Inter-satellite link-based laser communication system autonomous pointing method

Abstract

The invention relates to a laser communication system autonomous pointing method based on an inter-satellite link. The method comprises the steps that a laser communication system receives link building target satellite instantaneous orbit parameters transmitted by the inter-satellite link; the laser communication system converts the link establishment target satellite instantaneous orbit parameter transmitted by the inter-satellite link into a singular-point-free average orbit element, and the singular-point-free average orbit element serves as a link establishment target satellite orbit initial value of an inter-satellite link source; the laser communication system selects a link establishment target orbit initial value of an inter-satellite link source according to the instruction or the state, and calculates real-time orbit data of a link establishment target satellite; and the laser communication system automatically calculates a laser beam pointing angle according to the attitude and orbit data of the satellite and the real-time orbit data of the link building target satellite. According to the invention, the dependence of maintaining the inter-satellite laser link on the measurement and control conditions of the ground station can be reduced, and the laser beam pointing precision can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of space optical communication and relates to an autonomous pointing method of a laser communication system based on an intersatellite link. Background Art

[0002] Laser communication systems are communications payloads that use optical signals as carriers to achieve high-speed data transmission between satellites. With the construction of satellite networking constellations centered around intersatellite laser links, the scale of laser communication links has increased exponentially with the number of satellites, posing a significant challenge to the long-term maintenance of the links. Laser communication systems use the attitude and orbital data of the local satellite and the orbital data of the target satellite to control the pointing of the laser beam, driving the actuator to point toward the target satellite. The laser communication system can obtain the local satellite's attitude data in real time through the satellite attitude determination system, and the local satellite's orbital data can be transmitted in real time through the satellite navigation system. Both can operate independently of the ground measurement and control system. However, the orbital data of the target satellite is generally sent to the laser communication system at irregular intervals through ground-based command injection, which is highly dependent on the support conditions of the ground measurement and control system, making it difficult to apply to the autonomous maintenance of large-scale intersatellite laser links in networked constellations. In addition, the satellite is affected by various interference factors such as solar pressure, earth's gravitational perturbation and atmospheric perturbation during flight. The satellite orbit position error calculated recursively based on the initial value of the target satellite orbit noted in the ground command accumulates and increases over time, which will further lead to a decrease in the beam pointing accuracy, making it difficult to meet the high-precision maintenance requirements of the inter-satellite laser link.

[0003] Under intersatellite link conditions, the satellite platform can continuously or intermittently receive the instantaneous orbital data of the target satellite used by the laser communication system via a laser or microwave communication link. This intersatellite link-based target orbital data is not only highly accurate but also independent of ground-based measurement and control conditions. The laser communication system can use this intersatellite link-based target satellite orbital data, combined with the satellite's attitude and orbital data, to autonomously calculate the laser beam's pointing direction, thereby improving the autonomy and accuracy of intersatellite laser link maintenance. Summary of the Invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and propose an autonomous pointing method for a laser communication system based on an inter-satellite link. The laser communication system realizes autonomous pointing according to the orbit data of the link-building target satellite transmitted by the inter-satellite link, which not only reduces the dependence on ground measurement and control conditions, but also improves the pointing accuracy of the laser beam.

[0005] The solution to the technical problem of the present invention is: an autonomous pointing method for a laser communication system based on an intersatellite link, comprising the following steps:

[0006] The laser communication system receives the instantaneous orbit parameters of the link-building target satellite transmitted by the intersatellite link;

[0007] The laser communication system converts the instantaneous orbit parameters of the target satellite transmitted by the intersatellite link into the average orbit elements without singular points, which serve as the initial orbit values ​​of the target satellite from the intersatellite link.

[0008] The laser communication system selects and uses the initial orbit value of the target satellite for link establishment from the intersatellite link according to the command or status, and calculates the real-time orbit data of the target satellite for link establishment;

[0009] The laser communication system autonomously calculates the laser beam pointing angle based on the attitude and orbit data of the satellite and the real-time orbit data of the target satellite.

[0010] Furthermore, the instantaneous orbital parameters of the target satellite for establishing a link transmitted by the intersatellite link include the following two cases:

[0011] (1) Satellite orbit epoch time, initial values ​​of instantaneous position vector and instantaneous velocity vector of the target satellite in the J2000 inertial coordinate system;

[0012] (2) The satellite orbit epoch time and the satellite orbit parameters in Kepler form; the satellite orbit parameters in Kepler form include the semi-major axis, eccentricity, orbit inclination, right ascension of the ascending node, argument of perigee and mean anomaly.

[0013] Furthermore, the laser communication system converts the instantaneous orbital parameters of the target satellite for link establishment transmitted by the intersatellite link into the average orbital elements without singularities. First, the instantaneous orbital parameters of the satellite are converted into the average orbital elements, and then the average orbital elements are converted into the average orbital elements without singularities as the initial values ​​of the orbit of the target satellite for link establishment sourced from the intersatellite link.

[0014] Furthermore, the method for converting the average orbital elements into the average orbital elements without singular points is:

[0015]

[0016]

[0017] Where a0, e0, i0, Ω0, ω0, and M0 represent the satellite semi-major axis, eccentricity, orbit inclination, right ascension of the ascending node, argument of perigee, and mean anomaly in the sense of the mean orbit, respectively; represents the product of eccentricity and the cosine of the argument of perigee, represents the product of eccentricity and the sine of the argument of perigee, represents the sum of the argument of perigee and the mean anomaly; R e is the radius of the Earth; after conversion, define represents the mean number of orbital elements without singularities.

[0018] Furthermore, the laser communication system selects to use the initial value of the link establishment target orbit from the intersatellite link according to the instruction or status, including the following situations:

[0019] After receiving the target satellite orbit parameters, the laser communication system is set to automatically use the data to start the calculation process; or, it is set to first store the target satellite orbit parameters and then start the calculation process by sending a command enable through the ground measurement and control station.

[0020] Furthermore, the calculating of the real-time orbit data of the link-building target satellite includes calculating an extrapolated instantaneous position vector and an extrapolated instantaneous velocity vector of the link-building target satellite in a J2000 inertial coordinate system.

[0021] Furthermore, the extrapolated instantaneous position vector and the extrapolated instantaneous velocity vector are calculated as follows:

[0022] Let t k Indicates the time of pointing angle calculation, calculate t k The long-term term a of the semi-major axis of the moment orbit:

[0023]

[0024] Calculate t k Secular term of orbital inclination

[0025]

[0026] Calculate t k Long-term term of right ascension of ascending node

[0027]

[0028] Where J2 represents the second-order harmonic coefficient, μ E represents the Earth's gravitational constant, t0 is the satellite orbit epoch time;

[0029] Calculate t k Time long-term items

[0030]

[0031] Calculate t k Time long-term items

[0032]

[0033] Calculate t k Time long-term items

[0034]

[0035] Calculate t k The instantaneous semi-major axis a at time:

[0036]

[0037] Calculate t k The instantaneous orbital inclination at time i m :

[0038]

[0039] Calculate t k The right ascension root number Ω of the instantaneous ascending node at the moment:

[0040]

[0041] Among them, the range of Ω is Ω∈[-π,π);

[0042] Calculate t k Moment ξ:

[0043]

[0044] Calculate t k The instantaneous η:

[0045]

[0046] Calculate t k The instantaneous mean anomaly M at time:

[0047]

[0048] Among them, the range of M is M∈[-π,π);

[0049] Calculate t k The instantaneous true anomaly f:

[0050]

[0051] Among them, the range of f is f∈[-π,π);

[0052] Calculate t k Instantaneous latitude argument u at time:

[0053]

[0054] Where, e represents t k The instantaneous orbital eccentricity at time t is calculated as The range of u is u∈[-π,π);

[0055] Calculate t kPosition vector of the target satellite in the J2000 inertial coordinate system at the moment of link establishment

[0056]

[0057] Where r represents the instantaneous distance from the center of the earth, which is calculated as r = a(1-ξcosu+ηsinu);

[0058] Calculate t k Velocity vector of target satellite in J2000 inertial system at the moment of link establishment

[0059]

[0060] Furthermore, the laser communication system autonomously calculates the laser beam pointing angle based on the attitude and orbit data of the local satellite and the real-time orbit data of the target satellite to be linked, including: calculating the laser beam pointing angle based on the angular velocity of the local satellite's center of mass coordinate system relative to the J2000 inertial coordinate system, the attitude angle of the local satellite's center of mass coordinate system relative to the local satellite's orbital coordinate system, the position vector and velocity vector of the local satellite in the J2000 inertial coordinate system, and the position velocity of the target satellite to be linked in the J2000 inertial coordinate system.

[0061] Furthermore, the method for calculating the laser beam pointing angle is specifically as follows:

[0062] Calculate t k The attitude transformation matrix from the local orbit coordinate system os to the local center of mass coordinate system b at time

[0063] Where φ, θ, and γ represent the roll angle, pitch angle, and yaw angle of the local satellite's center of mass coordinate system relative to the local satellite's orbital coordinate system, respectively;

[0064] Calculate t k The attitude transformation matrix of the satellite orbital coordinate system os relative to the J2000 inertial coordinate system at time

[0065] Among them, i s represents the orbital inclination of the local star, Ω s Indicates the right ascension of the ascending node of this star, u s Represents the latitude argument of this star;

[0066] Calculate t k The projection vector of the laser pointing vector in the local satellite mass center coordinate system at this moment is

[0067]

[0068] in, Indicates t k Position vector projection of the local satellite in the J2000 inertial coordinate system at this moment;

[0069] The laser beam pointing angle is defined as the pointing vector and the satellite center of mass coordinate system +X b O+Y b Plane angle, and close to +Z b The direction sign is positive, and the azimuth of the laser beam is defined as the direction vector at +X b O+Y b Planar projection and +X b The angle between the axes is positive if the rotation sign is counterclockwise; where +X b 、+Y b 、+Z b and O represent the positive direction of X axis, Y axis, Z axis and the origin of the coordinate system of the satellite center of mass coordinate system respectively; calculate t k The laser beam pointing to the elevation angle β in the satellite's mass center coordinate system at the moment b :

[0070]

[0071] Among them, β b The range is

[0072] Calculate t k The laser beam pointing azimuth angle α in the satellite's center of mass coordinate system at the moment b :

[0073]

[0074] Among them, α b The range is α b ∈[-π,π); Represents vectors Projected components in the satellite's barycentric coordinate system.

[0075] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of an autonomous pointing method for an intersatellite link-based laser communication system.

[0076] The beneficial effects of the present invention compared with the prior art are:

[0077] By utilizing the method of the present invention, the laser communication system realizes autonomous pointing of the laser communication system by using the instantaneous orbit data of the target satellite for link establishment transmitted through the inter-satellite link, combined with the attitude and orbit data of the local satellite. This not only reduces the dependence of maintaining the inter-satellite laser link on the measurement and control conditions of the ground station, but also effectively improves the pointing accuracy of the laser beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 This is a flow chart of an autonomous pointing method for a laser communication system based on an intersatellite link according to the present invention;

[0079] Figure 2 This is a simulation diagram of the pointing error of a dual-star laser communication system at an 800km orbital altitude according to an embodiment of the present invention. DETAILED DESCRIPTION

[0080] The present invention will be further described below with reference to specific drawings.

[0081] The laser communication system calculates the laser beam pointing angle using the local satellite's attitude and orbit data, as well as the orbit data of the target satellite, and drives the actuator to the target position, achieving laser beam pointing control. The satellite platform transmits the local satellite's attitude and orbit data to the laser communication system via a bus, serving as a spatiotemporal reference for laser beam pointing calculations. The initial orbit value of the target satellite is transmitted to the laser communication system via an intersatellite link, where it is converted into average orbital elements and recursively calculated into the real-time orbit data of the target satellite. Finally, combining the local satellite's attitude and orbit data with the target satellite's orbit data, the laser communication system performs autonomous pointing calculations.

[0082] Specifically, the present invention proposes an autonomous pointing method for a laser communication system based on an intersatellite link, such as Figure 1 As shown, the following steps are included:

[0083] S1, the laser communication system receives the instantaneous orbit parameters of the target satellite for link establishment transmitted by the inter-satellite link;

[0084] S2. The laser communication system converts the instantaneous orbital parameters of the target satellite transmitted by the intersatellite link into the average orbital elements without singular points, which serve as the initial orbital values ​​of the target satellite for the intersatellite link.

[0085] S3. The laser communication system selects and uses the initial orbit value of the link establishment target satellite from the intersatellite link source according to the instruction or status, and calculates the real-time orbit data of the link establishment target satellite;

[0086] S4. The laser communication system autonomously calculates the laser beam pointing angle based on the attitude and orbit data of the satellite and the real-time orbit data of the target satellite.

[0087] The laser communication system in step S1 receives the instantaneous orbit parameters of the target satellite for link establishment transmitted by the intersatellite link, including the following two situations:

[0088] (1) Satellite orbit epoch time, initial values ​​of the instantaneous position vector and instantaneous velocity vector of the target satellite in the J2000 inertial coordinate system (i.e., the instantaneous position vector and velocity vector calculated in real time on the target satellite);

[0089] (2) The satellite orbit epoch time and the satellite orbit parameters in Kepler form; the satellite orbit parameters in Kepler form include the semi-major axis, eccentricity, orbit inclination, right ascension of the ascending node, argument of perigee and mean anomaly.

[0090] The present invention takes the instantaneous J2000 inertial coordinate system position vector and velocity vector of the target satellite for establishing a link through intersatellite link transmission as an example to illustrate the implementation method of the invention.

[0091] The laser communication system described in step S1 converts the instantaneous orbital parameters of the target satellite for link establishment, transmitted via the intersatellite link, into singularity-free average orbital elements. The target satellite data for link establishment, transmitted via the intersatellite link, includes the initial values ​​of the instantaneous position vector and the initial values ​​of the instantaneous velocity vector at epoch t0 of the satellite's orbit and in the J2000 inertial coordinate system. First, the initial values ​​of the instantaneous position vector and the initial values ​​of the instantaneous velocity vector of the target satellite for link establishment in the J2000 coordinate system are converted into average orbital elements according to a common method. Furthermore, these conversions are made into singularity-free orbital elements, taking into account the small eccentricity of the satellite's orbit, to avoid numerical singularities in the orbit calculation process.

[0092] The calculation method for converting the average orbital elements into the average orbital elements without singular points is as follows:

[0093]

[0094] Where a0, e0, i0, Ω0, ω0, and M0 represent the satellite semi-major axis, eccentricity, orbit inclination, right ascension of the ascending node, argument of perigee, and mean anomaly in the sense of the mean orbit, respectively; represents the product of eccentricity and the cosine of the argument of perigee, represents the product of eccentricity and the sine of the argument of perigee, represents the sum of the argument of perigee and the mean anomaly; R e =6378.137km represents the radius of the earth; after conversion, the definition is represents the mean number of orbital elements without singularities.

[0095] In step S3, the laser communication system selects to use the initial value of the link establishment target orbit from the intersatellite link source according to the instruction or status, including the following situations:

[0096] After receiving the target satellite's orbital parameters, the laser communication system can be set to automatically use this data to start the calculation process. Alternatively, it can be set to first store the target satellite's orbital parameters and then start the calculation process by sending a command from the ground control station.

[0097] Furthermore, the calculation of the real-time orbit data of the target satellite in step S3 includes calculating the extrapolated instantaneous position vector and the extrapolated instantaneous velocity vector of the target satellite in the J2000 inertial coordinate system. The specific calculation process is as follows:

[0098] Let t k Indicates the time of pointing angle calculation, calculate t k The long-term term a of the semi-major axis of the moment orbit:

[0099]

[0100] Calculate t k Secular term of orbital inclination

[0101]

[0102] Calculate t k Long-term term of right ascension of ascending node

[0103]

[0104] Among them, J2=0.00108268 represents the second-order harmonic coefficient, μ E =3.986004418×10 14 m 3 / s 2 represents the Earth's gravitational constant, t0 is the satellite orbit epoch time;

[0105] Calculate t k Time long-term items

[0106]

[0107] Calculate t k Time long-term items

[0108]

[0109] Calculate t k Time long-term items

[0110]

[0111] Calculate t k The instantaneous semi-major axis a at time:

[0112]

[0113] Calculate t k The instantaneous orbital inclination at time i m :

[0114]

[0115] Calculate t k The right ascension root number Ω of the instantaneous ascending node at the moment:

[0116]

[0117] Here, the range of Ω is Ω∈[-π,π).

[0118] Calculate t k Moment ξ:

[0119]

[0120] Calculate t k The instantaneous η:

[0121]

[0122] Calculate t k The instantaneous mean anomaly M at time:

[0123]

[0124] Among them, the range of M is M∈[-π,π).

[0125] Calculate t k The instantaneous true anomaly f:

[0126]

[0127] Here, the range of f is f∈[-π,π).

[0128] Calculate t k Instantaneous latitude argument u at time:

[0129] u=arctan(-η,ξ)+f (20)

[0130] Where, e represents t k The instantaneous orbital eccentricity at time t is calculated as The range of u is u∈[-π,π).

[0131] Calculate t k The position vector of the target satellite in the J2000 inertial coordinate system i at time

[0132]

[0133] Wherein, r represents the instantaneous distance from the center of the earth, and the calculation method is r=a(1-ξcosu+ηsinu).

[0134] Calculate t k Velocity vector of target satellite in J2000 inertial system at the moment of link establishment

[0135]

[0136] In step S4, the laser communication system autonomously calculates the laser beam pointing angle based on the attitude and orbit data of the local satellite and the real-time orbit data of the target satellite. This includes calculating the laser beam pointing angle based on the angular velocity of the local satellite's center of mass coordinate system relative to the J2000 inertial coordinate system, the attitude angle of the local satellite's center of mass coordinate system relative to the local satellite's orbital coordinate system, the position vector and velocity vector of the local satellite in the J2000 inertial coordinate system, and the position and velocity of the target satellite in the J2000 inertial coordinate system. The specific calculation process is as follows:

[0137] Calculate t k The attitude transformation matrix from the local orbit coordinate system os to the local center of mass coordinate system b at time

[0138] Among them, φ, θ, and γ represent the roll angle, pitch angle, and yaw angle of the local satellite's center of mass coordinate system relative to the local satellite's orbital coordinate system, respectively.

[0139] Calculate t k The attitude transformation matrix of the satellite orbital coordinate system os relative to the J2000 inertial coordinate system at time

[0140] Among them, i s Indicates the inclination of the local star's orbit. Ω s Indicates the right ascension of the ascending node of this star, u s Represents the latitude argument of this star.

[0141] Calculate t k The projection vector of the laser pointing vector in the local satellite mass center coordinate system at this moment is

[0142]

[0143] in, Indicates t kThe position vector projection of this satellite in the J2000 inertial coordinate system at this moment can be obtained by outputting the orbital parameters of the satellite navigation system carried by this satellite.

[0144] The laser beam pointing angle is defined as the pointing vector and the satellite center of mass coordinate system +X b O+Y b Plane angle, and close to +Z b The direction sign is positive. The azimuth of the laser beam is defined as the direction of the pointing vector at +X b O+Y b Planar projection and +X b The angle between the axes is positive if the rotation sign is counterclockwise; where +X b 、+Y b 、+Z b and O represent the positive direction of the X axis, the positive direction of the Y axis, the positive direction of the Z axis and the origin of the coordinate system of the satellite's center of mass, respectively. k The laser beam pointing to the elevation angle β in the satellite's mass center coordinate system at the moment b :

[0145]

[0146] Among them, β b The range is

[0147] Calculate t k The laser beam pointing azimuth angle α in the satellite's center of mass coordinate system at the moment b :

[0148]

[0149] Among them, α b The range is α b ∈[-π,π); Represents vectors Projected components in the satellite's barycentric coordinate system.

[0150] At this point, the autonomous pointing calculation process of the laser communication system proposed in the present invention is completed.

[0151] The method of the present invention can be applied to realize autonomous pointing calculation of a laser communication system under the condition that an intersatellite link continuously or discontinuously transmits orbital parameters of a link-building target satellite.

[0152] Example 1

[0153] The effectiveness of the method of the present invention is illustrated by simulating the pointing direction of a laser communication system between two satellites at an altitude of 800 km. The simulation parameters are set as follows: the semi-major axis of the local satellite orbit carrying the laser communication system is 7178.126 km, the orbital eccentricity is 0.0015, the orbital inclination is 85.16°, the orbital right ascension of the ascending node is 30.05°, the perigee argument is 45.17°, and the mean anomaly is 25.15°. The semi-major axis of the orbit of the target satellite for laser link establishment is 7178.141 km, the orbital eccentricity is 0.00184, the orbital inclination is 85.07°, the orbital right ascension of the ascending node is 30.13°, the perigee argument is 55.39°, and the mean anomaly is 35.02°. The attitude angles of the three axes of the local satellite's center of mass coordinate system relative to the orbital coordinate system are all set to 0°. The pointing angle of the laser communication system is described in the local satellite's center-of-mass coordinate system. The period of the target satellite orbit for receiving the intersatellite link transmission by the laser communication system is 600 seconds. The simulation step size is set to 1 second, and the total simulation time is set to 43200 seconds.

[0154] like Figure 2 The simulation results shown are as follows: the average azimuth error and the average elevation error of the laser beam pointing system of the method of the present invention are 0.025° and 0.013° respectively; the average azimuth error and the average elevation error of the laser beam pointing calculated by the ground injection target star orbit method are -0.072° and 0.019° respectively; and the error fluctuation range of the method of the present invention is significantly smaller than that of the traditional method, which effectively improves the beam pointing accuracy of the laser communication system.

[0155] The present application provides a computer-readable storage medium storing computer instructions. When the computer instructions are executed on a computer, the computer executes Figure 1 The method described.

[0156] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage and optical storage, etc.) that contain computer-usable program code.

[0157] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0158] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0159] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0160] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

[0161] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An autonomous pointing method for a laser communication system based on an intersatellite link, characterized in that: The following steps are involved: The laser communication system receives the instantaneous orbit parameters of the link-building target satellite transmitted by the intersatellite link; The laser communication system converts the instantaneous orbit parameters of the target satellite transmitted by the intersatellite link into the average orbit elements without singular points, which serve as the initial orbit values ​​of the target satellite from the intersatellite link. The laser communication system selects and uses the initial orbit value of the target satellite for link establishment from the intersatellite link according to the command or status, and calculates the real-time orbit data of the target satellite for link establishment; The laser communication system autonomously calculates the laser beam pointing angle based on the attitude and orbit data of the satellite and the real-time orbit data of the target satellite.

2. The autonomous pointing method of an intersatellite link-based laser communication system according to claim 1, characterized in that: The instantaneous orbit parameters of the target satellite for establishing a link transmitted by the intersatellite link include the following two cases: (1) Satellite orbit epoch time, initial values ​​of instantaneous position vector and instantaneous velocity vector of the target satellite in the J2000 inertial coordinate system; (2) The satellite orbit epoch time and the satellite orbit parameters in Kepler form; the satellite orbit parameters in Kepler form include the semi-major axis, eccentricity, orbit inclination, right ascension of the ascending node, argument of perigee and mean anomaly.

3. The autonomous pointing method for an intersatellite link-based laser communication system according to claim 1, characterized in that: The laser communication system converts the instantaneous orbital parameters of the target satellite for link establishment transmitted by the intersatellite link into the average orbital elements without singular points. First, the instantaneous orbital parameters of the satellite are converted into the average orbital elements, and then the average orbital elements are further converted into the average orbital elements without singular points as the initial values ​​of the orbit of the target satellite for link establishment sourced from the intersatellite link.

4. The autonomous pointing method for an intersatellite link-based laser communication system according to claim 3, characterized in that: The method to convert the mean orbital elements into the mean orbital elements without singularity is: Where a0, e0, i0, Ω0, ω0, and M0 represent the satellite semi-major axis, eccentricity, orbit inclination, right ascension of the ascending node, argument of perigee, and mean anomaly in the sense of the mean orbit, respectively; represents the product of eccentricity and the cosine of the argument of perigee, represents the product of eccentricity and the sine of the argument of perigee, represents the sum of the argument of perigee and the mean anomaly; R e is the radius of the Earth; after conversion, define represents the mean number of orbital elements without singularities.

5. The autonomous pointing method for an intersatellite link-based laser communication system according to claim 1, characterized in that: The laser communication system selects and uses the initial value of the link establishment target orbit from the intersatellite link according to the instruction or status, This includes the following situations: After receiving the target satellite orbit parameters, the laser communication system is set to automatically use the data to start the calculation process; or, it is set to first store the target satellite orbit parameters and then start the calculation process by sending a command enable through the ground measurement and control station.

6. The autonomous pointing method for an intersatellite link-based laser communication system according to claim 4, characterized in that: The calculating of the real-time orbit data of the link-building target satellite includes calculating the extrapolated instantaneous position vector and the extrapolated instantaneous velocity vector of the link-building target satellite in the J2000 inertial coordinate system.

7. The autonomous pointing method of an intersatellite link-based laser communication system according to claim 6, characterized in that: The extrapolated instantaneous position vector and the extrapolated instantaneous velocity vector are calculated as follows: Let t k Indicates the time of pointing angle calculation, calculate t k Secular term of the semi-major axis of the moment orbit Calculate t k Secular term of orbital inclination Calculate t k Long-term term of right ascension of ascending node Where J2 represents the second-order harmonic coefficient, μ E represents the Earth's gravitational constant, t0 is the satellite orbit epoch time; Calculate t k Time long-term items Calculate t k Time long-term items Calculate t k Time long-term items Calculate t k The instantaneous semi-major axis a at time: Calculate t k The instantaneous orbital inclination at time i m : Calculate t k The right ascension root number Ω of the instantaneous ascending node at the moment: Among them, the range of Ω is Ω∈[-π,π); Calculate t k Moment ξ: Calculate t k The instantaneous η: Calculate t k The instantaneous mean anomaly M at time: Among them, the range of M is M∈[-π,π); Calculate t k The instantaneous true anomaly f: Among them, the range of f is f∈[-π,π); Calculate t k Instantaneous latitude argument u at time: u=arctan(-η,ξ)+f (20) Where, e represents t k The instantaneous orbital eccentricity at time t is calculated as The range of u is u∈[-π,π); Calculate t k Position vector of the target satellite in the J2000 inertial coordinate system at the moment of link establishment Where r represents the instantaneous distance from the center of the earth, which is calculated as r = a(1-ξcosu+ηsinu); Calculate t k Velocity vector of target satellite in J2000 inertial system at the moment of link establishment 8. The autonomous pointing method for an intersatellite link-based laser communication system according to claim 7, characterized in that: The laser communication system autonomously calculates the laser beam pointing angle based on the attitude and orbit data of the local satellite and the real-time orbit data of the target satellite to be linked, including: calculating the laser beam pointing angle based on the angular velocity of the local satellite's center of mass coordinate system relative to the J2000 inertial coordinate system, the attitude angle of the local satellite's center of mass coordinate system relative to the local satellite's orbital coordinate system, the position vector and velocity vector of the local satellite in the J2000 inertial coordinate system, and the position and velocity of the target satellite to be linked in the J2000 inertial coordinate system.

9. The autonomous pointing method for an intersatellite link-based laser communication system according to claim 8, characterized in that: The method for calculating the laser beam pointing angle is specifically as follows: Calculate t k The attitude transformation matrix from the local orbit coordinate system os to the local center of mass coordinate system b at time Where φ, θ, and γ represent the roll angle, pitch angle, and yaw angle of the local satellite's center of mass coordinate system relative to the local satellite's orbital coordinate system, respectively; Calculate t k The attitude transformation matrix of the satellite orbital coordinate system os relative to the J2000 inertial coordinate system at time Among them, i s represents the orbital inclination of the local star, Ω s Indicates the right ascension of the ascending node of this star, u s Represents the latitude argument of this star; Calculate t k The projection vector of the laser pointing vector in the local satellite mass center coordinate system at this moment is in, Indicates t k Position vector projection of the local satellite in the J2000 inertial coordinate system at this moment; The laser beam pointing angle is defined as the pointing vector and the satellite center of mass coordinate system +X b O+Y b Plane angle, and close to +Z b The direction sign is positive, and the azimuth of the laser beam is defined as the direction vector at +X b O+Y b Planar projection and +X b The angle between the axes is positive if the rotation sign is counterclockwise; where +X b 、+Y b 、+Z b and O represent the positive direction of X axis, Y axis, Z axis and the origin of the coordinate system of the satellite center of mass coordinate system respectively; calculate t k The laser beam pointing to the elevation angle β in the satellite's mass center coordinate system at the moment b : Among them, β b The range is Calculate t k The laser beam pointing azimuth angle α in the satellite's center of mass coordinate system at the moment b : Among them, α b The range is α b ∈[-π,π); Represents vectors Projected components in the satellite's barycentric coordinate system.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are implemented.

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