A method for determining satellite-to-ground laser link communication availability based on sky infrared remote sensing images

Abstract

A detection method for determining the communication availability of a satellite-to-ground laser link based on sky infrared remote sensing images comprises the following steps: 1) obtaining meteorological information and sky infrared remote sensing images above a satellite-to-ground laser communication ground station; 2) calculating the corresponding elevation angle and position relationship between the satellite and the ground station at each moment, and calculating the cloud base height and cloud optical depth of the spatial region through which the satellite-to-ground link passes based on the meteorological information and the sky infrared remote sensing images; 3) using a Monte Carlo laser vector transmission model to model the cloud laser channel based on the corresponding elevation angle and position relationship, cloud base height, and cloud optical depth results between the satellite and the ground station at each moment, and normalizing the residual to serve as a reference value for the link communication availability; 4) judging the communication availability of the laser link between the satellite and the ground station based on the atmospheric turbulence obtained in step 1; and 5) predicting future sky infrared remote sensing image change information of a specified satellite-to-ground laser ground station using machine learning technology.

Description

Technical Field

[0001] The present invention relates to the field of satellite-to-ground laser communications, and in particular to a method for determining the availability of satellite-to-ground laser link communications based on sky infrared remote sensing images. Background Art

[0002] An integrated space-ground information network is essential infrastructure for the future development of an information-based society. The growing demand for communications demands greater data capacity and higher transmission rates in future space communications networks. Compared to traditional microwave communications, laser communications offer advantages such as high speed and wide bandwidth, strong anti-interference capabilities, and enhanced confidentiality. Laser communications effectively avoid the limitations of microwave bandwidth bottlenecks and are a key technology and primary means for achieving high-speed backbone connectivity between space-based and terrestrial resources in future intersatellite and space-ground communications.

[0003] However, satellite-to-ground laser communications are affected by atmospheric factors. Cloud cover, fog, and haze in the atmosphere can severely attenuate laser transmission signals. The absorption and scattering of laser signals by ice crystals and water droplets in the clouds can even more seriously cause errors in satellite-received information or communication interruptions. The increase in wireless transmission traffic has also led to higher market demands for the functionality and availability of satellite communication ground stations. Satellite-to-ground laser ground stations must not only be able to complete communication functions but also be able to operate normally within a specified time period. If this normal operating capability is characterized by "communication availability," then if the current communication availability of the satellite-to-ground laser link can be determined or the future communication availability can be known in advance, it will be possible to better plan autonomous network topology in advance, rationally allocate link resources, and provide guarantees for 24-hour connectivity of the satellite-to-ground laser backbone network in the future.

[0004] The parameters used to determine communication availability primarily include determining whether the temperature is within the operating temperature range of the satellite-to-ground laser communication ground station, determining whether the atmospheric turbulence in the satellite-to-ground communication link exceeds the ground station's correction capability, and determining whether the margin of the satellite-to-ground communication link under cloud attenuation is greater than zero. These parameters must be available day and night, but obtaining all-weather cloud data is currently a major challenge.

[0005] Currently, cloud data can be obtained primarily through visual observation, millimeter-wave radar, and ground-based radiometers. Visual observation is the most commonly used method for estimating cloud thickness and determining cloud height, but its drawbacks include large human observation errors and poor nighttime lighting conditions, making it difficult to ensure the accuracy and consistency of cloud observation data throughout the day and night. Millimeter-wave radar uses millimeter-wave electromagnetic wave pulses to detect the sky and receives backscattered echoes to determine cloud positions. However, these devices are expensive and have significant losses, are significantly affected by weather conditions, and are severely attenuated during rainfall. Ground-based radiometers receive atmospheric microwave radiation from the ground to estimate cloud optical depth and other data, but rely on direct or indirect solar radiation and can only be used during daylight hours, failing to meet the requirements of continuous daytime operation.

[0006] In summary, current cloud data acquisition technologies either have the problem of high detection equipment cost, high maintenance and use costs, and are not suitable for rainy weather. Or they are limited by the lack of solar radiation and poor lighting conditions at night, making it impossible to obtain accurate cloud data at night under normal means. Both have the problem of incomplete link communication availability judgment indicators obtained daily, and are unable to conveniently and reliably provide the indicator parameters required for satellite-to-ground laser link communication availability judgment. Summary of the Invention

[0007] The purpose of the present invention is to provide a detection method for determining the availability of satellite-to-ground laser link communications based on sky infrared remote sensing images. The method can economically and feasibly obtain various judgment indicators including cloud data and meteorological data day and night under various meteorological conditions, and be used for judging the availability of satellite-to-ground laser link communications around the clock. The method can analyze and predict whether a specified satellite-to-ground laser ground station is suitable for satellite-to-ground laser link establishment at a certain moment in the future based on future changes in sky infrared remote sensing images and meteorological information predicted in advance, and the corresponding laser link quality, so as to be used for planning network topology link establishment and rationally allocating link resources in advance.

[0008] The technical solution of the present invention is: a detection method for determining the availability of satellite-to-ground laser link communication based on sky infrared remote sensing images, the steps of which are as follows:

[0009] Step 1: Obtain meteorological information and sky infrared remote sensing images above the satellite-to-ground laser communication ground station.

[0010] Step 2: Calculate the corresponding pitch angle and position relationship between the satellite and the ground station at each moment. Based on meteorological information and infrared remote sensing images of the sky, calculate the cloud base height and cloud optical depth of the space area where the satellite-to-ground link passes.

[0011] Step 3: Based on the corresponding pitch angle and position relationship between the satellite and the ground station at each moment, the cloud base height, and the cloud optical depth results, the cloud laser channel is modeled using the Monte Carlo laser vector transmission model. The loss and margin on the link between the satellite and the ground station are calculated, and the margin is normalized as a reference value for the link communication availability.

[0012] Step 4: Based on the meteorological information such as atmospheric turbulence obtained in step 1 and the link margin and link communication availability reference value calculated in step 3, the communication availability of the laser link between the satellite and the ground station is determined.

[0013] Step 5: Use machine learning to predict future infrared remote sensing image changes for a designated satellite-to-ground laser ground station. Use meteorological forecasting technology to predict future weather information for the designated satellite-to-ground laser ground station. Combined with these predicted future infrared remote sensing image changes and future weather information for the designated satellite-to-ground laser ground station, combined with the aforementioned communication availability detection method, it is possible to analyze and predict whether the designated satellite-to-ground laser ground station is suitable for satellite-to-ground laser link establishment at a certain point in the future, as well as the corresponding laser link quality after the link is established. This is used to plan network topology link establishment in advance and rationally allocate link resources.

[0014] The specific steps of obtaining the corresponding pitch angle and position relationship between the satellite and the ground station at each moment in step 2 are as follows: reading the two-row orbital elements of the satellite (the two-row orbital elements are a set of orbital parameters generated based on perturbation theory for predicting the position and velocity of Earth orbiters. By solving the differential equation of atmospheric drag, the thermospheric atmospheric density can be inverted. The orbital elements are a set of parameters used to describe the state of the satellite in its orbit. Usually, it refers to the six parameters required to describe the motion of celestial bodies along conic sections using the classical law of universal gravitation), using an orbital calculation module such as a geosynchronous orbit meteorological satellite to calculate the (x, y, z) coordinates of the satellite at each moment in the field of view angle range coordinate system of the satellite-to-ground laser ground station, and then calculating the distance, azimuth and pitch angle of the satellite relative to the satellite-to-ground laser ground station as the angle and position relationship.

[0015] The specific steps for obtaining the cloud base height and cloud thickness above the satellite-to-ground laser ground station described in step 2 are as follows:

[0016] Step 2-1: Establish a calculation model for cloud base height and cloud optical depth based on the global meteorological database and sky infrared remote sensing image experiments.

[0017] Step 2-2: Substitute the meteorological information parameters and sky infrared remote sensing image information at each moment into the above cloud optical depth and cloud base height calculation model to calculate the corresponding cloud optical depth and cloud base height.

[0018] Furthermore, the Monte Carlo laser vector transmission model is used to model the cloud laser channel and calculate the cloud attenuation loss on the link between the satellite and the ground station. The calculation formula is as follows:

[0019]

[0020] in It represents the attenuation per unit length of cloud layer (dB / km). The values ​​of a and b are determined by the cloud base height h, the operating frequency of the satellite system, etc. e L is the effective length through the cloud area (km), which is determined by the optical depth of the cloud layer τ, the pitch angle of the earth station relative to the satellite, etc. If there is no cloud above the ground station according to the infrared remote sensing image of the sky, then L e is 0, at which point the cloud attenuation loss L r Also 0.

[0021] Furthermore, the margin ω of the link between the satellite and the ground station is calculated using the following formula:

[0022] ω=EIRP-L r #(2)

[0023] EIRP is the effective isotropic radiated power (dB), which is used to describe the transmission capability of a ground station or satellite system. The specific value is determined by the output power of the ground station or satellite transmitter, feeder loss, and antenna radiation capability. It is different for different ground station satellite selections and communication requirements. r is the cloud attenuation loss calculated by formula (1).

[0024] Furthermore, based on meteorological information such as atmospheric turbulence and link loss values, the communication availability of the laser link between the satellite and the ground station at this moment is determined, and the following conditions are determined in turn: The specific determination steps are as follows:

[0025] ① Determine whether the temperature is within the operating temperature range of the satellite-to-ground laser communication ground station;

[0026] ② Determine whether the atmospheric turbulence of the satellite-to-ground communication link exceeds the correction capability of the ground station;

[0027] ③ Determine whether the margin ω of the communication link between the satellite and the ground station is greater than zero.

[0028] Furthermore, the above conditions are judged in sequence. As long as any one of the above conditions is not met, it can be determined that the laser communication link between the satellite and the ground station is unavailable. Only when the above three conditions are met at the same time, it can be determined that the laser communication link between the satellite and the ground station is available, and the link between the satellite and the ground station can be established.

[0029] If ω>0, it means that there is a communication margin when the communication signal reaches the ground station or satellite receiver, indicating that the link can achieve basic communication functions. Then the link margin ω is normalized as a parameter indicator of communication availability. It can be calculated as follows:

[0030]

[0031] The calculated value obtained by setting formula (3) It is a communication availability parameter indicator to characterize the quality of the laser link after the satellite-ground link is established. For multiple links at the same time at the same ground station, The larger the value, the less impact the atmospheric environment factors will have on the satellite-to-ground laser link after it is established, and the better the communication availability. This link can be preferred when selecting a link.

[0032] Furthermore, a cloud base height and cloud optical depth calculation model was established using a global meteorological database and sky infrared remote sensing images. This model calculates the cloud base height and cloud optical depth in the space region where the satellite-to-ground link passes. The specific steps are as follows:

[0033] Step 2-3: Calibrate the infrared remote sensing camera under experimental conditions, and calculate the total infrared radiation value of the atmosphere and clouds using the grayscale value of the original sky infrared remote sensing image obtained by the infrared remote sensing camera;

[0034] Step 2-4: Use the atmospheric transport model MODTRAN to divide the regions into mid-high and low latitudes and spring, summer, autumn and winter seasons, and establish the atmospheric water content and atmospheric net radiation value models respectively to obtain the corresponding atmospheric water content PWV and atmospheric net radiation value L A At the same time, using the global climate observation data set, the ground dew point temperature T and atmospheric water vapor content PWV were extracted according to the characteristics of mid-high and low latitude regions and spring, summer, autumn and winter seasons, and the corresponding statistical models were established. The function forms corresponding to the specific models are:

[0035] PWV=exp(k*T+b)#(4)

[0036] Among them, k and b are fitting coefficients, and their specific values ​​vary depending on the region and season. Finally, the ground dew point temperature T and the atmospheric net radiation value L are obtained. A Statistical mathematical models between;

[0037] Step 2-5: Subtract the total radiation value obtained in step 1 from the atmospheric radiation value obtained in step 2 to obtain the net radiation value of the cloud, L CldAssuming the cloud is a blackbody, the cloud base temperature is calculated using Planck's blackbody radiation law. Using atmospheric temperature profile data (specific values ​​of atmospheric temperature above a ground station and corresponding altitude), the temperature lapse rate (the rate of change of temperature with altitude at each moment) is calculated. Based on the temperature lapse rate and cloud base temperature, the cloud base height and cloud optical depth are calculated.

[0038] Furthermore, the cloud base height is calculated. The specific steps are as follows:

[0039] Step 2-6: Calculate the total infrared radiation value of the sky by inverting the grayscale value of the original sky infrared remote sensing image obtained by the infrared remote sensing camera;

[0040] Step 2-7: Obtain the ground dew point temperature T at each moment, and substitute the ground dew point temperature T and the atmospheric net radiation value L A The statistical mathematical model between them is used to obtain the net atmospheric radiation value at each moment;

[0041] Step 2-8: Compare the total radiation value calculated in step 1 with the calculated atmospheric radiation value L A Subtract and get the net radiation value L of the cloud Cld Assuming that the cloud is a black body, we can substitute Planck's black body radiation law to obtain the cloud bottom temperature T b ;

[0042] Step 2-9: Using the atmospheric temperature profile data (the atmospheric temperature above the ground station and the corresponding altitude values), calculate the vertical rate of change of the actual atmospheric temperature with altitude, that is, the vertical temperature lapse rate K;

[0043] Step 2-10: Substitute the temperature vertical lapse rate K into the formula Calculate the cloud base height h. Where T o is the ambient temperature of the ground station, T b is the cloud base temperature inverted in step 3.

[0044] The specific steps for calculating the cloud optical depth are as follows:

[0045] Step 2-11: Calculate the current average atmospheric transmittance τ by simulating the atmospheric transmission model MODTRAN based on latitude and seasonal characteristics;

[0046] Step 2-12: Using the formula The cloud optical depth τ is calculated, where L A 、T b are the cloud net radiation value and cloud base temperature, respectively.

[0047] The meteorological information above the satellite-to-ground laser communication ground station described in step 1 includes: ground meteorological information of the ground station and space meteorological information above the ground station, wherein the ground meteorological information includes the ambient temperature and ground dew point temperature of the satellite-to-ground laser communication ground station; the space meteorological information includes the atmospheric temperature profile data (the temperature of the atmosphere at different altitudes) and atmospheric turbulence information above the ground station.

[0048] The present invention can economically and feasibly obtain various judgment indicators including cloud data and meteorological data day and night under various meteorological conditions, and is used to judge the availability of all-weather satellite-to-ground laser link communications. Based on the future change information of the sky infrared remote sensing image and meteorological information predicted in advance, it can analyze and predict whether a specified satellite-to-ground laser ground station is suitable for satellite-to-ground laser link establishment at a certain moment in the future, as well as the corresponding laser link quality, so as to plan the network topology link establishment and reasonably allocate link resources in advance.

[0049] Beneficial effects: The present invention is aimed at the field of satellite-to-ground laser communications and provides a method for determining the availability of satellite-to-ground laser link communications based on sky infrared remote sensing images. By combining infrared band all-sky remote sensing images with collected ground station meteorological data, it can provide judgment index parameters for day and night all-weather data for the quantitative analysis of the availability of satellite-to-ground laser communication ground stations. This solves the problem that existing methods lack a complete data source and can only perform qualitative statistical analysis based on discrete data with large range and poor accuracy. At the same time, the cost of obtaining relevant data is low, and it has good accuracy and reliability. Combining the sky infrared remote sensing image information predicted by artificial intelligence and other methods with the meteorological information of a designated satellite-to-ground laser ground station obtained by meteorological forecasting technology, using the above-mentioned communication availability judgment method, it is possible to predict in advance whether a designated location is suitable for laser link establishment and predict the link quality, thereby providing a reference for planning network topology link establishment in advance and reasonably allocating link resources, which will help alleviate the problems of data backlog and link congestion caused by cloud cover and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The figure is a flow chart of a method for detecting the availability of satellite-to-ground laser link communication.

[0051] Figure 2 This is the flow chart for calculating cloud base height.

[0052] Figure 3 Flowchart for calculating cloud optical depth. DETAILED DESCRIPTION

[0053] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0054] Figure 1The flowchart of the satellite-to-ground laser link communication availability detection method provided by the present invention is schematically shown.

[0055] like Figure 1 As shown, the method for detecting the communication availability of the satellite-to-ground laser communication link needs to obtain ground weather information and space weather information of the satellite-to-ground laser communication ground station.

[0056] Meteorological information acquired from a satellite-to-ground laser communication ground station includes both ground-based and space-based weather information. Ground-based weather information includes the ambient temperature and ground dew point temperature of the satellite-to-ground laser communication ground station. Space-based weather information refers to the atmospheric temperature and atmospheric turbulence at various altitudes above the ground station at all times. Both ground-based and space-based weather information are used as the final meteorological information for the satellite-to-ground laser communication ground station.

[0057] Temperature sensors, pressure sensors, and other sensors can be deployed indoors and outdoors to measure layered space weather information at specified temporal and spatial resolutions. For example, a satellite-to-ground laser communication ground station can measure temperature, ground dew point temperature, pressure, and other space weather information at a 10-second temporal resolution, with both horizontal and vertical resolutions of 20 km. Meteorological data collected by various temperature and pressure sensors is aggregated to produce the final ground station weather information output. Infrared remote sensing images of the sky can be acquired using an infrared remote sensing camera, capturing infrared images of the sky in the infrared band.

[0058] Based on the above-mentioned infrared remote sensing image information of the sky and the meteorological information data of the satellite-to-ground laser ground station, the cloud base height and cloud optical depth calculation model given below are substituted to calculate the cloud base height and cloud optical depth of the spatial area through which the link passes.

[0059] The sky infrared remote sensing image described in step 1 can be obtained by using an infrared remote sensing camera to collect sky infrared images in infrared bands.

[0060] The calculation of the satellite's elevation angle and positional relationship relative to the ground station described in step 2 is specifically as follows: first, the coordinates of the target satellite within the field of view angle range of the satellite-to-ground laser communication ground station are calculated at each moment, and based on the above coordinates, the distance, azimuth, and elevation angle of the satellite relative to the satellite-to-ground laser communication ground station are calculated at each moment as the angle and positional relationship. Exemplarily, by reading two rows of roots of the target satellite, an orbit calculation module such as a geosynchronous meteorological satellite is used to calculate the (x, y, z) coordinates of the target satellite in the coordinate system at each moment within the field of view angle range of the ground station.

[0061] Step 2: Calculate the cloud base height and cloud thickness above the satellite-to-ground laser communication ground station based on meteorological information and infrared remote sensing images of the sky. The specific steps are as follows:

[0062] Step 2-1: Establish a calculation model for cloud base height and cloud optical depth based on the global meteorological database and sky infrared remote sensing image experiments.

[0063] Step 2-2: Substitute the meteorological information parameters and sky infrared remote sensing image information at each moment into the above cloud optical depth and cloud base height calculation model to calculate the corresponding cloud optical depth and cloud base height.

[0064] Step 2-1 includes the following steps: 1. Build a cloud base height and cloud optical depth calculation model based on the ERA-Interim and ECWMF global meteorological databases and sky infrared remote sensing image experiments. The method is as follows:

[0065] Step 2-1.1: Calibrate the infrared remote sensing camera under experimental conditions. When there are clouds in the original infrared remote sensing image, use the grayscale value of the original infrared remote sensing image obtained by the infrared remote sensing camera to calculate the total infrared radiation value of the atmosphere and clouds.

[0066] Step 2-1.2: Based on the ERA-Interim and ECMWF atmospheric databases, we extracted and analyzed meteorological data for the region over the past five years, including surface dew point temperature, surface ambient temperature, atmospheric water vapor content (PWW), and atmospheric temperature profiles. We also used the MODTRAN atmospheric radiation transfer model to analyze these data based on regional latitude and longitude, seasonal characteristics, and other factors. Ultimately, we developed a relationship model between atmospheric radiation values ​​and these meteorological data for the corresponding region and season, ultimately achieving the goal of calculating atmospheric radiation values ​​using these four meteorological data.

[0067] Step 2-1.3: Subtract the total radiation value obtained in step 1.1 from the atmospheric radiation value obtained in step 1.2 to obtain the net radiation value of the cloud. Assuming the cloud is a blackbody, calculate the cloud base temperature using Planck's blackbody radiation law. Use atmospheric temperature profile data (specific values ​​of atmospheric temperature above a ground station and corresponding altitude) to determine the vertical temperature lapse rate (the rate of change of temperature with altitude at each moment). Calculate the cloud base height based on the vertical temperature lapse rate and the cloud base temperature.

[0068] Step 2-2.1: Substitute the meteorological information parameters and sky infrared remote sensing image information at each moment into the above cloud optical depth and cloud base height calculation model to calculate the corresponding cloud optical depth and cloud base height.

[0069] Figure 2 The specific flow chart of cloud base height calculation is given schematically. The specific steps are as follows:

[0070] In step 1, the infrared remote sensing camera is calibrated to obtain the total infrared radiation value of the atmosphere and clouds. This includes:

[0071] Step 1.1: In an experimental setting, aim an infrared remote sensing camera at a surface blackbody source, ensuring that the blackbody fills the camera's field of view. Control the blackbody's temperature from 10°C to 100°C in 1°C increments. Take 100 images of the blackbody at each temperature and calculate the average grayscale value of each pixel. Analyze and fit the data to establish a mathematical relationship between the surface blackbody source's temperature and grayscale value.

[0072] Step 1.2: Establish the relationship between temperature and radiation value based on Planck's blackbody radiation law, and establish the relationship between the average pixel grayscale value of the infrared remote sensing image and the scene source radiation value. That is, determine the relationship between the average grayscale value of the image pixels output by the infrared remote sensing camera and the total radiation value received. Use the grayscale value of the original remote sensing image obtained by the infrared remote sensing camera to invert and calculate the total infrared radiation value of the sky.

[0073] Step 2: Obtain the radiation value under the atmospheric path.

[0074] Step 2.1: Use the atmospheric transport model MODTRAN to divide the atmospheric water content and atmospheric net radiation value models according to the mid-high and low latitude regions and the spring, summer, autumn and winter seasons, and obtain the corresponding atmospheric water content PWW and atmospheric net radiation value L A The corresponding statistical mathematical model between them.

[0075] Step 2.2: Using the ERA-Interim and ECMWF global climate observation datasets, we also divided the ground dew point temperature T and atmospheric water vapor content PWV according to the characteristics of mid-high and low latitude regions and spring, summer, autumn and winter seasons, and established corresponding statistical models. The function forms corresponding to the specific models are:

[0076] PWV=exp(k*T+b)#(1)

[0077] Among them, k and b are fitting coefficients, and their specific values ​​vary in different regions and seasons.

[0078] Step 2.3: Combine steps 2.1 and 2.2 above to establish the ground dew point temperature T and the atmospheric net radiation value L A Mathematical statistical models between.

[0079] Step 3: Calculate the cloud base height.

[0080] Step 3.1: Compare the calculated global radiation value with the calculated atmospheric radiation value L A Subtract and get the net radiation value L of the cloud Cld Assuming that the cloud is a black body, we can substitute Planck's black body radiation law to obtain the cloud bottom temperature T b .

[0081] Step 3.2: Using the atmospheric temperature profile data (the atmospheric temperature above the ground station and the corresponding altitude values), calculate the rate of change of the actual atmospheric temperature with altitude, that is, the vertical temperature lapse rate K.

[0082] Step 3.3: Substitute the temperature vertical lapse rate K into the formula Calculate the cloud base height h. Where T o is the ambient temperature of the ground station, T b is the cloud base temperature inverted in step 1 above.

[0083] Figure 3 The calculation model flow chart of cloud optical depth is given in detail. The specific steps are as follows:

[0084] Step 1: Calculate the current average atmospheric transmittance τ by simulating the atmospheric transmission model MODTRAN based on latitude and seasonal characteristics.

[0085] Step 2: Use the formula The cloud optical depth τ is calculated, where L A 、T b are the cloud net radiation value and cloud base temperature, respectively.

[0086] To calculate the pitch angle and position information of the satellite at each moment within the field of view of the satellite-to-ground laser communication ground station, an orbit calculation module such as the Himawari-8 geosynchronous orbit meteorological satellite can be used to calculate the (x, y, z) coordinates of the satellite in the coordinate system at each moment within the field of view of the ground station, and then calculate the distance, azimuth and pitch angle of the satellite relative to the satellite-to-ground laser communication ground station as the angle and position relationship.

[0087] Based on the corresponding angle and position relationship between the satellite and the ground station at each moment, the cloud base height and the cloud optical depth results, the Monte Carlo laser vector transmission model is used to model the cloud laser channel and calculate the loss on the link between the satellite and the ground station. The cloud attenuation loss is calculated as follows:

[0088]

[0089] in It represents the attenuation per unit length of cloud layer (dB / km). The values ​​of a and b are determined by the cloud base height h, the operating frequency of the satellite system, etc. e represents the effective length through the cloud area (km), which is determined by the optical depth of the cloud layer τ, the pitch angle of the earth station relative to the satellite, etc. If there is no cloud above the ground station according to the infrared remote sensing image of the sky, then L e is 0.

[0090] According to the loss of the link between the satellite and the ground station at each moment, the margin ω of the link between the satellite and the ground station is calculated. The calculation formula is as follows:

[0091] ω=EIRP-L r #(3)

[0092] EIRP is the effective isotropic radiated power (dB), which is used to describe the transmission capability of a ground station or satellite system. The specific value is determined by the output power of the ground station or satellite transmitter, feeder loss, and antenna radiation capability. It is different for different ground station satellite selections and communication requirements. r is the cloud attenuation loss calculated by formula (2).

[0093] The conditions for determining the availability of satellite-to-ground laser link communications include:

[0094] ① Determine whether the temperature is within the operating temperature range of the satellite-to-ground laser communication ground station;

[0095] ② Determine whether the atmospheric turbulence of the satellite-to-ground communication link exceeds the correction capability of the ground station;

[0096] ③ Determine whether the margin ω of the communication link between the satellite and the ground station is greater than zero.

[0097] The above conditions are judged in turn. As long as any one of the above conditions is not met, it can be determined that the laser communication link between the satellite and the ground station is unavailable. Only when the above three conditions are met at the same time can it be determined that the laser communication link between the satellite and the ground station is available and a link can be established between the satellite and the ground station.

[0098] If ω>0, it means that there is a communication margin when the communication signal reaches the ground station or satellite receiver, indicating that the link can achieve basic communication functions. Then, the margin ω of the link between the satellite and the ground station is normalized and can be calculated as follows:

[0099]

[0100] The calculated value obtained by setting formula (4) It is a communication availability parameter indicator to characterize the quality of the laser link after the satellite-ground link is established. For multiple links at the same time at the same ground station, The larger the value, the less impact the atmospheric environment factors will have on the satellite-to-ground laser link after it is established, and the better the communication availability. This link can be preferred when selecting a link.

[0101] It should be understood that the atmospheric turbulence information, cloud information and loss corresponding to different angles and positional relationships may be different. Therefore, the corresponding atmospheric turbulence information, cloud cover information and loss should be obtained for different angles and positional relationships for judgment.

[0102] Based on the above satellite-to-ground laser link communication availability determination method, whether a designated location is suitable for laser link establishment and link quality are predicted in the future. Step 5 is as follows:

[0103] Step 5-1: The sky infrared remote sensing images obtained by long-term observations above the designated laser ground station can be used as a training dataset and processed into a time series dataset of sky infrared remote sensing images with custom time intervals at certain time intervals. Based on the different change characteristics of different types of clouds, the sky infrared remote sensing images can be roughly classified before prediction. Based on the classification results, change prediction models for different types of clouds are trained. A sky infrared remote sensing image prediction model is established using algorithms such as neural networks, random forests, and K-nearest neighbors. The above time series dataset is used as input, and recent live sky infrared remote sensing images are used as output. The mean absolute error and mean square error are used to evaluate the quality of the model. The model with the highest accuracy is selected as the final sky infrared remote sensing image prediction model to predict the changes in clouds in the sky infrared remote sensing image at the next moment. This allows the prediction of sky infrared remote sensing image change information in the future based on the current sky infrared remote sensing image of the designated laser ground station.

[0104] Step 5-2: Use weather forecasting technology to predict accurate weather information for the designated area in advance.

[0105] Step 5-3: Based on the information obtained in steps 5-1 and 5-2 above, calculate the cloud base height and cloud thickness, and then calculate the link margin value and communication availability parameter index Combined with the above-mentioned judgment conditions for the availability of satellite-to-ground laser link communication, if the three conditions for communication availability judgment are met at the same time, it is predicted that the link can be used to establish link communication in the future. Otherwise, it is predicted that the link cannot be used to establish link communication in the future, so as to predict in advance whether the specified location is suitable for laser link establishment. If there are multiple links between the satellite and the ground station that can simultaneously meet the three conditions for communication availability judgment in the future, then the corresponding links of the multiple satellite-to-ground links within the time are used. The value size compares the link quality. The larger the value, the smaller the impact of atmospheric environmental factors on the satellite-to-ground laser link after it is established in the future, and the better the communication availability, the more inclined to choose it. The communication link with the largest value is selected, thereby providing a reference for planning the satellite-to-ground network topology and link establishment in advance and reasonably allocating link resources, or directly planning the network topology and link establishment and reasonably allocating link resources.

Claims

1. A detection method for determining the availability of satellite-to-ground laser link communication based on sky infrared remote sensing images, characterized in that: The following steps are involved: Step 1: Obtain meteorological information and sky infrared remote sensing images above the satellite-to-ground laser communication ground station; The meteorological information includes: ground meteorological information of the ground station and space meteorological information above the ground station, wherein the ground meteorological information includes the ambient temperature and ground dew point temperature of the satellite-to-ground laser communication ground station; the space meteorological information includes atmospheric temperature profile data above the ground station and atmospheric turbulence information; Step 2: Calculate the corresponding pitch angle and position relationship between the satellite and the ground station at each moment. Based on meteorological information and infrared remote sensing images of the sky, calculate the cloud base height and cloud optical depth of the space area where the satellite-to-ground link passes. Step 3: Based on the corresponding elevation angle and position relationship between the satellite and the ground station at each moment, the cloud base height, and the cloud optical depth, a Monte Carlo laser vector transmission model is used to model the cloud laser channel. The loss and margin on the link between the satellite and the ground station are calculated, and the margin is normalized to serve as a reference value for link communication availability. Step 4: Determine the communication availability of the laser link between the satellite and the ground station based on the atmospheric temperature profile data above the ground station obtained in step 1, the atmospheric turbulence meteorological information, and the link margin and link communication availability reference values ​​calculated in step 3; Step 5: Use machine learning technology to predict future changes in infrared remote sensing images of the sky at the designated satellite-to-ground laser ground station, and use meteorological forecasting technology to predict future weather information for the designated satellite-to-ground laser ground station. Combined with the method for determining the communication availability of the laser link between the satellite and the ground station in step 4, it is possible to analyze and predict whether the designated satellite-to-ground laser communication ground station is suitable for satellite-to-ground laser link establishment at a certain point in the future, as well as the quality of the laser link after the link is established. This is used to plan network topology link establishment in advance and reasonably allocate link resources. The specific steps are as follows: read the two-row orbital elements of the satellite, use the geosynchronous orbit meteorological satellite orbit calculation module to calculate the (x, y, z) coordinates of the satellite at each moment in the field of view angle range coordinate system of the satellite-to-ground laser ground station, and then calculate the distance, azimuth and pitch angle of the satellite relative to the satellite-to-ground laser ground station as the corresponding pitch angle and position relationship between the satellite and the ground station in step 2; The specific steps for calculating the cloud base height and cloud optical depth of the space region where the satellite-to-ground link passes, as described in step 2, are as follows: Step 2-1: Establish a cloud base height and cloud optical depth calculation model based on the global meteorological database and sky infrared remote sensing image experiments; Step 2-2: Substitute the meteorological information parameters and sky infrared remote sensing image information at each moment into the above cloud optical depth and cloud base height calculation model to calculate the corresponding cloud optical depth and cloud base height.

2. The method according to claim 1, wherein: The cloud laser channel is modeled using the Monte Carlo laser vector transmission model to calculate the cloud attenuation loss on the link between the satellite and the ground station. The calculation formula is as follows: in Indicates the attenuation per unit length of cloud layer, in dB / km; the values ​​of a and b are determined by the cloud base height h and the operating frequency of the satellite system; L e It represents the effective length through the cloud area, in km, which is determined by the optical depth of the cloud layer τ and the pitch angle of the earth station relative to the satellite. If there is no cloud above the ground station according to the infrared remote sensing image of the sky, then L e is 0, at which point the cloud attenuation loss L r Also 0.

3. The method according to claim 1, wherein: Calculate the link margin ω between the satellite and the ground station using the following formula: ω=EIRP-L r #(2) EIRP is the effective isotropic radiated power, in dB, which is used to describe the transmission capability of a ground station or satellite system. It is determined by the output power of the ground station or satellite transmitter, feeder loss, and antenna radiation capability. r is the cloud attenuation loss calculated by formula (1); If ω>0, the link margin ω is normalized as the reference value of communication availability Calculate as follows:

4. The method according to claim 3, wherein: Based on atmospheric turbulence weather information and link loss values, the communication availability of the laser link between the satellite and the ground station at this moment is determined by determining whether the following conditions are met. The specific communication availability detection method is as follows: Condition 1: Determine whether the temperature is within the operating temperature range of the satellite-to-ground laser communication ground station; Condition 2: Determine whether the atmospheric turbulence of the satellite-to-ground communication link exceeds the correction capability of the ground station; Condition 3: Determine whether the margin ω of the communication link between the satellite and the ground station is greater than zero.

5. The method according to claim 4, wherein: Determine whether the conditions are met in turn. As long as any one of conditions 1, 2, and 3 is not met, it can be determined that the laser communication link between the satellite and the ground station is unavailable. Only when the above three conditions are met at the same time can it be determined that the laser communication link between the satellite and the ground station is available and a link can be established between the satellite and the ground station. At the same time, set the calculated value of formula (3) is a communication availability parameter indicator, which is used to characterize the quality of the laser link after the satellite-to-ground link is established, and The larger the value, the less impact the atmospheric environment factors will have on the satellite-to-ground laser link after it is established, and the better the communication availability.

6. The method according to claim 2, wherein: Using a global meteorological database and infrared remote sensing images of the sky, a cloud base height and cloud optical depth calculation model was established. This model calculates the cloud base height and cloud optical depth in the space region where the satellite-to-ground link passes. The specific steps are as follows: Step 2-3: Calibrate the infrared remote sensing camera under experimental conditions, and calculate the total infrared radiation value of the atmosphere and clouds using the grayscale value of the original sky infrared remote sensing image obtained by the infrared remote sensing camera; Step 2-4: Use the atmospheric transport model MODTRAN to divide the regions into mid-high and low latitudes and spring, summer, autumn and winter seasons, and establish the atmospheric water content and atmospheric net radiation value models respectively to obtain the corresponding atmospheric water content PWV and atmospheric net radiation value L A The corresponding statistical mathematical model between them is constructed; at the same time, the global climate observation data set is used, and the ground dew point temperature T and atmospheric water vapor content PWV are extracted according to the characteristics of mid-high and low latitude regions and spring, summer, autumn and winter seasons. The corresponding statistical models are established respectively. The function forms corresponding to the specific models are: PWV=exp(k*T+c)#(4) Among them, k and c are fitting coefficients, and their specific values ​​vary with different regions and seasons. Finally, the ground dew point temperature T and the atmospheric net radiation value L are obtained. A Statistical mathematical models between; Step 2-5: Subtract the total infrared radiation value obtained in step 2-3 from the atmospheric net radiation value obtained in step 2-4 to obtain the cloud net radiation value L Cld , assuming that the cloud is a black body at this time, the cloud base temperature is calculated according to Planck's blackbody radiation law; using the atmospheric temperature profile data, that is, the specific values ​​of the atmospheric temperature above the ground station and the corresponding height, the vertical temperature lapse rate is obtained, that is, the rate of change of temperature with height at each moment, and the cloud base height and cloud optical depth are calculated based on the vertical temperature lapse rate and cloud base temperature.

7. The method according to claim 2, wherein: To calculate the cloud base height, the specific steps are as follows: Step 2-6: Calculate the total infrared radiation value of the sky by inverting the grayscale value of the original sky infrared remote sensing image obtained by the sky infrared remote sensing camera; Step 2-7: Obtain the ground dew point temperature T at each moment, and substitute the ground dew point temperature T and the atmospheric net radiation value L A The statistical mathematical model between them is used to obtain the net atmospheric radiation value at each moment; Step 2-8: Compare the total infrared radiation value calculated in step 2-6 with the atmospheric net radiation value L calculated in step 2-7. A Subtract and get the net radiation value L of the cloud Cld Assuming that the cloud is a black body, we can substitute Planck's black body radiation law to obtain the cloud bottom temperature T b ; Step 2-9: Using the atmospheric temperature profile data, i.e., the atmospheric temperature above the ground station and the corresponding altitude values, calculate the vertical rate of change of the actual atmospheric temperature with altitude, i.e., the vertical temperature lapse rate K; Step 2-10: Substitute the temperature vertical lapse rate K into the formula Calculate the cloud base height h, where T o is the ambient temperature of the ground station, T b is the cloud base temperature retrieved in step 2-8.

8. The method according to claim 1, wherein: The method for determining the communication availability of the laser link between the satellite and the ground station described in step 5 is combined with the method described in step 4 to predict whether the designated location is suitable for laser link establishment and the link quality in the future. The steps are as follows: Step 5-1: Use the infrared remote sensing images of the sky obtained by long-term observations above the designated laser ground station as a training dataset, and use machine learning artificial intelligence technology to perform predictive modeling. Based on the current cloud map of the designated laser ground station, predict the changes in the infrared remote sensing images of the sky in the future. Step 5-2: Use weather forecasting technology to predict accurate weather information for the designated area in advance; Step 5-3: Combined with the method for determining the communication availability of the laser link between the satellite and the ground station in step 4, predict in advance whether the designated location is suitable for laser link establishment and predict the link quality, thereby providing a reference for planning network topology link establishment in advance and reasonably allocating link resources.

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