A space-ground integrated global environmental monitoring system based on a constellation of cube satellites

Abstract

The application provides a global environment monitoring system based on a constellation of cube satellites, comprising a monitoring satellite constellation subsystem, an ocean monitoring buoy subsystem and a ground data processing subsystem, wherein the monitoring satellite constellation subsystem is composed of three 6u cube satellites; the ocean monitoring buoy subsystem is arranged in the sea area near all global coastal nuclear power plants, can detect radioactive substances leaked into seawater in real time, and sends the detected data to the satellite constellation subsystem, thereby forming a real-time monitoring network for global nuclear power plants; the ground data processing subsystem is mainly used for controlling satellite operation and receiving satellite data, can acquire monitoring data of the atmosphere and the ocean by the monitoring satellite constellation subsystem and monitoring data of the ocean by the ocean monitoring buoy subsystem, judges, and positions and warns of environmental accidents such as nuclear leakage of nuclear power plants.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental monitoring, and particularly relates to a space-ground integrated global environmental protection monitoring system based on a cubic satellite constellation. BACKGROUND

[0002] Ocean resources are essential important resources for human survival. Since the Second World War, atomic energy has been used more and more widely. Nuclear power plants have great development prospects due to their advantages of low pollution and high energy, and are valued by countries around the world. However, once an accident occurs in a nuclear power plant, radioactive substances inside the nuclear power plant will be released, which will bring serious disaster to the surrounding area of the nuclear power plant and even the world. Once the radioactive substances are released and enter the ocean, they will cause great harm to the ecological system, and will also cause fatal radioactive substances to enter the human body through drinking water, marine products and the like, directly endangering human life and health. Therefore, ocean nuclear pollution is a kind of environmental problem with great threat. Therefore, rapid environmental protection monitoring of ocean nuclear pollution is imperative.

[0003] Current ocean nuclear pollution monitoring is mainly "ground-based" ocean environment monitoring, which relies on near-shore monitoring stations, ocean monitoring special ships and ocean monitoring buoys. The near-shore monitoring station can realize effective monitoring of ocean nuclear pollution by arranging monitoring stations at various monitoring points along the coastline. The near-shore monitoring station can realize long-time and high-precision data collection, is easy to maintain and has relatively low cost. However, the monitoring position of the near-shore monitoring station is limited by the coastline, and can only monitor the coastline, and cannot monitor the sea area far from the coastline. Although the ocean monitoring special ship can realize all-time monitoring of data, the ocean monitoring special ship is limited by the moving speed of the ship, and when the monitoring points in the sea area are far apart, it takes a long time, and the operation and maintenance of the ocean environment monitoring ship costs a huge amount of money. According to estimation, the annual operation and maintenance cost of a 500t ship is about 10 million yuan.

[0004] At the same time, global warming is caused by the continuous accumulation of greenhouse effect, which leads to the imbalance of energy absorption and emission of the geosystem, and the energy is continuously accumulated in the geosystem, thereby causing temperature rise and global climate warming. Global warming may lead to great changes in global precipitation distribution, melting of glaciers and permafrost, rising of sea level, and increase of extreme weather events, which will directly or indirectly threaten the existing living conditions of human beings in terms of physical health and safety, living safety and crop safety.

[0005] Greenhouse gases are the culprits of global warming. The most significant greenhouse gas in the atmosphere is carbon dioxide. Due to the expansion of industrial production, the increase in the number of motor vehicles and the like, the emission of greenhouse gases is increasing day by day, which leads to more and more serious greenhouse effect of the earth, and has directly or indirectly affected the survival of earth organisms. Therefore, the monitoring of carbon dioxide is particularly important. SUMMARY

[0006] The technical problem solved by the present application is to provide a global environmental monitoring system based on a constellation of cubic satellites, which can monitor the concentration of greenhouse gases and the source of the greenhouse gases, and monitor the ocean nuclear pollution.

[0007] To solve the above technical problem, the present application provides a global environmental monitoring system based on a constellation of cubic satellites, which can monitor the concentration of greenhouse gases and the source of the greenhouse gases, and monitor the ocean nuclear pollution.

[0008] The specific technical solution is as follows:

[0009] The global environmental monitoring system based on a constellation of cubic satellites comprises a monitoring satellite constellation subsystem, an ocean monitoring buoy subsystem, and a ground data processing subsystem, the monitoring satellite constellation subsystem is composed of three 6u cubic satellites, the ocean monitoring buoy subsystem is arranged in the sea area near the coastal nuclear power plant, can detect the radioactive substances leaked into the seawater in real time, and send the detected data to the satellite constellation subsystem, thereby forming a real-time monitoring network for global nuclear power plants, the ground data processing subsystem is mainly used for controlling the satellite operation and receiving the satellite data, can obtain the monitoring data of the atmosphere and the ocean by the monitoring satellite constellation subsystem and the monitoring data of the ocean by the ocean monitoring buoy subsystem, and judge and locate and warn the environmental accidents such as nuclear leakage of the nuclear power plant.

[0010] Further, the monitoring satellite constellation subsystem is composed of three cubic satellites which are not coplanar, the cubic satellite adopts a 6u size rectangular body and a deployed solar wing configuration, has a three-axis stable attitude control capability, the monitoring satellite constellation subsystem comprises a comprehensive information management module, an attitude control module, a power module, and a data processing module, the comprehensive information management module is responsible for the management and control of the on-orbit flight task of the cubic satellite, is composed of multiple plug-in computer processing boards, the attitude control module is responsible for the attitude control of the cubic satellite, comprises one sun sensor, two star sensors, three reaction flywheels, and one mechanical gyroscope, the power module is responsible for the power management and power distribution of the cubic satellite, comprises a deployed solar cell panel, a power management single-chip microcomputer, and a storage battery, wherein the storage battery adopts a multifunctional lithium battery structure integrated with the side cabin plate, effectively increases the space inside the satellite, and the data processing and transmission module is responsible for pre-processing the ground image information obtained by the camera load, and receiving the real-time monitoring data sent by the sea buoy.

[0011] Further, the payload of the CubeSat of the monitoring satellite constellation subsystem includes a visible-infrared integrated multi-spectral camera and an Internet of Things payload, the multi-spectral camera can detect the spectral information of the target, obtain high-spectral-resolution continuous and narrow-band image data, and monitor the growth of marine algae and other marine organisms, the change of seawater color, and the absorption of CO2 in the atmosphere to special spectrum; the Internet of Things payload terminal is an ultra-long distance wireless transmission scheme based on spread spectrum technology, which is divided into an on-board part and a sea surface buoy part, the Internet of Things payload terminal on the satellite collects radioactive material detection data and buoy coordinates emitted by the buoys arranged on the sea surface.

[0012] Further, the monitoring of the growth of marine algae and other marine organisms and the change of seawater color mainly refers to the fact that marine algae plants have a greater impact on seawater color, including diatoms, green algae, blue-green algae, red algae and brown algae. When nuclear pollution radioactive substances enter the ocean, the enrichment of radionuclides causes marine organisms to suffer internal or external radiation and die, resulting in eutrophication of seawater. At the same time, most blue-green algae have stronger resistance to nuclear radiation, while diatoms, green algae and red algae are relatively weak. Eutrophic seawater allows blue-green algae to multiply rapidly, and blue-green algae, as prokaryotes, are rich in chlorophyll. The large number of blue-green algae makes the chlorophyll in the ocean reach about 1.5-2 times the original level, causing the color of the ocean water to change, with strong absorption in the blue-green band and strong scattering in the red and near-infrared bands, thus presenting a characteristic brown color. Therefore, the use of a multi-spectral camera with blue, green, red and near-infrared optical channels for ocean imaging can indirectly observe the distribution of radioactive substances in the ocean, thereby achieving monitoring of changes in nuclear radiation water pollution.

[0013] Further, in the LoRa-based satellite Internet of Things scheme, the Internet of Things terminal of the monitoring satellite constellation subsystem and the sea surface buoy both use LoRa modulation technology and are adapted according to the communication situation.

[0014] Further, the satellite-borne LoRa Internet of Things payload includes a memory, an MCU, a power supply module, a power amplifier / LNA module, a CAN communication interface, a 28V power supply interface and a UART data interface. The LoRa module realizes the functions of data modulation and demodulation and self-organizing network. The memory realizes the function of storing the received data. The power amplifier / LNA is a bidirectional amplifier that can undertake power amplification during transmission and low-noise amplification during reception. The MCU realizes the functions of reading and writing data streams and configuring parameters of the LoRa module.

[0015] Further, the ocean monitoring buoy subsystem includes a plurality of ocean buoys arranged near a nuclear power plant, which can automatically detect radioactive substances in seawater and transmit detection data to the CubeSat through the Internet of Things, and the CubeSat transmits the data to the ground station,

[0016] Further, the ocean buoy includes a monitoring module, a positioning module, an Internet of Things module, a power module and a power supply module. The monitoring module includes a radiation detection unit and a mass spectrometry detection unit, which are used to automatically monitor and detect radioactive substances in the water body. The radiation detection unit is used to detect the radiation dose of gamma rays, and the mass spectrometry detection unit is mainly used to detect radioactive particles in the ocean. The positioning module is equipped with a global positioning system, which is used to obtain real-time position information of the buoy. The Internet of Things module is equipped with an Internet of Things payload antenna system, which can communicate with the monitoring satellite constellation subsystem and send water quality information detected by the buoy to the monitoring satellite constellation subsystem. The power supply module includes a battery array and a battery, which provide power for all devices on the buoy. The buoy will change its position with the movement of seawater, and the power module corrects the position of the buoy according to the information of the positioning module.

[0017] Further, the main task of the ground data processing subsystem is to control the cube satellite constellation system. The method for receiving and processing data by the ground data processing subsystem includes the following steps:

[0018] Step one, receiving the greenhouse gas remote sensing image, the ocean blue-green algae remote sensing image and the buoy detection data returned by the satellite;

[0019] Step two, pre-processing the above data, including noise reduction, fitting, interpolation, and removing data outliers, specific noise and interference;

[0020] Step three, post-processing the data, including image processing, signal processing, multi-information fusion and state optimal estimation;

[0021] Step four, forming regional and global greenhouse gas daily concentration estimation, regional and global ocean radioactive material daily concentration estimation, regional and global greenhouse gas concentration long-period statistical analysis, and regional and global ocean radioactive material concentration long-period statistical analysis.

[0022] Further, the space-ground integrated environmental protection monitoring system based on the cube satellite constellation has three operation modes:

[0023] 1) Global survey mode

[0024] During daily operation, the system is in global survey mode. In the global survey mode, the cube satellite constellation subsystem operates in a predetermined orbit, and the cube satellite performs nadir scanning by side swing control of the remote sensing payload to monitor the global in the maximum ground coverage mode. The ocean monitoring buoy subsystem collects data of the corresponding water area and uploads it to the cube satellite constellation subsystem through the Internet of Things. The ground data processing subsystem is responsible for collecting remote sensing data of each orbit of the over-the-top satellite and data of the ocean monitoring buoy subsystem, generating global greenhouse gas concentration distribution map, global ocean radioactive material content distribution map and other refined high-level data.

[0025] 2) Area detailed investigation mode

[0026] When the area detailed investigation is needed, the system runs the area detailed investigation mode, under the area detailed investigation mode, the CubeSat constellation subsystem runs on the predetermined orbit, the CubeSat autonomously plans the area scanning attitude sequence, conducts the attitude control, and investigates the specific area, so as to realize the longest time monitoring of the target area in the reentry period. Specifically, firstly, the target area is scanned by the CubeSat to plan the attitude sequence; then the ground station uploads the related attitude instructions to the satellite; the corresponding area of the ocean monitoring buoy subsystem collects the water data and uploads the satellite; the ground data processing subsystem is responsible for collecting the remote sensing data and buoy data of each orbit of the over-the-top satellite, and generating the greenhouse gas concentration distribution map of the target area, the area ocean radioactive material content distribution map and the carbon emission estimation data in the specific time interval;

[0027] 3) Emergency response mode

[0028] When the emergency response is needed, the emergency response mode of the system is triggered manually by the ground data processing subsystem or automatically triggered by the alarm of the detection value of the corresponding buoy, under the emergency response mode, the CubeSat constellation runs on the predetermined orbit, and the CubeSat conducts the staring observation on the hot area through the attitude control, so as to realize the longest time monitoring of the hot area in the reentry period. Specifically, when the buoy detects that the 37Cs content greatly exceeds the normal value range, or the concentration value increases for consecutive days, the corresponding alarm can be sent; then the ground station uploads the staring imaging instructions to the satellite or the satellite autonomously plans the staring imaging instructions to the area where the corresponding buoy is located, and the ground data processing subsystem generates the greenhouse gas concentration distribution map, the ocean radioactive material content distribution map, the greenhouse gas propagation prediction map and the ocean radioactive material propagation prediction map of the accident area in combination with the collected remote sensing data and buoy data of each orbit of the over-the-top satellite.

[0029] Compared with the prior art, the present application has the following advantages: the advantages of high precision, fast response ground monitoring means and wide coverage of the CubeSat system are combined, the possible nuclear leakage accidents occurring in the world can be quickly and effectively warned, and the diffusion and propagation path of the radioactive material of the nuclear pollution can be accurately predicted. By using the monitoring system, the harm to the safety of the organisms and the human beings caused by the nuclear power plant accidents can be effectively reduced, and the ecological civilization of the earth can be protected.

[0030] Firstly, the fast warning and the long period monitoring of the ocean nuclear radiation are combined

[0031] Secondly, the ocean nuclear radiation monitoring and the atmospheric greenhouse gas monitoring are combined

[0032] Thirdly, the construction cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 An environmental monitoring system schematic diagram;

[0034] Figure 2 is a cube star schematic diagram;

[0035] Figure 3 is a cube star system composition schematic diagram;

[0036] Figure 4 is a satellite LoRa Internet of Things payload composition schematic diagram;

[0037] Figure 5 is a nuclear pollution monitoring buoy schematic diagram;

[0038] Figure 6 is a ground processing subsystem data processing flowchart.

[0039] Figure legend: 1, TT&C antenna, 2, TT&C unit, 3, Internet of Things antenna, 4, data transmission unit, 5, camera main payload, 6, power management unit, 7, gyroscope, 8, flywheel, 9, integrated information management module, 10, data processing module, 11, star sensor, 12, solar sensor, 13, cube star constellation subsystem, 14, ground data processing subsystem, 15, ocean monitoring buoy subsystem, 16, Internet of Things, 17, visible light infrared integrated camera, 18, atmospheric greenhouse gas monitoring, 19, ocean nuclear pollution monitoring, 20, atmosphere, 21, ocean, 22, Internet of Things module, 23, global positioning module, 24, solar panel, 25, buoy main body, 26, pollution monitoring module, 27, power module DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the application will be described below with reference to the accompanying drawings. Figures 1-6 The technical solutions in the embodiments of the application will be described below with reference to the accompanying drawings.

[0041] A global environmental monitoring system based on a cube star constellation, comprising a monitoring satellite constellation subsystem, an ocean monitoring buoy subsystem and a ground data processing subsystem, the monitoring satellite constellation subsystem comprising three 6u cube stars; the ocean monitoring buoy subsystem is arranged in the sea area near a coastal nuclear power plant, can detect radioactive substances leaked into seawater in real time, and sends the detected data to the satellite constellation subsystem, thereby forming a real-time monitoring network for global nuclear power plants; the ground data processing subsystem is mainly used for controlling satellite operation and receiving satellite data, can obtain monitoring data of the atmosphere and the ocean from the monitoring satellite constellation subsystem and monitoring data of the ocean from the ocean monitoring buoy subsystem, and judges and locates and warns of environmental accidents such as nuclear leakage of nuclear power plants.

[0042] To construct a high-timeliness and high-precision global greenhouse gas and marine pollution monitoring constellation system, and meet the working condition requirements of cameras and Internet of Things payloads, in combination with the overall mission design of the constellation, the satellite constellation design should meet the following index requirements:

[0043] (1) To achieve coverage monitoring of global greenhouse gases and marine environment, realize greenhouse gas diffusion analysis and emission source positioning, the constellation should meet the following requirements: within 24 hours, global atmosphere coverage is achieved, the ground coverage rate is greater than 90%, and the global land coverage rate (except polar regions) is 100%;

[0044] (2) To achieve monitoring, early warning and source positioning of global marine pollution, especially nuclear pollution, the constellation should meet the following requirements: within 12 hours, all global nuclear power plants are fully covered, and the single observation time is greater than 5 seconds;

[0045] (3) To meet the observation and communication requirements of camera, Internet of Things antenna and other payloads, the satellite orbit height is not more than 550 km.

[0046] On the basis of the basic index requirements, to reduce system cost and operation and maintenance expenses, the constellation configuration design should be optimized on the basis of fully utilizing satellite maneuvering observation capability and fully considering target distribution characteristics. The satellite attitude maneuvering and stabilization performance and the load observation capability are examined, and it is considered that a single satellite has 45° side swing observation capability, that is, a single satellite has an equivalent field of view of 45° half field of view.

[0047] Global geographic information and nuclear power plant location information are introduced, and the coverage performance is iteratively calculated by using an optimization method to obtain a minimum 3-cube constellation. The satellite constellation is composed of three groups of non-coplanar cube satellites, and the orbit elements are shown in Table 1.

[0048] Table 1 Orbit elements of the constellation

[0049] Symbol Number of orbits Parameter a Semi-major axis 6928.137 km e Eccentricity 0 i Orbital inclination 78° ΔΩ Longitude of ascending node 26.098° Δω Argument of perigee 0° △f True anomaly 140.662°

[0050] That is, the right ascension difference between adjacent orbital planes is 26.098°, and the phase difference of the mean anomaly angle between the cube satellites corresponding to the adjacent orbital planes is 140.662°.

[0051] The observation capability of the constellation is verified, and the observation coverage capability of the constellation is simulated and verified at the epoch time t0 of UTC time January 1, 2022, 0 o'clock. The space position of the constellation at the epoch time is shown in Table 2.

[0052] Table 2 Space position of the constellation at the epoch time

[0053] Serial number Longitude of ascending node Argument of perigee True anomaly 1 47° 0° 0° 2 73.098° 0° 140.662° 3 99.196° 0° 281.324°

[0054] According to the simulation results, the 3 CubeStar constellation achieves global coverage observation of greenhouse gases within 24 hours, with an observation coverage rate of 92%, among which the observation coverage rate of land areas below 84 degrees latitude reaches 100%, meeting the overall mission requirements of the constellation.

[0055] According to the simulation results, the 3 CubeStar constellation achieves global coverage of nuclear power plants within 12 hours, with a coverage time of more than 5 seconds for a single nuclear power plant, meeting the overall requirements of the constellation design.

[0056] Further, the monitoring satellite constellation subsystem is composed of 3 non-coplanar CubeSats, which adopt a 6u size rectangular body and deployable solar wings, with three-axis stabilized attitude control capability. The monitoring satellite constellation subsystem includes an integrated information management module 9, an attitude control module, a power module, and a data processing module 10. The integrated information management module 9 is responsible for the management and control of the CubeSat on-orbit flight mission, composed of multiple plug-in computer processing boards. The attitude control module is responsible for the attitude control of the CubeSat, including 1 sun sensor 12, 2 star sensors 11, 3 reaction flywheels 8, and 1 mechanical gyroscope 7. The power module is responsible for power management and distribution of the CubeSat, including deployable solar panels, power management single-chip microcomputers, and batteries, among which the battery adopts a multifunctional lithium battery structure integrated with the side cabin plate, effectively increasing the space inside the satellite. The data processing module 10 is responsible for preprocessing the ground image information obtained by the camera payload and receiving real-time monitoring data sent by the sea buoy. The main performance indicators of the CubeSat are shown in Table 3 below.

[0057] Table 3 Main performance indicators of CubeSat (6u)

[0058]

[0059] Further, the payload of the monitoring satellite constellation subsystem of the CubeSat includes a visible and infrared integrated multi-spectral camera 17 and an Internet of Things payload. The multi-spectral camera 17 can detect the spectral information of the target, obtain high-spectral resolution continuous and narrow-band image data, and monitor the growth of marine organisms such as seaweed, changes in seawater color, and the absorption of CO2 in the atmosphere on special spectra. The Internet of Things payload terminal is an ultra-long distance wireless transmission scheme based on spread spectrum technology, divided into an on-board part and a sea buoy part. The on-board Internet of Things payload terminal collects radioactive material detection data and buoy coordinates emitted by the buoys arranged on the sea surface.

[0060] The detection principle of greenhouse gases is as follows:

[0061] The atmospheric CO2, CH4, H2O and other gas molecules have different absorption capacity for light of different spectral bands, so a multi-spectral camera can be used to observe the light reflected by the ground in the spectral bands located at the center of the strong absorption band and the weak absorption band of the monitored gas, and the light of the sun in the two spectral bands is calibrated. By comparing the intensity information of the two spectral bands, the information related to the concentration of the monitored gas can be extracted by using the method of path integral differential absorption.

[0062] Table 4 Infrared spectral absorption band of main atmospheric molecules

[0063] Gas composition Strong absorption band center wavelength / μm Weak absorption band center wavelength / μm H2O 1.4 / 1.9 / 2.7 / 6.3 / 13.0-10000 0.9 / 1.1 CO2 2.7 / 4.3 / 14.7 1.4 / 1.6 / 2.0 / 5.0 / 9.4 / 10.4 O3 4.7 / 9.6 / 14.1 3.3 / 3.6 / 5.7 CH4 3.3 / 3.8 / 7.7 None [N2O] 4.5 / 7.8 3.9 / 4.1 / 9.6 / 17.0 CO 4.7 2.3

[0064] Taking CO2 gas monitoring as an example, the concentration of CO2 can be calculated by comparing the ratio of the ground reflected light intensity in the high absorption rate spectral band of CO2 in the infrared spectral band and the ground reflected light intensity in the low absorption rate spectral band of CO2, and according to the initial value of each spectrum calibrated by the sun. The CO2 concentration at the subsolar point. Among them, for a single spectral band, the formula is as follows:

[0065]

[0066] In the formula, I(λ) is the real-time value of the spectrum, I0(λ) is the initial value of the spectrum, λ is the wavelength, L is the optical path, σ i (λ) and σ i '(λ) represent the "wideband" absorption cross section and the rapidly changing "wideband" absorption cross section, respectively, σ i '(λ) is also called differential absorption cross section, c i is the concentration of the measured gas, ε R (λ) and ε M (λ) represent Rayleigh scattering and Mie scattering coefficients, respectively.

[0067] In order to exclude the influence of other gas components, a double-spectral band differential method can be used to correct the calculated concentration data to obtain more accurate CO2 concentration.

[0068] Further, the monitoring of the growth of the seaweed and the change of the seawater color mainly refers to the fact that the marine algae plants have a greater impact on the color of seawater, including diatoms, green algae, blue algae, red algae and brown algae. When the nuclear pollution radioactive substances enter the ocean, the enriched nuclear substances cause the marine organisms to suffer from internal or external radiation and die, resulting in eutrophication of seawater. At the same time, since most blue algae have stronger anti-nuclear radiation ability, diatoms, green algae and red algae have relatively weak anti-nuclear radiation ability, the eutrophication of seawater causes the blue algae to breed in large quantities, and the blue algae belong to prokaryotes and are rich in chlorophyll. The breeding of the blue algae in large quantities causes the chlorophyll a in the ocean to reach about 1.5-2 times the original level, which causes the color of the ocean water body to change, and there is strong absorption in the blue-green wave band and strong scattering in the red and near-infrared wave bands, so that the ocean appears a characteristic brown color. Therefore, the multi-spectral camera with blue, green and red and near-infrared optical channels is used to image the ocean, which can indirectly observe the distribution of the radioactive substances in the ocean, and thus the change of the nuclear radiation water pollution can be monitored. Specifically, the method comprises the following steps:

[0069] 1) When the nuclear pollution radioactive substances enter the ocean, the enriched nuclear substances cause the marine organisms to suffer from internal or external radiation and die, resulting in eutrophication of seawater. Most blue algae have stronger anti-nuclear radiation ability, and the eutrophication of seawater causes the blue algae to breed in large quantities. The breeding of the blue algae in large quantities causes the chlorophyll a in the ocean to reach about 1.5-2 times the original level, which causes the color of the ocean water body to change, and there is strong absorption in the blue-green wave band and strong scattering in the red and near-infrared wave bands, so that the ocean appears a characteristic brown color;

[0070] 2) A multi-spectral camera with blue, green and red and near-infrared optical channels is installed on a satellite to image the ocean, and image data returned by the multi-spectral camera on the satellite to the ground is processed;

[0071] 3) The chlorophyll a concentration of the ocean water body is inversed by using the processed image data returned by the multi-spectral camera to the ground;

[0072] The chlorophyll a is a pigment commonly contained in marine phytoplankton, and its concentration can reflect the biomass of marine phytoplankton to a certain extent. When the chlorophyll concentration on the sea surface increases, the reflection intensity at the wave band of 685 nm increases. The processed image data is converted into remote sensing reflectivity value, and then the chlorophyll a concentration information in the ocean water body is calculated through a standard empirical algorithm;

[0073] 4) The nuclear radiation concentration in the ocean water body is inversed according to the chlorophyll a concentration of the ocean water body;

[0074] The propagation of blue algae in the sea can be simplified as an S-shaped curve. When the biomass reaches a certain level, it is affected by the total amount of nutrients, and the population size has the maximum capacity K allowed by the environment. When the population size reaches K, the population size will stop growing, i.e., the growth rate at this time is 0. Sometimes it will remain relatively stable above and below the maximum value. Due to the pollution of nuclear waste in seawater, the death of other organisms, and the increase of nutrients in seawater, the value of K increases, which is reflected in the increase of chlorophyll a content;

[0075] After the satellite is launched into orbit, the k value is calibrated by observing and inverting the ocean color of each place. When the k value of a certain sea area reaches more than twice the normal value, combined with the actual situation of the local area, it is determined whether the marine water body is polluted by nuclear waste;

[0076] If there is nuclear pollution, the concentration A(x) of nuclear radiation in the marine water body is calculated using the following function:

[0077] A(x)=bf(y)+c

[0078] Where A(x) represents the concentration of nuclear radiation in the marine water body, f(y) is the concentration of chlorophyll a in the marine water body, and b and c are coefficients.

[0079] Further, the method for processing the image data transmitted by the multispectral camera on the satellite to the ground is as follows:

[0080] A. Radiometric calibration of the image data transmitted by the multispectral camera on the satellite to the ground. Radiometric calibration is the process of converting the gray scale value DN recorded by each detection unit of the multispectral camera into the actual physical meaning of the actual ground object radiation brightness. The observation count value DN of the satellite multispectral camera can be converted into equivalent apparent radiation brightness data using the following formula:

[0081] L=C·DN+B

[0082] Where L is the radiation brightness after spectral conversion of a certain band, DN is the gray scale value of the satellite multispectral camera; C is the calibration slope, B is the calibration intercept, and C and B are constants.

[0083] B. Atmospheric correction of the radiometrically calibrated data

[0084] The data after radiation calibration needs to be corrected by atmosphere, and after the atmospheric correction, the error caused by atmospheric scattering, absorption and reflection can be eliminated to obtain the actual reflectivity. The sea surface spectrum curve after atmospheric correction is closer to the true value. The FLAASH atmospheric correction model is used to correct the data after radiation calibration. The FLAASH atmospheric correction model first corrects the adjacent pixel effect and then calculates the visibility of the whole radiation image. The FLAASH atmospheric correction model can generate a classification image of cirrus and thin clouds, smooth the spectrum and eliminate noise. After atmospheric correction by the FLAASH atmospheric correction model, the image will become clear, the color will be more realistic, and the spectral line will be closer to the real object spectrum line. According to the image information of the multi-spectral camera, the parameters are set, and the image atmospheric correction result is output.

[0085] C. Marine area extraction

[0086] The whole image after atmospheric correction includes marine area and land area, and only the marine area is needed to participate in the calculation in the inversion calculation process, so the marine area range needs to be extracted. The normalized difference marine water index method is used to extract the marine water range.

[0087] The normalized difference marine water index is based on the fact that the reflectivity of marine water is very high in the green band and very strong in the infrared band. Therefore, the normalized marine water index is proposed:

[0088] (GREEN-NIR) / (GREEN+NIR)>T

[0089] GREEN represents the green band, NIR represents the infrared band, and T represents the extraction threshold.

[0090] Further, in the open sea area, the reflectivity of cyanobacteria in the near-infrared band is high, and the reflectivity in the red band is low. The normalized difference marine water index, as one of the main monitoring bands for monitoring marine water color, can better reflect the steep slope effect and improve the monitoring efficiency.

[0091] Further, in the near-shore sea area, because the water is shallow, the underwater sediment will also affect the reflection of the red and near-infrared bands. At the same time, because of the leakage of radioactive substances from the coastal nuclear power plant, the first affected area is the near-shore sea area. In addition, the change in the number of plants in other marine areas will also cause changes in the normalized difference marine water index. Cyanobacteria contain a large amount of chlorophyll a, and chlorophyll a has an absorption peak in the 433nm-453nm wavelength band, and high reflection regions in the 480nm-500nm, 510nm-530nm, and 555nm-575nm wavelength bands. Therefore, the above spectrum can be used to observe the near-shore sea area.

[0092] Further, in the Internet of Things payload, the monitoring satellite constellation subsystem and the sea surface buoy in the LoRa-based satellite Internet of Things solution both use LoRa modulation technology, and are adapted according to the communication situation.

[0093] Table 5 Performance parameters of the Internet of Things communication system

[0094] Item Index parameter Operating frequency 470-510 MHz Operating bandwidth 500 kHz Spreading factor 9 Coding efficiency 4 / 5 Data rate (before / after coding) 8789 / 7031 Reception sensitivity -122 dBm Reception demodulation signal-to-noise ratio -12.5 dB Satellite-ground communication distance More than 2100 km

[0095] Further, the satellite-borne LoRa Internet of Things payload includes a memory, an MCU, a power module, a power amplifier / LNA module, a CAN communication interface, a 28V power supply interface and a UART data interface, the LoRa module realizes the functions of data modulation and demodulation and self-organizing network, the memory realizes the function of storing the received data, the power amplifier / LNA is a bidirectional amplifier, which can undertake the functions of power amplification during transmission and low-noise amplification during reception, and the MCU realizes the functions of reading and writing data streams and configuring parameters of the LoRa module.

[0096] Further, the ocean monitoring buoy subsystem includes a plurality of ocean buoys arranged near the nuclear power plant, which can automatically detect radioactive substances in seawater and send detection data to the CubeSat through the Internet of Things, and then the CubeSat transmits the data to the ground station.

[0097] Further, the ocean buoy includes a monitoring module, a positioning module, an Internet of Things module, a power module and a power module, the monitoring module includes a radiation detection unit and a mass spectrometry detection unit, which are used to automatically monitor and detect radioactive substances in water, the radiation detection unit is used to detect the radiation dose of gamma rays, and the mass spectrometry detection unit is mainly used to detect radioactive particles in the ocean; the positioning module is equipped with a global positioning system for obtaining real-time position information of the buoy; the Internet of Things module is equipped with an Internet of Things payload antenna system, which can communicate with the monitoring satellite constellation subsystem and send water quality information detected by the buoy to the monitoring satellite constellation subsystem; the power module includes a battery array and a battery, which provide power for all devices on the buoy, the buoy will change position with the movement of seawater, and the power module corrects the position of the buoy according to the information of the positioning module.

[0098] Further, the main task of the ground data processing subsystem is to measure and control the CubeSat constellation system, and the method for receiving and processing data by the ground data processing subsystem includes the following steps:

[0099] Step one, receiving the greenhouse gas remote sensing image, the ocean blue-green algae remote sensing image and the buoy detection data returned by the satellite;

[0100] Step two, pre-processing the above data, including noise reduction, fitting, interpolation, and removing data outliers, specific noise and interference;

[0101] Step three, post-processing of data, including image processing, signal processing, multi-information fusion and state optimal estimation;

[0102] Step four, forming regional and global greenhouse gas concentration estimates, regional and global ocean radioactive material concentration estimates, regional and global greenhouse gas concentration long-period statistical analysis, and regional and global ocean radioactive material concentration long-period statistical analysis.

[0103] Further, the space-ground integrated environmental protection monitoring system based on the CubeSat constellation has three operating modes:

[0104] 1) Global survey mode

[0105] In daily operation, the system is in global survey mode. In the global survey mode, the CubeSat constellation subsystem operates on a predetermined orbit, and the CubeSat performs nadir scanning by side swing control of the remote sensing payload to monitor the global in the maximum ground coverage mode. The ocean monitoring buoy subsystem collects data of the corresponding water area and uploads it to the CubeSat constellation subsystem through the Internet of Things. The ground data processing subsystem is responsible for collecting the remote sensing data of each orbit of the over-the-horizon satellite and the data of the ocean monitoring buoy subsystem, and generating global greenhouse gas concentration distribution maps, global ocean radioactive material content distribution maps, and other refined advanced data.

[0106] 2) Regional detailed investigation mode

[0107] When regional detailed investigation is needed, the system operates in regional detailed investigation mode. In the regional detailed investigation mode, the CubeSat constellation subsystem operates on a predetermined orbit, and the CubeSat autonomously plans a sequence of scanning attitudes for the region, controls the attitude, and conducts detailed investigation of the specific region to achieve the longest time monitoring of the target region within the reentry period. Specifically, first, a sequence of scanning attitudes for the target region is planned. Then, the ground station sends relevant attitude instructions to the satellite. The ocean monitoring buoy subsystem in the corresponding region collects water data and uploads it to the satellite. The ground data processing subsystem is responsible for collecting the remote sensing data of each orbit of the over-the-horizon satellite and the buoy data, and generating greenhouse gas concentration distribution maps of the target region, regional ocean radioactive material content distribution maps, and specific time interval carbon emission estimation data.

[0108] 3) Emergency response mode

[0109] When an emergency response is needed, the emergency response mode of the system is triggered manually by the ground data processing subsystem or automatically by the alarm of the corresponding regional buoy detection value, in the emergency response mode, the CubeSat constellation operates on a predetermined orbit, and the CubeSat performs staring observation on the hot area through attitude control, so as to realize the longest time monitoring of the hot area in the reentry period. Specifically, when the buoy with a faster response detects that the 37Cs content greatly exceeds the conventional value range, or the concentration value increases for many consecutive days, the corresponding alarm can be sent out; then, the ground station sends a staring imaging instruction to the satellite or the satellite autonomously plans to perform staring imaging on the area where the corresponding buoy is located, and the ground data processing subsystem generates the greenhouse gas concentration distribution map, the marine radioactive material content distribution map, the greenhouse gas propagation prediction map and the marine radioactive material propagation prediction map of the accident area in combination with the collected over-the-top satellite per-orbit remote sensing data and buoy data.

[0110] The above description is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made under the inventive concept of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A global environmental monitoring system based on a constellation of cubic satellites, comprising a monitoring satellite constellation subsystem, an ocean monitoring buoy subsystem and a ground data processing subsystem, the monitoring satellite constellation subsystem being composed of 3 6u cubic satellites; the ocean monitoring buoy subsystem being arranged in the sea area near the coastal nuclear power plant, capable of detecting radioactive substances leaked into seawater in real time and sending the detected data to the satellite constellation subsystem, forming a real-time monitoring network for the nuclear power plant; the ground data processing subsystem being used for controlling satellite operation and receiving satellite data, acquiring monitoring data of the atmosphere and the ocean by the monitoring satellite constellation subsystem and monitoring data of the ocean by the ocean monitoring buoy subsystem, making judgments and positioning and warning nuclear leakage accidents of the nuclear power plant; The global environmental monitoring system based on a constellation of cubic satellites has three operating modes: 1) Global survey mode In daily operation, the system is in global survey mode, the cubic satellite constellation subsystem operates on a predetermined orbit, the cubic satellite performs nadir scanning by side swing control of the remote sensing payload to monitor the global in the maximum ground coverage mode; the ocean monitoring buoy subsystem collects data of the corresponding water area and uploads it to the cubic satellite constellation subsystem through the Internet of Things; the ground data processing subsystem is responsible for collecting remote sensing data of each orbit of the over-the-horizon satellite and data of the ocean monitoring buoy subsystem, generating global greenhouse gas concentration distribution maps and global ocean radioactive material content distribution maps; 2) Regional detailed investigation mode When regional detailed investigation is needed, the system operates in regional detailed investigation mode, the cubic satellite constellation subsystem operates on a predetermined orbit, the cubic satellite autonomously plans a sequence of scanning attitudes for the region, controls the attitude and investigates the specific region, realizes the longest time monitoring of the target region within the reentry period, first plans a sequence of scanning attitudes for the cubic satellite for the target region; then the ground station uploads relevant attitude instructions to the satellite; the ocean monitoring buoy subsystem in the corresponding region collects water area data and uploads it to the satellite; the ground data processing subsystem is responsible for collecting remote sensing data of each orbit of the over-the-horizon satellite and buoy data, generating greenhouse gas concentration distribution maps of the target region, regional ocean radioactive material content distribution maps and carbon emission estimation data in a specific time interval; 3) Emergency response mode When emergency response is needed, the emergency response mode of the system is triggered manually by the ground data processing subsystem or automatically triggered by the alarm of the buoy detection value in the corresponding region, the cubic satellite constellation operates on a predetermined orbit, the cubic satellite performs staring observation on the hot spot area by attitude control, realizes the longest time monitoring of the hot spot area within the reentry period, when the buoy detects that the 37Cs content greatly exceeds the normal value range or the concentration value increases for several consecutive days, it sends an alarm; Then, the ground station uploads or the satellite autonomously plans staring imaging instructions for the region where the buoy is located, and the ground data processing subsystem generates greenhouse gas concentration distribution maps, ocean radioactive material content distribution maps, greenhouse gas propagation prediction maps and ocean radioactive material propagation prediction maps of the accident area in combination with the collected remote sensing data of each orbit of the over-the-horizon satellite and buoy data.

2. The global environmental protection monitoring system based on the constellation of cubic satellites according to claim 1, characterized in that, The monitoring satellite constellation subsystem is composed of three non-coplanar cubic satellites, which adopt a 6u size rectangular body and a deployed solar wing configuration, and have a three-axis stabilized attitude control capability. The monitoring satellite constellation subsystem includes an integrated information management module, an attitude control module, a power supply module, and a data processing module. The integrated information management module is responsible for the management and control of the on-orbit flight mission of the cubic satellite, and is composed of multiple plug-in computer processing boards. The attitude control module is responsible for the attitude control of the cubic satellite, including one sun sensor, two star sensors, three reaction flywheels, and one mechanical gyroscope. The power supply module is responsible for the power management and distribution of the cubic satellite, including a deployed solar cell panel, a power management single-chip microcomputer, and a storage battery. The storage battery adopts a multifunctional lithium battery structure integrated with the side cabin plate. The data processing and transmission module is responsible for preprocessing the ground image information obtained by the camera payload, and simultaneously receiving real-time monitoring data sent by the sea buoy.

3. The global environmental protection monitoring system based on the constellation of cubic satellites according to claim 2, characterized in that, The payload of the cubic satellite of the monitoring satellite constellation subsystem includes a visible light and infrared integrated multi-spectral camera and an Internet of Things payload. The multi-spectral camera can detect the spectral information of the target, obtain high-spectral resolution continuous and narrow-band image data, and monitor the growth of seaweed in the ocean, the change of seawater color, and the absorption of CO2 in the atmosphere to special spectrum. The Internet of Things payload terminal is divided into an on-board part and a sea buoy part. The on-board Internet of Things payload terminal collects radioactive material detection data and buoy coordinates emitted by the buoy arranged on the sea surface.

4. The global environmental protection monitoring system based on the constellation of cubic satellites according to claim 3, characterized in that, The multi-spectral camera adopts blue, green, and red optical channels to image the ocean, indirectly observe the distribution of radioactive substances in the ocean, and further realize the monitoring of nuclear radiation water pollution changes.

5. The global environmental protection monitoring system based on the constellation of cubic satellites according to claim 3, characterized in that, In the LoRa-based satellite Internet of Things scheme, the Internet of Things terminal of the monitoring satellite constellation subsystem and the sea buoy both adopt LoRa modulation technology.

6. The global environmental protection monitoring system based on the constellation of cubic satellites according to claim 5, characterized in that, The on-board LoRa Internet of Things payload includes a memory, an MCU, a power supply module, a power amplifier / LNA module, a CAN communication interface, a 28V power supply interface, and a UART data interface. The LoRa module realizes data modulation and demodulation functions and self-organizing network functions. The memory realizes the function of storing the received data. The power amplifier / LNA is a bidirectional amplifier that can undertake power amplification during transmission and low-noise amplification during reception. The MCU realizes the functions of reading and writing data streams and configuring parameters of the LoRa module.

7. The global environmental protection monitoring system based on the constellation of cubic satellites according to any one of claims 1-6, characterized in that, The ocean monitoring buoy subsystem includes multiple ocean buoys arranged near nuclear power plants, which can automatically detect radioactive substances in seawater and send detection data to the cubic satellite through the Internet of Things, and then the cubic satellite transmits the data to the ground station.

8. The integrated space-ground global environmental monitoring system based on the constellation of cubic satellites according to claim 7, characterized in that, The marine buoy comprises a monitoring module, a positioning module, an Internet of Things module, a power module and a power supply module, the monitoring module comprises a radiation detection unit and a mass spectrometry detection unit, is used for automatically monitoring and detecting radioactive substances in water, the radiation detection unit is used for detecting the radiation dose of gamma rays, and the mass spectrometry detection unit detects radioactive particles in the sea; the positioning module is equipped with a global positioning system and is used for obtaining real-time position information of the buoy; the Internet of Things module is provided with an Internet of Things load antenna system, can communicate with a monitoring satellite constellation subsystem, and sends water quality information detected by the buoy to the monitoring satellite constellation subsystem; the power supply module comprises a battery array and a battery, provides electric energy for all equipment on the buoy, the buoy changes position with the movement of seawater, and the power module corrects the position of the buoy according to the information of the positioning module.

9. The global environmental protection monitoring system based on the constellation of cubic satellites according to any one of claims 1-6, 8, characterized in that, The task of the ground data processing subsystem is to control the cube satellite constellation system, and the method for receiving and processing data by the ground data processing subsystem comprises the following steps: Step one, receiving the greenhouse gas remote sensing image, the marine blue-green algae remote sensing image and the buoy detection data returned by the satellite; Step two, pre-processing the above data, including noise reduction, fitting, interpolation, and removing data outliers, specific noise and interference; Step three, post-processing the data, including image processing, signal processing, multi-information fusion and state optimal estimation; Step four, forming regional and global greenhouse gas daily concentration estimation, regional and global marine radioactive material daily concentration estimation, regional and global greenhouse gas concentration long-period statistical analysis, and regional and global marine radioactive material concentration long-period statistical analysis.

Images