A Method and Apparatus for Thermal Infrared Satellite Radiometric Calibration Based on Multi-Level Targets

Abstract

This application provides a method and apparatus for radiometric calibration of thermal infrared satellites based on multi-energy-level targets, comprising: acquiring payload performance parameters of a thermal infrared satellite; acquiring transit information of the thermal infrared satellite; identifying multiple targets with different energy levels within the dynamic range of the thermal infrared satellite's payload based on the payload performance parameters and transit information; measuring the ground radiation parameters and atmospheric parameters of each target during the transit information; calculating the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the ground radiation parameters and atmospheric parameters; calculating the digital quantization value of the area where the target is located; and determining the absolute radiometric calibration coefficient of the thermal infrared satellite based on the digital quantization value and equivalent entrance pupil radiance of each target. This reduces the deviation in absolute radiometric calibration within the dynamic range of the thermal infrared satellite's payload, improving the accuracy of subsequent quantitative applications and comprehensive analysis.

Description

Technical Field

[0001] This application relates to the field of remote sensing calibration technology, and in particular to a method and apparatus for thermal infrared satellite radiometric calibration based on multi-level targets. Background Technology

[0002] With the rapid development of remote sensing technology, my country has made remarkable achievements in the field of satellite remote sensing, successfully launching a variety of operational Earth observation satellite remote sensors that cover the data acquisition needs of land, meteorology, oceanography and other industries. These sensors have provided a large amount of valuable data for the implementation of major national strategies, land spatial planning, resource surveys, environmental monitoring, disaster early warning and other purposes, and have become an important supporting tool for modernization and sustainable development.

[0003] Because thermal infrared satellites are subject to various factors during launch and in-orbit operation, such as vibration, space ions, component aging, and changes in space environment conditions, the quality of remote sensing data degrades to varying degrees, thus affecting data processing and application. Therefore, regular on-orbit radiometric calibration of thermal infrared satellite remote sensing data is necessary. Thermal infrared satellite radiometric calibration is the process of converting the digital quantized values ​​recorded by the sensors into physically meaningful radiant energy values.

[0004] However, existing on-orbit absolute radiometric calibration of thermal infrared satellites typically selects only a single target: a body of water as the reference target. Since water temperatures are generally low, it can only serve as the low end point for thermal infrared absolute radiometric calibration. Furthermore, single-point calibration often assumes a zero bias and only calculates the calibration gain, leading to significant deviations in absolute radiometric calibration within the dynamic range of the thermal infrared satellite's payload. This affects the accuracy of subsequent quantitative applications and comprehensive analysis. Summary of the Invention

[0005] This application provides a method and apparatus for radiometric calibration of thermal infrared satellites based on multi-level targets, which can reduce the deviation of absolute radiometric calibration within the dynamic range of thermal infrared satellite payloads and improve the accuracy of subsequent quantitative applications and comprehensive analysis.

[0006] Firstly, this application discloses a method for radiometric calibration of thermal infrared satellites based on multi-level targets, the method comprising:

[0007] Obtain payload performance parameters of thermal infrared satellites;

[0008] Acquire the transit information of thermal infrared satellites, which is used to indicate the spatiotemporal positional relationship and visibility characteristics of thermal infrared satellites and designated areas on the ground;

[0009] Based on payload performance parameters and overflight information, multiple targets with different energy levels are identified within the dynamic range of the thermal infrared satellite's payload.

[0010] Based on the transit information, measure the ground radiation parameters and atmospheric parameters of each of the multiple targets when the thermal infrared satellite passes over.

[0011] Calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the parameter values ​​of ground radiation and atmospheric parameters;

[0012] Calculate the digital quantization value of the region where the target is located;

[0013] The absolute radiometric calibration coefficients of the thermal infrared satellite are determined based on the digital quantization values ​​and equivalent entrance pupil radiance of each of the multiple targets.

[0014] According to the above scheme, ground radiation and atmospheric synchronous measurements of different targets with different energy levels are conducted during satellite transit. Based on the ground radiation and atmospheric parameters of the targets, the equivalent entrance pupil radiance of the targets under the thermal infrared satellite is calculated. Based on the observation images during the thermal infrared satellite transit, the digital quantization value of the target's location is calculated. Using the equivalent entrance pupil radiance and digital quantization value corresponding to each of the multiple targets, the absolute radiometric calibration coefficients of the thermal infrared satellite are determined. Since the absolute radiometric calibration coefficients are determined based on multiple targets with different energy levels, this solves the problem of poor on-orbit radiometric calibration accuracy caused by traditional field calibration using water bodies as a single reference target, thus improving the on-orbit absolute radiometric calibration accuracy of the thermal infrared satellite payload.

[0015] In one possible implementation, payload performance parameters include the spatial resolution, spectral range, and spectral response function of the thermal infrared satellite.

[0016] In one possible implementation, the differences in characteristics exhibited by multiple targets with different energy levels are represented by the different materials of the multiple targets;

[0017] The differences in characteristics exhibited by multiple targets due to their different materials include the target's surface temperature, material emissivity, and / or the target's radiance under solar irradiance.

[0018] In one possible implementation, based on transit information, the parameter values ​​of ground radiation parameters and atmospheric parameters for each of multiple targets are measured during the transit of a thermal infrared satellite, including:

[0019] Measure the brightness temperature data of the target, including the brightness temperature of the target above ground or above water;

[0020] The first data of the target is measured, including the target's above-ground radiance spectrum or above-water radiance spectrum;

[0021] The second data for the measurement target includes atmospheric downdraft radiation, atmospheric water vapor content, aerosol optical thickness, atmospheric ozone content, and atmospheric temperature, humidity and pressure profile information.

[0022] Based on the brightness temperature data, the first data, and the second data, the parameter values ​​of the ground radiation parameters and the atmospheric parameters are determined.

[0023] In one possible implementation, the ground radiation parameters include brightness temperature data, first data, surface temperature and surface emissivity, and the atmospheric parameters include atmospheric transmittance, atmospheric upward radiation and atmospheric downward radiation.

[0024] Based on the transit information, the ground radiation parameters and atmospheric parameters of each of the multiple targets were measured during the transit of the thermal infrared satellite, including:

[0025] Based on the downward atmospheric radiation value, the temperature and emissivity of the first data are separated to obtain the surface emissivity of the target;

[0026] The surface temperature of the target is determined based on brightness temperature data, surface emissivity, and atmospheric downdraft radiation.

[0027] Based on the transit information and second data, determine the atmospheric transmittance, upward atmospheric radiation value, and downward atmospheric radiation value of the target when the thermal infrared satellite passes over it.

[0028] In one possible implementation, the transit information includes the target's position, the target's elevation, the observation zenith angle of the thermal infrared satellite, and the observation azimuth angle of the thermal infrared satellite.

[0029] In one possible implementation, the equivalent entrance pupil radiance of the target under a thermal infrared satellite is calculated based on the parameter values ​​of ground radiation parameters and atmospheric parameters, including:

[0030] Based on the values ​​of atmospheric parameters and ground radiation parameters, calculate the thermal radiation brightness of the target as it passes through the atmosphere and reaches the top of the atmosphere.

[0031] Calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the thermal radiation brightness.

[0032] Secondly, this application provides a thermal infrared satellite radiometric calibration device based on a multi-level target, characterized in that the device comprises:

[0033] The first acquisition module is used to acquire the payload performance parameters of the thermal infrared satellite;

[0034] The second acquisition module is used to acquire the transit information of the thermal infrared satellite. The transit information is used to indicate the spatiotemporal position relationship and visibility characteristics of the thermal infrared satellite and a specified area on the ground.

[0035] The first determination module is used to determine multiple targets within the dynamic range of the thermal infrared satellite's payload, based on payload performance parameters and transit information. These multiple targets have different energy levels.

[0036] The measurement module is used to measure the ground radiation parameters and atmospheric parameters of each of the multiple targets when the thermal infrared satellite passes over, based on the overpass information.

[0037] The first calculation module is used to calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the parameter values ​​of the ground radiation parameters and the atmospheric parameters.

[0038] The second calculation module is used to calculate the digital quantization value of the target area;

[0039] The second determining module is used to determine the absolute radiometric calibration coefficient of the thermal infrared satellite based on the digital quantization values ​​and equivalent entrance pupil radiance of each of the multiple targets.

[0040] According to the above scheme, ground radiation and atmospheric synchronous measurements of different targets with different energy levels are conducted during satellite transit. Based on the ground radiation and atmospheric parameters of the targets, the equivalent entrance pupil radiance of the targets under the thermal infrared satellite is calculated. Based on the observation images during the thermal infrared satellite transit, the digital quantization value of the target's location is calculated. Using the equivalent entrance pupil radiance and digital quantization value corresponding to each of the multiple targets, the absolute radiometric calibration coefficients of the thermal infrared satellite are determined. Since the absolute radiometric calibration coefficients are determined based on multiple targets with different energy levels, this solves the problem of poor on-orbit radiometric calibration accuracy caused by traditional field calibration using water bodies as a single reference target, thus improving the on-orbit absolute radiometric calibration accuracy of the thermal infrared satellite payload.

[0041] In one possible implementation, payload performance parameters include the spatial resolution, spectral range, and spectral response function of the thermal infrared satellite.

[0042] In one possible implementation, the differences in characteristics exhibited by multiple targets with different energy levels are represented by the different materials of the multiple targets;

[0043] The differences in characteristics exhibited by multiple targets due to their different materials include the target's surface temperature, material emissivity, and / or the target's radiance under solar irradiance.

[0044] In one possible implementation, the measurement module is used for:

[0045] Measure the brightness temperature data of the target, including the brightness temperature of the target above ground or above water;

[0046] The first data of the target is measured, including the target's above-ground radiance spectrum or above-water radiance spectrum;

[0047] The second data for the measurement target includes atmospheric downdraft radiation, atmospheric water vapor content, aerosol optical thickness, atmospheric ozone content, and atmospheric temperature, humidity and pressure profile information.

[0048] Based on the brightness temperature data, the first data, and the second data, the parameter values ​​of the ground radiation parameters and the atmospheric parameters are determined.

[0049] In one possible implementation, the ground radiation parameters include brightness temperature data, first data, surface temperature and surface emissivity, and the atmospheric parameters include atmospheric transmittance, atmospheric upward radiation and atmospheric downward radiation.

[0050] Based on the transit information, the ground radiation parameters and atmospheric parameters of each of the multiple targets were measured during the transit of the thermal infrared satellite, including:

[0051] Based on the downward atmospheric radiation value, the temperature and emissivity of the first data are separated to obtain the surface emissivity of the target;

[0052] The surface temperature of the target is determined based on brightness temperature data, surface emissivity, and atmospheric downdraft radiation.

[0053] Based on the transit information and second data, determine the atmospheric transmittance, upward atmospheric radiation value, and downward atmospheric radiation value of the target when the thermal infrared satellite passes over it.

[0054] In one possible implementation, the transit information includes the target's position, the target's elevation, the observation zenith angle of the thermal infrared satellite, and the observation azimuth angle of the thermal infrared satellite.

[0055] In one possible implementation, the equivalent entrance pupil radiance of the target under a thermal infrared satellite is calculated based on the parameter values ​​of ground radiation parameters and atmospheric parameters, including:

[0056] Based on the values ​​of atmospheric parameters and ground radiation parameters, calculate the thermal radiation brightness of the target as it passes through the atmosphere and reaches the top of the atmosphere.

[0057] Calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the thermal radiation brightness.

[0058] Thirdly, this application provides a computing device, including a processor, a memory, and a computer program stored in the memory and executable on the processor. When executed by the processor, the computer program implements the methods provided in the first aspect or any possible implementation of the first aspect.

[0059] Fourthly, this application provides a computer storage medium storing instructions that, when executed on a computer, cause the computer to perform the method provided in the first aspect or any possible implementation thereof. Attached Figure Description

[0060] Figure 1 A flowchart illustrating a thermal infrared satellite radiometric calibration method based on a multi-level target provided in an embodiment of this application is shown.

[0061] Figure 2 A flowchart illustrating another thermal infrared satellite radiometric calibration method based on a multi-level target provided in this application embodiment is shown.

[0062] Figure 3 This illustration shows a schematic diagram of a thermal infrared satellite radiometric calibration device based on a multi-level target, according to an embodiment of this application.

[0063] Figure 4 A schematic diagram of the structure of a computing device provided in an embodiment of this application is shown. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be described below with reference to the accompanying drawings.

[0065] In the description of the embodiments of this application, the words "exemplary," "for example," or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary," "for example," or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the words "exemplary," "for example," or "for instance" is intended to present the relevant concepts in a specific manner.

[0066] In the description of the embodiments in this application, the term "and / or" is merely a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. Furthermore, unless otherwise stated, the term "multiple" means two or more. For example, multiple systems refer to two or more systems, and multiple screen terminals refer to two or more screen terminals.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. The terms "comprising," "including," "having," and their variations all mean "including but not limited to," unless otherwise specifically emphasized.

[0068] With the rapid development of remote sensing technology, my country has made remarkable achievements in the field of satellite remote sensing, successfully launching a variety of operational Earth observation satellite remote sensors that cover the data acquisition needs of land, meteorology, oceanography and other industries. These sensors have provided a large amount of valuable data for the implementation of major national strategies, land spatial planning, resource surveys, environmental monitoring, disaster early warning and other purposes, and have become an important supporting tool for modernization and sustainable development.

[0069] Because thermal infrared satellites are subject to various factors during launch and in-orbit operation, such as vibration, space ions, component aging, and changes in space environment conditions, the quality of remote sensing data degrades to varying degrees, thus affecting data processing and application. Therefore, regular on-orbit radiometric calibration of thermal infrared satellite remote sensing data is necessary. Thermal infrared satellite radiometric calibration is the process of converting the digital quantized values ​​recorded by the sensors into physically meaningful radiant energy values.

[0070] However, existing on-orbit absolute radiometric calibration of thermal infrared satellites typically selects only a single target: water bodies as the reference target. Traditional thermal infrared satellite payload on-orbit absolute radiometric calibration usually only uses high-altitude, dry, clean, and minimally disturbed high-temperature lakes with uniform temperature distribution, such as Qinghai Lake, as the calibration reference target. Because of its small horizontal temperature gradient and limited dynamic range, the bias is often assumed to be 0 during calibration calculations, only calculating the calibration gain, leading to deviations in the radiometric calibration results and affecting subsequent quantitative analysis. Furthermore, due to the low surface temperature of water bodies, radiometric calibration by thermal infrared satellite payloads can only meet the accuracy requirements at the low end of the calibration range. For surface targets with higher temperatures, such as sandy areas and bare soil, there are technical problems such as poor accuracy of the calibration coefficients at the low-temperature end at the high-temperature end.

[0071] Based on this, this application provides a method and apparatus for radiometric calibration of thermal infrared satellites based on multi-energy-level targets. In this scheme, ground radiation and atmospheric synchronous measurements of different targets are conducted during satellite transit using targets of different energy levels. The equivalent entrance pupil radiance of the target under the thermal infrared satellite is calculated based on the target's ground radiation parameters and atmospheric parameters. The digital quantization value of the target's region is calculated based on the observed images during the thermal infrared satellite transit. The absolute radiometric calibration coefficients of the thermal infrared satellite are determined using the equivalent entrance pupil radiance and digital quantization values ​​corresponding to multiple targets. Since the absolute radiometric calibration coefficients are determined based on multiple targets of different energy levels, this solves the problem of poor on-orbit radiometric calibration accuracy caused by traditional field calibration using water bodies as a single reference target, thus improving the on-orbit absolute radiometric calibration accuracy of thermal infrared satellite payloads.

[0072] Figure 1 This application provides a method for radiometric calibration of thermal infrared satellites based on multi-level targets. This method can be applied to devices or platforms with computing and storage capabilities, such as computing devices (e.g., servers) and computing device clusters (e.g., cloud computing platforms). Figure 1 As shown, the thermal infrared satellite radiometric calibration method based on multi-level targets provided in this application includes the following steps S101 to S107.

[0073] S101, obtain the payload performance parameters of the thermal infrared satellite.

[0074] The selection of a reference target for on-orbit absolute radiometric calibration of a satellite remote sensing payload directly affects the accuracy of the on-orbit radiometric calibration. The selection of the reference target requires comprehensive consideration of factors such as the target's radiometric characteristics, atmospheric conditions, the performance parameters of the thermal infrared satellite payload, and satellite transit conditions to ensure the accuracy and reliability of the calibration results. According to an embodiment of this application, in S101, the payload performance parameters of the thermal infrared satellite include the thermal infrared satellite payload's spatial resolution, spectral range, and spectral response function.

[0075] S102, acquire the transit information of the thermal infrared satellite. The transit information is used to indicate the spatiotemporal position relationship and visibility characteristics of the thermal infrared satellite and the designated area on the ground.

[0076] The transit information includes the target's location, elevation, observation zenith angle of the thermal infrared satellite, and observation azimuth angle of the thermal infrared satellite.

[0077] S103 identifies multiple targets within the dynamic range of the thermal infrared satellite's payload, based on payload performance parameters and transit information. These targets have different energy levels.

[0078] In the embodiments of this application, the differences in characteristics exhibited by multiple targets with different energy levels are due to the different materials of multiple targets; the differences in characteristics exhibited by multiple targets with different materials are the surface temperature, material emissivity and / or the radiance of the target under solar irradiation.

[0079] Among them, energy level can refer to the energy level of the target's thermal infrared radiation.

[0080] Specifically, based on the aforementioned thermal infrared satellite payload performance parameters, the requirements for the area size and temperature field uniformity of multi-energy level targets are determined. For example, the target area is required to be no less than 10×10 satellite observation pixels with good uniformity to ensure that sufficiently uniform and stable multi-energy level targets can be provided, achieving high-precision radiometric calibration of the thermal infrared satellite payload within its dynamic range. Simultaneously, based on the aforementioned satellite transit conditions, it is determined that the atmospheric conditions for multi-material targets are stable and cloudless during synchronous observation, and the satellite observation zenith angle is no greater than 15°.

[0081] Furthermore, the target uniformity across multiple energy levels can be assessed through spatiotemporal heterogeneity. For example, based on the spatial resolution of the thermal infrared satellite payload, a buffer zone with a radius of no less than 7 satellite observation pixels is set, and the standard deviations of surface temperature and surface emissivity within the region under different times and seasons are calculated. The temperature standard deviation should be less than 1K, and the emissivity standard deviation should be less than 0.01.

[0082] In some embodiments, traditional thermal infrared satellite payloads typically select only high-altitude, dry, clean, and uniformly distributed plateau lakes, such as Qinghai Lake, as calibration reference targets for on-orbit absolute radiometric calibration. Due to the small horizontal temperature gradient and dynamic range of its water surface, the bias is usually assumed to be 0 during calibration calculations, and only the calibration gain is calculated, leading to deviations in the radiometric calibration results and affecting subsequent quantitative analysis. At the same time, due to the low surface temperature of the water body, the radiometric calibration of thermal infrared satellite payloads can only meet the accuracy requirements at the low end of the radiometric calibration. For surface targets with higher temperatures, such as sandy land and bare soil, there are technical problems such as poor accuracy of the calibration coefficients at the low-temperature end at the high-temperature end.

[0083] In some embodiments, after determining targets at multiple energy levels, it is also possible to determine the geographical location information of the targets.

[0084] In this embodiment, by selecting targets of different materials at low, medium, and high energy levels for calibration, the technical problem of poor on-orbit radiometric calibration accuracy caused by traditional on-orbit calibration based on a single water body reference target can be effectively solved. This expands the dynamic range of thermal infrared payload radiometric calibration, ensures the stability of thermal infrared payload calibration results, and enables calibration coefficients to have high accuracy at low, medium, and high temperatures, thereby improving calibration accuracy and providing a guarantee for further improving the quality of satellite thermal infrared remote sensing data applications. The multi-energy-level, multi-target characteristics are reflected in the fact that different material targets will have significant differences in surface temperature, material emissivity, and radiation intensity due to solar irradiance.

[0085] In some embodiments, since water has a large specific heat capacity, high emissivity, and low temperature, uniform and stable water bodies, such as large-area inland lakes and seawater, can be selected as low-energy targets; while large-area uniform targets, such as natural scenes like bare soil and sandy land and artificial targets of different gray levels like black paint, can be selected as medium- and high-energy targets in the thermal infrared calibration process.

[0086] S104, based on the transit information, measure the ground radiation parameters and atmospheric parameters of each of the multiple targets when the thermal infrared satellite passes over.

[0087] For targets at different energy levels (low, medium, and high), the ground radiation parameters and atmospheric parameters of multiple targets at different energy levels are measured simultaneously during satellite transit. For example, the ground radiation parameters and atmospheric parameters of multiple targets at different energy levels are measured simultaneously within half an hour before and after satellite transit.

[0088] In some embodiments, in S104, the parameter values ​​of ground radiation parameters and atmospheric parameters of multiple targets with different energy levels can be measured simultaneously through the following process. For example... Figure 2 As shown, firstly, the brightness temperature data of the target is measured, including the target's brightness temperature above ground or above water. Next, the first data of the target is measured, including the target's radiation spectrum above ground or above water. Then, the second data of the target is measured, including atmospheric downdraft radiation, atmospheric water vapor content, aerosol optical thickness, atmospheric ozone content, and atmospheric temperature, humidity, and pressure profiles. Finally, based on the brightness temperature data, the first data, and the second data, the parameter values ​​of the ground radiation parameters and the atmospheric parameters are determined.

[0089] For example, the brightness temperature data of the target is obtained by synchronous measurement using an infrared radiometer; the target's above-ground / above-water radiation is obtained by measurement using a Fourier transform infrared spectrometer; the atmospheric downdraft radiation is obtained by measurement using a gold plate; the atmospheric water vapor content and aerosol optical thickness are obtained by synchronous measurement using a solar photometer; the atmospheric ozone content is obtained by synchronous measurement using an ozone meter; and the atmospheric temperature, humidity and pressure profile information is obtained by measurement using an atmospheric radiosonde.

[0090] In this embodiment of the application, the ground radiation parameters include brightness temperature data, first data, surface temperature and surface emissivity, and the atmospheric parameters include atmospheric transmittance, atmospheric upward radiation and atmospheric downward radiation.

[0091] In some embodiments, such as Figure 2 As shown, based on the transit information, the ground radiation parameters and atmospheric parameters of each of the multiple targets are measured when the thermal infrared satellite passes over the area. The specific process includes the following:

[0092] First, based on the downward atmospheric radiation value, the temperature and emissivity of the first data are separated to obtain the surface emissivity of the target.

[0093] Next, based on brightness temperature data, surface emissivity, and atmospheric downdraft radiation, the target's surface temperature is determined. Among these, the surface temperature T... s Satisfy the following formula (1):

[0094]

[0095] Among them, L Radiometer Brightness temperature data is obtained by constructing a temperature-radiance lookup table based on the Planck function using the infrared radiometer payload response function, and then converting the measured brightness temperatures above ground / above water; ε and L ↓ atm B represents the equivalent surface emissivity and atmospheric downdraft radiation obtained by convolving the surface emissivity and atmospheric downdraft radiation obtained above with the response of the infrared radiometer payload; -1 This is the inverse operation of the Planck function.

[0096] Finally, based on the transit information and second data, the atmospheric transmittance, upward atmospheric radiation, and downward atmospheric radiation values ​​corresponding to the target at the time of the thermal infrared satellite's transit are determined. Specifically, the synchronously measured atmospheric parameter data are preprocessed to obtain atmospheric effect parameters such as atmospheric transmittance, upward and downward atmospheric radiation, etc., at the time of satellite transit. Specifically, based on an atmospheric radiative transfer model (such as MODTRAN), the atmospheric temperature, humidity, and pressure profile information obtained from the atmospheric radiosonde is used as input, while atmospheric water vapor content and aerosol optical thickness obtained synchronously from the solar photometer, atmospheric ozone content obtained synchronously from the ozone meter, multi-level multi-target location information, elevation, satellite observation zenith angle, and observation azimuth angle are used as auxiliary inputs to calculate the atmospheric transmittance, upward atmospheric radiation, and downward atmospheric radiation values ​​corresponding to the time of satellite transit.

[0097] S105. Calculate the equivalent entrance pupil radiance of the target under thermal infrared satellite conditions based on the parameter values ​​of ground radiation and atmospheric parameters.

[0098] Specifically, based on the values ​​of atmospheric parameters and ground radiation parameters, the thermal radiation brightness of the target reaching the top of the atmosphere is calculated; based on the thermal radiation brightness, the equivalent entrance pupil radiance of the target under the thermal infrared satellite is calculated.

[0099] For example, such as Figure 2 As shown, after acquiring brightness temperature data, surface emissivity, surface temperature, and atmospheric effect parameters such as atmospheric transmittance and upward and downward atmospheric radiation during satellite transit for targets at multiple energy levels, the thermal radiation brightness of the target reaching the top of the atmosphere is calculated based on the thermal infrared radiation transfer equation. Thermal radiation brightness L TOA,i (λ) satisfies the following formula (2):

[0100]

[0101] Among them, L TOA,i (λ) represents the radiance of target i at different energy levels reaching the top of the atmosphere, where λ is the wavelength, and τ i (λ) represents atmospheric transmittance, L ↑ atm,i (λ), L ↓ atm,i (λ) represent atmospheric upward radiation and atmospheric downward radiation, respectively, L G,i (λ) represents the radiance data of target i at different energy levels, ε i (λ), T s,i These represent the target emission rate and the average surface temperature of the target during the satellite's transit period, respectively.

[0102] Furthermore, by combining the spectral response function of the thermal infrared satellite payload, the equivalent entrance pupil radiance of the thermal infrared satellite is calculated. The equivalent entrance pupil radiance satisfies the following formula (3):

[0103]

[0104] Among them, L b,i For the equivalent entrance pupil radiance of target i at different energy levels on thermal infrared satellite b, rsf b (λ) is the spectral response function of the thermal infrared satellite b.

[0105] S106, calculates the digital quantization value of the target area based on the observation images of the thermal infrared satellite passing overhead.

[0106] For example, based on the multi-energy-level, multi-target locations and synchronous observations, satellite transit images are screened using spatial and temporal matching, selecting image data with good imaging conditions during the synchronous measurement period and no cloud cover in the surrounding area. After reading the image data, based on the target latitude and longitude range of multiple energy levels (i.e., the geographical location information of the target), the digital quantization values ​​of at least 10×10 windows of anomaly-free pixels around the target area in the thermal infrared satellite payload image are extracted; the extracted multi-pixel digital quantization values ​​are statistically analyzed, and the average value of the digital quantization values ​​of the target area is calculated.

[0107] S107. Determine the absolute radiometric calibration coefficients of the thermal infrared satellite based on the digital quantization values ​​and equivalent entrance pupil radiance of each of the multiple targets.

[0108] The absolute radiometric calibration coefficients of the thermal infrared satellites were obtained by regression calculation using the least squares optimization criterion. The absolute radiometric calibration coefficients of the thermal infrared satellites were calculated by regression calculation using the average of the equivalent entrance pupil radiance of the target thermal infrared satellites at multiple energy levels paired with the corresponding digitally quantized values ​​observed by the satellites, based on the least squares optimization criterion. The absolute radiometric calibration coefficients satisfy the following formula (4):

[0109] L = gain·DN + bias (4)

[0110] Among them, gain and bias are the gain coefficient and bias coefficient of the absolute radiometric calibration of the thermal infrared satellite in orbit, respectively.

[0111] According to the embodiments of this application, ground radiation and atmospheric synchronous measurements of different targets with different energy levels are conducted during satellite transit. Based on the ground radiation parameters and atmospheric parameters of the targets, the equivalent entrance pupil radiance of the targets under the thermal infrared satellite is calculated. Based on the observed images during the thermal infrared satellite transit, the digital quantization value of the target's location is calculated. Using the equivalent entrance pupil radiance and digital quantization value corresponding to each of the multiple targets, the absolute radiometric calibration coefficients of the thermal infrared satellite are determined. Since the absolute radiometric calibration coefficients are determined based on multiple targets with different energy levels, this solves the problem of poor on-orbit radiometric calibration accuracy caused by traditional field calibration using water bodies as a single reference target, thus improving the on-orbit absolute radiometric calibration accuracy of the thermal infrared satellite payload.

[0112] Based on the same concept as the embodiments of the method in this application, this application also provides a thermal infrared satellite radiometric calibration device based on a multi-level target. The thermal infrared satellite radiometric calibration device based on a multi-level target includes several modules, each module being used to execute various steps in the thermal infrared satellite radiometric calibration method based on a multi-level target provided in this application. The division of modules is not limited here. Those skilled in the art will clearly understand that in practical applications, the various steps in the thermal infrared satellite radiometric calibration method based on a multi-level target provided in this application can be assigned to different modules as needed, that is, the internal structure of the device can be divided into different modules to complete all or part of the functions described above. The modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more modules can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the modules in the above device can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0113] Figure 3 This application provides an embodiment of a thermal infrared satellite radiometric calibration device based on a multi-level target. For example... Figure 3 As shown, the embodiment of this application provides a thermal infrared satellite radiometric calibration device based on multi-level targets, including:

[0114] The first acquisition module 301 is used to acquire the payload performance parameters of the thermal infrared satellite;

[0115] The second acquisition module 302 is used to acquire the transit information of the thermal infrared satellite. The transit information is used to indicate the spatiotemporal position relationship and visibility characteristics between the thermal infrared satellite and a specified area on the ground.

[0116] The first determining module 303 is used to determine multiple targets within the dynamic range of the thermal infrared satellite's payload based on payload performance parameters and transit information. These multiple targets have different energy levels.

[0117] Measurement module 304 is used to measure the ground radiation parameters and atmospheric parameters of each of the multiple targets when the thermal infrared satellite passes over, based on the overpass information.

[0118] The first calculation module 305 is used to calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the parameter values ​​of the ground radiation parameters and the parameter values ​​of the atmospheric parameters.

[0119] The second calculation module 306 is used to calculate the digital quantization value of the area where the target is located;

[0120] The second determining module 307 is used to determine the absolute radiometric calibration coefficient of the thermal infrared satellite based on the digital quantization values ​​and equivalent entrance pupil radiance of each of the multiple targets.

[0121] According to the above scheme, ground radiation and atmospheric synchronous measurements of different targets with different energy levels are conducted during satellite transit. Based on the ground radiation and atmospheric parameters of the targets, the equivalent entrance pupil radiance of the targets under the thermal infrared satellite is calculated. Based on the observation images during the thermal infrared satellite transit, the digital quantization value of the target's location is calculated. Using the equivalent entrance pupil radiance and digital quantization value corresponding to each of the multiple targets, the absolute radiometric calibration coefficients of the thermal infrared satellite are determined. Since the absolute radiometric calibration coefficients are determined based on multiple targets with different energy levels, this solves the problem of poor on-orbit radiometric calibration accuracy caused by traditional field calibration using water bodies as a single reference target, thus improving the on-orbit absolute radiometric calibration accuracy of the thermal infrared satellite payload.

[0122] In one possible implementation, payload performance parameters include the spatial resolution, spectral range, and spectral response function of the thermal infrared satellite.

[0123] In one possible implementation, the differences in characteristics exhibited by multiple targets with different energy levels are represented by the different materials of the multiple targets;

[0124] The differences in characteristics exhibited by multiple targets due to their different materials include the target's surface temperature, material emissivity, and / or the target's radiance under solar irradiance.

[0125] In one possible implementation, the measurement module is used for:

[0126] Measure the brightness temperature data of the target, including the brightness temperature of the target above ground or above water;

[0127] The first data of the target is measured, including the target's above-ground radiance spectrum or above-water radiance spectrum;

[0128] The second data for the measurement target includes atmospheric downdraft radiation, atmospheric water vapor content, aerosol optical thickness, atmospheric ozone content, and atmospheric temperature, humidity and pressure profile information.

[0129] Based on the brightness temperature data, the first data, and the second data, the parameter values ​​of the ground radiation parameters and the atmospheric parameters are determined.

[0130] In one possible implementation, the ground radiation parameters include brightness temperature data, first data, surface temperature and surface emissivity, and the atmospheric parameters include atmospheric transmittance, atmospheric upward radiation and atmospheric downward radiation.

[0131] Based on the transit information, the ground radiation parameters and atmospheric parameters of each of the multiple targets were measured during the transit of the thermal infrared satellite, including:

[0132] Based on the downward atmospheric radiation value, the temperature and emissivity of the first data are separated to obtain the surface emissivity of the target;

[0133] The surface temperature of the target is determined based on brightness temperature data, surface emissivity, and atmospheric downdraft radiation.

[0134] Based on the transit information and second data, determine the atmospheric transmittance, upward atmospheric radiation value, and downward atmospheric radiation value of the target when the thermal infrared satellite passes over it.

[0135] In one possible implementation, the transit information includes the target's position, the target's elevation, the observation zenith angle of the thermal infrared satellite, and the observation azimuth angle of the thermal infrared satellite.

[0136] In one possible implementation, the equivalent entrance pupil radiance of the target under a thermal infrared satellite is calculated based on the parameter values ​​of ground radiation parameters and atmospheric parameters, including:

[0137] Based on the values ​​of atmospheric parameters and ground radiation parameters, calculate the thermal radiation brightness of the target as it passes through the atmosphere and reaches the top of the atmosphere.

[0138] Calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the thermal radiation brightness.

[0139] The following describes a computing device provided by an embodiment of this application.

[0140] Figure 4 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Figure 4 As shown, the computer device provided in this application embodiment can be used to implement the Tibetan multilingual speech recognition and speech recognition joint model training method or speech recognition method described in the above method embodiments.

[0141] The computer device may include a processor 401 and a memory 402 storing computer program instructions.

[0142] Specifically, the processor 401 may include a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits that can be configured to implement the embodiments of this application.

[0143] Memory 402 may include mass storage for data or instructions. For example, and not limitingly, memory 402 may include a hard disk drive (HDD), floppy disk drive, flash memory, optical disk, magneto-optical disk, magnetic tape, or Universal Serial Bus (USB) drive, or a combination of two or more of these. Where appropriate, memory 402 may include removable or non-removable (or fixed) media. Where appropriate, memory 402 may be internal or external to the integrated gateway disaster recovery device. In a particular embodiment, memory 402 is non-volatile solid-state memory.

[0144] Memory may include read-only memory (ROM), random access memory (RAM), disk storage media devices, optical storage media devices, flash memory devices, and electrical, optical, or other physical / tangible memory storage devices. Therefore, typically, memory includes one or more tangible (non-transitory) computer-readable storage media (e.g., memory devices) encoded with software including computer-executable instructions, and when the software is executed (e.g., by one or more processors), it is operable to perform the operations described with reference to the methods according to this application.

[0145] The processor 401 reads and executes computer program instructions stored in the memory 402 to implement any of the Tibetan multilingual speech recognition and speech recognition joint model training methods or speech recognition methods in the above embodiments.

[0146] In one example, the electronic device may also include a communication interface 403 and a bus 410. For example, Figure 4 As shown, the processor 401, memory 402, and communication interface 403 are connected through bus 410 and complete communication with each other.

[0147] The communication interface 403 is mainly used to realize communication between various modules, devices, units and / or equipment in the embodiments of this application.

[0148] Bus 410 includes hardware, software, or both, that couples components of an electronic device together. For example, and not limitingly, the bus may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), HyperTransport (HT) interconnect, an Industry Standard Architecture (ISA) bus, an Infinite Bandwidth Interconnect, a Low Pin Count (LPC) bus, a memory bus, a Microchannel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local (VLB) bus, or other suitable buses, or combinations of two or more of these. Where appropriate, bus 810 may include one or more buses. Although specific buses are described and illustrated in embodiments of this application, this application contemplates any suitable bus or interconnect.

[0149] Furthermore, in conjunction with the above embodiments, this application embodiment can be implemented using a computer storage medium. This computer storage medium stores computer program instructions; when these computer program instructions are executed by a processor, they implement any of the methods described in the above embodiments.

[0150] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0151] It should also be noted that the exemplary embodiments mentioned in this application describe methods or systems based on a series of steps or apparatus. However, this application is not limited to the order of the above steps; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0152] The aspects of this application have been described above with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It should be understood that each block in the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that these instructions, executable via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field-programmable logic circuit. It is also understood that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can also be implemented by dedicated hardware performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0153] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A method for radiometric calibration of thermal infrared satellites based on multi-level targets, characterized in that, The method includes: Obtain payload performance parameters of thermal infrared satellites; The transit information of the thermal infrared satellite is obtained, and the transit information is used to indicate the spatiotemporal position relationship and visibility characteristics of the thermal infrared satellite and a specified area on the ground; Based on the payload performance parameters and the transit information, multiple targets within the dynamic range of the thermal infrared satellite's payload are identified, and these multiple targets have different energy levels. The differences in characteristics exhibited by the different energy levels of the multiple targets are due to the different materials of the multiple targets. The differences in characteristics exhibited by the different materials of the multiple targets are the surface temperature, material emissivity, and / or the radiance of the target under solar irradiance. Based on the transit information, the ground radiation parameters and atmospheric parameters of each of the plurality of targets are measured when the thermal infrared satellite passes over, including: Measure the brightness temperature data of the target, including the brightness temperature of the target above ground or above water; The first data of the target is measured, the first data including the ground radiance spectrum or the water radiance spectrum of the target; The second data for measuring the target includes atmospheric downdraft radiation, atmospheric water vapor content, aerosol optical thickness, atmospheric ozone content, and atmospheric temperature, humidity and pressure profile information. Based on the brightness temperature data, the first data, and the second data, determine the parameter values ​​of the ground radiation parameter and the atmospheric parameter. Based on the parameter values ​​of the ground radiation parameters and the parameter values ​​of the atmospheric parameters, calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite; Calculate the digital quantization value of the area where the target is located based on the observation image of the thermal infrared satellite passing overhead; The absolute radiometric calibration coefficient of the thermal infrared satellite is determined based on the digital quantization values ​​and equivalent entrance pupil radiance corresponding to each of the multiple targets.

2. The method according to claim 1, characterized in that, The payload performance parameters include the spatial resolution, spectral range, and spectral response function of the thermal infrared satellite.

3. The method according to claim 1, characterized in that, The ground radiation parameters include brightness temperature data, first data, surface temperature and surface emissivity, and the atmospheric parameters include atmospheric transmittance, atmospheric upward radiation and atmospheric downward radiation. The step of measuring the ground radiation parameters and atmospheric parameters of each of the plurality of targets during the transit of the thermal infrared satellite, based on the transit information, includes: Based on the atmospheric downdraft radiation value, the first data is separated into temperature and emissivity to obtain the surface emissivity of the target; The surface temperature of the target is determined based on the brightness temperature data, the surface emissivity, and the atmospheric downdraft. Based on the transit information and the second data, determine the atmospheric transmittance, atmospheric up-radiation value, and atmospheric down-radiation value of the target when the thermal infrared satellite passes over it.

4. The method according to claim 3, characterized in that, The transit information includes the target's location, the target's elevation, the observation zenith angle of the thermal infrared satellite, and the observation azimuth angle of the thermal infrared satellite.

5. The method according to claim 3 or 4, characterized in that, The step of calculating the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the parameter values ​​of the ground radiation parameters and the atmospheric parameters includes: Based on the values ​​of the atmospheric parameters and the ground radiation parameters, the thermal radiation brightness of the target reaching the top of the atmosphere after passing through the atmosphere is calculated. Based on the thermal radiation brightness, calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite.

6. A thermal infrared satellite radiometric calibration device based on multi-level targets, characterized in that, The device includes: The first acquisition module is used to acquire the payload performance parameters of the thermal infrared satellite; The second acquisition module is used to acquire the transit information of the thermal infrared satellite, which is used to indicate the spatiotemporal position relationship and visibility characteristics of the thermal infrared satellite and a designated area on the ground. The first determining module is used to determine multiple targets within the dynamic range of the payload of the thermal infrared satellite based on the payload performance parameters and the transit information. The multiple targets have different energy levels. The difference in characteristics exhibited by the different energy levels of the multiple targets is due to the different materials of the multiple targets. The difference in characteristics exhibited by the different materials of the multiple targets is due to the surface temperature, material emissivity and / or the radiance of the target under solar irradiation. The measurement module is used to measure the ground radiation parameters and atmospheric parameters of each of the plurality of targets when the thermal infrared satellite passes over, based on the passing information, including: Measure the brightness temperature data of the target, including the brightness temperature of the target above ground or above water; The first data of the target is measured, the first data including the ground radiance spectrum or the water radiance spectrum of the target; The second data for measuring the target includes atmospheric downdraft radiation, atmospheric water vapor content, aerosol optical thickness, atmospheric ozone content, and atmospheric temperature, humidity and pressure profile information. Based on the brightness temperature data, the first data, and the second data, determine the parameter values ​​of the ground radiation parameter and the atmospheric parameter. The first calculation module is used to calculate the equivalent entrance pupil radiance of the target under the thermal infrared satellite based on the parameter values ​​of the ground radiation parameters and the parameter values ​​of the atmospheric parameters. The second calculation module is used to calculate the digital quantization value of the area where the target is located; The second determining module is used to determine the absolute radiometric calibration coefficient of the thermal infrared satellite based on the digital quantization value and equivalent entrance pupil radiance corresponding to each of the plurality of targets.

7. A computing device, characterized in that, It includes a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the method as described in any one of claims 1-5.

8. A computer storage medium, characterized in that, The computer storage medium stores instructions that, when executed on the computer, cause the computer to perform the method as described in any one of claims 1-5.

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