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

Abstract

The application provides a laser terminal calibration method and system based on inter-orbit mutual transmission of stars, comprising: before the establishment of an inter-orbit communication link, using a star sensor or ground assistance to perform static calibration on the laser terminal, so that the pointing error of the optical axis is less than 0.1°; after the establishment of the communication link, real-time exchange of the orbit parameters of two stars is performed, the relative orbit normal vector is calculated through coordinate transformation, and a dynamic fusion reference is generated in combination with the static calibration result. The application takes real-time orbit mutual transmission data as a dynamic correction input, and no longer depends on the initial static calibration result, so that the fusion reference optimization of calibration and orbit mutual transmission is realized. Compared with the traditional static calibration method which depends on the ground station or the inertial reference of a single star, the application breaks through the precision bottleneck of the 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 the micro-radian level, and greatly improves the establishment efficiency and reliability of the inter-orbit laser link.

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 pointing 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 realizes the real-time self-calibration of multiple light paths by the mutual cooperation of optical devices, 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 the calibration process does not affect the normal work of laser intersatellite communication, calibration area and communication area are separated, to realize full real-time automatic calibration. 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:

[0011] Step S1: static calibration of the satellite-borne laser communication terminal;

[0012] 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 the position vector, velocity vector and covariance information of the satellite;

[0013] Step S3: optimization of the calibration reference based on the static calibration and the real-time orbit parameters, dynamic correction of the laser terminal pointing using the optimized calibration reference, and realization of high-precision calibration.

[0014] Preferably, the step S1 includes preliminary optical axis calibration of the laser terminal using a star sensor to autonomously determine the attitude or through ground assistance.

[0015] Preferably, the step S3 includes:

[0016] 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;

[0017] Step S3.2: Fuse the relative orbit normal vector between the two stars and the static calibration result by a fusion algorithm to dynamically generate a fusion reference;

[0018] Step S3.3: Dynamically correct the laser terminal pointing using the fusion reference to achieve high-precision calibration.

[0019] Preferably, the step S3.1 comprises:

[0020] Converting the Earth-Centered Inertial System (ECI) to the Earth-Centered Earth-Fixed System (ECEF);

[0021]

[0022] 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;

[0023] According to the converted position vectors of the local star and the target star in the Earth-Centered Earth-Fixed System (ECEF) coordinate system, respectively, and the relative position vector in the Earth-Centered Earth-Fixed System (ECEF) coordinate system is

[0024]

[0025] The three axes of the local orbit coordinate system are defined by the position and velocity direction of the local star;

[0026] The x-axis is along the orbit velocity direction:

[0027] The z-axis is directed to the opposite direction of the Earth's center

[0028] The y-axis is the normal direction of the orbit plane, and the right-hand rule is:

[0029] Rotation matrix RLOC:

[0030]

[0031] The local orbit coordinate system axes are , , the projection components in the ECEF system;

[0032] Calculation of the relative position vector in the local orbit coordinate system:

[0033] ​ .

[0034] Preferably, the step S3.2 comprises:

[0035]

[0036] 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;

[0037] 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 linearly increases with the iteration number k:

[0038]

[0039] 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.

[0040] Preferably, the step S3.3 comprises:

[0041] Based on the current pointing vector P 测量 measured by the laser terminal, the error vector S(k) is calculated:

[0042] S(k)=P 测量 -P 融合

[0043] The micro terminal angle correction amount ΔΦ=[Δφ,Δθ,Δψ] that meets the preset requirements is constructed; wherein Δφ, Δθ, Δψ respectively represent the micro angle that meets the preset requirements and needs to be rotated around the X, Y, Z axes of the terminal itself, so that the actual pointing of the laser beam is as accurately as possible to the desired direction;

[0044] The influence of the terminal angle correction amount ΔΦ on the error S(k) is described based on the Jacobian matrix J(k);

[0045] The optimal correction amount ΔΦ is calculated by using the least square method principle:

[0046]

[0047] wherein, is the transpose of the Jacobian matrix, which maps the direction of the error vector to the direction of the angle correction;

[0048] 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.

[0049] According to the application, a laser terminal calibration system based on inter-satellite orbit mutual transmission is provided, comprising:

[0050] Module M1: static calibration of the space-borne laser communication terminal;

[0051] Module M2: construction of an inter-satellite laser communication link; transmission of real-time orbit parameters of two satellites based on the constructed inter-satellite laser communication link; wherein the real-time orbit parameters comprise a position vector, a velocity vector and covariance information of the satellite;

[0052] Module M3: optimization of calibration reference based on static calibration and real-time orbit parameters, dynamic correction of the laser terminal pointing using the optimized calibration reference, and realization of high-precision calibration.

[0053] Preferably, the module M1 comprises: preliminary optical axis calibration of the laser terminal by autonomous attitude determination of a star sensor or through ground assistance.

[0054] Preferably, the module M3 comprises:

[0055] Module M3.1: coordinate transformation of the real-time orbit parameters of two satellites to unify the real-time orbit parameters of two satellites to the same coordinate system, and calculation of the relative orbit normal vector between two satellites;

[0056] Module M3.2: fusion processing of the relative orbit normal vector between two satellites and the static calibration result through a fusion algorithm, and dynamic generation of a fusion reference;

[0057] Module M3.3: dynamic correction of the laser terminal pointing using the fusion reference, and realization of high-precision calibration.

[0058] Preferably, the module M3.1 comprises:

[0059] Conversion of the Earth-Centered Inertial System (ECI) to the Earth-Centered Earth-Fixed System (ECEF);

[0060]

[0061] 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;

[0062] According to the converted position vectors of the home satellite and the target satellite in the Earth-Centered Earth-Fixed System (ECEF) coordinate system, respectively, and the relative position vector in the Earth-Centered Earth-Fixed System (ECEF) coordinate system is For

[0063]

[0064] The three axes of the local orbital coordinate system are defined by the position and velocity direction of the star;

[0065] The x-axis is along the orbital velocity direction:

[0066] The z-axis is directed to the anti-center of the earth

[0067] The y-axis is the normal of the orbital plane, and the right-hand rule:

[0068] Rotation matrix RLOC:

[0069]

[0070] The local orbital coordinate system axes , , The projection component in the ECEF system;

[0071] The relative position vector calculation under the local orbital coordinate system:

[0072] ;

[0073] The module M3.2 includes:

[0074]

[0075] Wherein, ws(k) is a static weight factor; wd(k) is a dynamic weight factor; and ws(k)+wd(k)=1; P 轨道 The relative orbital normal vector between the two stars;

[0076] 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:

[0077]

[0078] 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;

[0079] The module M3.3 includes:

[0080] Based on the current pointing vector P measured by the laser terminal测量 , the error vector S(k) is calculated:

[0081] S(k)=P 测量 -P 融合

[0082] 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 which needs to be rotated 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 expected direction;

[0083] The influence of the terminal angle correction amount ΔΦ on the error S(k) is described based on the Jacobian matrix J(k);

[0084] The optimal correction amount ΔΦ is calculated by using the least square method principle:

[0085]

[0086] Wherein, is the transpose of the Jacobian matrix, which maps the direction of the error vector to the direction of the angle correction;

[0087] 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.

[0088] Compared with the prior art, the present application has the following beneficial effects:

[0089] 1、The present application can dynamically correct the calibration reference according to the actual orbit change through real-time mutual transmission of inter-satellite orbit parameters, and effectively eliminates the error influence caused by the orbit dynamics;

[0090] 2、The present application can effectively fuse the inter-satellite orbit dynamic data and static calibration results, construct a dynamic fusion reference, greatly improve the calibration accuracy, and improve the laser terminal pointing error to the micro-radian level, which meets the future high-bandwidth, long-distance inter-satellite laser communication requirements;

[0091] 3、The present 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 scene of no ground coverage, frequent maneuvering and complex tasks;

[0092] 4、The present application is suitable for complex space scenes such as multi-satellite networking and formation flight, supports flexible establishment and rapid reconstruction of links, and improves the overall communication ability and task adaptability of the constellation;

[0093] 5、The present application greatly shortens the time of inter-satellite link acquisition and establishment through high-precision and low-delay dynamic calibration, and improves the link stability and data throughput capacity;

[0094] 6. This invention breaks through the accuracy bottleneck of static calibration by fusing dynamic orbit data with static calibration results, effectively eliminating dynamic orbit errors and improving the accuracy of laser calibration to the microradian level, which greatly improves the establishment efficiency and reliability of inter-satellite laser links. At the same time, it not only improves the efficiency and reliability of link establishment, but also provides a solid technical guarantee for future constellation networking, intelligent networking and high-dynamic inter-satellite communication scenarios. Attached Figure Description

[0095] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0096] Figure 1 This is a flowchart of a laser terminal calibration method based on inter-satellite orbital communication.

[0097] Figure 2 This is a flowchart of a laser calibration method for inter-satellite orbital communication in an embodiment of the present invention.

[0098] Figure 3 This is a schematic diagram of inter-satellite orbital communication between two satellite laser terminals in an embodiment of the present invention. Detailed Implementation

[0099] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0100] Example 1

[0101] According to the present invention, a laser terminal calibration method based on inter-satellite orbital mutual transmission is provided, such as... Figure 1 As shown, it includes:

[0102] Step 101: Before establishing the inter-satellite communication link, perform static calibration on the onboard laser communication terminal;

[0103] Step 102: Establish an inter-satellite laser communication link between the two satellites;

[0104] Step 103: The two satellites transmit each other's real-time orbital parameters;

[0105] Step 104: Integrate static calibration and real-time track information to optimize the calibration benchmark and achieve high-precision calibration.

[0106] Specifically, step 101 includes: using a star sensor for autonomous attitude determination, or using ground-assisted preliminary optical axis calibration of the laser terminal to achieve static calibration of the spaceborne laser communication terminal.

[0107] Specifically, the orbit parameters include, but are not limited to, position vectors, velocity vectors and covariance information of the satellites.

[0108] Specifically, the fusion of static calibration and real-time orbit information optimizes the calibration reference to achieve high-precision calibration, including the following steps:

[0109] Step 1041: According to the exchanged orbit parameters, the coordinate transformation of the unified coordinate system is performed, and the relative orbit normal vector relationship between the two satellites is calculated;

[0110] Step 1042: The relative orbit normal vector is combined with the static calibration result to dynamically generate a fusion reference, and dynamic correction of the laser terminal pointing is realized.

[0111] Step 1043: Taking the orbit mutual transmission data as the dynamic correction input, the fusion reference is periodically or real-time optimized, the laser terminal pointing error is continuously corrected, and high-precision calibration is realized. The acquisition and processing of the orbit mutual transmission data in this embodiment are automatically completed in real time or periodically, ensuring the timeliness and accuracy of the fusion reference.

[0112] More specifically, the coordinate transformation includes unifying the orbit parameters of each satellite to the geocentric inertial system or the orbit local coordinate system for data processing.

[0113] The fusion reference is generated by using a weighted fusion algorithm of static calibration and orbit mutual transmission data to dynamically eliminate the superimposed effects of orbit errors and attitude errors.

[0114] Specifically, modern navigation and control algorithms such as weighted fusion and Kalman filtering are used to jointly process the coarse calibration result and the orbit mutual transmission dynamic data, and the fusion reference is optimized in real time, so that it can reflect the latest changes of the actual inter-satellite state.

[0115] Specifically, the fine calibration process can automatically adjust the pointing of the laser communication terminal according to the dynamic fusion reference, and realize high-precision calibration of the micro-radian level.

[0116] Specifically, the laser calibration result can be used as a high-precision pointing control reference for subsequent inter-satellite communication links, and the efficiency and reliability of link establishment are improved.

[0117] The present application innovatively introduces inter-satellite real-time orbit mutual transmission data into the laser terminal calibration process, and realizes high-precision laser calibration of the micro-radian level through a dynamic fusion reference optimization mechanism, breaking through the precision bottleneck and application limitations of traditional static calibration, providing key technical support for future high-performance inter-satellite laser communication networks and intelligent networking, and having wide engineering application value and development prospect.

[0118] Embodiment 2

[0119] Embodiment 2 is a preferred embodiment of Embodiment 1

[0120] According to the application, a laser terminal calibration method based on inter-satellite orbit mutual transmission is provided, which comprises the following steps: Figure 2 as shown in the figure, comprising:

[0121] Step 201: static calibration of the space-borne laser communication terminal;

[0122] Specifically, the step 201 comprises: adopting a star sensor to autonomously determine the posture or preliminarily calibrating the optical axis of the laser terminal through ground assistance.

[0123] 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 satellites;

[0124] Step 203: 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;

[0125] Specifically, the step 203 comprises:

[0126] Step 2031: performing coordinate transformation on the real-time orbit parameters of two satellites, so as to unify the real-time orbit parameters of two satellites to the same coordinate system, and calculating the relative orbit normal vector between two satellites;

[0127] Converting the ECI to the ECEF;

[0128]

[0129] 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;

[0130] According to the converted position vectors of the home satellite and the target satellite in the ECEF coordinate system respectively, the relative position vector in the ECEF coordinate system is and is

[0131]

[0132] The three axes of the local orbit coordinate system are defined by the position and velocity direction of the home satellite.

[0133] ​The x-axis is along the direction of the orbital velocity:

[0134] The z-axis is in the direction opposite to the center of the earth

[0135] The y-axis is the normal of the orbital plane, and the right-hand rule:

[0136] Rotation matrix RLOC:

[0137]

[0138] The local orbital coordinate system axes are respectively , , The projection component in the ECEF system;

[0139] The relative position vector calculation in the local orbital coordinate system:

[0140] .

[0141] Step 2032: Fuse the relative orbital normal vector between the two stars and the static calibration result through a fusion algorithm to dynamically generate a fusion reference;

[0142]

[0143] 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;

[0144] 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:

[0145]

[0146] 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.

[0147] Step 2033: dynamically correct the laser terminal pointing using the fusion reference to realize high-precision calibration;

[0148] Based on the current pointing vector P 测量 measured by the laser terminal, the error vector S(k) is calculated:

[0149] S(k)=P 测量-P 融合

[0150] Constructing the micro terminal angle correction amount ΔΦ=[Δφ, Δθ, Δψ] meeting the preset requirements; wherein Δφ, Δθ and Δψ respectively represent the micro angles meeting the preset requirements of rotating 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 expected direction;

[0151] The influence of the terminal angle correction amount ΔΦ on the error S(k) is described based on the Jacobian matrix J(k);

[0152] The optimal correction amount ΔΦ is calculated by using the least square method principle:

[0153]

[0154] Wherein, is the transpose of the Jacobian matrix, which maps the direction of the error vector to the direction of the angle correction;

[0155] 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.

[0156] 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, the laser terminal calibration method based on inter-orbit mutual transmission of stars can be understood by those skilled in the art as the preferred embodiment of the laser terminal calibration system based on inter-orbit mutual transmission of stars.

[0157] Example 3

[0158] Example 3 is a preferred example of example 1

[0159] 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;

[0160] The satellite system mainly includes the following key modules:

[0161] Optical head: a precise optical device responsible for transmitting or receiving laser signals.

[0162] Laser communication machine: used for realizing the functions of modulation, demodulation, coding, decoding and the like of data, and ensuring efficient and accurate information carried by laser.

[0163] Laser controller: based on calibration and the orbit of the opposite party, the pointing of the optical head is accurately controlled to realize the link establishment communication with the opposite laser terminal.

[0164] Network routing module: responsible for receiving and forwarding data packets in inter-satellite links, enabling information exchange and orbit parameters, etc.

[0165] Data processor: calculates real-time orbit parameters (such as position and velocity vectors) of the satellite based on data provided by the star sensor.

[0166] Star sensor: a high-precision optical attitude sensor that determines the precise attitude of the satellite in space by photographing the starry sky and identifying the positions of stars.

[0167] Static calibration phase:

[0168] Before establishing inter-satellite communication links, first perform static calibration of the laser terminal; the specific steps are as follows:

[0169] (1) After the satellite is in orbit, start the star sensor and other attitude measurement devices to obtain its own attitude parameters (such as quaternions, Euler angles, etc.).

[0170] (2) Adjust the optical axis of the laser terminal optical head to the initial predetermined direction through ground assistance or autonomous star sensor measurement, ensuring that the optical axis pointing error is less than 0.1°.

[0171] (3) When assisted by a ground station, issue reference attitude and orbit parameters measured by the ground through telemetry and remote control commands to assist in completing static calibration.

[0172] (4) Record the initial static calibration results as the initial conditions for generating the subsequent dynamic fusion reference.

[0173] 2. Link establishment phase

[0174] The ground station uploads the other satellite's orbit parameters (six quaternions) in advance, and the satellite performs orbit prediction and laser pointing tracking and capture to finally complete the link establishment.

[0175] 3. Inter-satellite orbit parameter exchange phase

[0176] After the two satellites enter the predetermined communication window and establish inter-satellite links, the two satellites exchange orbit parameters (six quaternions) in real time through the inter-satellite communication link.

[0177] 4. Data fusion phase

[0178] After the two satellites enter the predetermined communication window and establish inter-satellite links, enter the dynamic data fusion reference generation phase. The specific process is as follows:

[0179] (1) Coordinate system conversion

[0180] After receiving the other satellite's orbit parameters, convert them to the Earth-Centered Inertial (ECI) coordinate system or the local orbit coordinate system to ensure the uniformity and calculability of the data.

[0181] (2) Relative orbit normal vector calculation

[0182] Using the orbit data in the unified coordinate system, the spatial relative orientation (such as target direction vector, relative azimuth and elevation angle, etc.) between the satellite and the other satellite is calculated in real time, providing dynamic input for precision calibration.

[0183] (3) Static calibration result fusion

[0184] 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 the weight factor, the influence of static calibration and orbit data is reasonably distributed. The weight of static calibration is larger in the early stage, and the weight of orbit data is gradually increased as the orbit data accumulates and the precision improves.

[0185] The optical axis pointing obtained in the static calibration stage, i.e. the rotation matrix P 静态 of the laser terminal coordinate system to the platform coordinate system is combined with the spatial relative orientation data calculated by the orbit mutual transmission, i.e. the target direction vector P 轨道 , to obtain the dynamically optimized target pointing P 融合 , which can be regarded as the theoretical direction vector. However, early orbit 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 orbit data fusion is defined:

[0186]

[0187] 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 orbit data accumulates, 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 increases linearly with the iteration number k:

[0188]

[0189] 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 taken as 0.1, and k is the iteration number of orbit data fusion.

[0190] For example, at the initial chain establishment t=0, wd=0.2, ws=0.8. After 1 time of orbit data fusion, t=1 min, wd=0.3, ws=0.7. After 6 times or more of orbit data fusion, wd=0.8, ws=0.2.

[0191] (4) Dynamic fusion reference optimization

[0192] Recursive least square method, Kalman filter and other fusion algorithms are adopted to dynamically combine the static calibration results and orbit intercommunication data, and to output the optimal laser terminal pointing correction in real time. The correction includes the compensation of orbit changes, attitude disturbances, terminal structure errors and other multi-source errors.

[0193] Recursive least square method or Kalman filter is adopted to dynamically combine the static calibration results and orbit intercommunication data:

[0194] (1) Define error vector

[0195] Based on the current pointing vector P measured by the laser terminal 测量 , the error vector S(k) can be calculated as the deviation of the theoretical pointing vector P 融合 from the actual pointing vector P 测量 :

[0196] S(k)=P 测量 -P 融合

[0197] (2) Optimization algorithm

[0198] Find a small terminal angle correction ΔΦ=[Δφ,Δθ,Δψ], where Δφ, Δθ, Δψ represent the small angles that need to be rotated around the X, Y, Z axes of the terminal itself, so that the actual pointing of the laser beam can be as accurately as possible to the desired direction;

[0199] (3) Establish model

[0200] Based on the Jacobian matrix J(k), the influence of the small angle correction ΔΦ on the error S(k) is described.

[0201] (4) Solve correction

[0202] Using the least square method, the optimal correction ΔΦ can be calculated by the following formula:

[0203]

[0204] is the transpose of the Jacobian matrix, which maps the direction of the error vector to the direction of the angle correction. The final optimal angle correction ΔΦ=[Δφ,Δθ,Δψ] is calculated.

[0205] (5) Execute correction

[0206] The laser controller receives ΔΦ and drives the precise pointing mechanism to adjust in real time according to the calculated small angle.

[0207] (6) Closed-loop feedback

[0208] The terminal will continuously measure the new actual pointing P测量 New track data comes in to generate new P 轨道 Fusion of the target pointing P after dynamic optimization 融合 Calculate new S(k+1), solve new ΔΦ{k+1} again, and so on, dynamically and in real time to maintain high-precision alignment of the laser beam. The weight wd also increases continuously with the number of track data fusion until the upper limit 0.8.

[0209] Reference Figure 3 The schematic diagram of inter-orbit track data transmission between two satellite laser terminals is shown in the following figure, and the implementation is as follows.

[0210] Take the satellite 1 track parameter sent to satellite 2 as an example. After the inter-satellite laser link between satellite 1 and satellite 2 is established, the first star sensor 101 of satellite 1 obtains the real-time track parameter of satellite 1, which is forwarded to the first laser communication machine 105 through the first network routing module 103, and the first laser communication machine 105 is modulated and coded, and then transmitted to the second optical head 206 of satellite 2 through the inter-satellite link by the first optical head 106, and the second optical head 206 of satellite 2 is transmitted to the second laser communication machine 205, and after decoding and demodulation, it is transmitted to the second network routing module 203 of the home star, and the second network routing module 203 is directly forwarded to the second data processor 202, and the second data processor 202 is converted after the coordinate system and sent to the second laser controller 204, the second laser controller 204 calculates the relative track normal vector of satellite 1 and satellite 2, and fuses the optical axis pointing obtained in the static calibration stage, and outputs the optimal laser terminal pointing correction amount in real time.

[0211] 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 calibration of laser communication terminals, 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 inter-satellite autonomous navigation, intelligent networking, on-orbit adaptive control and other emerging technologies, to further improve the intelligentization, automation and high reliability level of space information network.

[0212] Those skilled in the art know that, in addition to implementing the system, device and each module thereof provided by the present application in the form of pure computer readable program code, the same program can also be implemented in the form of logic gate, switch, special integrated circuit, programmable logic controller and embedded microcontroller, etc. by logically programming the method steps. Therefore, the system, device and each module thereof provided by the present 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.

[0213] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily without conflict.

Claims

1. A laser terminal calibration method based on inter-satellite orbital mutual propagation, characterized in that, include: Step S1: Perform static calibration on the spaceborne laser communication terminal; Step S2: Establish inter-satellite laser communication links; The real-time orbital parameters of the two satellites are transmitted based on the constructed inter-satellite laser communication link; wherein, the real-time orbital parameters include: the satellite's position vector, velocity vector and its covariance information; Step S3: Based on static calibration and real-time track parameters, optimize the calibration benchmark, and use the optimized calibration benchmark to dynamically correct the laser terminal pointing to achieve high-precision calibration; Step S1 includes: performing preliminary optical axis calibration of the laser terminal using a star sensor for autonomous attitude determination or with ground assistance. Step S3 includes: Step S3.1: Perform coordinate transformation on the real-time orbital parameters of the two satellites to unify the real-time orbital parameters of the two satellites into the same coordinate system, and calculate the relative orbital normal vector between the two satellites; Step S3.2: The relative orbital normal vector between the two stars and the static calibration result are fused using a fusion algorithm to dynamically generate a fusion benchmark; Step S3.3: Dynamically correct the laser terminal pointing using the fusion reference to achieve high-precision calibration; Step S3.1 includes: Transform the geocentric inertial frame ECI to the geocentric solid frame ECEF; in, It is a precession-nutation matrix. It is the Greenwich Mean Time rotation matrix. Let be the satellite's position vector in the geocentric inertial coordinate system. This represents the satellite's position vector in the Earth-centered Earth-fixed coordinate system. Based on the position vectors of the local star and the target star in the ECEF coordinate system obtained by the respective transformations, and Therefore, the relative position vector in the geocentric ECEF coordinate system for The three axes of the local orbital coordinate system are defined by the position and velocity direction of the local satellite. The x-axis is along the direction of the orbital velocity: ; The z-axis points in the opposite direction to the Earth's center. ; The y-axis is the normal to the orbital plane, and the right-hand rule applies: ; Rotation matrix R LOC : These are the local orbital coordinate system axes. , , Projected components in the ECEF system; Calculation of relative position vector in local orbital coordinate system: ； Step S3.2 includes: Where ws(k) is the static weight factor; wd(k) is the dynamic weight factor; and ws(k) + wd(k) = 1; P 轨道 This is the relative orbital normal vector between the two stars; As orbital data accumulates, the dynamic weight gradually increases with the number of orbital data fusion iterations, achieving a transition from a static benchmark to a dynamic fusion benchmark; as shown in the following formula, the dynamic weight wd increases linearly with the number of iterations k: Where 0.8 is the upper limit of dynamic weight, the initial values ​​of dynamic weight are wd(0)=0.2 and ws(0)=0.8, α is the growth step size, and k is the number of iterations for track data fusion.

2. The laser terminal calibration method based on inter-satellite orbital mutual transmission according to claim 1, characterized in that, Step S3.3 includes: Based on the current pointing vector P actually measured by the laser terminal 测量 The error vector S(k) is calculated as follows: S(k)=P 测量 -P 融合 Construct a small terminal angle correction amount ΔΦ=[Δφ,Δθ,Δψ] that meets the preset requirements; where Δφ, Δθ, and Δψ represent the small angles that need to be rotated around the terminal's own X, Y, and Z axes to meet the preset requirements, so that the actual direction of the laser beam is aligned with the desired direction as accurately as possible. The influence of the terminal angle correction ΔΦ on the error S(k) is described based on the Jacobian matrix J(k); The optimal correction ΔΦ is calculated using the least squares method: in, It is the transpose of the Jacobian matrix, and its function is 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 precision pointing mechanism to make real-time adjustments according to the optimal correction amount.

3. A laser terminal calibration system based on inter-satellite orbital inter-transmission, characterized in that, include: Module M1: Performs static calibration on the spaceborne laser communication terminal; Module M2: Establishes inter-satellite laser communication links; The real-time orbital parameters of the two satellites are transmitted based on the constructed inter-satellite laser communication link; wherein, the real-time orbital parameters include: the satellite's position vector, velocity vector and its covariance information; Module M3: Based on static calibration and real-time track parameter optimization calibration benchmark, the laser terminal pointing is dynamically corrected using the optimized calibration benchmark to achieve high-precision calibration; The module M1 includes: using a star sensor for autonomous attitude determination or using ground assistance to perform preliminary optical axis calibration of the laser terminal; The module M3 includes: Module M3.1: Performs coordinate transformation on the real-time orbital parameters of the two satellites to unify the real-time orbital parameters of the two satellites into the same coordinate system, and calculates the relative orbital normal vector between the two satellites; Module M3.2: The relative orbital normal vector between the two satellites and the static calibration results are fused using a fusion algorithm to dynamically generate a fusion reference. Module M3.3: Utilizes a fusion reference to dynamically correct the laser terminal pointing, achieving high-precision calibration; The module M3.1 includes: Transform the geocentric inertial frame ECI to the geocentric solid frame ECEF; in, It is a precession-nutation matrix. It is the Greenwich Mean Time rotation matrix. Let be the satellite's position vector in the geocentric inertial coordinate system. This represents the satellite's position vector in the Earth-centered Earth-fixed coordinate system. Based on the position vectors of the local star and the target star in the ECEF coordinate system obtained by the respective transformations, and Therefore, the relative position vector in the geocentric ECEF coordinate system for The three axes of the local orbital coordinate system are defined by the position and velocity direction of the local satellite. The x-axis is along the direction of the orbital velocity: ; The z-axis points in the opposite direction to the Earth's center. ; The y-axis is the normal to the orbital plane, and the right-hand rule applies: ; Rotation matrix R LOC : These are the local orbital coordinate system axes. , , Projected components in the ECEF system; Calculation of relative position vector in local orbital coordinate system: ； The module M3.2 includes: Where ws(k) is the static weight factor; wd(k) is the dynamic weight factor; and ws(k) + wd(k) = 1; P 轨道 This is the relative orbital normal vector between the two stars; As orbital data accumulates, the dynamic weight gradually increases with the number of orbital data fusion iterations, achieving a transition from a static benchmark to a dynamic fusion benchmark; as shown in the following formula, the dynamic weight wd increases linearly with the number of iterations k: Where 0.8 is the upper limit of dynamic weight, the initial values ​​of dynamic weight are wd(0)=0.2 and ws(0)=0.8, α is the growth step size, and k is the number of iterations for track data fusion.

4. The laser terminal calibration system based on inter-satellite orbital mutual transmission according to claim 3, characterized in that, 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 as follows: S(k)=P 测量 -P 融合 Construct a small terminal angle correction amount ΔΦ=[Δφ,Δθ,Δψ] that meets the preset requirements; where Δφ, Δθ, and Δψ represent the small angles that need to be rotated around the terminal's own X, Y, and Z axes to meet the preset requirements, so that the actual direction of the laser beam is aligned with the desired direction as accurately as possible. The influence of the terminal angle correction ΔΦ on the error S(k) is described based on the Jacobian matrix J(k); The optimal correction ΔΦ is calculated using the least squares method: in, It is the transpose of the Jacobian matrix, and its function is 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 precision pointing mechanism to make real-time adjustments according to the optimal correction amount.

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