Laser terminal calibration method and system based on inter-satellite orbit mutual transmission

Abstract

The invention provides a laser terminal calibration method and system based on inter-satellite orbit mutual transmission, and the method comprises the steps: carrying out the static calibration of a laser terminal through employing a star sensor or ground assistance before the establishment of an inter-satellite communication link, and enabling the pointing error of an optical axis to be smaller than 0.1 degree; after a communication link is established, orbit parameters of two satellites are exchanged in real time, a relative orbit normal vector is calculated through coordinate transformation, and a fusion reference is dynamically generated in combination with a static calibration result. According to the method, the real-time track mutual transmission data is used as dynamic correction input, the initial static calibration result is not only relied on any more, and fusion benchmark optimization of calibration and track mutual transmission is achieved. Compared with a traditional static calibration method depending on a ground station or a single-star inertial reference, the method breaks through the precision bottleneck of static calibration through the fusion of the orbit dynamic data and the static calibration result, effectively eliminates the orbit dynamic error, improves the laser calibration precision to a micro-radian level, and improves the calibration precision. And the establishment efficiency and reliability of the inter-satellite laser link are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of satellite inter-satellite laser communication and calibration technology, in particular to a laser terminal calibration method and system based on inter-satellite orbit mutual transmission. BACKGROUND

[0002] With the continuous growth of space information demand, inter-satellite laser communication as a new generation of high-bandwidth, low-latency, anti-jamming space communication means has become an important development direction in the field of satellite communication. In the process of establishing inter-satellite laser communication link, high-precision pointing and calibration of laser terminal is the core prerequisite to ensure reliable link connection. However, due to the influence of factors such as complex current orbit environment, strong satellite dynamics and attitude control accuracy, the traditional laser calibration method still has many challenges in practical application.

[0003] The existing space-borne laser calibration method mainly relies on the following two ways: one is to rely on ground station assistance, to provide satellite with orbit determination and attitude determination data through ground measurement and control system, and then to calculate and correct the pointing error of laser terminal in reverse; the other is to use the inertial reference or star sensor data of single satellite itself to calibrate the laser terminal autonomously. These two methods have their own advantages and disadvantages, but it is difficult to completely eliminate the influence of orbit dynamic error.

[0004] Although ground-assisted calibration can improve the initial calibration accuracy to a certain extent, it relies on ground measurement and control resources, the link establishment period is long, and it cannot respond to the changes of inter-satellite relative motion in real time. When the satellite enters the area without ground station coverage or needs high-frequency dynamic link switching, the limitation of ground assistance is particularly prominent. In addition, the error and delay of ground measurement and control link will also affect the accuracy of the final calibration.

[0005] Single-satellite inertial reference calibration mainly uses the attitude information measured by star sensor and the orbit parameters to correct the pointing of laser terminal. This method has a certain autonomy and real-time performance, but its accuracy is limited by single-satellite attitude measurement error, orbit calculation error and terminal mechanical adjustment error, etc., and it is difficult to meet the demand of micro-arc degree level high-precision pointing in large-scale constellation laser communication. Especially in the scene of multi-satellite cooperation, rapid maneuvering or dramatic changes of orbit dynamics, the single-satellite reference method is difficult to eliminate the cumulative effect of multiple errors over time.

[0006] In addition, with the rapid growth of the number of inter-satellite laser communication links and the expansion of constellation networking scale, the drawbacks of traditional static calibration method are becoming more and more obvious. Static calibration cannot reflect the dynamic changes of satellite orbit and attitude in real time, resulting in continuous accumulation of laser terminal pointing error in the process of link establishment and maintenance, which seriously affects the capture probability, establishment speed and communication stability of the link. Although the calibration effect can be improved by improving the single-machine attitude measurement accuracy or introducing environmental compensation means, it cannot fundamentally solve the problem of high-precision calibration caused by orbit dynamic error from the system level.

[0007] Therefore, there is an urgent need for a method capable of dynamically eliminating orbit and attitude errors to achieve high-precision laser calibration at the level of micro-radians, in order to meet the urgent needs of satellite intersatellite laser communication for high reliability, high precision and strong autonomy. This not only has important significance for improving the efficiency of intersatellite link establishment and communication quality, but also provides key technical support for future satellite constellation applications and space information network construction.

[0008] Patent document CN118631335A (application number: 202310193816.X) discloses a kind of laser intersatellite on-orbit full real-time self-calibration system, the system is realized through the mutual cooperation of optical device real-time self-calibration of multiple light paths by automatic adjustment galvanometer, including transmitting laser, optical fiber, transmitting mirror group, first galvanometer, first wavelength dichroic piece, second galvanometer, first blazed grating, first corner, second wavelength dichroic piece, light splitting piece, fine tracking lens group, fine tracking camera, second blazed grating, second corner, receiving mirror group, DWDM dense wavelength division multiplexing, calibration laser, communication receiving end, and calibration process does not affect the normal work of laser intersatellite communication, calibration area and communication area are separated, full real-time automatic calibration is realized. SUMMARY

[0009] In view of the defects in the prior art, the purpose of the present application is to provide a laser terminal calibration method and system based on intersatellite orbit mutual transmission.

[0010] According to the laser terminal calibration method based on intersatellite orbit mutual transmission provided by the present application, the following steps are included: Step S1: static calibration of the satellite-borne laser communication terminal; Step S2: construction of an intersatellite laser communication link; transmission of real-time orbit parameters of two satellites based on the constructed intersatellite laser communication link; wherein the real-time orbit parameters include position vector, velocity vector and covariance information of the satellites; Step S3: optimization of calibration reference based on static calibration and real-time orbit parameters, dynamic correction of laser terminal pointing using the optimized calibration reference, and realization of high-precision calibration.

[0011] Preferably, the step S1 includes preliminary optical axis calibration of the laser terminal by using star sensor autonomous attitude determination or through ground assistance.

[0012] Preferably, the step S3 includes: Step S3.1: coordinate transformation of the real-time orbit parameters of the two satellites to unify the real-time orbit parameters of the two satellites to the same coordinate system, and calculation of the relative orbit normal vector between the two satellites; Step S3.2: fusion processing of the relative orbit normal vector between the two satellites and the static calibration result through a fusion algorithm to dynamically generate a fusion reference. Step S3.3: Dynamic correction of laser terminal pointing with fusion reference, high-precision calibration is realized.

[0013] Preferably, the step S3.1 comprises: Converting the Earth-Centered Inertial System (ECI) to the Earth-Centered Earth-Fixed System (ECEF);

[0014] wherein, is the precession-nutation matrix, is the Greenwich Sidereal Time rotation matrix, is the position vector of the satellite in the Earth-Centered Inertial System coordinate system, is the position vector of the satellite in the Earth-Centered Earth-Fixed System coordinate system; The position vectors of the primary star and the target star in the Earth-Centered Earth-Fixed System (ECEF) coordinate system obtained by respective conversion are and Therefore, the relative position vector in the Earth-Centered Earth-Fixed System (ECEF) coordinate system is

[0015] The three axes of the local orbital coordinate system are defined by the position and velocity direction of the primary star; The x-axis is along the orbital velocity direction:

[0016] The z-axis is directed to the opposite direction of the Earth's center

[0017] The y-axis is the normal direction of the orbital plane, and the right-hand rule is:

[0018] Rotation matrix RLOC:

[0019] The local orbital coordinate system axes are , , The projection components in the ECEF system; The relative position vector in the local orbital coordinate system is calculated as: .

[0020] Preferably, the step S3.2 comprises:

[0021] wherein ws(k) is a static weight factor; wd(k) is a dynamic weight factor; and ws(k)+wd(k)=1; P 轨道 is the relative orbital normal vector between the two stars;​ With the accumulation of orbit data, the dynamic weight gradually increases with the increase of the number of orbit data fusion, realizing the transition from static reference to dynamic fusion reference; as shown in the following formula, the dynamic weight wd linearly increases with the iteration number k:

[0022] Wherein, 0.8 is the upper limit of the dynamic weight, the initial value of the dynamic weight wd(0)=0.2, ws(0)=0.8, α is the growth step, and k is the iteration number of orbit data fusion.

[0023] Preferably, the step S3.3 comprises: Based on the current pointing vector P actually measured by the laser terminal 测量 , the error vector S(k) is calculated: S(k)=P 测量 -P 融合 The micro terminal angle correction amount ΔΦ=[Δφ, Δθ, Δψ] satisfying the preset requirement is constructed; wherein Δφ, Δθ and Δψ respectively represent the micro angle satisfying the preset requirement required to rotate around the X, Y and Z axes of the terminal itself, so that the actual pointing of the laser beam is as accurately as possible to the desired direction; The influence of the terminal angle correction amount ΔΦ on the error S(k) is described based on the Jacobian matrix J(k); The optimal correction amount ΔΦ is calculated by using the least square method principle:

[0024] Wherein, is the transpose of the Jacobian matrix, which maps the direction of the error vector to the direction of the angle correction; The laser controller receives the optimal correction amount ΔΦ, and drives the precise pointing mechanism to adjust in real time according to the optimal correction amount.

[0025] According to the laser terminal calibration system based on inter-satellite orbit mutual transmission provided by the application, comprising: Module M1: static calibration of the spaceborne laser communication terminal; Module M2: constructing an inter-satellite laser communication link; transmitting the real-time orbit parameters of two satellites based on the constructed inter-satellite laser communication link; wherein the real-time orbit parameters include the position vector, velocity vector and covariance information of the satellite; Module M3: optimizing the calibration reference based on the static calibration and the real-time orbit parameters, dynamically correcting the pointing of the laser terminal by using the optimized calibration reference, and realizing high-precision calibration.

[0026] Preferably, said module M1 comprises: adopting a star sensor to autonomously determine the attitude or to preliminarily calibrate the optical axis of the laser terminal through ground assistance.

[0027] Preferably, said module M3 comprises: Module M3.1: coordinate transformation of real-time orbit parameters of two stars to unify the real-time orbit parameters of two stars to the same coordinate system, and calculation of the relative orbit normal vector between two stars; Module M3.2: fusion processing of the relative orbit normal vector between two stars and the static calibration result through a fusion algorithm to dynamically generate a fusion reference; Module M3.3: dynamic correction of the pointing of the laser terminal by using the fusion reference to realize high-precision calibration.

[0028] Preferably, said module M3.1 comprises: Converting the Earth-Centered Inertial System (ECI) to the Earth-Centered Earth-Fixed System (ECEF);

[0029] wherein, is the precession-nutation matrix, is the Greenwich Sidereal Time rotation matrix, is the position vector of the satellite in the Earth-Centered Inertial System coordinate system, is the position vector of the satellite in the Earth-Centered Earth-Fixed System coordinate system; The position vectors of the target star and the local star in the Earth-Centered Earth-Fixed System (ECEF) coordinate system obtained through the respective conversions are and Therefore, the relative position vector in the Earth-Centered Earth-Fixed System (ECEF) coordinate system is

[0030] The three axes of the local orbit coordinate system are defined by the position and velocity direction of the local star; The x-axis is along the direction of the orbit velocity:

[0031] The z-axis is directed to the opposite direction of the Earth's center

[0032] The y-axis is the normal direction of the orbit plane, and the right-hand rule is:

[0033] Rotation matrix RLOC:

[0034] The local orbit coordinate system axes are , , the projection components in the ECEF system;​ The relative position vector in the local orbital coordinate system is calculated as follows: The module M3.2 comprises:

[0035] wherein ws(k) is a static weight factor; wd(k) is a dynamic weight factor; and ws(k)+wd(k)=1; P 轨道 is the relative orbital normal vector between the two stars; With accumulation of the orbital data, the dynamic weight is gradually increased with the increase of the number of orbital data fusion, so as to realize the transition from the static reference to the dynamic fusion reference; as shown in the following formula, the dynamic weight wd is linearly increased according to the iteration number k:

[0036] wherein 0.8 is the upper limit of the dynamic weight, the initial value of the dynamic weight wd(0)=0.2, ws(0)=0.8, a is the growth step, and k is the iteration number of the orbital data fusion; The module M3.3 comprises: Based on the current pointing vector P 测量 measured by the laser terminal, the error vector S(k) is calculated as follows: S(k)=P 测量 -P 融合 The micro terminal angle correction amount ΔΦ=[Δφ, Δθ, Δψ] satisfying the preset requirement is constructed; wherein Δφ, Δθ and Δψ respectively represent the micro angles satisfying the preset requirement which need to be rotated around the X, Y and Z axes of the terminal itself, so that the actual pointing of the laser beam can be as accurately as possible to the expected direction; The influence of the terminal angle correction amount ΔΦ on the error S(k) is described based on the Jacobian matrix J(k); The optimal correction amount ΔΦ is calculated by using the least square method principle:

[0037] wherein, is the transpose of the Jacobian matrix, which is used to map the direction of the error vector to the direction of the angle correction; The laser controller receives the optimal correction amount ΔΦ, and drives the precise pointing mechanism to perform real-time adjustment according to the optimal correction amount.

[0038] Compared with the prior art, the present application has the following beneficial effects: 1、The present application can dynamically correct the calibration reference according to the actual orbital change through real-time mutual transmission of the interstellar orbital parameters, and effectively eliminate the error influence caused by the orbital dynamics; ​2、The application can effectively fuse inter-satellite orbit dynamic data and static calibration results, construct a dynamic fusion reference, greatly improve the calibration accuracy, improve the laser terminal pointing error to the micro-radian level, and meet the future high-bandwidth, long-distance inter-satellite laser communication requirements; 3、The application is completed by inter-satellite communication and autonomous navigation throughout the calibration process, and is free from dependence on ground stations, and can efficiently operate in the absence of ground coverage, frequent maneuvering, and complex task scenarios; 4、The application is applicable to complex space scenarios such as multi-satellite networking and formation flight, supports flexible establishment and rapid reconstruction of links, and improves the overall communication capability and task adaptability of the constellation; 5、The application greatly shortens the time for inter-satellite link acquisition and establishment through high-precision and low-delay dynamic calibration, and improves the link stability and data throughput capability; 6、The application breaks through the precision bottleneck of static calibration by fusing orbit dynamic data and static calibration results, effectively eliminates orbit dynamic errors, improves the laser calibration accuracy to the micro-radian level, greatly improves the establishment efficiency and reliability of the inter-satellite laser link, and not only improves the link establishment efficiency and reliability, but also provides a solid technical guarantee for future constellation networking, intelligent networking, and high-dynamic inter-satellite communication scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0039] Other features, objects, and advantages of the application will become more apparent after reading the detailed description of non-limiting embodiments with reference to the following drawings: Figure 1 A flowchart of a laser terminal calibration method based on inter-satellite orbit intercommunication.

[0040] Figure 2 A flowchart of a laser calibration method based on inter-satellite orbit intercommunication in an embodiment of the application.

[0041] Figure 3 A schematic diagram of inter-satellite orbit intercommunication of two satellite laser terminals in an embodiment of the application. DETAILED DESCRIPTION

[0042] The application will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the application. These all belong to the protection scope of the application.

[0043] Embodiment 1 According to the laser terminal calibration method based on inter-satellite orbit intercommunication provided by the application, as shown in Figure 1 , comprising: Step 101: static calibration of the spaceborne laser communication terminal before the establishment of the inter-satellite communication link; Step 102: establishment of the inter-satellite laser communication link between the two satellites; Step 103: transmission of real-time orbit parameters of the other satellite by the two satellites; Step 104: fusion of the static calibration and real-time orbit information to optimize the calibration reference, and realization of high-precision calibration.

[0044] Specifically, the step 101 comprises: autonomous attitude determination by a star sensor, or preliminary optical axis calibration of the laser terminal by ground assistance, to realize static calibration of the spaceborne laser communication terminal.

[0045] Specifically, the orbit parameters include, but are not limited to, the position vector, velocity vector and covariance information of the satellite.

[0046] Specifically, the fusion of the static calibration and real-time orbit information to optimize the calibration reference and realize high-precision calibration comprises the following steps: Step 1041: coordinate transformation in a unified coordinate system according to the exchanged orbit parameters, to calculate the relative orbit normal vector relationship between the two satellites; Step 1042: joint of the relative orbit normal vector and the static calibration result to dynamically generate a fusion reference, and realization of dynamic correction of the laser terminal pointing; Step 1043: periodic or real-time optimization of the fusion reference with the orbit inter-transmission data as the dynamic correction input, continuous correction of the laser terminal pointing error, and realization of high-precision calibration. The acquisition and processing of the orbit inter-transmission data in this embodiment are automatically completed in real time or periodically, to ensure the timeliness and precision of the fusion reference.

[0047] More specifically, the coordinate transformation comprises data processing in the geocentric inertial system or the orbit local coordinate system.

[0048] The fusion reference is generated by using a weighted fusion algorithm of the static calibration and the orbit inter-transmission data, to dynamically eliminate the superimposed effects of the orbit error and the attitude error.

[0049] Specifically, modern navigation and control algorithms such as weighted fusion and Kalman filtering are used to jointly process the rough calibration result and the orbit inter-transmission dynamic data, to realize real-time optimization of the fusion reference, so that it can reflect the latest changes of the actual inter-satellite state.

[0050] Specifically, the fine calibration process can automatically adjust the pointing of the laser communication terminal according to the dynamic fusion reference, to realize high-precision calibration in the order of microradians.

[0051] Specifically, the laser calibration result can be used as a high-precision pointing control reference for the subsequent inter-satellite communication link, to improve the efficiency and reliability of the link establishment.

[0052] The application innovatively introduces inter-orbit data exchange between satellites into the laser terminal calibration process, realizes high-precision laser calibration of micro-radian level through a dynamic fusion reference optimization mechanism, breaks through the precision bottleneck and application limitations of traditional static calibration, provides key technical support for future high-performance inter-satellite laser communication networks and intelligent networking, and has wide engineering application value and development prospects.

[0053] Embodiment 2 Embodiment 2 is a preferred example of embodiment 1 According to the laser terminal calibration method based on inter-orbit data exchange between satellites provided by the application, as shown in the figure, it comprises: Figure 2 The step 201 comprises: Step 201: Static calibration of the satellite-borne laser communication terminal; Specifically, the step 201 comprises: adopting a star sensor to autonomously determine the orientation or preliminarily calibrating the optical axis of the laser terminal through ground assistance.

[0054] Step 202: Constructing an inter-satellite laser communication link; transmitting real-time orbit parameters of two satellites based on the constructed inter-satellite laser communication link; wherein the real-time orbit parameters comprise: position vector, velocity vector and covariance information of the satellite; Step 203: Optimizing the calibration reference based on the static calibration and the real-time orbit parameters, and dynamically correcting the pointing of the laser terminal by using the optimized calibration reference to realize high-precision calibration; Specifically, the step 203 comprises: Step 2031: Coordinate transformation is performed on the real-time orbit parameters of the two satellites to unify the real-time orbit parameters of the two satellites to the same coordinate system, and the relative orbit normal vector between the two satellites is calculated; Converting the ECI to the ECEF;

[0055] Wherein, is the precession-nutation matrix, is the Greenwich sidereal time rotation matrix, is the position vector of the satellite in the ECI coordinate system, is the position vector of the satellite in the ECEF coordinate system; The position vectors of the home satellite and the target satellite in the ECEF coordinate system obtained by the respective conversion are and Therefore, the relative position vector in the ECEF coordinate system is

[0056] ​The three axes of the local orbital coordinate system are defined by the position and velocity direction of the satellite; The x-axis is along the orbital velocity direction:

[0057] The z-axis is pointing to the anti-center of the earth

[0058] The y-axis is the normal of the orbital plane, and the right-hand rule:

[0059] The rotation matrix RLOC:

[0060] The three axes of the local orbital coordinate system are defined by the position and velocity direction of the satellite; 、 、 The projection component in the ECEF system; The relative position vector calculation in the local orbital coordinate system: .

[0061] Step 2032: Fuse the relative orbital normal vector between the two satellites and the static calibration result through a fusion algorithm to dynamically generate a fusion reference;

[0062] wherein ws(k) is a static weight factor; wd(k) is a dynamic weight factor; and ws(k)+wd(k)=1; P 轨道 is the relative orbital normal vector between the two satellites; As the orbital data accumulates, the dynamic weight gradually increases with the increase of the number of orbital data fusion, realizing the transition from the static reference to the dynamic fusion reference; as shown in the following formula, the dynamic weight wd increases linearly according to the iteration number k:

[0063] wherein 0.8 is the upper limit of the dynamic weight, the initial value of the dynamic weight wd(0)=0.2, ws(0)=0.8, a is the growth step, and k is the iteration number of orbital data fusion.

[0064] Step 2033: Use the fusion reference to dynamically correct the pointing of the laser terminal to realize high-precision calibration; Based on the current pointing vector P 测量 measured by the laser terminal, the error vector S(k) is calculated: S(k)=P 测量 -P 融合 Constructing a micro terminal angle correction amount ΔΦ=[Δφ, Δθ, Δψ] that meets the preset requirements; wherein Δφ, Δθ, Δψ respectively represent a micro angle that needs to be rotated around the X, Y, Z axis of the terminal itself to meet the preset requirements, so that the actual pointing of the laser beam is as accurately as possible to the desired direction. The influence of the terminal angle correction amount ΔΦ on the error S(k) is described based on the Jacobian matrix J(k); The optimal correction amount ΔΦ is calculated using the least square method principle:

[0065] Wherein, The transpose of the Jacobian matrix is used to map the direction of the error vector to the direction of the angle correction; The laser controller receives the optimal correction amount ΔΦ and drives the precise pointing mechanism to adjust in real time according to the optimal correction amount.

[0066] The application also provides a laser terminal calibration system based on inter-orbit mutual transmission of stars, which can be realized by executing the process steps of the laser terminal calibration method based on inter-orbit mutual transmission of stars, that is, those skilled in the art can understand the laser terminal calibration method based on inter-orbit mutual transmission of stars as the preferred embodiment of the laser terminal calibration system based on inter-orbit mutual transmission of stars.

[0067] Example 3 Example 3 is a preferred example of example 1 The application is suitable for a satellite system equipped with an optical head, a laser communication machine, a laser controller, a network routing module, a data processor and a star sensor; The satellite system mainly includes the following key modules: Optical head: a precise optical device responsible for transmitting or receiving laser signals.

[0068] Laser communication machine: used to realize functions such as modulation, demodulation, encoding, decoding and the like of data, to ensure efficient and accurate information carried by laser.

[0069] Laser controller: based on calibration and the orbit of the other party, the pointing of the optical head is accurately controlled to realize the link establishment communication with the other party laser terminal.

[0070] Network routing module: responsible for receiving and forwarding data packets in the inter-satellite link, realizing the exchange of information and orbit parameters and the like data between stars.

[0071] Data processor: according to the data provided by the star sensor, the real-time orbit parameters (such as position and velocity vector) of the satellite are calculated.

[0072] Star sensor: a high-precision optical attitude sensor that determines the precise attitude of a satellite in space by photographing the starry sky and identifying the positions of stars.

[0073] Static calibration phase: Before the establishment of the inter-satellite communication link, the static calibration of the laser terminal is carried out first; the specific steps are as follows: (1) After the satellite is in orbit, start the attitude measurement device such as the star sensor to obtain its own attitude parameters (such as quaternions, Euler angles, etc.).

[0074] (2) Adjust the optical axis of the optical head of the laser terminal to the initial predetermined direction through ground assistance or autonomous star sensor measurement, and ensure that the optical axis pointing error is less than 0.1°.

[0075] (3) When assisted by the ground station, the reference attitude and orbit parameters determined by the ground are issued through telemetry and remote control instructions to assist in completing the static calibration.

[0076] (4) Record the initial static calibration results as the initial conditions for the subsequent dynamic fusion reference generation.

[0077] 2. Link establishment phase The ground station uploads the orbit parameters (six quaternions) of the other satellite in advance, and the satellite performs orbit prediction and laser pointing tracking and capture to finally complete the link establishment.

[0078] 3. Inter-satellite orbit parameter exchange phase After the two satellites enter the predetermined communication window and establish the inter-satellite link, the two satellites exchange orbit parameters (six quaternions) in real time through the inter-satellite communication link.

[0079] 4. Data fusion phase After the two satellites enter the predetermined communication window and establish the inter-satellite link, enter the dynamic data fusion reference generation phase. The specific process is as follows: (1) Coordinate system conversion After receiving the orbit parameters of the other satellite, convert them to the geocentric inertial coordinate system or the local orbit coordinate system to ensure the uniformity and calculability of the data of the two satellites.

[0080] (2) Relative orbit normal vector calculation Using the orbit data in the unified coordinate system, calculate the spatial relative orientation (such as target direction vector, relative azimuth and elevation angle, etc.) between the two satellites in real time to provide dynamic input for precise calibration.

[0081] (3) Static calibration result fusion The optical axis pointing obtained in the static calibration stage is combined with the spatial relative orientation data as the input of the dynamic fusion reference. By setting a weight factor, the influence of the static calibration and the track data is reasonably distributed. The initial static calibration weight is larger, and the weight of the track data is gradually increased as the track data accumulates and the accuracy improves.

[0082] The optical axis pointing obtained in the static calibration stage, i.e. the rotation matrix P 静态 The spatial relative orientation data calculated by mutual transmission with the track, i.e. the target direction vector P 轨道 are combined to obtain the dynamically optimized target pointing P 融合 , which can be regarded as a theoretical direction vector. However, early track single-point data may also have small fluctuations, and the credibility of the two in fusion needs to be balanced. Therefore, the following weighted formula for static calibration and track data fusion is defined:

[0083] By setting the weight factors ws(k) (static weight) and wd(k) (dynamic weight), the influence of the two is distributed, where ws+wd=1. As the track data accumulates, the dynamic weight gradually increases as the number of track data fusion increases, realizing the transition from static reference to dynamic fusion reference. As shown in the following formula, the dynamic weight wd increases linearly with the iteration number k:

[0084] where 0.8 is the upper limit of the dynamic weight, the initial value of the dynamic weight wd(0)=0.2, ws(0)=0.8, a is the growth step, which can be 0.1, and k is the iteration number of track data fusion.

[0085] For example, when the initial chain is established at t=0, wd=0.2 and ws=0.8. After one track data fusion at t=1 min, wd=0.3 and ws=0.7. When the track data fusion is performed 6 times or more, wd=0.8 and ws=0.2.

[0086] (4) Dynamic fusion reference optimization Recursive least squares, Kalman filtering and other fusion algorithms are used to dynamically combine the static calibration results and the track mutual transmission data, and to output the optimal laser terminal pointing correction in real time. The correction includes the compensation of track changes, attitude disturbances, terminal structure errors and other multi-source errors.

[0087] Recursive least squares or Kalman filtering is used to dynamically fuse the static calibration results and the track mutual transmission data: (1) Define the error vector Based on the current pointing vector P 测量The error vector S(k) can be calculated as the deviation of the actual pointing vector P 融合 from the theoretical pointing vector P 测量 : S(k)=P 测量 -P 融合 (2) Optimization algorithm Find a small terminal angle correction ΔΦ=[Δφ,Δθ,Δψ], where Δφ, Δθ, Δψ represent the small angle of rotation around the terminal's own X, Y, Z axis, respectively, so that the actual pointing of the laser beam is as accurate as possible to the desired direction; (3) Model establishment Based on the Jacobian matrix J(k), the influence of the small angle correction ΔΦ on the error S(k) is described.

[0088] (4) Solve the correction Using the least squares method, the optimal correction ΔΦ can be calculated by the following formula:

[0089] is the transpose of the Jacobian matrix, which maps the direction of the error vector to the direction of the angle correction. The final calculation of the optimal angle correction ΔΦ=[Δφ,Δθ,Δψ].

[0090] (5) Execute the correction The laser controller receives ΔΦ and drives the precise pointing mechanism to make real-time adjustments according to the calculated small angle.

[0091] (6) Closed-loop feedback The terminal continuously measures the new actual pointing P 测量 , the new orbit data generates a new P 轨道 , and the target pointing P 融合 is fused after dynamic optimization, and the new S(k+1) is calculated, and the new ΔΦ{k+1} is solved again, and the cycle is repeated, so that the laser beam is dynamically and real-time high-precision alignment. The weight wd will also increase continuously with the number of orbit data fusion until the upper limit of 0.8.

[0092] Reference Figure 3 The inter-orbit transfer of two satellite laser terminals is shown in the figure, and the specific implementation is as follows.

[0093] Taking satellite 1 orbit parameter sending satellite 2 as an example. After the inter-satellite laser link of satellite 1 and satellite 2 is established, the first star sensor 101 of satellite 1 obtains the real-time orbit parameter of satellite 1, and transmits the real-time orbit parameter to the first laser communication machine 105 through the first network routing module 103, the first laser communication machine 105 transmits the real-time orbit parameter to the second optical head 206 of satellite 2 through the inter-satellite link after modulation and coding by the first optical head 106, the second optical head 206 of satellite 2 transmits the real-time orbit parameter to the second laser communication machine 205, and the second laser communication machine 205 transmits the real-time orbit parameter to the second network routing module 203 of the satellite after decoding and demodulation, the second network routing module 203 directly transmits the real-time orbit parameter to the second data processor 202, the second data processor 202 transmits the real-time orbit parameter to the second laser controller 204 after coordinate system conversion, and the second laser controller 204 calculates the relative orbit normal vector of satellite 1 and satellite 2, and fuses the optical axis pointing obtained in the static calibration stage to output the optimal laser terminal pointing correction amount in real time.

[0094] The application can be widely applied to low-orbit satellite networking, geosynchronous orbit high-speed communication, deep space exploration multi-spacecraft formation cooperation and other space task scenes. The dynamic fusion reference idea and technical route are not only suitable for laser communication terminal calibration, but also can be popularized to high-precision directional antennas, inter-satellite measurement loads and other high-dynamic and high-precision space pointing control fields. In the future, with the expansion of constellation scale and the improvement of satellite intelligence level, the method of the application can also be deeply integrated with emerging technologies such as inter-satellite autonomous navigation, intelligent networking and on-orbit adaptive control, to further improve the intelligence, automation and high reliability level of space information network.

[0095] Those skilled in the art know that, in addition to implementing the system, device and each module thereof provided by the application in a pure computer readable program code manner, the same program can also be implemented in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and each module thereof provided by the application can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures in the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing methods and structures in the hardware component.

[0096] The specific embodiments of the application are described above. It should be understood that the application is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essential content of the application. The embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other without conflict.

Claims

1. A laser terminal calibration method based on inter-orbit mutual transmission of stars, characterized in that, The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite.

2. The laser terminal calibration method based on inter-orbit transfer of stars according to claim 1, characterized in that, The application relates to a high-precision calibration method for a laser terminal on a satellite.

3. The method of claim 1, wherein, The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite.

4. The laser terminal calibration method based on inter-orbit transfer of stars according to claim 3, characterized in that, The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. wherein is the precession-nutation matrix, is the Greenwich Sidereal Time rotation matrix, is the position vector of the satellite in the Earth-Centered Inertial coordinate system, is the position vector of the satellite in the Earth-Centered Fixed coordinate system; According to the converted position vectors of the sun and the target star in the ECEF coordinate system respectively, the relative position vector in the ECEF coordinate system is and Therefore, the relative position vector in the ECEF coordinate system is ​ The application relates to a high-precision calibration method for a laser terminal on a satellite. The x-axis is along the track velocity direction: z axis is the direction opposite to the center of the earth The y-axis is the normal of the track surface, right-hand rule: The application relates to a high-precision calibration method for a laser terminal on a satellite. are local orbital coordinate system axes , , projected components in ECEF The application relates to a high-precision calibration method for a laser terminal on a satellite. 。 5. The method according to claim 3, wherein, The application relates to a high-precision calibration method for a laser terminal on a satellite. where ws(k) is a static weight factor; wd(k) is a dynamic weight factor; and ws(k) + wd(k) = 1; P 轨道 is the relative orbital normal vector between the two stars; The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite.

6. The method of claim 3, wherein, The application relates to a high-precision calibration method for a laser terminal on a satellite. Based on the current pointing vector P actually measured by the laser terminal 测量 , the error vector S(k) is calculated: S(k) = P 测量 - P 融合 The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. wherein is the transpose of the Jacobian matrix, which acts to map the direction of the error vector into the direction of the angle correction; The application relates to a high-precision calibration method for a laser terminal on a satellite.

7. A laser terminal calibration system based on inter-orbit transfer of stars, characterized in that, The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite.

8. The laser terminal calibration system based on inter-orbit transfer of stars according to claim 7, characterized in that, The application relates to a high-precision calibration method for a laser terminal on a satellite.

9. The laser terminal calibration system based on inter-orbit transfer of stars according to claim 7, characterized in that, The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal on a satellite. The application relates to a high-precision calibration method for a laser terminal Module M3.1: Coordinate transformation is performed on real-time orbit parameters of two stars to unify the real-time orbit parameters of the two stars to the same coordinate system, and a relative orbit normal vector between the two stars is calculated; Module M3.2: The relative orbit normal vector between the two stars and the static calibration result are fused by a fusion algorithm to dynamically generate a fusion reference; Module M3.3: The fusion reference is used to dynamically correct the pointing of the laser terminal to achieve high-precision calibration.

10. The laser terminal calibration system based on inter-orbit transfer of stars according to claim 9, characterized in that, The module M3.1 includes: Converting the Earth-Centered Inertial System (ECI) to the Earth-Centered Earth-Fixed System (ECEF); wherein, is the precession-nutation matrix, is the Greenwich Sidereal Time rotation matrix, is the position vector of the satellite in the Earth-Centered Inertial coordinate system, is the position vector of the satellite in the Earth-Centered Fixed coordinate system; According to the converted position vectors of the sun and the target star in the ECEF coordinate system respectively, the relative position vector in the ECEF coordinate system is and Therefore, the relative position vector in the ECEF coordinate system is ​ The three axes of the local orbit coordinate system are defined by the position and velocity direction of the star; The x-axis is along the track velocity direction: The z-axis points to the opposite direction of the center of the earth The y-axis is the normal of the track surface, right-hand rule: Rotation matrix RLOC: are the local orbital coordinate system axes , , projected components in ECEF Relative position vector calculation in the local orbit coordinate system: ； The module M3.2 includes: where ws(k) is a static weight factor; wd(k) is a dynamic weight factor; and ws(k) + wd(k) = 1; P 轨道 is the relative orbital normal vector between the two stars; As the orbit data accumulates, the dynamic weight gradually increases with the increase in the number of orbit data fusion, realizing the transition from a static reference to a dynamic fusion reference; as shown in the following formula, the dynamic weight wd linearly increases with the iteration number k: wherein 0.8 is the upper limit of the dynamic weight, the initial value of the dynamic weight wd(0)=0.2, ws(0)=0.8, a is the growth step, and k is the iteration number of orbit data fusion; The module M3.3 includes: Based on the current pointing vector P actually measured by the laser terminal 测量 , the error vector S(k) is calculated: S(k) = P 测量 - P 融合 A small terminal angle correction amount ΔΦ=[Δφ, Δθ, Δψ] that meets the preset requirements is constructed; wherein Δφ, Δθ, and Δψ respectively represent small angles that need to be rotated around the X, Y, and Z axes of the terminal itself to meet the preset requirements, so that the actual pointing of the laser beam is as accurate as possible to the desired direction; The influence of the terminal angle correction amount ΔΦ on the error S(k) is described based on the Jacobian matrix J(k); The least squares method is used to calculate the optimal correction amount ΔΦ: wherein is the transpose of the Jacobian matrix, which acts to map the direction of the error vector into the direction of the angle correction; The laser controller receives the optimal correction amount ΔΦ and drives the precise pointing mechanism to perform real-time adjustment according to the optimal correction amount.

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