A high-precision ranging method and system based on spaceborne laser communication

Abstract

This invention relates to the field of laser communication technology and discloses a high-precision ranging method and system based on spaceborne laser communication. The method includes: when two terminals send communication signals, aligning the falling edge of the last bit of the frame synchronization header of the data frame with the leading edge of the local satellite clock's integer second pulse as a ranging identifier; modulating the baseband signal containing the ranging identifier into an optical signal and transmitting it into free space; receiving the downlink optical signal from the cooperating terminal and demodulating it into a baseband signal; performing multi-level time delay calibration to obtain the time delay parameters of the system's transceiver channel, and using a code synchronization loop in the communication link to recover the symbol clock phase; and calculating the distance and clock difference between the two terminals based on the arrival time of the ranging identifier and the time delay parameters using a bidirectional one-way ranging model. The above method integrates laser communication and ranging, ensuring high ranging accuracy while saving hardware resources, and is suitable for inter-satellite and satellite-to-ground high-precision laser ranging and high-speed data transmission integration scenarios.

Description

Technical Field

[0001] This invention relates to the field of laser communication technology, and in particular to a high-precision ranging method and system based on spaceborne laser communication. Background Technology

[0002] High-precision distance measurement is a core technology in fields such as satellite navigation, deep space exploration, inter-satellite links, and formation flying. Accurate ranging capabilities directly determine the system's positioning accuracy, time synchronization level, and autonomous operation capability.

[0003] Early ranging technologies often employed independent ranging frames or dedicated ranging signals. These methods typically required dedicated physical channels or time windows for transmitting and receiving ranging signals, offering the advantages of simple design and ease of implementation. However, their drawbacks were also apparent: firstly, they consumed significant hardware resources, requiring independent transmitters, receivers, or processing units, increasing system size, weight, and power consumption; secondly, they had low spectrum utilization efficiency, monopolizing a segment of bandwidth in scarce spectrum resources and reducing the overall communication capacity of the system; and finally, they suffered from poor anti-interference and concealment, as dedicated ranging signals were easily identified and interfered with. To address these issues, integrated communication and ranging technology has become a development trend. This technology aims to embed ranging functionality into communication signals, achieving resource sharing and thus overcoming many of the shortcomings of independent ranging systems.

[0004] While existing integrated communication and ranging solutions attempt to embed ranging codes into communication frames, they fail to effectively utilize the inherent code and frame synchronization mechanisms of the communication system. Ranging accuracy is limited by frame boundary detection errors, making it difficult to achieve sub-centimeter accuracy. Furthermore, system latency is significantly affected by temperature drift, and the lack of effective online calibration and correction mechanisms results in insufficient long-term ranging stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-precision, low-complexity, and high-stability integrated laser communication and ranging method and system. It makes full use of the code synchronization loop phase information in the coherent communication receiver to achieve millimeter-level ranging accuracy, while supporting Gbps-level communication rates and having full-link time delay calibration and temperature drift compensation capabilities.

[0006] On the one hand, the present invention provides a high-precision ranging method based on spaceborne laser communication, comprising the following steps: S1: When the two terminals send communication signals, the falling edge of the last bit of the frame synchronization header of the data frame is aligned with the leading edge of the local satellite clock's integer second pulse as a ranging identifier; S2: Modulate the baseband signal containing the ranging identifier into an optical signal and transmit it into free space; S3: Receive downlink optical signals from cooperating terminals and demodulate them into baseband signals; S4: Perform multi-level delay calibration, obtain the delay parameters of the system's transmit and receive channels, and use a code synchronization ring in the communication link to restore the symbol clock phase; S5: Based on the arrival time of the ranging identifier and the time delay parameter, calculate the distance and clock difference between the two terminals using a two-way one-way ranging model.

[0007] Furthermore, in step S1, the ranging identifier is the last falling edge of the frame synchronization symbol, which does not participate in channel coding in the data frame; The process of sending communication signals between two terminals also includes: The transmitting end generates a baseband data frame triggered by an integer second pulse, and aligns the trailing edge of the frame header with the pulse to form the ranging identifier. The timing information obtained from local demodulation is inserted into a specific field of the data frame to provide input data for distance calculation for cooperating satellites.

[0008] Furthermore, before performing the calculation in step S5, the receiving end performs code synchronization processing on the sampled signal to recover the symbol clock and extract the phase information of each symbol. Based on the phase information, the arrival time of the frame header trailing edge is located, and time stamping is completed; Extract the timing information sent by the cooperating terminal from the parsed frame structure.

[0009] Further, in step S4, the multi-level time delay calibration includes: S41: Perform fixed delay calibration on the ADC and DAC modules; S42: Configuring multi-level delay calibration paths via a fiber optic switching matrix to achieve hierarchical closed-loop calibration, including: Fiber optic loop calibration: After the baseband signal passes through the laser modulator, it is directly looped back to the coherent receiver through the fiber optic switching matrix; Fiber optic loop calibration: The baseband signal is passed through a laser modulator, then through a fiber optic switching matrix to the laser receiving front end, and then looped back to the coherent receiver. S43: Correct system delay drift based on ambient temperature; S44: In each calibration path, the falling edge of the last bit of the frame synchronization header is used as the ranging identifier. The Gardner timing error detection algorithm is used to recover the symbol clock phase through the code synchronization loop, extract the symbol count and interpolation phase, and calculate the loopback delay as the system delay parameter of the corresponding path.

[0010] Preferably, in step S43, the drift correction includes: If calibration results exist for multiple temperature points, linear interpolation is used to estimate the system's distance from zero at the current temperature. If only a calibration result for a single temperature point exists, the zero distance value at the current temperature is calculated using a physical model based on the thermal expansion coefficient and refractive index temperature coefficient of the optical fiber.

[0011] More preferably, the calculation of the distance to zero at the current temperature using a physical model includes: Get the current temperature Read temperature The refractive index of the fiber below Stored at temperature The system distance from zero at that time and refractive index; When the calibration task begins, read the current system temperature: If there are calibration results for the system's distance from zero at multiple temperatures, such as when the temperature has been obtained... and temperature System distance to zero calibration results at that time and Then, based on the principle of linear interpolation, the current temperature is calculated. The system distance from zero at that time ( ) is represented as: ; When only a single temperature exists When the system is calibrated to zero, the current temperature is calculated using the formula. The system distance from zero at that time : , in, for Fiber length at the following temperature is the linear thermal expansion coefficient of optical fiber. The temperature coefficient of refractive index of optical fiber. The refractive index of the optical fiber is denoted as .

[0012] Furthermore, in step S44, the Gardner timing error detection algorithm further includes: The loop bandwidth is set based on a preset ratio of symbol rate to suppress phase noise while ensuring dynamic tracking capability. Standard deviation of clock error measurement under Gaussian white noise input. Represented as: , Its distance measurement standard deviation Represented as: , in, For phase detector gain, For signal power, For symbol period, For loop bandwidth, For noise power density, At the speed of light, Energy for each symbol.

[0013] Further, in step S5, the bidirectional one-way ranging model is represented as: , , in, The distance between the two terminals. The clock difference between the two terminals. At the speed of light, and These are the one-way propagation times of the signal measured at the two terminals, respectively. This is the total fixed delay of the two terminal transmit and receive channels. This is the difference in fixed latency between the two terminal's transmit and receive channels.

[0014] On the other hand, the present invention provides a high-precision ranging system based on spaceborne laser communication for performing any of the above methods, comprising: The data processing platform is used to perform communication signal processing and ranging calculations; The analog-to-digital converter and digital-to-analog converter are used to convert between analog and digital signals, sample the received coherent mixing signal, and convert the baseband signal into an analog signal to drive the optical modulator. The transmitting module includes a reference clock unit, an integer pulse synchronization unit, a ranging frame encoder, and an electro-optic modulator. The integer pulse synchronization unit ensures that the falling edge of the last bit of the frame synchronization header is strictly aligned with the integer pulse of the local satellite clock, serving as a ranging identifier. The ranging frame encoder generates a communication data frame containing the ranging identifier. The receiving module includes a coherent receiver, a code synchronization ring, a frame synchronization unit, a numerically controlled oscillator time stamp module, and a distance calculation unit. The code synchronization ring is used to recover the symbol clock phase of the received signal, the frame synchronization unit is used to identify the frame synchronization header, and the numerically controlled oscillator time stamp module measures the arrival time of the ranging marker based on the phase output by the code synchronization ring. The calibration control module includes a fiber optic switching matrix that supports two working modes: full switching and routing switching. The fiber optic switching matrix can switch different signal paths to achieve three modes: fiber optic small loop calibration, fiber optic large loop calibration, and full link calibration. The optical subsystem includes an optical emitting unit, a beam splitter, and an optical fiber coupler. In the full-link calibration mode, the beam splitter separates a portion of the emitted beam into optical signals for calibration. The temperature control and correction module includes a temperature sensing unit and a zero-value correction algorithm unit. The temperature sensing unit is used to monitor the temperature of key nodes in the system, and the zero-value correction algorithm unit corrects the zero value of the ranging in real time according to the temperature change, so as to ensure that the ranging accuracy is not affected by temperature drift.

[0015] In addition, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the cross-layer collaborative resilience assessment method for low-Earth orbit mega-constellations as described above.

[0016] Meanwhile, an electronic device is provided, comprising: one or more processors; and a storage device for storing one or more programs, which, when executed by the one or more processors, cause the one or more processors to implement the cross-layer collaborative resilience assessment method for low-Earth orbit mega-constellations as described above.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention embeds the ranging identifier into the frame synchronization header of the communication data frame and uses the inherent symbol synchronization and frame synchronization mechanism of the communication link to perform high-precision time extraction. This achieves complete sharing of hardware processing channels, spectrum resources and signal processing algorithms, effectively overcoming the problems of high hardware resource consumption and low spectrum efficiency of independent ranging systems. This invention uses strict alignment between the falling edge of the last bit of the frame synchronization header and the whole second pulse of the local high-stability satellite clock as the ranging reference, and uses the code synchronization loop at the receiving end to recover the symbol phase to accurately locate the arrival time of the identifier, thereby improving the ranging accuracy to the level of symbol phase, breaking through the limitation of frame boundary detection error on accuracy in traditional schemes. This invention adopts a multi-level time delay calibration system, which can dynamically configure the calibration path and accurately measure and compensate for the inherent delay and temperature drift of the system's transmit and receive channels in real time, thus fundamentally ensuring the accuracy and stability of the zero-value of the ranging. This invention addresses the challenge of large temperature variations in spaceborne environments by designing an adaptive correction strategy that maintains high accuracy without requiring frequent ground calibration. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of a high-precision ranging method based on spaceborne laser communication according to the present invention; Figure 2 This is a schematic diagram of the task processing of a laser communication and ranging integrated method based on data frame synchronization header phase ranging according to the present invention. Figure 3 This is a schematic diagram illustrating the principle of distance calculation for ranging frame generation and return frame according to the present invention. Figure 4 This is a flowchart of a temperature delay calibration method according to the present invention; Figure 5 This is a block diagram of a high-precision ranging system based on spaceborne laser communication according to the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The specific embodiments of the present invention will be described below with reference to the accompanying drawings and examples.

[0021] Example 1 In this embodiment, an observation constellation (such as an Earth imaging or atmospheric sounding constellation) consisting of multiple low-Earth orbit remote sensing satellites needs to achieve two core functions: first, high-speed, real-time transmission of remote sensing data and collaborative commands between satellites (requiring Gbps-level communication rates); and second, real-time measurement of inter-satellite relative distances with millimeter to sub-centimeter accuracy to support precise formation control, autonomous orbit determination, or data fusion and calibration based on inter-satellite ranging.

[0022] Please refer to details. Figure 1 The technical solution for a high-precision ranging method based on spaceborne laser communication provided in this embodiment includes the following steps: S1: When the two terminals send communication signals, the falling edge of the last bit of the frame synchronization header of the data frame is aligned with the leading edge of the local satellite clock's integer second pulse as a ranging identifier; S2: The baseband signal containing the ranging identifier is modulated into an optical signal and transmitted into free space. Specifically, the uplink modulated electrical signal containing the ranging frame output from the high-speed digital processing baseband is loaded onto the modulation light source by a laser modulator to form an uplink optical signal. After being amplified by an optical power amplifier through the fully switched path of the fiber optic switching matrix, it is transmitted into free space by the optical system. S3: Receives downlink optical signals from cooperating terminals and demodulates them into baseband signals. Specifically, the downlink optical signals received by the optical system pass through the laser receiving front end, then enter the coherent receiver through the fiber optic switching matrix. After demodulation into downlink baseband electrical signals containing ranging frame calculation information, these signals are sent to the high-speed digital processing baseband. S4: Perform multi-level delay calibration, including ADC / DAC delay calibration, fiber optic link delay calibration, temperature delay calibration, obtain the delay parameters of the system's transceiver channel, and use a code synchronization loop in the communication link to recover the symbol clock phase; S5: Based on the arrival time of the ranging identifier and the time delay parameter, calculate the distance and clock difference between the two terminals using a two-way one-way ranging model.

[0023] The specific task processing procedure of the laser communication and ranging integrated method based on data frame synchronization header phase ranging is as follows: Figure 2 As shown.

[0024] The measurement identifier mentioned in steps S1 and S5 is the falling edge of the last bit of the frame synchronization symbol, which does not participate in channel coding in the data frame. For example... Figure 3 As shown, specifically, the two terminals transmit at their respective satellite clocks at the exact second, selecting the last falling edge of the frame synchronization symbol in the data frame to achieve integrated communication and ranging. Since this is a frame synchronization field, this position does not participate in LDPC encoding and can be directly used for subsequent phase extraction without affecting ranging accuracy. In step S1, when the transmitting end sends the communication signal, it also includes: The transmitting end generates a baseband data frame triggered by an integer second pulse, and aligns the trailing edge of the frame header with the pulse to form the ranging identifier. The timing information obtained from local demodulation is inserted into a specific field of the data frame to provide input data for distance calculation for cooperating satellites.

[0025] Before performing the calculation in step S5, the receiving end performs code synchronization processing on the sampled signal, recovers the symbol clock, and extracts the phase information of each symbol. Based on the phase information, the arrival time of the frame header trailing edge is located, and time stamping is completed; Extract the timing information sent by the cooperating terminal from the parsed frame structure.

[0026] Specifically, the sending end: S11: Perform frequency multiplication based on the reference clock to generate the operating clock required by the system; S12: Triggered by the synchronization pulse, the ranging encoding module generates a baseband data frame. It ensures that the trailing edge of the data frame header is strictly aligned with the synchronization pulse to form a ranging identifier. S13: Insert the "timing" information obtained from local demodulation into a specific field of the data frame to provide input data for distance calculation for cooperating satellites.

[0027] At the receiving end: S51: Perform code synchronization processing on the sampled signal to recover the symbol clock and accurately extract the phase information of each symbol; S52: Using the symbol phase information provided by the code synchronization module, accurately locate the arrival time of the frame header trailing edge in the demodulated data, and complete high-precision time marking in the NCO time stamp module; S53: The complete frame structure is parsed through the frame synchronization module, and the timing information transmitted by the cooperating satellite is demodulated from it.

[0028] In step S4, the multi-level time delay calibration includes: S41: Perform fixed delay calibration on the ADC and DAC modules; S42: Configuring multi-level delay calibration paths via a fiber optic switching matrix to achieve hierarchical closed-loop calibration, including: Fiber optic loop calibration: After the baseband signal passes through the laser modulator, it is directly looped back to the coherent receiver through the fiber optic switching matrix; Fiber optic loop calibration: The baseband signal is passed through a laser modulator, then through a fiber optic switching matrix to the laser receiving front end, and then looped back to the coherent receiver. S43: Correct system delay drift based on ambient temperature; S44: In each calibration path, the falling edge of the last bit of the frame synchronization header is used as the ranging identifier. The Gardner timing error detection algorithm is used to recover the symbol clock phase through the code synchronization loop, extract the symbol count and interpolation phase, and calculate the loopback delay as the system delay parameter of the corresponding path.

[0029] Specifically, in step S42, the specific calibration information flow directions of the two calibration paths include: Fiber optic small loop calibration path: high-speed data processing baseband -> laser modulator -> fiber optic switching matrix -> coherent receiver -> high-speed data processing baseband; this path is enabled during subsystem self-closed loop testing and can be applied to self-closed loop testing of ground equipment ranging function and ranging performance. The fiber optic large-loop calibration path is: high-speed data processing baseband -> laser modulator -> fiber optic switching matrix -> laser receiving front-end -> coherent receiver -> high-speed data processing baseband. This path is activated before wired docking between the spaceborne laser payload and ground equipment and can be used for wired docking tests.

[0030] Secondly, in step S43, the drift correction includes: If calibration results exist for multiple temperature points, linear interpolation is used to estimate the system's distance from zero at the current temperature. If only a calibration result for a single temperature point exists, the zero distance value at the current temperature is calculated using a physical model based on the thermal expansion coefficient and refractive index temperature coefficient of the optical fiber.

[0031] Among them, such as Figure 4As shown, this invention also discloses a temperature drift correction mechanism, wherein calculating the distance to zero at the current temperature using a physical model includes: Get the current temperature Read temperature The refractive index of the fiber below Stored at temperature The system distance from zero at that time and refractive index; When the calibration task begins, read the current system temperature: If there are calibration results for the system's distance from zero at multiple temperatures, such as when the temperature has been obtained... and temperature System distance to zero calibration results at that time and Then, based on the principle of linear interpolation, the current temperature is calculated. The system distance from zero at that time ( ) is represented as: ; When only a single temperature exists When the system is calibrated to zero, the current temperature is calculated using the formula. The system distance from zero at that time : , in, for Fiber length at the following temperature is the linear thermal expansion coefficient of optical fiber. The temperature coefficient of refractive index of optical fiber. The refractive index of the optical fiber is denoted as .

[0032] Furthermore, in step S44, the Gardner timing error detection algorithm further includes: The loop bandwidth is set based on a preset ratio of symbol rate to suppress phase noise while ensuring dynamic tracking capability. Standard deviation of clock error measurement under Gaussian white noise input. Represented as: , Its distance measurement standard deviation Represented as: , in, For phase detector gain, For signal power, For symbol period, For loop bandwidth, For noise power density, At the speed of light, Energy for each symbol.

[0033] Since noise is the main factor affecting ranging accuracy, Gardner timing error detection algorithm is used to extract symbol synchronization timing error. The loop bandwidth of the synchronization loop is set to one-thousandth of the symbol rate to suppress phase noise while ensuring dynamic tracking capability.

[0034] Finally, in step S5, the bidirectional one-way ranging model is represented as: , , in, The distance between the two terminals. The clock difference between the two terminals. At the speed of light, and These are the one-way propagation times of the signal measured at the two terminals, respectively. This is the total fixed delay of the two terminal transmit and receive channels. This is the difference in fixed latency between the two terminal's transmit and receive channels.

[0035] In summary, by embedding ranging markers that are strictly aligned with the satellite clock into the laser communication data frames, using the code synchronization loop to extract the phase to achieve high-precision time measurement, and combining multi-level time delay calibration and temperature drift correction, the high-precision inter-satellite / satellite-to-ground distance and clock difference are finally calculated in real time based on the bidirectional one-way ranging model, thus realizing the integration of communication and ranging.

[0036] Based on this, the present invention also provides a high-precision ranging system based on spaceborne laser communication, such as... Figure 5 As shown, it includes: The data processing platform is used to perform communication signal processing and ranging calculations. Specifically, the platform implements a code synchronization loop function to lock the symbol clock of the received signal and extract phase information; it also implements a frame synchronization function to identify frame boundaries and support accurate positioning of ranging markers. The analog-to-digital converter and digital-to-analog converter are used to convert between analog and digital signals, sample the received coherent mixing signal, and convert the baseband signal into an analog signal to drive the optical modulator. The transmitting module includes a reference clock unit, an integer pulse synchronization unit, a ranging frame encoder, and an electro-optic modulator. The integer pulse synchronization unit ensures that the falling edge of the last bit of the frame synchronization header is strictly aligned with the integer pulse of the local satellite clock, serving as a ranging identifier. The ranging frame encoder generates a communication data frame containing the ranging identifier. The receiving module includes a coherent receiver, a code synchronization ring, a frame synchronization unit, a numerically controlled oscillator time stamp module, and a distance calculation unit. The code synchronization ring is used to recover the symbol clock phase of the received signal, the frame synchronization unit is used to identify the frame synchronization header, and the numerically controlled oscillator time stamp module measures the arrival time of the ranging marker based on the phase output by the code synchronization ring. The calibration control module includes a fiber optic switching matrix that supports two working modes: full switching and routing switching. The fiber optic switching matrix can switch different signal paths to achieve three modes: fiber optic small loop calibration, fiber optic large loop calibration, and full link calibration. The optical subsystem includes an optical emitting unit, a beam splitter, and an optical fiber coupler. In the full-link calibration mode, the beam splitter separates a portion of the emitted beam into optical signals for calibration. The temperature control and correction module includes a temperature sensing unit and a zero-value correction algorithm unit. The temperature sensing unit is used to monitor the temperature of key nodes in the system, and the zero-value correction algorithm unit corrects the zero value of the ranging in real time according to the temperature change, so as to ensure that the ranging accuracy is not affected by temperature drift.

[0037] It should be noted that the steps in the high-precision ranging method based on spaceborne laser communication provided in this embodiment can be implemented based on the corresponding modules in the high-precision ranging system based on spaceborne laser communication. Those skilled in the art can refer to the technical solution of the system to implement the steps of the method. That is, the embodiments in the system can be understood as preferred examples of implementing the method, and will not be elaborated here.

[0038] Besides implementing the system and its various devices provided by this invention in purely computer-readable program code, the same functions can be achieved by logically programming the method steps, making the system and its various devices of this invention appear as logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices provided by this invention can be considered as a hardware component, and the devices included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0039] Finally, it should be noted that the above description is only a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be pointed out that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

[0040] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A high-precision ranging method based on spaceborne laser communication, characterized in that, Includes the following steps: S1: When the two terminals send communication signals, the falling edge of the last bit of the frame synchronization header of the data frame is aligned with the leading edge of the local satellite clock's integer second pulse as a ranging identifier; S2: Modulate the baseband signal containing the ranging identifier into an optical signal and transmit it into free space; S3: Receive downlink optical signals from cooperating terminals and demodulate them into baseband signals; S4: Perform multi-level delay calibration, obtain the delay parameters of the system's transmit and receive channels, and use a code synchronization ring in the communication link to restore the symbol clock phase; S5: Based on the arrival time of the ranging identifier and the time delay parameter, calculate the distance and clock difference between the two terminals using a two-way one-way ranging model.

2. The high-precision ranging method based on spaceborne laser communication according to claim 1, characterized in that, In step S1, the ranging identifier is the last falling edge of the frame synchronization symbol, which does not participate in channel coding in the data frame; The process of sending communication signals between two terminals also includes: The transmitting end generates a baseband data frame triggered by an integer second pulse, and aligns the trailing edge of the frame header with the pulse to form the ranging identifier. The timing information obtained from local demodulation is inserted into a specific field of the data frame to provide input data for distance calculation for cooperating satellites.

3. The high-precision ranging method based on spaceborne laser communication according to claim 2, characterized in that, Before performing the calculation in step S5, the receiving end performs code synchronization processing on the sampled signal, recovers the symbol clock, and extracts the phase information of each symbol. Based on the phase information, the arrival time of the frame header trailing edge is located, and time stamping is completed; Extract the timing information sent by the cooperating terminal from the parsed frame structure.

4. The high-precision ranging method based on spaceborne laser communication according to claim 1, characterized in that, In step S4, the multi-level time delay calibration includes: S41: Perform fixed delay calibration on the ADC and DAC modules; S42: Configuring multi-level delay calibration paths via a fiber optic switching matrix to achieve hierarchical closed-loop calibration, including: Fiber optic loop calibration: After the baseband signal passes through the laser modulator, it is directly looped back to the coherent receiver through the fiber optic switching matrix; Fiber optic loop calibration: The baseband signal is passed through a laser modulator, then through a fiber optic switching matrix to the laser receiving front end, and then looped back to the coherent receiver. S43: Correct system delay drift based on ambient temperature; S44: In each calibration path, the falling edge of the last bit of the frame synchronization header is used as the ranging identifier. The Gardner timing error detection algorithm is used to recover the symbol clock phase through the code synchronization loop, extract the symbol count and interpolation phase, and calculate the loopback delay as the system delay parameter of the corresponding path.

5. The high-precision ranging method based on spaceborne laser communication according to claim 3, characterized in that, In step S43, the drift correction includes: If calibration results exist for multiple temperature points, linear interpolation is used to estimate the system's distance from zero at the current temperature. If only a calibration result for a single temperature point exists, the zero distance value at the current temperature is calculated using a physical model based on the thermal expansion coefficient and refractive index temperature coefficient of the optical fiber.

6. The high-precision ranging method based on spaceborne laser communication according to claim 4, characterized in that, The calculation of the distance to zero at the current temperature using a physical model includes: Get the current temperature Read temperature The refractive index of the fiber below Stored at temperature The system distance from zero at that time and refractive index; When the calibration task begins, read the current system temperature: If there are calibration results for the system's distance from zero at multiple temperatures, such as when the temperature has been obtained... and temperature System distance to zero calibration results at that time and Then, based on the principle of linear interpolation, the current temperature is calculated. The system distance from zero at that time ( ) is represented as: ； When only a single temperature exists When the system is calibrated to zero, the current temperature is calculated using the formula. The system distance from zero at that time : ， in, for Fiber length at the following temperature is the linear thermal expansion coefficient of optical fiber. The temperature coefficient of refractive index of optical fiber. The refractive index of the optical fiber is given.

7. The high-precision ranging method based on spaceborne laser communication according to claim 4, characterized in that, In step S44, the Gardner timing error detection algorithm further includes: The loop bandwidth is set based on a preset ratio of symbol rate to suppress phase noise while ensuring dynamic tracking capability. Standard deviation of clock error measurement under Gaussian white noise input. Represented as: ， Its distance measurement standard deviation Represented as: ， in, For phase detector gain, For signal power, For symbol period, For loop bandwidth, For noise power density, At the speed of light, Energy for each symbol.

8. The high-precision ranging method based on spaceborne laser communication according to claim 1, characterized in that, In step S5, the bidirectional one-way ranging model is represented as: ， ， in, The distance between the two terminals. The clock difference between the two terminals. At the speed of light, and These are the one-way propagation times of the signal measured at the two terminals, respectively. This is the total fixed delay of the two terminal transmit and receive channels. This is the difference in fixed latency between the two terminal's transmit and receive channels.

9. A high-precision ranging system based on spaceborne laser communication for performing the method as described in any one of claims 1-8, characterized in that, include: The data processing platform is used to perform communication signal processing and ranging calculations; The analog-to-digital converter and digital-to-analog converter are used to convert between analog and digital signals, sample the received coherent mixing signal, and convert the baseband signal into an analog signal to drive the optical modulator. The transmitting module includes a reference clock unit, an integer pulse synchronization unit, a ranging frame encoder, and an electro-optic modulator. The integer pulse synchronization unit ensures that the falling edge of the last bit of the frame synchronization header is strictly aligned with the integer pulse of the local satellite clock, serving as a ranging identifier. The ranging frame encoder generates a communication data frame containing the ranging identifier. The receiving module includes a coherent receiver, a code synchronization ring, a frame synchronization unit, a numerically controlled oscillator time stamp module, and a distance calculation unit. The code synchronization ring is used to recover the symbol clock phase of the received signal, the frame synchronization unit is used to identify the frame synchronization header, and the numerically controlled oscillator time stamp module measures the arrival time of the ranging marker based on the phase output by the code synchronization ring. The calibration control module includes a fiber optic switching matrix that supports two working modes: full switching and routing switching. The fiber optic switching matrix can switch different signal paths to achieve three modes: fiber optic small loop calibration, fiber optic large loop calibration, and full link calibration. The optical subsystem includes an optical emitting unit, a beam splitter, and an optical fiber coupler. In the full-link calibration mode, the beam splitter separates a portion of the emitted beam into optical signals for calibration. The temperature control and correction module includes a temperature sensing unit and a zero-value correction algorithm unit. The temperature sensing unit is used to monitor the temperature of key nodes in the system, and the zero-value correction algorithm unit corrects the zero value of the ranging in real time according to the temperature change, so as to ensure that the ranging accuracy is not affected by temperature drift.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the high-precision ranging method based on spaceborne laser communication as described in any one of claims 1-8.

11. An electronic device, characterized in that, include: One or more processors; A storage device for storing one or more programs, which, when executed by one or more processors, cause the one or more processors to implement the high-precision ranging method based on spaceborne laser communication as described in any one of claims 1-8.

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