various forms, including electromagnetic, optical, and so on, or suitable combinations thereof. A computer-readable medium can be any computer-readable medium other than a computer-readable storage medium, which can be connected to an instruction execution system, apparatus, or device to enable communication, propagation, or transmission of a program for use. The program code located on the computer-readable medium can be propagated through any suitable medium, including radio, cable, fiber optic cable, radio frequency signals, or similar media, or any combination of the above media.

[0110] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the application requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of the single embodiments disclosed above.

[0111] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of scope in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0112] Although this application has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate this application, and various equivalent changes or substitutions can be made without departing from the spirit of this application. Therefore, any changes or modifications to the above embodiments within the essential spirit of this application will fall within the scope of the claims of this application.

Claims

1. A method for reconstructing a laser inter-satellite link after a break, comprising: Step S11: The two satellites establish laser inter-satellite links according to the ground-planned link establishment tasks, wherein each of the two satellites is equipped with at least one laser terminal; Step S12: The laser terminals on the two satellites respectively perform unidirectional precise ranging using laser signals and send the unidirectional ranging values ​​to each other. The two satellites respectively perform adaptive extrapolation based on the bidirectional ranging values ​​to obtain estimated autonomous orbit determination data. The bidirectional ranging values ​​include a first ranging value from one satellite to the other, and a second ranging value from the other satellite to the same satellite. Step S13: When the laser inter-satellite link is interrupted, the two satellites select data that meets the laser terminal capture requirements from the first orbit data injected on the ground and the autonomous orbit determination orbit data, respectively, and use the selected orbit data to recapture the signal, thereby completing the reconstruction of the laser inter-satellite link.

2. The laser inter-satellite link reconstruction method as described in claim 1, characterized in that, Before step S13, the method further includes: The default link establishment data mode for each satellite is the ground-injected orbital data mode; and Each satellite continuously checks whether it has received an autonomous orbit selection command from the ground control center. When the autonomous orbit selection command is received, the satellite's link establishment data mode is changed to the autonomous orbit selection data mode, and step S13 is executed. When the autonomous orbit selection command is not received, the satellite continuously checks whether the reference time of the first orbit data injected by the ground has expired. If it has not expired, the satellite's link establishment data mode remains the mode of using ground-injected orbit data. If it has expired, the satellite's link establishment data mode is changed to the autonomous orbit selection data mode, and step S13 is executed.

3. The laser inter-satellite link reconstruction method as described in claim 1, characterized in that, The steps for the two satellites to select data that meets the laser terminal's capture requirements from the first orbital data injected from the ground and the autonomous orbital data, respectively, include: The error is continuously compared between the first orbit calculated from the first orbit data and the autonomous orbit calculated from the autonomous orbit data. When the error is less than a preset threshold, the first orbit data is selected as the selected orbit data. When the error is greater than the preset threshold, the autonomous orbit data is selected as the selected orbit data.

4. The laser inter-satellite link reconstruction method as described in claim 3, characterized in that, The preset threshold is the maximum trajectory error corresponding to the signal capture capability of the laser terminal.

5. The laser inter-satellite link reconstruction method as described in claim 1, characterized in that, In step S12, the step of obtaining the estimated autonomous orbit data by adaptive extrapolation of the two satellites based on the two-way ranging values ​​includes: Step S121: Perform a one-step prediction and estimation of satellite position velocity and clock error state quantities based on the parameters injected by the ground station, wherein the parameters include algorithm parameters and orbital parameters; Step S122: Accumulate the bidirectional ranging values ​​to form orbit determination observations and time synchronization observations; Step S123: Use a Kalman filter to perform autonomous orbit determination and time synchronization processing on the orbit determination observations and time synchronization observations respectively. Use multiple sets of bidirectional ranging values ​​accumulated at each epoch to obtain the optimal estimate of the state variables. Use the optimal estimate of the state variables at different epochs to fit the autonomous orbit determination trajectory data. The autonomous orbit determination trajectory data includes the orbit parameters and clock difference.

6. The laser inter-satellite link reconstruction method as described in claim 5, characterized in that, In step S123, the state variables of the current epoch are predicted one step by using the optimal estimate of the previous epoch. The gain matrix is ​​calculated by combining the orbit determination observation and the time synchronization observation, thereby completing the optimal estimate of the state variables of the current epoch.

7. The laser inter-satellite link reconstruction method as described in claim 5, characterized in that, In step S123, the optimal estimate of the state variables is obtained by using the accumulated four or more sets of bidirectional ranging values ​​from each epoch.

8. The laser inter-satellite link reconstruction method as described in claim 5, characterized in that, In step S121, when the ground station re-injects the parameters, the adaptive extrapolation is performed using the re-injected parameters.

9. A laser inter-satellite link reconnection system, characterized in that, This includes an adaptive extrapolation algorithm unit, an orbit autonomous selection logic unit, and a control unit installed on the satellite. The adaptive extrapolation algorithm unit is used to perform adaptive extrapolation based on the two-way ranging values ​​to obtain the estimated autonomous orbit determination data. The two-way ranging values ​​include the first ranging value measured by the local satellite from another satellite and the second ranging value measured by another satellite from the local satellite. The local satellite and the other satellite are each equipped with at least one laser terminal. The local satellite and the other satellite can establish laser inter-satellite links according to the link establishment tasks planned on the ground. When the autonomous orbit selection logic unit is activated, it is used to select data that meets the laser terminal capture requirements from the first orbit data injected on the ground and the autonomous orbit determination orbit data as the selected orbit data. The control unit is used to control the satellite to reacquire the signal using the selected orbit data when the laser inter-satellite link is interrupted, thereby completing the reconstruction of the laser inter-satellite link.

10. The laser inter-satellite link reconnection system as described in claim 9, characterized in that, The default link establishment data mode of the satellite is the ground-injected orbit data mode. The control unit is also used to continuously determine whether it receives an autonomous orbit selection command from the ground control center. When the autonomous orbit selection command is received, the link establishment data mode of the satellite is changed to the autonomous orbit selection data mode, and the autonomous orbit selection logic unit is enabled. When the autonomous orbit selection command is not received, the satellite continuously determines whether the reference time of the first orbit data injected from the ground has expired. If it has not expired, the satellite's link establishment data mode remains the mode of using ground-injected orbit data. If it has expired, the satellite's link establishment data mode is changed to the autonomous orbit selection data mode, and the autonomous orbit selection logic unit is activated.

11. The laser inter-satellite link reconnection system as described in claim 9, characterized in that, The step of the orbit autonomous selection logic unit selecting data that meets the laser terminal capture requirements from the first orbit data injected on the ground and the autonomous orbit determination orbit data includes: The error is continuously compared between the first orbit calculated from the first orbit data and the estimated orbit calculated from the autonomous orbit determination orbit data. When the error is less than a preset threshold, the first orbit data is selected as the selected orbit data. When the error is greater than the preset threshold, the autonomous orbit determination orbit data is selected as the selected orbit data.

12. The laser inter-satellite link reconnection system as described in claim 11, characterized in that, The preset threshold is the maximum trajectory error corresponding to the signal capture capability of the laser terminal.

13. The laser inter-satellite link reconnection system as described in claim 9, characterized in that, The adaptive extrapolation algorithm unit obtains the estimated autonomous orbit determination data by adaptive extrapolation based on the bidirectional ranging values, including the following steps: Step S121: Perform a one-step prediction and estimation of satellite position velocity and clock error state quantities based on the parameters injected by the ground station, wherein the parameters include algorithm parameters and orbital parameters; Step S122: Accumulate the bidirectional ranging values ​​to form orbit determination observations and time synchronization observations; Step S123: Use a Kalman filter to perform autonomous orbit determination and time synchronization processing on the orbit determination observations and time synchronization observations respectively. Use multiple sets of bidirectional ranging values ​​accumulated at each epoch to obtain the optimal estimate of the state variables. Use the optimal estimate of the state variables at different epochs to fit the autonomous orbit determination trajectory data. The autonomous orbit determination trajectory data includes the orbit parameters and clock difference.

14. The laser inter-satellite link reconnection system as described in claim 13, characterized in that, In step S123, the state variables of the current epoch are predicted one step by using the optimal estimate of the previous epoch. The gain matrix is ​​calculated by combining the orbit determination observation and the time synchronization observation, thereby completing the optimal estimate of the state variables of the current epoch.

15. The laser inter-satellite link reconnection system as described in claim 13, characterized in that, In step S123, the optimal estimate of the state variables is obtained by using the accumulated four or more sets of bidirectional ranging values ​​from each epoch.

16. The laser inter-satellite link reconnection system as described in claim 13, characterized in that, In step S121, when the ground station re-injects the parameters, the adaptive extrapolation is performed using the re-injected parameters.

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