Method for inter-satellite laser terminal acquisition without coarse acquisition

Abstract

The application discloses an intersatellite laser terminal acquisition method without a coarse acquisition tracking device, which comprises the following steps: calculating and adjusting a satellite platform to a target attitude according to position information of a target satellite and a satellite and a real-time value of an attitude of the satellite, simultaneously determining a target value of a light axis pointing vector; dividing an acquisition uncertain area (a parent area) into a plurality of sub-areas, and numbering according to a rectangular spiral line track; pointing the light axis to a first sub-area to perform beam scanning, detecting a light spot intensity to identify an effective light spot, and calculating an angle of the pointing target vector according to a miss distance and a galvanometer angle; if a preset acquisition frequency threshold is reached, the scanning range is reduced and the scanning is continued; when the effective light spot is detected again in the reduced scanning area, it is determined that the acquisition is completed and a tracking state is entered; if the acquisition is not completed after all the sub-areas are scanned, the acquisition is ended. The application realizes high-efficiency and accurate acquisition of the intersatellite laser terminal under the condition of the coarse acquisition tracking device, and improves the reliability and stability of intersatellite communication.

Description

Technical Field

[0001] This invention relates to the field of spacecraft communication technology, specifically to an inter-satellite laser terminal acquisition method without coarse tracking devices. Background Technology

[0002] As a new type of national information infrastructure, space-based information network systems possess unique advantages in covering all regions, airspace, and sea areas, and can be widely applied in various fields such as remote sensing monitoring, weather forecasting, marine development, and military operations. Composed of low-Earth orbit (LEO) and medium-to-high Earth orbit (MEO) constellations, they achieve efficient data transmission through inter-satellite laser links, becoming the mainstream technology for future space-based communications. However, the implementation of inter-satellite laser links faces technical challenges, particularly the effective acquisition, alignment, and tracking of laser beams.

[0003] Traditional laser terminal designs include coarse and fine tracking devices, and the corresponding acquisition strategies are designed for other designs with coarse tracking devices. Currently, there are reports of laser terminals without coarse tracking devices, such as the paper Riesing, Kathleen M. et al., “On-orbit results of pointing, acquisition, and tracking for the TBIRD CubeSat mission.” LASE (2023). This paper introduces a method using a satellite platform to achieve beam pointing and track the communication link between the satellite and the ground, but it does not describe its acquisition strategy. The literature R. Ruddenklau and G. Schitter, "Optimization of acquisition patterns for establishing interCubeSat optical communications," in Journal of Optical Communications and Networking, vol. 16, no. 8, pp. 814-821, August 2024, doi:10.1364 / JOCN.518004, introduces a method using a satellite platform to perform a rectangular spiral skip scan in an uncertain region. Each step of the satellite platform involves the laser terminal scanning within a small area. The literature only provides simulation analysis of the scanning pattern and compares the acquisition probabilities under different scanning patterns, without providing specific acquisition strategies. Patent literature CN 116318394, "A beacon-free composite scanning method for a lightweight laser communication terminal," proposes a composite scanning method using a two-dimensional turntable and a fine-tracking galvanometer. The two-dimensional turntable performs a grating spiral skip scan, and the fine-tracking galvanometer performs a grating scan within a sub-region. This patent only describes the scanning method; its performance and stability in practical applications still require further evaluation and optimization.

[0004] Therefore, although significant progress has been made in the construction and application of space-based information network systems, many technical challenges remain in the implementation of laser links and the acquisition, alignment, and tracking of laser beams. Thus, researching and developing more advanced and efficient laser terminals and their acquisition strategies is of great significance for promoting the further development of space-based information network systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes an inter-satellite laser terminal acquisition method without a coarse tracking device, aiming to solve the problem of how an inter-satellite laser terminal can efficiently and accurately acquire target satellites without the assistance of a coarse tracking device. This invention solves the problem of missed scans caused by attitude drift during large-scale scanning by dividing the uncertain region (parent region) into several sub-regions; it solves the problem of target angle ambiguity caused by rapid scanning by calculating the target angle using detector miss distance and fine tracking angle; it further improves target positioning accuracy by averaging multiple target angle calculations; and it further improves the acquisition probability by gradient reduction of the uncertain region.

[0006] The technical solution of the present invention is as follows:

[0007] An inter-satellite laser terminal acquisition method without coarse tracking device, characterized by comprising the following steps:

[0008] S1. Attitude Calculation and Adjustment:

[0009] Based on the position information of the target satellite and the current satellite, as well as the real-time attitude value of the current satellite, calculate the target values ​​of yaw angle, pitch angle, and roll angle required for the satellite platform to adjust to the target attitude value; at the same time, calculate the target value of the optical axis pointing vector.

[0010] Adjust the satellite platform's attitude to converge to the target attitude value, and calculate the real-time pointing vector of the optical axis;

[0011] S2. Optical axis pointing and capture area division:

[0012] Receive the target vector and real-time vector pointing to the optical axis, calculate the difference between the pointing vectors, and adjust the angle of the laser terminal so that the optical axis points to the uncertain capture area, i.e. the geometric center of the capture parent area;

[0013] Based on the size of the capture parent region, the preset capture sub-region size, and the capture sub-region overlap factor, the capture parent region is divided into multiple sub-regions, and each sub-region is numbered and sorted according to the rectangular spiral trajectory.

[0014] S3. Beam Scanning and Capture:

[0015] The laser terminal uses a precision tracking device to point the optical axis to the geometric center of the first sub-region and begins to perform beam scanning;

[0016] During the scanning process, the intensity of the light spot is detected by a tracking detector. When the intensity of the light spot exceeds a preset threshold, it is considered a valid light spot, and the amount of the light spot missing the target and the current angle of the galvanometer are recorded.

[0017] Based on the miss distance and the galvanometer angle, calculate the angle of the vector pointing towards the target;

[0018] If the number of captures reaches the preset threshold, the average value of the effective spot angle pointing to the target is calculated and used as the new center of the beam scan, and the scan coverage is reduced to 1 / 4 of the current sub-region.

[0019] S4. Capture Judgment and Control:

[0020] Continue beam scanning within the reduced scanning area;

[0021] If the tracking detector detects a valid light spot again and the light spot intensity exceeds the preset threshold, it is determined that the capture is complete and the tracking state is entered.

[0022] If no valid spot is detected within the preset capture statistics period, check if there are any unscanned sub-regions.

[0023] If there are unscanned sub-regions, the beam scanning process of step S3 is repeated, pointing to the geometric center of the next sub-region.

[0024] If all sub-regions have been scanned but the capture is not yet complete, then the capture operation ends.

[0025] Furthermore, in step S1, the attitude adjustment of the satellite platform is achieved through the attitude control system on the satellite, which includes thrusters, reaction wheels or other attitude control mechanisms.

[0026] Furthermore, in step S2, each sub-region is numbered and sorted according to the rectangular spiral trajectory. Specifically, the sub-region whose geometric center coincides with the geometric center of the parent region is numbered 1. Then, each sub-region is assigned a number 1, 2, 3...M according to the rectangular spiral trajectory, where M is the total number of sub-regions divided by the captured parent region.

[0027] Furthermore, step S3 also includes: setting scanning parameters for each sub-region, including the azimuth axis scanning range Xr, i.e., the scanning angle range on the horizontal plane; the pitch axis scanning azimuth Yr, i.e., the scanning angle on the vertical plane; the scanning step Stp, i.e., the angle increment of each scan; and the scanning step interval StpTm, i.e., the time interval between two scans; and setting capture parameters, including the capture spot intensity threshold Pthrh, the capture statistical period ΔTm, the capture count threshold Nthrh, i.e., how many effective spot detections are needed to consider capture successful, and the capture timer CapTm, used to record the duration of each scan attempt.

[0028] Furthermore, in step S3, based on the off-target amount (Δθ) xmn ,Δθ ymn ) and galvanometer angle (θ) fxmn ,θ fymnThe angle pointing towards the target vector is calculated using the following formula:

[0029] θ fsdmn =θ fxmn +Δθ xmn

[0030] θ fydmn =θ fymn +Δθ ymn

[0031] In the formula, θ fxdmn θ is the X-axis angle of the target vector calculated for the nth effective light spot within sub-region m. fydmn The y-axis angle of the target vector is calculated for the nth effective light spot within sub-region m, Δθ. xmn Let Δθ be the X-axis miss distance of the nth effective spot within sub-region m. ymn Let θ be the Y-axis miss distance of the nth effective spot within sub-region m. fxmn Let θ be the X-axis angle of the galvanometer corresponding to the nth effective light spot within sub-region m. fymn The angle of the galvanometer corresponding to the nth effective spot in sub-region m is given.

[0032] Furthermore, in step S3, the average value of the effective light spot's pointing vector angle towards the target is calculated using the following formula:

[0033]

[0034] In the formula, The average angle of the target vector along the X-axis. Ncap is the average angle of the target vector along the Y-axis, and Ncap is the number of captures.

[0035] Furthermore, in step S4, the preset acquisition statistics period is determined based on the relative motion speed between satellites and the performance parameters of the laser terminal.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1) By dividing the uncertain region into several sub-regions and using a rectangular spiral trajectory for scanning, the problem of missed scans caused by attitude drift during large-scale scanning is solved.

[0038] 2) By using the spot miss distance measured by the detector and the current angle of the galvanometer, the angle of the vector pointing to the target is calculated, which solves the problem of target angle ambiguity caused by rapid scanning.

[0039] 3) By repeatedly calculating the target angle and taking the average value, the target positioning accuracy was further improved.

[0040] 4) After capturing an effective spot, the average value of the vector angle pointing to the target is used as the beam scanning center, and the scanning coverage is reduced, which further improves the capture probability.

[0041] 5) This invention solves the problem of how an inter-satellite laser terminal can efficiently and accurately capture a target satellite without the assistance of a coarse acquisition device, and achieves precise alignment and capture of the target satellite, providing reliable technical support for inter-satellite laser communication. Attached Figure Description

[0042] Figure 1 Sub-region distribution diagram

[0043] Figure 2 This is a flowchart of the inter-satellite laser terminal acquisition method without coarse tracking device according to the present invention. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the scope of protection of the present invention.

[0045] This embodiment proposes an inter-satellite laser terminal acquisition method without coarse tracking devices, which achieves efficient and accurate acquisition of target satellites. Figure 2 This is a flowchart of the inter-satellite laser terminal acquisition method without a coarse-tracking device according to the present invention. As shown in the figure, an inter-satellite laser terminal acquisition method without a coarse-tracking device includes the following steps:

[0046] Step 1: The satellite platform calculates the target values ​​for the satellite's attitude adjustment and the target values ​​for the optical axis pointing vector of the laser terminal;

[0047] In inter-satellite laser communication, to ensure the laser beam accurately points to and captures the target satellite, it is first necessary to calculate the target attitude adjustment values ​​of the launching satellite (the local satellite) and the target optical axis pointing vector value of the laser terminal. This is the foundation for laser communication capture and tracking. Furthermore, the calculation period must be longer than the platform's attitude control stabilization time. This is because the satellite platform's attitude adjustment is a dynamic process that requires time to reach a stable state. If the calculation period is too short, the satellite platform may begin executing the laser communication task before stabilizing to the target attitude, thus affecting the accuracy and reliability of the communication.

[0048] These attitude target values ​​are calculated based on the positional relationship between the target satellite and the local satellite, as well as the current real-time attitude value of the local satellite. This allows for the calculation of the target attitude that the satellite platform needs to adjust to, so that the laser terminal can accurately point at the target satellite.

[0049] The target values ​​for attitude adjustment of this satellite include (α) d ,β d ,γ d ), that is, the target yaw angle α.d Target pitch angle β d and roll angle target value γ d .

[0050] The optical axis pointing vector target value includes (Az) d El d ), that is, the target angle Az pointing to the vector azimuth. d Pointing vector pitch target angle El d ;

[0051] Step 2: The satellite platform adjusts its attitude to converge to the target attitude value, and calculates the real-time pointing vector (Az) of the optical axis based on the real-time attitude value. p El p ), where Az p El is the real-time azimuth angle of the pointing vector. p The pitch angle is the real-time angle of the pointing vector.

[0052] Step 3: After the satellite platform's attitude converges, the target pointing vector value and the real-time pointing vector value are transmitted to the laser terminal. The laser terminal then calculates the difference between the optical axis pointing target vector and the real-time vector to obtain the pointing vector difference. Where ΔAz is the azimuth difference of the pointing vector and ΔEl is the pitch difference of the pointing vector. The laser terminal precision tracking device adjusts its own angle according to the difference of the pointing vector so that the optical axis points to the geometric center of the uncertain capture area (hereinafter referred to as the capture parent area).

[0053] Step 4: Inject scan capture parameters. Based on the capture parent region size, capture sub-region size, and capture sub-region overlap factor, divide the capture parent region into M sub-regions. Number the sub-region whose geometric center coincides with the geometric center of the parent region as 1. Then, assign numbers 1, 2, 3...M to each sub-region in sequence according to the rectangular spiral trajectory. The sub-region distribution diagram is shown in the figure. In the figure, the circle represents the geometric center of each sub-region, and the black line is the sub-region jump trajectory.

[0054] The scanning parameters within the sub-region include the azimuth axis scanning range Xr, the elevation axis scanning azimuth Yr, the scanning step Stp, and the scanning step interval StpTm; the capture parameters include: the capture spot intensity threshold Pthrh, the capture statistics period ΔTm, the capture count threshold Nthrh, and the capture timer CapTm.

[0055] Step 5: The laser terminal uses a precision tracking device to point the optical axis to the geometric center of sub-region 1, captures the statistical period ΔTm, resets the capture count Ncap to zero, resets the capture timer CapTm to zero, and begins beam scanning; the capture timer starts timing.

[0056] Step 6: Check if the capture timer has timed out. If the capture timer has timed out (CapTm > ΔTM), where CapTm is the capture timer and ΔTm is the capture statistics period, then proceed to step 13; otherwise, proceed to step 7.

[0057] Step 7: The intensity P of the detected light spot on the tracking detector is determined. If the intensity of the light spot exceeds the threshold Pthrh (i.e., P>Pthrh), the light spot is valid and step 8 is executed. Otherwise, the detected light spot is invalid and step 6 is executed.

[0058] Step 8: Obtain the spot miss distance (Δθ) measured by the detector. xmn ,Δθ ymn ), where Δθ xmn Let Δθ be the X-axis miss distance of the nth effective spot within sub-region m. ymn The Y-axis miss distance of the nth effective spot within sub-region m, and the current angle of the galvanometer (θ). fxmn ,θ fymn ), where θ fxmn Let θ be the X-axis angle of the galvanometer corresponding to the nth effective light spot within sub-region m. fymn For the galvanometer Y-axis angle corresponding to the nth effective spot in sub-region m, the target-pointing vector angle is calculated using the following formula.

[0059] θ fxdmn =θ fxmn +Δθ xmn

[0060] θ fydmn =θ fymn +Δθ ymn

[0061] Where, θ fxdmn θ is the X-axis angle of the target vector calculated for the nth effective light spot within sub-region m. fydmn The Y-axis angle of the target vector is calculated for the nth effective light spot within sub-region m.

[0062] Step 9: Increment the capture count by 1. Determine if the capture count exceeds the capture count threshold. If the capture count is greater than or equal to the capture count threshold (i.e., Ncap ≥ Nthrh), proceed to step 10; otherwise, proceed to step 6. Here, Ncap is the capture count and Nthrh is the capture count threshold.

[0063] Step 10: Take the average value of the target pointing vector angles calculated from the effective light spots within sub-region m.

[0064]

[0065] in The average angle of the target vector along the X-axis. This represents the average angle of the Y-axis pointing towards the target vector.

[0066] Step 11: Using the average angle of the vector pointing to the target as the center of the beam scan, the scanning coverage area is reduced to 1 / 4 of a sub-region, and this scanning area is numbered as m. 1 / 4 With all other scanning parameters remaining unchanged, beam scanning is performed;

[0067] Step 12: The intensity P of the detected light spot on the tracking detector. sub If the light spot intensity exceeds the threshold Pthrh, i.e., P sub If >Pthrh is selected, the capture is considered complete and the tracking state is entered; otherwise, the scanning state is maintained until the remote control command terminates the capture process.

[0068] Step 13: Check if the sub-region number is less than M. If the sub-region number is less than M, proceed to step 14; otherwise, end the capture process.

[0069] Step 14: According to the sub-region number, the optical axis points to the geometric center of the next sub-region, the capture count Ncap is cleared to zero, the capture timer CapTm is cleared to zero, and the beam scan is started; the capture timer starts timing, and step 6 is executed.

[0070] The inter-satellite laser terminal acquisition method without coarse tracking device in this embodiment achieves efficient and accurate acquisition of target satellites through meticulous step design and innovative technical means, and has important practical value and application prospects.

Claims

1. A method for capturing inter-satellite laser terminals without coarse tracking devices, characterized in that, Includes the following steps: S1. Attitude Calculation and Adjustment: Based on the position information of the target satellite and the current satellite, as well as the real-time attitude value of the current satellite, calculate the target values ​​of yaw angle, pitch angle, and roll angle required for the satellite platform to adjust to the target attitude value; at the same time, calculate the target value of the optical axis pointing vector. Adjust the satellite platform's attitude to converge to the target attitude value, and calculate the real-time pointing vector of the optical axis; S2. Optical axis pointing and capture area division: Receive the target vector and real-time vector pointing to the optical axis, calculate the difference between the pointing vectors, and adjust the angle of the laser terminal so that the optical axis points to the uncertain capture area, i.e. the geometric center of the capture parent area; Based on the size of the capture parent region, the preset capture sub-region size, and the capture sub-region overlap factor, the capture parent region is divided into multiple sub-regions, and each sub-region is numbered and sorted according to the rectangular spiral trajectory. S3. Beam Scanning and Capture: The laser terminal uses a precision tracking device to point the optical axis to the geometric center of the first sub-region and begins to perform beam scanning; During the scanning process, the intensity of the light spot is detected by a tracking detector. When the intensity of the light spot exceeds a preset threshold, it is considered a valid light spot, and the amount of the light spot missing the target and the current angle of the galvanometer are recorded. Based on the miss distance and the galvanometer angle, calculate the angle of the vector pointing towards the target; If the number of captures reaches the preset threshold, the average value of the effective spot angle pointing to the target is calculated and used as the new center of the beam scan, and the scan coverage is reduced to 1 / 4 of the current sub-region. S4. Capture, Judgment, and Control: Continue beam scanning within the reduced scanning area; If the tracking detector detects a valid light spot again and the light spot intensity exceeds the preset threshold, it is determined that the capture is complete and the tracking state is entered. If no valid spot is detected within the preset capture statistics period, check if there are any unscanned sub-regions. If there are unscanned sub-regions, the beam scanning process of step S3 is repeated, pointing to the geometric center of the next sub-region. If all sub-regions have been scanned but the capture is not yet complete, then the capture operation ends.

2. The inter-satellite laser terminal acquisition method without coarse tracking device according to claim 1, characterized in that, In step S1, the attitude adjustment of the satellite platform is achieved through the attitude control system on the satellite, which includes thrusters, reaction wheels or other attitude control mechanisms.

3. The inter-satellite laser terminal acquisition method without coarse tracking device according to claim 1, characterized in that, In step S2, each sub-region is numbered and sorted according to the rectangular spiral trajectory. Specifically, the sub-region whose geometric center coincides with the geometric center of the parent region is numbered 1. Then, each sub-region is assigned a number 1, 2, 3...M according to the rectangular spiral trajectory, where M is the total number of sub-regions divided by the captured parent region.

4. The inter-satellite laser terminal acquisition method without coarse tracking device according to claim 1, characterized in that, Step S3 further includes: setting scanning parameters for each sub-region, including the azimuth axis scanning range Xr, i.e., the scanning angle range on the horizontal plane; the pitch axis scanning azimuth Yr, i.e., the scanning angle on the vertical plane; the scanning step Stp, i.e., the angle increment of each scan; and the scanning step interval StpTm, i.e., the time interval between two scans; and setting capture parameters, including the capture spot intensity threshold Pthrh, the capture statistical period ΔTm, the capture number threshold Nthrh, i.e., how many effective spot detections are required to consider capture successful, and the capture timer CapTm, used to record the duration of each scan attempt.

5. The inter-satellite laser terminal acquisition method without coarse tracking device according to claim 4, characterized in that, In step S3, the off-target distance (Δθ) is used as a reference. xmn , Δθ ymn ) and galvanometer angle (θ) fxmn θ fymn The angle pointing towards the target vector is calculated using the following formula: i fxdmn =θ fxmn +Δθ xmn i fydmn =θ fymn +Δθ ymn In the formula, θ fxdmn θ is the X-axis angle of the target vector calculated for the nth effective light spot within sub-region m. fydmn The y-axis angle of the target vector is calculated for the nth effective light spot within sub-region m, Δθ. xmn Let Δθ be the X-axis miss distance of the nth effective spot within sub-region m. ymn Let θ be the Y-axis miss distance of the nth effective spot within sub-region m. fxmn Let θ be the X-axis angle of the galvanometer corresponding to the nth effective light spot within sub-region m. fymn The angle of the galvanometer corresponding to the nth effective spot in sub-region m is given.

6. The inter-satellite laser terminal acquisition method without coarse tracking device according to claim 5, characterized in that, In step S3, the average value of the effective light spot's pointing vector angle towards the target is calculated using the following formula: In the formula, The average angle of the vector pointing to the target along the X-axis. Ncap is the average angle of the target vector along the Y-axis, and Ncap is the number of captures.

7. The inter-satellite laser terminal acquisition method without coarse tracking device according to claim 1, characterized in that, In step S4, the preset acquisition statistics period is determined based on the relative motion speed between satellites and the performance parameters of the laser terminal.

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