System and method for comprehensive demonstration and verification for earth-moon super-long distance optical communication

Abstract

The application provides a kind of comprehensive demonstration verification system and method for earth-moon super long distance optical communication, comprising: dynamic pointing simulation module, for generating time series pointing model based on real earth-moon orbit parameters, and driving pointing mechanism to produce micro-arc degree level dynamic pointing disturbance, so as to simulate the angular velocity change and attitude offset in the process of earth-moon line-of-sight change under ground environment;Weak signal link simulation module, for constructing attenuation link covering 60-80dB and maintaining beam consistency to reconstruct the equivalent optical power characteristics of 380-400km earth-moon link;Turbulence injection and adaptive optical compensation module, for generating dynamic phase distortion according to ground-based atmospheric turbulence model and earth-moon line-of-sight elevation angle change, and realizing closed-loop compensation through wavefront detector and deformable mirror;Three-parameter synchronous measurement module, for synchronous acquisition and correlation analysis of pointing deviation, far-field spot shape and communication bit error rate.

Description

Technical Field

[0001] This invention relates to the fields of deep space communication and space optical communication technology. Specifically, it relates to a comprehensive demonstration and verification system and method for ultra-long-distance optical communication between Earth and the Moon. More specifically, it relates to a comprehensive demonstration and verification system and method for reproducing the ultra-long-distance laser communication link environment between Earth and the Moon under ground conditions. It can be used for ground pre-verification of high-speed optical communication payloads between Earth and the Moon, evaluation of weak signal link characteristics, verification of adaptive optics compensation effects, and improvement of the maturity of optical communication technology for deep space missions. Background Technology

[0002] With the continued advancement of existing deep space exploration projects, scientific exploration missions to the Earth-Moon and beyond place higher demands on high-speed data transmission capabilities. Traditional S / X / Ka band microwave communication is no longer sufficient to meet the massive downlink data demands of scientific payloads in deep space exploration. Laser communication, with its advantages of high bandwidth, high security, and strong anti-interference capabilities, has become a key direction for the international development of deep space telemetry, tracking, and command (TT&C) capabilities. NASA's LLCD experiment on the Lunar Reconnaissance Orbiter (LADEE) has achieved a downlink rate of 622 Mbps between the Earth and the Moon, verifying the feasibility of long-distance laser communication.

[0003] However, the Earth-Moon laser communication link is extremely complex due to factors such as massive free-space losses over a distance of 380,000 to 400,000 km, extremely weak signal reception conditions, atmospheric turbulence disturbances on the ground, and dynamic pointing errors caused by the relative motion between the satellite and the ground. The Earth-Moon link requires the terminal to have pointing accuracy better than 1 μrad, and the link verification system needs high-precision measurement capabilities with a resolution of 0.2 μrad, weak signal link simulation capabilities, and dynamic turbulence compensation capabilities.

[0004] Currently, most laser communication verification platforms built both domestically and internationally are geared towards "space-to-ground communication" or "short-range links," and their characteristics include: (1) The link attenuation is limited, making it difficult to simulate the weak signal scenario over the ultra-long distance between the Earth and the Moon; (2) The simplified dynamic pointing disturbance model cannot reproduce the actual changes in angular velocity caused by the change in lunar line of sight geometry with orbital changes; (3) Turbulence simulations are often static or semi-static, lacking real-time phase disturbances coupled with dynamic changes in the orbit; (4) Existing verification systems generally lack the ability to test the three parameters of “pointing error, spot quality and bit error rate” simultaneously, and cannot form a quantitative link performance mapping model.

[0005] In summary, existing technologies cannot provide a ground-based integrated demonstration and verification system that can fully reproduce the key influencing factors of the Earth-Moon link, and cannot meet the system-level verification requirements before the development of Earth-Moon laser communication payloads. Therefore, a new technical solution is urgently needed to address this issue. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a comprehensive demonstration and verification system and method for ultra-long-distance optical communication between the Earth and the Moon.

[0007] A comprehensive demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon, provided by the present invention, includes: The dynamic pointing simulation module is used to generate a time-series pointing model based on real Earth-Moon orbital parameters and drive the pointing mechanism to generate micro-radian level dynamic pointing disturbances, thereby simulating the changes in angular velocity and attitude deviation during the change of the Earth-Moon line of sight in the ground environment. The weak signal link simulation module is used to construct an attenuation link covering 60-80dB and maintain beam consistency in order to reconstruct the equivalent optical power characteristics of an approximate Earth-Moon distance link that meets preset requirements. The turbulence injection and adaptive optics compensation module is used to generate dynamic phase distortion based on the ground-based atmospheric turbulence model and the change of the Earth-Moon line of sight elevation angle, and to achieve closed-loop compensation through a wavefront detector and a deformable mirror. The communication performance verification module is used to test the communication performance of the terminal under test in a simulated Earth-Moon link environment. The three-parameter synchronous measurement module is used to synchronously collect and correlate the pointing deviation, far-field spot morphology, and communication bit error rate.

[0008] Preferably, the dynamic pointing simulation module includes: generating a realistic line-of-sight change model based on Earth-Moon orbit and attitude data; converting the line-of-sight change model into a sequence of commands for azimuth and pitch angles over time, and driving a two-axis or three-axis pointing platform to operate, causing the laser communication terminal under test or equivalent transmitting optomechanical component mounted on it to generate dynamic pointing disturbances on the order of microradius, thereby reproducing the dynamic changes in line-of-sight caused by changes in Earth-Moon distance, lunar orbit flight, and attitude maneuvers in a ground environment; wherein, the two-axis or three-axis pointing platform is driven by Earth-Moon orbit calculation parameters.

[0009] Preferably, the attenuation link in the weak signal link simulation module is set in the folded optical path between the transmitter and the receiver; Meanwhile, a far-field monitoring camera is configured in the attenuation link to monitor the spot shape, energy distribution and center drift in real time. By fine-tuning the attitude of the optical elements, the beam quality and spatial distribution are ensured to meet the preset requirements under different attenuation conditions, so that the optical characteristics are consistent with the real Earth-Moon link even under extremely weak signal conditions that meet the preset requirements.

[0010] Preferably, the turbulence injection and adaptive optics compensation module is arranged in the optical path of the receiving end, and includes: a turbulence injection submodule and an adaptive optics compensation submodule; The turbulence injection submodule includes: using a programmable phase screen or equivalent spatial light modulator, based on the selected Kolmogorov turbulence model or layered atmospheric model, combined with the observation station's atmospheric structure constant Cn², line-of-sight elevation angle and wind speed parameters, to generate time-varying wavefront phase perturbations, which are then superimposed onto the propagating beam to simulate the effects of atmospheric turbulence under different altitudes, weather conditions and elevation angles. The adaptive optics compensation submodule includes a Shack-Hartmann wavefront sensor and a deformable mirror. The Shack-Hartmann wavefront sensor measures the wavefront slope after turbulence modulation in real time, the wavefront error distribution is obtained using a reconstruction algorithm, and the control quantity of the deformable mirror drive unit is calculated to achieve closed-loop compensation for wavefront distortion.

[0011] Preferably, the communication performance verification module supports multiple modulation schemes and different rate levels, and is used to measure indicators including link bit error rate, packet loss rate and data throughput under different pointing, different attenuation and different turbulence conditions.

[0012] Preferably, the three-parameter synchronous measurement module includes: The pointing deviation is obtained through a high-precision angle measuring device at the transmitting or receiving end. The far-field spot shape is obtained by a monitoring camera deployed on the focal plane or near-focal plane of the receiving end. Based on the far-field spot shape, the center position, full width at half maximum (FWHM), ellipticity, and energy distribution of the spot are analyzed in real time. The communication error rate is obtained from statistics obtained by the communication performance verification module.

[0013] A comprehensive demonstration and verification method for ultra-long-distance optical communication between the Earth and the Moon, provided by the present invention, includes: Step S1: Generate a line-of-sight change sequence based on the Earth-Moon orbit and mission design parameters, and drive the dynamic pointing simulation module to construct a dynamic pointing environment; Step S2: Set up a weak signal link simulation module between the transmitter and receiver, and adjust the link attenuation to a power level equivalent to the target Earth-Moon distance through the weak signal link simulation module; Step S3: Load the corresponding atmospheric turbulence phase disturbance in the optical path of the receiver through the turbulence injection and adaptive optics compensation module, and turn the adaptive optics compensation on or off as needed; Step S4: Test the communication performance of the terminal under test in a simulated Earth-Moon link environment using the communication performance verification module; Step S5: Using the three-parameter synchronous measurement module, the pointing error, beam parameters, and bit error rate are synchronously recorded and classified under different operating conditions to form link performance data under different pointing accuracies, different attenuation levels, and different turbulence intensities. By performing correlation analysis on the multidimensional data, the quantitative relationship between pointing error, beam quality, and communication bit error rate is obtained, which is used to guide the design margin of the spaceborne terminal and the formulation of link control strategies.

[0014] Preferably, the dynamic pointing simulation module includes: generating a realistic line-of-sight change model based on Earth-Moon orbit and attitude data; converting the line-of-sight change model into a sequence of commands for azimuth and pitch angles over time, and driving a two-axis or three-axis pointing platform to operate, causing the laser communication terminal under test or equivalent transmitting optomechanical component mounted on it to generate dynamic pointing disturbances on the order of microradians, thereby reproducing the dynamic changes in line-of-sight caused by changes in Earth-Moon distance, lunar orbit flight, and attitude maneuvers in a ground environment; wherein, the two-axis or three-axis pointing platform is driven by Earth-Moon orbit calculation parameters; The attenuation link in the weak signal link simulation module is set in the folded optical path between the transmitter and receiver, and includes: a multi-stage adjustable optical attenuator, a neutral density filter, a beam splitter and a folding mirror. Meanwhile, a far-field monitoring camera and a beam quality assessment unit are configured in the attenuation link to monitor the beam shape, energy distribution and center drift in real time. By fine-tuning the attitude of the optical elements, the beam quality and spatial distribution are ensured to meet the preset requirements under different attenuation conditions, so that the optical characteristics are consistent with the real Earth-Moon link even under extremely weak signal conditions that meet the preset requirements.

[0015] Preferably, the turbulence injection and adaptive optics compensation module is arranged in the optical path of the receiving end, and includes: a turbulence injection submodule and an adaptive optics compensation submodule; The turbulence injection submodule includes: using a programmable phase screen or equivalent spatial light modulator, based on the selected Kolmogorov turbulence model or layered atmospheric model, combined with the observation station's atmospheric structure constant Cn², line-of-sight elevation angle and wind speed parameters, to generate time-varying wavefront phase perturbations, which are then superimposed onto the propagating beam to simulate the effects of atmospheric turbulence under different altitudes, weather conditions and elevation angles. The adaptive optics compensation submodule includes a Shack-Hartmann wavefront sensor, a deformable mirror, and a wavefront controller. The Shack-Hartmann wavefront sensor measures the wavefront slope after turbulence modulation in real time, and the wavefront error distribution is obtained using a reconstruction algorithm. The control quantity of the deformable mirror drive unit is calculated to achieve closed-loop compensation for wavefront distortion.

[0016] Preferably, the three-parameter synchronous measurement module includes: The pointing deviation is obtained through a high-precision angle measurement device at the transmitting or receiving end, using an angle deviation testing system composed of a laser interferometer, a long-focal-length collimator, a large-aperture plane mirror, and a CCD camera. The far-field spot morphology is acquired by a monitoring camera deployed on the focal plane or near-focal plane of the receiving end, and the center position, full width at half maximum (FWHM), ellipticity, and energy distribution of the spot are analyzed in real time. The communication bit error rate is obtained from statistics by the communication performance verification module; The communication performance verification module supports multiple modulation schemes and different rate levels, and is used to measure indicators including link bit error rate, packet loss rate and data throughput under different pointing, attenuation and turbulence conditions.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves high-fidelity reproduction of the real geometric environment of the Earth and the Moon through a dynamic pointing simulation module driven by orbit calculation, breaking through the limitation of traditional verification platforms that can only simulate simplified dynamic or static targets. 2. The present invention, through a weak signal link simulation module composed of multi-level adjustable optical attenuation, can achieve link attenuation on the order of 60 to 80 dB while maintaining stable beam quality. For the first time, it provides an engineering-usable weak signal testing method for ultra-long-distance Earth-Moon laser links under ground conditions. 3. This invention introduces an integrated module of turbulence injection and adaptive optics compensation, which organically combines atmospheric turbulence modeling, adaptive wavefront detection and compensation capabilities. It can quantitatively evaluate the degree of improvement of link performance by the adaptive optics system under different atmospheric conditions, and provide a basis for the engineering design of ground-based laser communication stations. 4. This invention achieves synchronous measurement and correlation analysis of pointing error, beam quality and bit error rate through a three-parameter synchronous measurement module and a unified control and data processing platform. It establishes a quantitative mapping relationship between the Earth-Moon laser communication link from "geometric and channel environment" to "link performance indicators", providing a tool for joint optimization of spaceborne terminals and ground station systems. 5. This invention adopts a modular and reconfigurable system architecture. By adjusting the pointing model, attenuation parameters and turbulence model, it can be extended to support optical communication demonstration and verification in satellite-to-ground, inter-satellite and other deep space scenarios, and has good versatility and engineering promotion value.

[0018] 6. This invention solves the problem that existing technologies cannot simultaneously reproduce real Earth-Moon geometry, weak signal links, and complex atmospheric disturbances. It can be used for ground-based pre-research and verification of Earth-Moon communication payloads, satellite missions, and on-orbit terminals, and has high reliability, high scalability, and practical engineering value. Attached Figure Description

[0019] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 Logical block diagram of a comprehensive demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon; Figure 2 This is a schematic diagram of the system composition of the simulation test platform; Figure 3 Connection diagram for ground dynamic docking demonstration and verification system. Detailed Implementation

[0020] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0021] Example 1 According to the present invention, a comprehensive demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon is provided, such as... Figure 1 As shown, it includes: The dynamic pointing simulation module is used to generate a time-series pointing model based on real Earth-Moon orbital parameters and drive the pointing mechanism to generate micro-radian level dynamic pointing disturbances, thereby simulating the changes in angular velocity and attitude deviation during the change of the Earth-Moon line of sight in the ground environment. The weak signal link simulation module includes: an adjustable optical attenuation array and a far-field beam monitoring unit, used to construct an attenuation link covering 60-80dB and maintain beam consistency, so as to reconstruct the equivalent optical power characteristics of the Earth-Moon 380,000-400,000 km link; The turbulence injection and adaptive optics compensation module is used to generate dynamic phase distortion based on the ground-based atmospheric turbulence model and the change of the Earth-Moon line of sight elevation angle, and to achieve closed-loop compensation through a wavefront detector and a deformable mirror. The communication performance verification module is used to test the acquisition, tracking, and bit error rate performance of the terminal under test in a simulated Earth-Moon link environment for laser communication links. The three-parameter synchronous measurement module is used to synchronously collect and correlate the pointing deviation, far-field spot morphology, and communication bit error rate.

[0022] The modules are integrated through an optomechanical platform to form a reconfigurable verification system, which is used to reproduce the Earth-Moon ultra-long-distance laser communication environment under ground conditions.

[0023] Specifically, the dynamic pointing simulation module includes: generating a realistic line-of-sight change model based on Earth-Moon orbit and attitude data; converting the line-of-sight change model into a sequence of commands for azimuth and pitch angles over time, and driving a two-axis or three-axis pointing platform to operate, causing the laser communication terminal under test or the equivalent transmitting optomechanical component installed on it to generate dynamic pointing disturbances on the order of microradius, thereby reproducing the dynamic changes in line-of-sight caused by changes in Earth-Moon distance, lunar orbit flight, and attitude maneuvers in a ground environment; wherein, the two-axis or three-axis pointing platform is driven by Earth-Moon orbit calculation parameters.

[0024] The dynamic pointing simulation module has a pointing accuracy better than 1 μrad and a measurement resolution of 0.2 μrad.

[0025] Specifically, in the weak signal link simulation module, the attenuation link is set in the folded optical path between the transmitter and the receiver; Meanwhile, a far-field monitoring camera is configured in the attenuation link to monitor the spot shape, energy distribution and center drift in real time. By fine-tuning the attitude of the optical elements, the beam quality and spatial distribution are ensured to meet the preset requirements under different attenuation conditions, so that the optical characteristics are consistent with the real Earth-Moon link even under extremely weak signal conditions that meet the preset requirements.

[0026] Specifically, the turbulence injection and adaptive optics compensation module is arranged in the optical path of the receiving end, and includes: a turbulence injection submodule and an adaptive optics compensation submodule; The turbulence injection submodule includes: using a programmable phase screen or equivalent spatial light modulator, based on the selected Kolmogorov turbulence model or layered atmospheric model, combined with the observation station's atmospheric structure constant Cn², line-of-sight elevation angle and wind speed parameters, to generate time-varying wavefront phase perturbations, which are then superimposed onto the propagating beam to simulate the effects of atmospheric turbulence under different altitudes, weather conditions and elevation angles. The adaptive optics compensation submodule includes a Shack-Hartmann wavefront sensor and a deformable mirror. The Shack-Hartmann wavefront sensor measures the wavefront slope after turbulence modulation in real time, the wavefront error distribution is obtained using a reconstruction algorithm, and the control quantity of the deformable mirror drive unit is calculated to achieve closed-loop compensation for wavefront distortion.

[0027] Specifically, the communication performance verification module supports multiple modulation schemes and different rate levels, and is used to measure indicators including link bit error rate, packet loss rate and data throughput under different pointing, different attenuation and different turbulence conditions.

[0028] The communication performance verification module supports link rates from 10 Mbps to 1 Gbps, modulation schemes such as OOK / PSK / PPM, and FEC coding tests.

[0029] Specifically, the three-parameter synchronous measurement module is used to establish a correlation model between pointing error, spot offset and bit error rate, in order to evaluate the impact of disturbance on communication performance; The pointing deviation is obtained through a high-precision angle measuring device at the transmitting or receiving end. The far-field spot shape is obtained by a monitoring camera deployed on the focal plane or near-focal plane of the receiving end. Based on the far-field spot shape, the center position, full width at half maximum (FWHM), ellipticity, and energy distribution of the spot are analyzed in real time. The communication error rate is obtained from statistics obtained by the communication performance verification module.

[0030] The integrated demonstration and verification system for ultra-long-distance optical communication between Earth and the Moon adopts a modular optomechanical platform and can switch between satellite-to-ground, Earth-to-Moon, or deep space link verification modes.

[0031] The integrated demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon also supports interconnection with an on-orbit laser terminal for conducting semi-physical simulation verification of the Earth-Moon link.

[0032] This embodiment generates a time-series pointing error based on real Earth-Moon orbital parameters, simulates geometric losses at the 380,000-400,000 km level through an adjustable energy attenuation link, and realizes the realistic reproduction of ground-based atmospheric turbulence by using dynamic phase distortion injection and adaptive optics (AO) compensation. At the same time, it constructs a three-parameter synchronous monitoring mechanism for pointing deviation, spot consistency, and bit error rate (BER), which can quantitatively evaluate the communication performance of the Earth-Moon link in complex environments such as weak signals, disturbances, and line-of-sight changes.

[0033] Example 2 Example 2 is a preferred example of Example 1. The purpose of this invention is to overcome the shortcomings of existing technologies in terms of insufficient ground-based demonstration and verification capabilities for ultra-long-distance Earth-Moon laser communication. It addresses the problem that existing experimental systems cannot simultaneously reproduce the real geometric changes of the Earth-Moon link, extremely weak signal reception conditions, atmospheric turbulence disturbances, and the combined effects of these factors on link communication performance. This makes it impossible to provide engineering-level and system-level ground verification methods for spaceborne Earth-Moon laser communication terminals. Existing space-to-ground or short-range optical communication test systems are mostly geared towards low-Earth orbit or medium-to-high Earth orbit scenarios, supporting only low-to-medium attenuation link loss simulations and simplified pointing disturbance models. Turbulence simulations are mostly static or semi-static, and typically only evaluate a single link indicator, failing to establish a quantitative relationship between pointing accuracy, beam quality, and bit error rate performance. This makes it difficult to meet the overall requirements of ground-based demonstration and verification systems for Earth-Moon high-speed laser communication technology research.

[0034] To address the aforementioned technical problems, this invention proposes a comprehensive demonstration and verification system and method for ultra-long-distance optical communication between the Earth and the Moon.

[0035] The comprehensive demonstration and verification system for ultra-long-distance Earth-Moon laser communication includes: constructing a controllable laser transmission link under ground conditions; and comprehensively simulating and jointly verifying key influencing factors of the Earth-Moon laser communication link by deploying dynamic pointing simulation modules, weak signal link simulation modules, turbulence injection and adaptive optics compensation modules, three-parameter synchronous measurement modules, and communication performance verification modules at both ends of the optical path and within the link. The system utilizes a unified system control and data processing platform to synchronously collect and correlate pointing errors, far-field spot parameters, and communication bit error rate, forming a complete mapping from "geometric and channel environment" to "link performance indicators," providing a basis for spaceborne terminal design, link budgeting, and on-orbit test scheme optimization.

[0036] The comprehensive demonstration and verification system for ultra-long-distance laser communication between the Earth and the Moon includes: a dynamic pointing simulation module, a weak signal link simulation module, a turbulence injection and adaptive optics compensation module, a three-parameter synchronous measurement module, a communication performance verification module, and a system control and data processing platform. These components are integrated on a unified optical experimental platform through an optomechanical structure.

[0037] The dynamic pointing simulation module generates a realistic line-of-sight change model based on Earth-Moon orbit and attitude data. This model is then converted into a sequence of commands for azimuth and pitch angles over time, driving a high-precision two- or three-axis pointing platform. This causes the laser communication terminal or equivalent transmitting optomechanical assembly mounted on the platform to generate dynamic pointing disturbances on the order of microradians, thereby reproducing the dynamic changes in line-of-sight caused by changes in Earth-Moon distance, lunar orbit, and attitude maneuvers in a ground-based environment. The angle measurement resolution of this device is preferably better than 0.2 μrad to meet the verification requirement of pointing accuracy better than 1 μrad.

[0038] The weak signal link simulation module is located in the folded optical path between the transmitter and receiver. It consists of a multi-stage adjustable optical attenuator, a neutral density filter, a beam splitter, and a folding mirror. The overall attenuation range is preferably 60–80 dB to simulate the enormous energy attenuation caused by free space propagation of approximately 380,000–400,000 km between the Earth and the Moon, as well as additional atmospheric and optical losses. A far-field monitoring camera and a beam quality assessment unit are configured in the attenuation link to monitor the beam pattern, energy distribution, and center drift in real time. By fine-tuning the attitude of the optical components, the stability of beam quality and spatial distribution under different attenuation conditions is ensured, thus maintaining optical characteristics consistent with the real Earth-Moon link even under extremely weak signal conditions.

[0039] The turbulence injection and adaptive optics compensation module is deployed in the optical path of the receiver. The turbulence injection section employs a programmable phase screen or an equivalent spatial light modulator. Based on the selected Kolmogorov turbulence model or stratified atmospheric model, combined with parameters such as the atmospheric structure constant Cn², line-of-sight elevation angle, and wind speed of the observation station, it generates time-varying wavefront phase perturbations and superimposes them onto the propagating beam to simulate the effects of atmospheric turbulence under different altitudes, weather conditions, and elevation angles. The adaptive optics compensation section consists of a Shack-Hartmann wavefront sensor, a deformable mirror, and a wavefront controller. The wavefront sensor measures the wavefront slope after turbulence modulation in real time, uses a reconstruction algorithm to obtain the wavefront error distribution, and calculates the control input to the deformable mirror drive unit to achieve closed-loop compensation for wavefront distortion. This module can operate at control frequencies of several hundred hertz, thus adapting to the characteristic timescale of ground-based atmospheric turbulence and supporting verification under various comparative conditions, such as turbulence off and on, and adaptive optics off and on.

[0040] The three-parameter synchronous measurement module is used to synchronously acquire three key parameters—pointing error, far-field spot size, and communication bit error rate—under a unified time reference. The pointing error is obtained through a high-precision angle measurement device at the transmitting or receiving end, which can be achieved using an angle deviation testing system composed of a laser interferometer, a long-focal-length collimator, a large-aperture plane mirror, and a CCD camera. The far-field spot parameters are acquired through a monitoring camera deployed at the focal plane or near-focal plane of the receiving end, allowing for real-time analysis of the spot's center position, full width at half maximum (FWHM), ellipticity, and energy distribution. The communication bit error rate is statistically obtained by the communication performance verification module.

[0041] The communication performance verification module includes uplink and downlink modulation and demodulation units, synchronization and encoding / decoding units, and bit error detection units. It supports multiple modulation methods and different rate levels and is used to measure link bit error rate, packet loss rate, and data throughput under different pointing, attenuation, and turbulence conditions.

[0042] The system control and data processing platform is connected to the above modules via wired or fiber optic networks. It is responsible for uniformly issuing dynamic pointing commands, attenuation level settings, turbulence phase screen loading, adaptive optics closed-loop control parameters, and communication test service configurations. It coordinates the actions of each module according to a predetermined process. At the same time, it synchronously collects, timestamps, and jointly analyzes multi-source data from pointing measurement, spot monitoring, and communication testing to generate a multidimensional dataset reflecting the performance of the Earth-Moon link, providing support for link design and parameter optimization.

[0043] According to the present invention, a method for demonstrating and verifying Earth-Moon laser communication based on the integrated demonstration and verification system includes: generating a line-of-sight change sequence based on Earth-Moon orbit and mission design parameters, driving a dynamic pointing simulation device to construct a dynamic pointing environment; setting up a weak signal link simulation device between the transmitter and receiver, adjusting the link attenuation to a power level equivalent to the target Earth-Moon distance; loading corresponding atmospheric turbulence phase disturbances into the optical path at the receiver, and turning adaptive optics compensation on or off as needed; synchronously recording and classifying the pointing error, beam parameters, and bit error rate under different operating conditions to form link performance data under different pointing accuracies, different attenuation levels, and different turbulence intensities; and obtaining a quantitative relationship between pointing error, beam quality, and communication bit error rate through correlation analysis of multidimensional data, which is used to guide the design margin of the spaceborne terminal and the formulation of link control strategies.

[0044] Example 3 Example 3 is a preferred example of Example 1. The satellite-to-ground laser communication system consists of an on-board terminal and a ground terminal; The onboard terminal serves as the transmitter of downlink information and also undertakes the function of receiving uplink information. In the downlink direction, the onboard terminal sequentially processes the input information sequence through an encoder for channel coding, performs interleaving through an interleaver, and inserts a synchronization header for downlink synchronization through a synchronization header inserter. The synchronization header is updated according to the uplink reception results to achieve adaptive adjustment of link parameters. The synchronized data enters the phase modulation module, and after phase modulation, it is sent to a laser to be converted into an optical signal. The modulated beam output from the laser is collimated and shaped by a lens group, and then the exit direction is adjusted by a reflector to form a downlink laser beam propagating along free space towards the ground. In the uplink direction, the onboard terminal receives the uplink optical signal from the ground through a lens group, filters out out-of-band interference, focuses it through a telescope, and performs photoelectric conversion by a detector. The converted electrical signal sequentially passes through a demodulator, a synchronization decision unit, a deinterleaver, and a decoder to recover the uplink information sequence, which is used to drive the interleaving depth and synchronization header update of the onboard terminal, realizing a two-way cooperative control process.

[0045] This embodiment provides a comprehensive demonstration and verification system and method for ultra-long-distance Earth-Moon laser communication. It is used to conduct integrated experimental verification of the pointing accuracy, adaptive optics compensation performance, bidirectional dynamic tracking capability, and communication performance under weak signal conditions of an Earth-Moon laser communication terminal under ground conditions. This system can serve as a key ground verification platform before the launch of a spaceborne Earth-Moon laser communication payload, reducing on-orbit testing risks, improving technology maturity, and can be extended for subsequent on-orbit verification missions of Earth-Moon communication and navigation networks.

[0046] The comprehensive demonstration and verification system for ultra-long-distance laser communication between the Earth and the Moon includes: a dynamic pointing simulation module, a weak signal link simulation module, a turbulence injection and adaptive optics compensation module, a three-parameter synchronous measurement module, a communication performance verification module, and a system control and data processing platform. All components are organically integrated onto a unified optical platform through an optomechanical structure and signal link. The system logic diagram is shown below. Figure 1 As shown.

[0047] Furthermore, such as Figure 2 As shown, the simulation test platform is centered on laser communication terminal I, and is surrounded by an orbital motion simulation unit, a satellite platform vibration simulation unit, a far-field transformation unit, a terminal I acquisition and tracking monitoring unit, and a bit error rate test unit. The system control unit coordinates the operation of each functional module. The orbital motion simulation and the satellite platform vibration simulation jointly apply dynamic disturbances to the laser communication terminal I. The output of terminal I is transformed into a bit error rate test link, and the acquisition and tracking monitoring results of terminal I are fed back to the system control unit to achieve joint verification of dynamic pointing, far-field beam, and communication performance.

[0048] like Figure 3 As shown, the integrated demonstration and verification system of this embodiment is arranged in a closed or semi-closed optical test straight channel. The total length of the channel is preferably 30 to 200 m, so as to take into account the needs of horizontal atmospheric channel simulation, adaptive optics link deployment and far-field spot observation. Figure 3 In the connection relationship shown, the transmitting and pointing analog end, the receiving and turbulence compensation end, and the intermediate folded optical path form an integral connection structure through a collimator, a folding mirror, and a mounting bracket, enabling each functional module to complete equivalent long-distance propagation, optical path folding, and component collaborative installation within a limited space.

[0049] The experimental system consists of a "transmitting and pointing simulation end" at one end, which houses a laser communication terminal or its equivalent simulation component, a dynamic pointing simulation module, and some optical collimating elements; and a "receiving and turbulence compensation end" at the other end, which houses a weak signal link simulation module, an adaptive optics device, a far-field monitoring camera, and a communication performance verification module. A folded optical path is formed between the two ends via a collimator, a folding mirror, and several support brackets, enabling long equivalent propagation distances and multi-node deployment within a limited space.

[0050] The system control and data processing platform is located in the laboratory control room and is connected to the above modules via fiber optic or network cables. It is used to uniformly issue control commands, collect various monitoring data, and complete the experimental process management.

[0051] The dynamic pointing simulation module includes: The dynamic pointing simulation device includes a high-precision two- or three-axis pointing platform, a drive control unit, an angle encoder, and a matching mechanical interface. The laser communication terminal under test or an equivalent transmitting optomechanical component is fixedly connected to the platform. Its azimuth and pitch axes are driven by servo motors, and real-time position feedback is achieved through a high-resolution angle encoder.

[0052] In the specific design, the angular resolution of the pointing platform is preferably better than 0.2 μrad to meet the verification requirement of the Earth-Moon laser link for terminal pointing accuracy better than 1 μrad.

[0053] The system control platform generates time-series pointing commands based on a preset Earth-Moon orbit and attitude change model. The orbit model can be based on a simplified Earth-Moon three-body motion model. The satellite's line-of-sight vector relative to the ground station can be calculated by mission design software or a self-developed program, and then the corresponding azimuth and elevation angles over time can be calculated.

[0054] These commands are sent to the pointing platform control unit, driving the servo motor to achieve micro-radian level dynamic pointing disturbances. Through closed-loop control with the angle encoder, the actual pointing trajectory strictly tracks the preset Earth-Moon link line-of-sight changes, thereby reproducing the pointing disturbance characteristics caused by changes in Earth-Moon distance and lunar orbital movement under ground test conditions.

[0055] When it is necessary to simulate attitude disturbances or platform jitter, a high-frequency, small-amplitude disturbance signal can be superimposed on the pointing trajectory. For example, the effect of reaction wheel torque or structural vibration on the optical axis pointing can be simulated to verify the dynamic tracking algorithm and actuator performance of the terminal under test.

[0056] The weak signal link simulation module includes: Optical attenuation link design: Considering the characteristics of the Earth-Moon distance exceeding 400,000 km, the extremely large geometric diffusion loss, and the non-negligible additional losses from atmospheric and optical links, this embodiment constructs an adjustable attenuation weak signal analog link between the transmitter and receiver.

[0057] This link typically includes multi-stage adjustable optical attenuators, variable neutral density filters, beam splitters, and several folding mirrors. Each stage of the optical attenuator can be continuously or steppedly adjusted by 10–20 dB, with an overall attenuation range of 60–80 dB. By combining different attenuation stages and levels, a smooth transition from a conventional strong signal to a weak Earth-Moon equivalent signal can be achieved.

[0058] Maintaining consistent light spot size: To maintain consistency in beam quality and spatial distribution under high attenuation conditions, this embodiment incorporates a far-field monitoring camera and a beam quality assessment unit in the attenuation link to monitor the beam morphology, center position, and energy distribution in real time. The system control platform fine-tunes the optical path attitude and attenuation element attitude based on the monitoring results, ensuring that the attenuation process does not introduce significant beam distortion or shift, and making the spatial characteristics of the beam seen at the receiver as consistent as possible with the actual Earth-Moon link.

[0059] The turbulence injection and adaptive optics compensation module includes: Turbulence simulation unit: In this embodiment, a programmable phase screen or equivalent spatial light modulator is arranged in the optical path at the receiving end to simulate the wavefront distortion caused by ground-based atmospheric turbulence. The turbulence model adopts the layered Kolmogorov turbulence model or its modified model, combined with the atmospheric structure constant Cn² distribution, wind speed and wind direction information of the actual observation station, to generate a phase distribution that varies with time.

[0060] The control platform loads these phase distributions onto the phase screen to inject dynamic disturbances into the light wavefront, thereby reproducing the turbulence effects under different elevation angles and atmospheric conditions.

[0061] Adaptive optics compensation link: An adaptive optics device is arranged behind the turbulence simulation unit, including a Shack-Hartmann wavefront sensor, a deformable mirror, a wavefront controller, and related optical beam splitting and imaging components. The wavefront sensor is used to measure the wavefront slope of the light after turbulence modulation, and the wavefront error is obtained through a reconstruction algorithm; the wavefront controller calculates the control voltage of each drive unit of the deformable mirror according to a preset control law, so as to realize real-time compensation for wavefront distortion.

[0062] The typical operating frequency of this compensation link can be in the hundreds of Hz range to adapt to the characteristic time of ground-based atmospheric turbulence. In the experiment, the far-field spot quality and communication performance under the two operating conditions of "adaptive optics off" and "adaptive optics on" can be compared to quantitatively evaluate the improvement effect of adaptive optics on the Earth-Moon laser communication link.

[0063] The three-parameter synchronous measurement module includes: The three-parameter synchronous measurement module in this embodiment is used to simultaneously acquire pointing deviation, far-field spot parameters and communication bit error rate, and establish the correlation between them.

[0064] Pointing deviation measurement: Using a high-resolution angle measuring device (such as a laser interferometer with a long focal length collimator and a large-aperture plane mirror) installed at the transmitting or receiving end, the instantaneous deviation of the optical axis of the measured terminal relative to the reference optical axis is obtained, achieving a measurement accuracy better than 0.2 μrad.

[0065] Far-field beam measurement: A monitoring camera or far-field detection array is configured at the receiving end to measure parameters such as the center position, diameter, ellipticity, and energy distribution of the received beam in real time, thereby reflecting the influence of turbulence and pointing disturbance on beam quality.

[0066] Bit error rate measurement: The communication performance verification module outputs real-time indicators such as bit error rate, packet loss rate, and throughput. The data is collected synchronously through the system control platform.

[0067] The three types of data are all timestamped and stored in the same data record file. Subsequent correlation analysis can reveal the quantitative impact of pointing deviation and spot changes on the bit error rate, thus providing a basis for designing the performance margin of the Earth-Moon link.

[0068] The communication performance verification module includes: The communication performance verification module includes an uplink / downlink modulation and demodulation unit, a synchronization and encoding / decoding unit, and a bit error detection unit. Its function is to test the communication performance of the terminal under test in a simulated Earth-Moon link environment.

[0069] In practical implementation, the downlink can adopt a high-speed modulation scheme, such as OOK, PPM or coherent modulation, to support data rates of 10Mbps to 1Gbps; the uplink can be configured with a relatively low rate, such as 20Mbps, for functions such as status feedback, reconfiguration command issuance and adaptive channel control, in order to match the envisioned goal of "research on Earth-Moon high-speed laser communication technology".

[0070] The bit error detection unit sends a predefined pseudo-random code sequence, counts the bit error rate at the receiving end, and records the bit error rate curves under different attenuation, different turbulence intensities, and different directional disturbance conditions, thereby forming a performance evaluation database for the Earth-Moon link.

[0071] Before the experiment, the lunar orbit and attitude parameters were configured in the system control platform to generate the corresponding pointing time series. Based on the expected channel conditions, the optical attenuation level and the target received power range were set. The target atmospheric turbulence parameters (Cn², wind speed, elevation angle variation range) were input, and the phase screen dynamic sequence was generated.

[0072] The optical components are calibrated, including optical axis alignment, focus position adjustment, camera exposure parameter setting, and adaptive optics closed-loop zeroing.

[0073] The experimental process may include the following steps: Initial link establishment: Under conditions of no turbulence, low attenuation, and static pointing, a stable optical link was established between the transmitter and receiver to confirm that each module was functioning normally.

[0074] Pointing to simulation and tracking verification: The dynamic pointing simulation device is activated, and the platform is driven to move according to the Earth-Moon line-of-sight time sequence. The terminal under test executes the capture and tracking algorithm, and the three-parameter module records the changes in pointing deviation, light spot, and bit error rate in real time to verify the robustness and stability of the tracking algorithm.

[0075] Weak signal link verification: Gradually increase the optical attenuation level to reduce the receiver power to near the equivalent level of satellite-to-ground or Earth-to-Moon systems. Record the bit error rate and communication interruption at each attenuation level to evaluate the communication performance of the tested terminal under weak signal conditions.

[0076] Turbulence and Adaptive Optics Validation: Under the condition of introducing dynamic turbulence, the adaptive optics compensation link was turned off and on respectively. The spot quality, received power fluctuation and bit error rate were compared between the two states to quantitatively evaluate the degree of improvement of link quality by adaptive optics.

[0077] Comprehensive operating condition test: Finally, a long-term communication test was conducted under the combined conditions of "dynamic pointing + high attenuation + dynamic turbulence + adaptive optics compensation". The link availability, average bit error rate and number of interruptions were statistically analyzed to form a comprehensive evaluation result of the Earth-Moon laser communication demonstration and verification.

[0078] The system control and data processing platform cleans and calibrates all test data, removes outliers, and categorizes and statistically analyzes the data according to operating conditions. By plotting relationship curves such as "pointing error - bit error rate," "spot drift - received power fluctuation," and "attenuation - bit error rate," the sensitivity of different factors to link performance is analyzed, providing a basis for subsequent spaceborne terminal design and ground station scheme optimization.

[0079] The integrated demonstration and verification system in this embodiment is not only suitable for ground-based pre-verification of Earth-Moon laser communication payloads, but can also be extended to verify near-Earth orbit satellite-to-ground links, inter-satellite links, and other deep-space target communication missions by adjusting the pointing model, link attenuation, and turbulence parameters. Combined with on-orbit satellite examples, a hardware-in-the-loop simulation approach can also be used to integrate the ground verification system with actual on-orbit links, enabling joint evaluation of Earth-Moon communication performance under complex network topologies.

[0080] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0081] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A comprehensive demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon, characterized in that, include: The dynamic pointing simulation module is used to generate a time-series pointing model based on real Earth-Moon orbital parameters and drive the pointing mechanism to generate micro-radian level dynamic pointing disturbances, thereby simulating the changes in angular velocity and attitude deviation during the change of the Earth-Moon line of sight in the ground environment. The weak signal link simulation module is used to construct an attenuation link covering 60-80dB and maintain beam consistency in order to reconstruct the equivalent optical power characteristics of an approximate Earth-Moon distance link that meets preset requirements. The turbulence injection and adaptive optics compensation module is used to generate dynamic phase distortion based on the ground-based atmospheric turbulence model and the change of the Earth-Moon line of sight elevation angle, and to achieve closed-loop compensation through a wavefront detector and a deformable mirror. The communication performance verification module is used to test the communication performance of the terminal under test in a simulated Earth-Moon link environment. The three-parameter synchronous measurement module is used to synchronously collect and correlate the pointing deviation, far-field spot morphology, and communication bit error rate.

2. The integrated demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon according to claim 1, characterized in that, The dynamic pointing simulation module includes: generating a realistic line-of-sight change model based on Earth-Moon orbit and attitude data; converting the line-of-sight change model into a sequence of commands for azimuth and pitch angles over time, and driving a two-axis or three-axis pointing platform to operate, causing the laser communication terminal under test or the equivalent transmitting optomechanical component installed on it to generate dynamic pointing disturbances on the order of microradius, thereby reproducing the dynamic changes in line-of-sight caused by changes in Earth-Moon distance, lunar orbit flight, and attitude maneuvers in a ground environment; wherein, the two-axis or three-axis pointing platform is driven by Earth-Moon orbit calculation parameters.

3. The integrated demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon according to claim 1, characterized in that, In the weak signal link simulation module, the attenuation link is set in the folded optical path between the transmitter and the receiver; Meanwhile, a far-field monitoring camera is configured in the attenuation link to monitor the spot shape, energy distribution and center drift in real time. By fine-tuning the attitude of the optical elements, the beam quality and spatial distribution are ensured to meet the preset requirements under different attenuation conditions, so that the optical characteristics are consistent with the real Earth-Moon link even under extremely weak signal conditions that meet the preset requirements.

4. The integrated demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon according to claim 1, characterized in that, The turbulence injection and adaptive optics compensation module is deployed in the optical path of the receiver and includes: a turbulence injection submodule and an adaptive optics compensation submodule; The turbulence injection submodule includes: using a programmable phase screen or equivalent spatial light modulator, based on the selected Kolmogorov turbulence model or layered atmospheric model, combined with the observation station's atmospheric structure constant Cn², line-of-sight elevation angle and wind speed parameters, to generate time-varying wavefront phase perturbations, which are then superimposed onto the propagating beam to simulate the effects of atmospheric turbulence under different altitudes, weather conditions and elevation angles. The adaptive optics compensation submodule includes a Shack-Hartmann wavefront sensor and a deformable mirror. The Shack-Hartmann wavefront sensor measures the wavefront slope after turbulence modulation in real time, the wavefront error distribution is obtained using a reconstruction algorithm, and the control quantity of the deformable mirror drive unit is calculated to achieve closed-loop compensation for wavefront distortion.

5. The integrated demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon according to claim 1, characterized in that, The communication performance verification module supports multiple modulation methods and different rate levels, and is used to measure indicators including link bit error rate, packet loss rate and data throughput under different pointing, different attenuation and different turbulence conditions.

6. The integrated demonstration and verification system for ultra-long-distance optical communication between the Earth and the Moon according to claim 1, characterized in that, The three-parameter synchronous measurement module includes: The pointing deviation is obtained through a high-precision angle measuring device at the transmitting or receiving end. The far-field spot shape is obtained by a monitoring camera deployed on the focal plane or near-focal plane of the receiving end. Based on the far-field spot shape, the center position, full width at half maximum (FWHM), ellipticity, and energy distribution of the spot are analyzed in real time. The communication error rate is obtained from statistics obtained by the communication performance verification module.

7. A comprehensive demonstration and verification method for ultra-long-distance optical communication between the Earth and the Moon, characterized in that, include: Step S1: Generate a line-of-sight change sequence based on the Earth-Moon orbit and mission design parameters, and drive the dynamic pointing simulation module to construct a dynamic pointing environment; Step S2: Set up a weak signal link simulation module between the transmitter and receiver, and adjust the link attenuation to a power level equivalent to the target Earth-Moon distance through the weak signal link simulation module; Step S3: Load the corresponding atmospheric turbulence phase disturbance in the optical path of the receiver through the turbulence injection and adaptive optics compensation module, and turn the adaptive optics compensation on or off as needed; Step S4: Test the communication performance of the terminal under test in a simulated Earth-Moon link environment using the communication performance verification module; Step S5: Using the three-parameter synchronous measurement module, the pointing error, beam parameters, and bit error rate are synchronously recorded and classified under different operating conditions to form link performance data under different pointing accuracies, different attenuation levels, and different turbulence intensities. By performing correlation analysis on the multidimensional data, the quantitative relationship between pointing error, beam quality, and communication bit error rate is obtained, which is used to guide the design margin of the spaceborne terminal and the formulation of link control strategies.

8. The comprehensive demonstration and verification method for ultra-long-distance optical communication between the Earth and the Moon according to claim 7, characterized in that, The dynamic pointing simulation module includes: generating a realistic line-of-sight change model based on Earth-Moon orbit and attitude data; converting the line-of-sight change model into a sequence of commands for azimuth and pitch angles over time, and driving a two-axis or three-axis pointing platform to operate, causing the laser communication terminal under test or equivalent transmitting optomechanical component mounted on it to generate dynamic pointing disturbances on the order of microradians, thereby reproducing the dynamic changes in line-of-sight caused by changes in Earth-Moon distance, lunar orbit flight, and attitude maneuvers in a ground environment; wherein, the two-axis or three-axis pointing platform is driven by Earth-Moon orbit calculation parameters; The attenuation link in the weak signal link simulation module is set in the folded optical path between the transmitter and receiver, and includes: a multi-stage adjustable optical attenuator, a neutral density filter, a beam splitter and a folding mirror. Meanwhile, a far-field monitoring camera and a beam quality assessment unit are configured in the attenuation link to monitor the beam shape, energy distribution and center drift in real time. By fine-tuning the attitude of the optical elements, the beam quality and spatial distribution are ensured to meet the preset requirements under different attenuation conditions, so that the optical characteristics are consistent with the real Earth-Moon link even under extremely weak signal conditions that meet the preset requirements.

9. The comprehensive demonstration and verification method for ultra-long-distance optical communication between the Earth and the Moon according to claim 7, characterized in that, The turbulence injection and adaptive optics compensation module is deployed in the optical path of the receiver and includes: a turbulence injection submodule and an adaptive optics compensation submodule; The turbulence injection submodule includes: using a programmable phase screen or equivalent spatial light modulator, based on the selected Kolmogorov turbulence model or layered atmospheric model, combined with the observation station's atmospheric structure constant Cn², line-of-sight elevation angle and wind speed parameters, to generate time-varying wavefront phase perturbations, which are then superimposed onto the propagating beam to simulate the effects of atmospheric turbulence under different altitudes, weather conditions and elevation angles. The adaptive optics compensation submodule includes a Shack-Hartmann wavefront sensor, a deformable mirror, and a wavefront controller. The Shack-Hartmann wavefront sensor measures the wavefront slope after turbulence modulation in real time, and the wavefront error distribution is obtained using a reconstruction algorithm. The control quantity of the deformable mirror drive unit is calculated to achieve closed-loop compensation for wavefront distortion.

10. The comprehensive demonstration and verification method for ultra-long-distance optical communication between the Earth and the Moon according to claim 7, characterized in that, The three-parameter synchronous measurement module includes: The pointing deviation is obtained through a high-precision angle measurement device at the transmitting or receiving end, using an angle deviation testing system composed of a laser interferometer, a long-focal-length collimator, a large-aperture plane mirror, and a CCD camera. The far-field spot morphology is acquired by a monitoring camera deployed on the focal plane or near-focal plane of the receiving end, and the center position, full width at half maximum (FWHM), ellipticity, and energy distribution of the spot are analyzed in real time. The communication bit error rate is obtained from statistics by the communication performance verification module; The communication performance verification module supports multiple modulation schemes and different rate levels, and is used to measure indicators including link bit error rate, packet loss rate and data throughput under different pointing, attenuation and turbulence conditions.

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