Ocean low-brightness optical satellite absolute radiometric calibration method, device and equipment based on marine pseudo-invariant field and medium

Abstract

The invention relates to an optical satellite absolute radiometric calibration method, device and equipment under ocean low brightness based on an offshore pseudo-invariant field and a medium, and belongs to the technical field of in-orbit absolute radiometric calibration. According to the method, a marine pseudo-invariant field with stable water and atmospheric optical characteristics is determined according to marine observation data of a calibrated optical satellite, the off-water radiance of the marine pseudo-invariant field is calculated according to the chlorophyll a concentration of the marine pseudo-invariant field, the zenith radiance is theoretically calculated, a data source is provided for absolute radiometric calibration of a satellite to be calibrated, and calibration is completed. The method explores the potential of the marine pseudo-invariant field in supplementing the traditional radiometric calibration method, gets rid of the limitation of a fixed and single marine optical buoy MOBY site data source, improves the data volume, the coverage area and the acquisition frequency of effective calibration data, provides guarantee for the continuity of an optical satellite observation task, and has a wide application prospect. And a plurality of calibration sources can be utilized to realize rapid and accurate calibration of the optical satellite, so that the calibration efficiency of the offshore optical satellite is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of on-orbit absolute radiometric calibration, and particularly to an absolute radiometric calibration method, device, equipment and medium for an optical satellite under low ocean brightness based on a maritime pseudo-invariant field. Background Art

[0002] Maintaining the long-term stability and consistency of the radiation characteristics of an optical satellite sensor is crucial for accurately obtaining optical remote sensing products. Although some optical satellites are equipped with on-board calibration systems to track the instrument radiation response changes caused by significant environmental changes and optical performance attenuation, in order to eliminate the residual errors in on-board radiometric calibration and the systematic biases in the atmospheric correction algorithm, it is still necessary to use on-site measured data for further correction. For optical sensors without on-board calibration systems, stable and accurate on-site data is even more needed to support their calibration. That is to say, on-site data is essential for calibration.

[0003] Currently, for the calibration of ocean targets, it is usually achieved by using a Marine Optical Buoy (MOBY). This buoy has been managed by the National Oceanic and Atmospheric Administration (NOAA) of the United States since the end of 1996 and is located in the sea area about 20 kilometers west of Lanai Island, Hawaii. The site selection and instrument configuration of MOBY are based on specific requirements, enabling it to provide high-quality on-site measurement data to support the radiometric calibration of multiple optical satellite sensors. However, there are the following problems when using the MOBY on-site measurement site for radiometric calibration: (1) There are relatively few effective radiometric calibration coefficients. Due to the strict standards for the matching between on-site measurements and synchronous satellite observations (such as the limitations of the observation time interval and observation geometry), combined with frequent solar flares and cloud cover, the number of effective matching data that MOBY can provide for a single optical satellite sensor each year is limited. For example, considering poor sea conditions and instrument failures, the number of matching points between on-site measurements and satellite observations is small. Even when there are satellite observations every day, only about no more than 20 sets of radiometric calibration coefficients can be obtained. Therefore, it may take 2 to 3 years to obtain stable radiometric calibration coefficients only by using the MOBY site; (2) There is a large dependence on on-site measurement data. With more than two decades of operation, the measurement quality of MOBY is declining, its regular update frequency has gradually decreased in recent years, and it is often difficult to obtain effective measurement data in some time periods. This seriously affects the temporal continuity and calibration accuracy of the radiometric calibration of optical satellite sensors. At the same time, as an on-site measurement site managed by NASA of the United States, there may be a situation where data cannot be obtained in the future, which will have a serious impact on satellite calibration (especially for domestic satellite sensors).

[0004] In summary, there is a technical problem of low calibration efficiency in maritime optical satellite calibration due to the low frequency of obtaining effective on-site data, small data volume, and difficulty in data acquisition. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a method, device, equipment, and medium for absolute radiometric calibration of an optical satellite under low brightness of the ocean based on a maritime pseudo-invariant field to solve the above technical problems.

[0006] In a first aspect, a method for absolute radiometric calibration of an optical satellite under low brightness of the ocean based on a maritime pseudo-invariant field is provided. The method includes: Selecting first observation data of an already calibrated optical satellite for the ocean, and comparing parameters in the first observation data with a preset threshold to determine a maritime pseudo-invariant field; Taking the chlorophyll a concentration of the maritime pseudo-invariant field as a single input of a bio-optical model to obtain hyperspectral water-leaving radiance, and taking the convolution of the hyperspectral water-leaving radiance and the spectral response function of the to-be-calibrated optical satellite as the target water-leaving radiance; Theoretically calculating the radiance at the top of the atmosphere according to the target water-leaving radiance, and then combining the digital values actually observed by the to-be-calibrated optical satellite to determine the absolute radiometric calibration coefficient of the to-be-calibrated optical satellite, thereby completing the absolute radiometric calibration of the to-be-calibrated optical satellite.

[0007] In a second aspect, a device for absolute radiometric calibration of an optical satellite under low brightness of the ocean based on a maritime pseudo-invariant field is provided. The device includes: A calibration field determination module, configured to select first observation data of an already calibrated optical satellite for the ocean, and compare parameters in the first observation data with a preset threshold to determine a maritime pseudo-invariant field; A target parameter acquisition module, configured to take the chlorophyll a concentration of the maritime pseudo-invariant field as a single input of a bio-optical model to obtain hyperspectral water-leaving radiance, and take the convolution of the hyperspectral water-leaving radiance and the spectral response function of the to-be-calibrated optical satellite as the target water-leaving radiance; A target satellite calibration module, configured to theoretically calculate the radiance at the top of the atmosphere according to the target water-leaving radiance, and then combine the digital values actually observed by the to-be-calibrated optical satellite to determine the absolute radiometric calibration coefficient of the to-be-calibrated optical satellite, thereby completing the absolute radiometric calibration of the to-be-calibrated optical satellite.

[0008] In a third aspect, an embodiment of the present invention provides a computer device, which includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for absolute radiometric calibration of an optical satellite under low brightness of the ocean based on a maritime pseudo-invariant field as described in the first aspect is implemented.

[0009] Fourthly, an embodiment of the present invention provides a computer-readable storage medium storing a computer program, which when executed by a processor implements the method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a marine pseudo-invariant field as described in the first aspect.

[0010] The beneficial effects of the present invention compared with the prior art are as follows: According to the observation data of the calibrated optical satellite on the ocean, the present invention determines a marine pseudo-invariant field with stable changing patterns of water body and atmospheric optical properties. Taking the chlorophyll a concentration of the marine pseudo-invariant field as a single input of the bio-optical model to obtain the hyperspectral water-leaving radiance, combining with the spectral response function of the to-be-calibrated optical satellite to obtain the target water-leaving radiance required for calibration and further determining the theoretically predicted radiance at the top of the atmosphere, and then combining with the actual observed digital value of the to-be-calibrated optical satellite to obtain the absolute radiometric calibration coefficient to complete the calibration. The present invention explores the potential of the marine pseudo-invariant field in supplementing traditional radiometric calibration methods, gets rid of the limitation of the existing calibration method by a single Marine Optical Buoy (MOBY) site, improves the coverage area of the effective calibration data volume, provides more data for calibration without high construction and maintenance costs, and can significantly improve the data update frequency compared with the existing MOBY sites, ensuring the continuity of the remote sensing observation task of the optical satellite sensor. Finally, based on multiple calibration sources that can provide the data required for calibration at high frequency, rapid and accurate calibration of the optical satellite can be achieved, significantly improving the calibration efficiency of the marine optical satellite. Description of the Drawings

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0012] Figure 1 It is a schematic diagram of an application environment of a method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a marine pseudo-invariant field provided in Embodiment 1 of the present invention; Figure 2 It is a schematic flowchart of a method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a marine pseudo-invariant field provided in Embodiment 1 of the present invention; Figure 3 It is a schematic diagram of the chlorophyll a concentration change sequence of the marine pseudo-invariant field OPIS-INP at different time scales during a known period provided in Embodiment 1 of the present invention; Figure 4It is a schematic diagram of the change sequence of chlorophyll a concentration of the offshore pseudo-invariant field OPIS-NPP in Shanghai during a known period under different time scales provided by Embodiment 1 of the present invention; Figure 5 It is a schematic diagram of the change sequence of chlorophyll a concentration of the offshore pseudo-invariant field OPIS-SPP in Shanghai during a known period under different time scales provided by Embodiment 1 of the present invention; Figure 6 It is a schematic diagram of the change sequence of chlorophyll a concentration of the offshore pseudo-invariant field OPIS-NAP in Shanghai during a known period under different time scales provided by Embodiment 1 of the present invention; Figure 7 It is a schematic diagram of the time series of the absolute radiometric calibration coefficients obtained based on the MOBY site data and the offshore pseudo-invariant field data provided by the comparative example of the present invention; Figure 8 It is a schematic diagram of the structure of an absolute radiometric calibration device for an optical satellite under low brightness of the ocean based on an offshore pseudo-invariant field provided by Embodiment 3 of the present invention; Figure 9 It is a schematic diagram of the structure of a computer device provided by Embodiment 4 of the present invention. Detailed implementation manners

[0013] The general concept of the present invention is as follows: With the help of a high-precision optical satellite that has completed absolute radiometric calibration, analyze the optical characteristics of the global ocean area through long-term observational data, select an area with low temporal variability and high spatial uniformity that can accurately characterize the interannual variation of ocean optical characteristics as the required offshore pseudo-invariant field (OPIS), use the determined offshore pseudo-invariant field as the calibration field for the satellite to be calibrated, estimate the water surface radiation of the calibration field based on the bio-optical model, specifically obtain the water-leaving radiance for calibration through the chlorophyll a (Chla) concentration of the offshore pseudo-invariant field, provide a data source for the absolute radiometric calibration of the satellite to be calibrated, get rid of the limitation of a fixed and single data source and increase the calibration data volume and acquisition frequency, and achieve efficient calibration of ocean optical satellite sensors and land optical satellite sensors with ocean observation capabilities.

[0014] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0015] It should be understood that, as used in the specification of the present invention and the appended claims, the term "comprising" indicates the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their combinations.

[0016] It should also be understood that the term "and / or" as used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0017] As used in the specification of the present invention and the appended claims, the term "if" can be interpreted as "when", "once", "in response to determining", or "in response to detecting" depending on the context. Similarly, the phrase "if determined" or "if [the described condition or event] is detected" can be interpreted as meaning "once determined", "in response to determining", "once [the described condition or event] is detected", or "in response to detecting [the described condition or event]" depending on the context.

[0018] In addition, in the description of the specification of the present invention and the appended claims, the terms "first", "second", "third", etc. are only used for descriptive distinction and should not be construed as indicating or implying relative importance.

[0019] Reference to "one embodiment" or "some embodiments" or the like described in the specification of the present invention means that a specific feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the present invention. Thus, statements such as "in one embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments", etc. that appear in different places in this specification are not necessarily all referring to the same embodiment, but rather mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "comprising", "including", "having", and their variants all mean "including but not limited to", unless otherwise specifically emphasized.

[0020] Embodiments of the present invention may acquire and process relevant data based on artificial intelligence technology. Among them, artificial intelligence (AI) is a theory, method, technology, and application system that uses a digital computer or a machine controlled by a digital computer to simulate, extend, and expand human intelligence, perceive the environment, acquire knowledge, and use the knowledge to obtain the best results.

[0021] The basic technologies of artificial intelligence generally include technologies such as sensors, dedicated artificial intelligence chips, cloud computing, distributed storage, big data processing technologies, operation / interaction systems, and mechatronics. The software technologies of artificial intelligence mainly include several major directions such as computer vision technology, robotics, biometric technology, speech processing technology, natural language processing technology, and machine learning / deep learning.

[0022] It should be understood that the magnitudes of the sequence numbers of the steps in the following embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0023] In order to illustrate the technical solution of the present invention, specific embodiments are used for illustration below.

[0024] An absolute radiometric calibration method for optical satellites under low brightness in the ocean based on a marine pseudo-invariant field provided in the first embodiment of the present invention can be applied in Figure 1 such application environments. The client includes but is not limited to terminal devices such as palm computers, desktop computers, laptop computers, ultra-mobile personal computers (UMPCs), netbooks, cloud terminal devices, and personal digital assistants (PDAs). The server can be implemented by an independent server or a server cluster composed of multiple servers. The sensing devices include but are not limited to calibrated optical satellites and optical satellites to be calibrated.

[0025] The above absolute radiometric calibration method can be specifically applied to Figure 1 the client in. The terminal device corresponding to the client connects to the target database through a preset Application Programming Interface (API). When the target data is driven to run to execute corresponding tasks, corresponding task logs will be generated, and the above task logs can be collected through the API. The above absolute radiometric calibration method can also be specifically applied to the server in FIG. 1. The computer device corresponding to the server connects to corresponding databases, rule bases, etc. to obtain corresponding data in the database. The above computer device can also connect to the client to collect data and control instructions sent by the client users. And, the above absolute radiometric calibration method can also be specifically applied to Figure 1 the sensing devices in.

[0026] See Figure 2 , which is a schematic flowchart of an absolute radiometric calibration method for optical satellites under low brightness in the ocean based on a marine pseudo-invariant field provided in the first embodiment of the present invention. The absolute radiometric calibration method may include the following steps: Step S101: Select the first observation data of the calibrated optical satellite for the ocean, and compare the parameters in the first observation data with the preset thresholds to determine the sea surface pseudo-invariant fields.

[0027] In order to provide stable and reliable calibration data to the to-be-calibrated optical satellite in the long term, in this embodiment, a water color satellite sensor with global ocean observation capabilities and good calibration accuracy (such as MODIS-Aqua) is first selected as the calibrated optical satellite. To ensure the stability and reliability of the data, the earth observation data products of the calibrated optical satellite in a long time series are obtained and recorded as the first observation data. The first observation data needs to include water body and atmospheric optical parameters, including: chlorophyll a concentration (Chl-a), remote sensing reflectance in each band (R rs ), aerosol optical thickness in the reference band ( τ 869), Ångström exponent (AE), coefficient of variation (CV), blue-green band ratio (BGR), and clear sky rate (CSR), etc.

[0028] Among them, the coefficient of variation gives the regional stability of each band, the blue-green band ratio indicates the cleanliness of the regional water body, and a higher clear sky rate can provide more effective matches. In this embodiment, according to whether the parameters in the first observation data are related to the temporal variability, spatial uniformity of the ocean region, and the interannual variation of ocean optical characteristics, the parameters in the first observation data are selected, and the selected parameters and corresponding parameter limit conditions are set for the parameters to complete the determination of the sea surface pseudo-invariant fields. The operator can flexibly set specific parameter items and parameter limit conditions according to the above parameter selection principles. As an example, in this embodiment, the sea surface pseudo-invariant fields are screened through the parameters and parameter limit conditions in Table 1 below, where the symbols μ and <> respectively represent calculating the average value and standard deviation of the parameters.

[0029] Table 1 Target parameters and thresholds for determining sea surface pseudo-invariant fields

[0030] In this embodiment, the calibrated optical satellite is specifically used to obtain the earth observation data products in the long time series from July 2002 to December 2016 as the first observation data, and four sea surface pseudo-invariant fields as shown in Table 2 below are determined according to the content of Table 1, which are located in the Indian Ocean (OPIS-INP), the North Pacific Ocean (OPIS-NPP), the South Pacific Ocean (OPIS-SPP), and the North Atlantic Ocean (OPIS-NAP). The specific ranges and central longitude and latitude of the four determined sea surface pseudo-invariant fields are shown in Table 2 below.

[0031] Table 2 Regional location information of the determined sea surface pseudo-invariant fields

[0032] In step S102, the chlorophyll a concentration of the offshore pseudo-invariant field is used as a single input of the bio-optical model to obtain the hyperspectral water-leaving radiance, and the convolution of the hyperspectral water-leaving radiance and the spectral response function of the optical satellite to be calibrated is used as the target water-leaving radiance.

[0033] In this embodiment, by using the chlorophyll a (Chla) concentration of the selected offshore pseudo-invariant field as a single input of the bio-optical model, the hyperspectral water-leaving radiance is constructed, and the subsequent absolute radiometric calibration process is realized based on the obtained hyperspectral water-leaving radiance.

[0034] Figures 3 to 6 The changing sequences of the Chla concentrations of four offshore pseudo-invariant fields, namely OPIS-INP, OPIS-NPP, OPIS-SPP, and OPIS-NAP, at different time scales during the period from July 2002 to December 2016 are shown in sequence. Specifically, Figures 3 to 6 Subgraphs (a), (b), and (c) in each figure show the daily, 8-day average, and monthly average sampling results of the Chla concentration in sequence, where the discrete points are the Chla concentration data observed by the satellite, i.e., the sampling values, and the curves represent the Chla concentration change curves at different time scales fitted according to the Chla concentration data observed by the satellite.

[0035] By observing the Chla concentration data of the four offshore pseudo-invariant fields in the above-mentioned earth observation data products, it can be seen that the Chla concentration in the offshore pseudo-invariant field shows the characteristic of stable change, which can provide a stable data basis for the subsequent absolute radiometric calibration.

[0036] In a preferred embodiment, the Chla concentration of the offshore pseudo-invariant field is determined based on the Chla concentration data of each offshore pseudo-invariant field in the above-mentioned earth observation data products by constructing a stable change model of the Chla concentration in each offshore pseudo-invariant field, and specifically, it can be determined by the Fourier function Concentration: , where , , and are all fixed parameters obtained by fitting, and the variable represents the number of days starting from the specified date. This model can provide the simulated Chla concentration by inputting the specified calibration time, providing data support for completing the subsequent calibration process. Specifically, the stable changing Chla concentration in the offshore pseudo-invariant field can be determined according to the time of the satellite data to be calibrated through the Chla concentration calculation formula, and then the obtained stable changing Chla concentration is used as a single input of the bio-optical model to obtain the hyperspectral water-leaving radiance.

[0037] Among them, the bio-optical model can directly adopt existing models, such as the OC series models. In this embodiment, the bio-optical model is not specifically limited, and the operator can specifically select according to requirements.

[0038] In a preferred embodiment, the Chla concentration is used as a single input of the bio-optical model to obtain the hyperspectral water-leaving radiance, which specifically includes: First, the total absorption coefficient is calculated from the Chla concentration through existing algorithms (such as Gaussian decomposition method, absorption coefficient decomposition model and backscattering coefficient model, LightGBM model under machine learning, etc.). a and the total backscattering coefficient b b , and then the remote sensing reflectance a and the total backscattering coefficient b b under the sea surface are calculated: r rs : , where and both represent fitting coefficients.

[0039] After that, r rs is further converted into the remote sensing reflectance above the sea surface: , where represents the water-atmosphere transmittance, represents the bidirectional correction factor, and in this embodiment, is preferably selected, .

[0040] Finally, the hyperspectral is converted into the hyperspectral water-leaving radiance : , where represents the extra-terrestrial solar irradiance of the optical satellite to be calibrated, represents the solar zenith angle, represents the atmospheric diffuse transmittance under the sensor detection band of the optical satellite to be calibrated.

[0041] The obtained hyperspectral water-leaving radiance is convolved with the spectral response function of the sensor of the optical satellite to be calibrated, and the target water-leaving radiance corresponding to the sensor of the optical satellite to be calibrated can be obtained, which is used as an important basis for the subsequent absolute radiometric calibration process. Among them It represents the detection band of the sensor of the optical satellite to be radiometrically calibrated. The spectral response function of the sensor of the optical satellite to be radiometrically calibrated can be determined according to the observation data of the optical satellite to be radiometrically calibrated in the marine pseudo-invariant field. The specific water-leaving radiance of the target corresponds to the water-leaving radiance of each band of the payload to be radiometrically calibrated of the optical satellite to be radiometrically calibrated.

[0042] Step S103: The top-of-atmosphere radiance is theoretically calculated based on the water-leaving radiance of the target, and then the absolute radiometric calibration coefficient of the optical satellite to be radiometrically calibrated is determined by combining the digital value actually observed by the optical satellite to be radiometrically calibrated, thus completing the absolute radiometric calibration of the optical satellite to be radiometrically calibrated.

[0043] The absolute radiometric calibration of the optical satellite is completed by relying on the absolute radiometric calibration coefficient. The absolute radiometric calibration coefficient of the sensor of the optical satellite to be radiometrically calibrated is determined by the top-of-atmosphere radiance obtained from theoretical calculation corresponding to the optical satellite to be radiometrically calibrated and the digital value actually observed by the sensor of the optical satellite to be radiometrically calibrated.

[0044] Among them, the digital value actually observed by the sensor of the optical satellite to be radiometrically calibrated can usually be obtained from the Level-1 A data of the satellite sensor, while the top-of-atmosphere radiance corresponding to the optical satellite to be radiometrically calibrated needs to be obtained by theoretical calculation based on the water-leaving radiance of the target: , Among them, represents the top-of-atmosphere radiance, represents the detection band of the sensor of the optical satellite to be radiometrically calibrated, represents the Rayleigh scattering contribution corresponding to the optical satellite to be radiometrically calibrated, represents the aerosol scattering contribution corresponding to the optical satellite to be radiometrically calibrated, represents the radiation contribution of the Rayleigh-aerosol coupling effect corresponding to the optical satellite to be radiometrically calibrated, represents the diffuse transmittance of the observation path of the sensor on the optical satellite from the sea surface to the satellite, represents the radiation contribution of the sea surface whitecap scattering corresponding to the optical satellite to be radiometrically calibrated, represents the atmospheric direct transmittance at the location of the optical satellite, represents the contribution of the solar flare corresponding to the optical satellite to be radiometrically calibrated, represents the water-leaving radiance of the target, represents the gas absorption along the solar zenith, represents the gas absorption along the satellite viewing path.

[0045] By combining the sea surface atmospheric pressure data and the observation geometric information, the Rayleigh scattering contribution of a specific satellite can be calculated according to the Rayleigh look-up table of the sensor to be radiometrically calibrated Based on the aerosol type (all the pseudo-invariant field areas at sea are marine aerosols) and the aerosol optical depth, the aerosol contribution can be derived through the atmospheric correction process. and Finally, by combining the reconstructed hyperspectral and the synchronous atmospheric parameters, the radiance at the top of the atmosphere can be obtained through theoretical simulation calculations. .

[0046] Based on the obtained radiance at the top of the atmosphere , and then combining with the digital values actually observed by the optical satellite to be calibrated, the absolute radiometric calibration coefficient of the optical satellite sensor to be calibrated can be calculated through the formula :

[0047] where represents the digital value at the top of the atmosphere actually observed by the sensor, is the radiance at the top of the atmosphere.

[0048] According to the obtained absolute radiometric calibration coefficient of the optical satellite sensor to be calibrated, the absolute radiometric calibration of the optical satellite sensor to be calibrated can be completed, and the purpose of absolute radiometric calibration of the optical satellite under low ocean brightness with the determined pseudo-invariant field at sea can be achieved.

[0049] The present invention also provides a second embodiment. In this embodiment, before completing the above step S102 and executing step S103, it further includes: Obtain the second observation data of the optical satellite to be calibrated in the pseudo-invariant field at sea. According to the latitude and longitude information in the second observation data, perform point-to-point spatial matching between the optical satellite to be calibrated and the pseudo-invariant field at sea with a preset spatial threshold, and screen the second observation data according to the observation geometry of the optical satellite to be calibrated to obtain the screened second observation data and use it for theoretical calculation of the radiance at the top of the atmosphere.

[0050] Specifically, it includes: 1) Acquisition of the observation data of the satellite to be calibrated Obtain the second observation data of the optical satellite sensor to be calibrated in the above-determined pseudo-invariant field area at sea. The second observation data includes but is not limited to the digital values of the observations at the top of the atmosphere in each band, latitude and longitude information, observation geometry information (including solar zenith angle and azimuth angle, satellite observation zenith angle and azimuth angle, relative azimuth angle), mask identification information, spectral response function, auxiliary data (sea surface atmospheric pressure, wind speed, relative humidity, water vapor content, etc.). These data are mainly used for the atmospheric correction process of the optical satellite sensor to be calibrated.

[0051] 2) Extraction of the region-matched data After determining the second observation data, using the longitude and latitude information of the optical satellite to be calibrated in the second observation data, the optical satellite to be calibrated and the offshore pseudo-invariant field are subjected to point-to-point spatial matching with a preset spatial threshold. To improve the absolute radiometric calibration accuracy, the principles to be followed in the matching process are as follows: Spatial matching principle: After obtaining the longitude and latitude, observation geometry, and top-of-atmosphere observation data of the sensor to be calibrated in a large area of the offshore pseudo-invariant field, point-to-point spatial matching is performed between the sensor and the center position of the offshore pseudo-invariant field. A preset spatial threshold with a value of 0.01° is set, and the closest pixel points within the threshold range are obtained through matrix operations as the matching points for the two, and duplicate matching points are removed, only retaining the one-to-one cases and relevant matching parameters, so as to completely match the pixel points of the sensor to be calibrated with the offshore pseudo-invariant field, providing a matching data set for the subsequent calculation of the absolute radiometric calibration coefficient.

[0052] Among them, the value of the preset spatial threshold is determined according to the spatial resolution of the sensor MODIS-Aqua used in the process of determining the offshore pseudo-invariant field, that is, determined according to the spatial resolution of the calibrated optical satellite. Based on the spatial resolution of the MODIS-Aqua sensor of 1 km, the value of the preset spatial threshold is correspondingly set to 0.01°. At the same time, the actual spatial resolution of the sensor on the optical satellite to be calibrated also needs to be considered. If the actual spatial resolution of the sensor on the optical satellite to be calibrated is lower than that of MODIS-Aqua, when the preset spatial threshold value is too small, the sensor resolution of the optical satellite to be calibrated cannot meet the requirements of this preset spatial threshold, thus affecting the spatial matching. Therefore, it is necessary to adjust the value of the preset spatial threshold according to the actual spatial resolution of the sensor on the optical satellite to be calibrated. That is, it is necessary to comprehensively consider the resolution of the optical satellite to be calibrated and the resolution of the calibrated optical satellite, and determine the value of this preset spatial threshold based on the lower resolution of the two.

[0053] Observation geometry limitation principle: Before performing absolute radiometric calibration on the sensor to be calibrated and the offshore pseudo-invariant field, it is also necessary to consider the observation geometry of the sensor to be calibrated, limit the observation geometry, or screen the observation data (second observation data) of the sensor to be calibrated with the observation geometry. For example, for the solar zenith angle, the matching data needs to be within 60°, and for the satellite observation zenith angle, the matching data needs to be within 40°.

[0054] Finally, the second observation data after screening is obtained after spatial matching.

[0055] 3) Effective pixel screening To further improve the calibration accuracy, optionally, after performing longitude and latitude matching on the sensor to be calibrated and the marine pseudo-invariant field, in this embodiment, effective matching pixel screening is also performed on the second observation data after screening through the pixel mask information in the observation data (second observation data) of the optical satellite sensor to be calibrated, and invalid pixels are removed, including clouds, flares, pixels with too large observation angles, etc. Finally, matching pixel points that meet the validity are determined, and the second observation data after secondary screening is obtained.

[0056] By removing invalid pixels in the matching pixels through the mask information, some influencing factors can be excluded during the absolute radiometric calibration process, and the absolute radiometric calibration accuracy of the optical satellite to be calibrated can be further improved. Moreover, after removing the invalid pixels, when actually calculating the top-of-atmosphere radiance, and can be directly processed as 0, because after screening through valid pixels, the retained data is not affected by solar flares and sea surface white caps. Therefore, valid pixel screening can also reduce the calculation amount during the calibration process to a certain extent and improve the calibration efficiency.

[0057] To verify the effect of the present invention, based on the content of the above embodiments of the present invention, the following comparative examples are used to compare the satellite absolute radiometric calibration results.

[0058] This comparative example selects the optical satellite sensor VIIRS carried on SNPP as the payload to be calibrated, and calculates its radiometric calibration coefficients under two radiometric calibration methods. Among them, one method uses the traditional calibration site MOBY to provide on-site measurement data; the other method uses the above four marine pseudo-invariant fields determined in the embodiments of the present invention to provide simulation data as input.

[0059] Through the above two radiometric calibration methods, a time series of absolute radiometric calibration coefficients as shown in Figure 7 is obtained in the time range from January 2012 to December 2014, and for the convenience of analysis and comparison, the absolute radiometric calibration coefficients are normalized.

[0060] Among them, the bands of 410 nm, 443 nm, 486 nm, 551 nm, and 671 nm of VIIRS-SNPP are involved in the calibration. Figure 7 Subgraphs (a) to (e) in

[0061] The comparison of the radiation calibration coefficients obtained from the pseudo-invariant field simulation data at sea and the field measurement data at the MOBY station in Table 3 shows that the average radiation calibration coefficients in each band obtained from the pseudo-invariant field simulation data at sea are g OPIS The average value of the radiation calibration coefficient g obtained from the field measurement data of the MOBY site MOBY Very close, the mean absolute percentage error MAPE between the two results is less than 5% in each band; at the same time, combined with the results in Table 3 and Figure 7 It can be seen that the absolute radiation calibration coefficient corresponding to the offshore pseudo-invariant field is stable at the first three wavelengths and is very close to the average value, while the absolute radiation calibration coefficient corresponding to the MOBY station at the last two wavelengths shows a slightly larger change. Therefore, the method of completing absolute radiation calibration based on the offshore pseudo-invariant field has enhanced the stability of the absolute radiation calibration coefficient obtained by the existing method of completing absolute radiation calibration based on the MOBY station, and the higher calibration frequency can significantly shorten the calibration time.

[0062] Table 3 Comparison of radiation calibration coefficients obtained based on offshore pseudo-invariant field simulation data and MOBY site field measurement data

[0063] From the comparison of the results of the two radiation calibration methods, the following preliminary conclusions can be obtained: First, the radiation calibration method based on the offshore pseudo-invariant field is compared with the radiation calibration method based on the field measurement site. The numerical values ​​of the calibration coefficients show good consistency, and the average absolute percentage difference MAPE between each band can be kept within 5%, indicating that the calibration accuracy of the present invention has reached a level similar to that of the traditional calibration method, indicating the effectiveness of the method of the present invention; secondly, after using the four offshore pseudo-invariant fields proposed by the present invention to participate in the radiation calibration calculation, within the three-year research period, the number of groups of effective calibration coefficients increased from 36 groups to 114 groups, and the four offshore pseudo-invariant fields provided 78 more groups of effective calibration results for the sensors to be calibrated. This makes it possible to accumulate absolute radiation calibration coefficients more quickly, thereby providing accurate business products more quickly, and also shows that the calibration method of the present invention has important application value and practical significance.

[0064] In summary, the present invention first completes the determination of the pseudo-invariant field at sea, and uses the pseudo-invariant field at sea to achieve the purpose of absolute radiation calibration of optical satellite sensors under low-brightness conditions in the ocean. Compared with the prior art, the present invention has the following beneficial effects: (1) As a general method, the present invention can use optical satellite sensors with high radiation calibration accuracy, long time span and large spatial coverage to analyze and determine the pseudo-invariant field at sea with stable variation characteristics, so as to be applied to the on-orbit absolute radiation calibration of sensors; (2) Compared with the traditional radiation calibration method based on on-site measurement stations, the present invention can effectively increase the frequency of on-orbit absolute radiation calibration, saving a great deal of manpower and material resources required for on-site measurement. At the same time, it helps newly launched sensors quickly obtain a large number of initial calibration coefficients, thus assisting the sensors to provide stable data products as soon as possible; (3) The present invention introduces the pseudo-invariant field at sea into the on-orbit absolute radiation calibration of sensors. Compared with the pseudo-invariant field on land under high brightness, it provides radiation calibration conditions in low-brightness scenarios, providing important data support for the absolute radiation calibration of sensors in the low-gain state; (4) The radiation calibration method in low-brightness scenarios based on the pseudo-invariant field at sea provided by the present invention is a method for constructing the radiance leaving water of hyperspectral. Therefore, it can be applied to the absolute radiation calibration of all optical satellite sensors capable of ocean observation, having good applicability. At the same time, it is not limited to sensors already in orbit. This method is also applicable to optical satellite sensors that have not been launched but meet the conditions for ocean observation, having both practical and future significance.

[0065] In addition, the method of the present invention combines the generation of pseudo-invariant field simulation data at sea with the observation data of optical satellite sensors, forming a matching calibration program that combines data matching and on-orbit absolute radiation calibration. By implementing the method of the present invention, continuous data matching and radiation calibration are achieved, thereby continuously tracking the change in the radiation performance of sensors during on-orbit operation and realizing correction. The continuously accumulated long-term calibration sequences of each sensor also provide data support for analyzing the overall change trend of the instrument. At the same time, the method for absolute radiation calibration of optical satellites under low brightness at sea based on the pseudo-invariant field of the present invention is a general method, which can provide an absolute radiation calibration method for ocean optical satellite sensors and land optical satellite sensors with ocean observation capabilities under low brightness conditions, including but not limited to domestic ocean color satellite sensors such as COCTS-HY1C / D, CZI-HY1C / D, etc., mainstream international ocean color satellite sensors such as MODIS-Terra / Aqua, VIIRS-SNPP / NOAA, OLCI-Sentinel3, and OCI-PACE, as well as land optical satellite sensors such as OLI-Landsat8 / 9, MSI-Sentinel2, etc.

[0066] Corresponding to the method of the above embodiment, Figure 8The block diagram of the optical satellite absolute radiometric calibration device based on the offshore pseudo-invariant field provided in the third embodiment of the present invention is shown. The above absolute radiometric calibration device is applied to a computer device, and the computer device is connected to a target database through a preset application programming interface. When the target database is driven to run to execute corresponding tasks, corresponding task logs will be generated, and the above task logs can be collected through the API. For the sake of convenience of description, only the parts related to the embodiments of the present invention are shown.

[0067] See Figure 8 , the absolute radiometric calibration device includes: A calibration field determination module 31, configured to select the first observation data of the ocean by a calibrated optical satellite, and compare the parameters in the first observation data with a preset threshold to determine an offshore pseudo-invariant field; A target parameter acquisition module 32, configured to use the chlorophyll a concentration of the offshore pseudo-invariant field as a single input of a bio-optical model to obtain the hyperspectral water-leaving radiance, and use the convolution of the hyperspectral water-leaving radiance and the spectral response function of the optical satellite to be calibrated as the target water-leaving radiance; A target satellite calibration module 33, configured to theoretically calculate the top-of-atmosphere radiance according to the target water-leaving radiance, and then combine the digital values actually observed by the optical satellite to be calibrated to determine the absolute radiometric calibration coefficient of the optical satellite to be calibrated, and complete the absolute radiometric calibration of the optical satellite to be calibrated.

[0068] Optionally, the above device further includes: A data matching and screening module, configured to perform the following after obtaining the target water-leaving radiance and before theoretically calculating the top-of-atmosphere radiance: Obtain the second observation data of the optical satellite to be calibrated in the offshore pseudo-invariant field, and perform point-to-point spatial matching between the optical satellite to be calibrated and the offshore pseudo-invariant field with a preset spatial threshold according to the latitude and longitude information in the second observation data, and screen the second observation data according to the observation geometry of the optical satellite to be calibrated, and theoretically calculate the top-of-atmosphere radiance with the screened second observation data.

[0069] Optionally, the data matching and screening module includes: A preset spatial threshold determination unit, configured to limit the preset spatial threshold to be determined according to the lower resolution of the resolution of the optical satellite to be calibrated and the resolution of the calibrated optical satellite.

[0070] Optionally, the data matching and screening module further includes: A pixel secondary screening unit, configured to perform the following after obtaining the screened second observation data and before theoretically calculating the top-of-atmosphere radiance: Screen the pixels of the second observed data after screening through the mask information of the pixels in the second observed data to obtain the second observed data after secondary screening and use it for theoretically calculating the top-of-atmosphere radiance.

[0071] Optionally, the target parameter acquisition module 32 includes: A chlorophyll a concentration calculation unit for determining the chlorophyll a concentration through a Fourier function :

[0072] Among them, , , and are all fixed parameters obtained by fitting, represents the number of days starting from a specified date.

[0073] Optionally, the target parameter acquisition module 32 further includes: A hyperspectral water-leaving radiance acquisition unit for defining the obtained hyperspectral water-leaving radiance, including: Determine the total absorption coefficient according to the chlorophyll a concentration and the total backscattering coefficient , and then calculate the remote sensing reflectance below the sea surface :

[0074] Among them, and both represent fitting coefficients; Convert to the remote sensing reflectance above the sea surface :

[0075] Among them, represents the water-atmosphere transmittance, represents the bidirectional correction factor; Then convert to the hyperspectral water-leaving radiance :

[0076] Among them, represents the extra-terrestrial solar irradiance corresponding to the to-be-calibrated optical satellite, represents the solar zenith angle, represents the atmospheric diffuse transmittance in the sensor detection band of the to-be-calibrated optical satellite.

[0077] Optionally, the target satellite calibration module 33 includes: The theoretical prediction unit for the top-of-atmosphere radiance is used to define the top-of-atmosphere radiance is:

[0078] Wherein, represents the sensor detection band of the to-be-calibrated optical satellite, represents the Rayleigh scattering contribution corresponding to the to-be-calibrated optical satellite, represents the aerosol scattering contribution corresponding to the to-be-calibrated optical satellite, represents the radiation contribution of the Rayleigh-aerosol coupling effect corresponding to the to-be-calibrated optical satellite, represents the diffuse transmittance of the observation path of the sensor on the to-be-calibrated optical satellite from the sea surface to the satellite, represents the radiation contribution of the sea surface whitecap scattering corresponding to the to-be-calibrated optical satellite, represents the atmospheric direct transmittance at the to-be-calibrated optical satellite, represents the contribution of the solar flare corresponding to the to-be-calibrated optical satellite, represents the target water-leaving radiance, represents the gas absorption along the solar zenith, represents the gas absorption along the satellite viewing path.

[0079] It should be noted that for the information interaction, execution process, etc. between the above modules, since they are based on the same concept as the method embodiment of the present invention, for their specific functions and the technical effects brought, reference can be specifically made to the method embodiment part, and details are not described herein again.

[0080] Figure 9 This is a schematic structural diagram of a computer device provided in Embodiment 4 of the present invention. As Figure 9 shown, the computer device of this embodiment includes: at least one processor ( Figure 9 only one is shown in the figure), a memory, and a computer program stored in the memory and executable on at least one processor. When the processor executes the computer program, it implements the steps in any of the above method embodiments of the absolute radiometric calibration method for optical satellites under low brightness based on the sea surface pseudo-invariant field.

[0081] This computer device may include, but is not limited to, a processor and a memory. Those skilled in the art can understand that Figure 9 this is only an example of a computer device and does not constitute a limitation on the computer device. The computer device may include more or fewer components than shown in the figure, or combine some components, or different components.

[0082] The so-called processor may be a CPU, and the processor may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0083] The memory includes a readable storage medium, internal memory, etc. Among them, the internal memory may be the memory of the computer device, and the internal memory provides an environment for the operation of the operating system and computer-readable instructions in the readable storage medium. The readable storage medium may be the hard disk of the computer device, and in some other embodiments, it may also be an external storage device of the computer device. For example, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the computer device. Further, the memory may also include both the internal storage unit of the computer device and the external storage device. The memory is used to store the operating system, application programs, boot loaders, data, and other programs, such as the program code of computer programs. The memory may also be used to temporarily store the data that has been output or will be output.

[0084] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above division of each functional unit and module is used as an example. In actual applications, the above functions can be allocated to different functional units and modules according to needs, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiments can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction and do not limit the protection scope of the present invention. The specific working processes of the units and modules in the above device can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein. If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above method embodiments of the present invention, a computer program can be used to instruct the relevant hardware to complete. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file or some intermediate form, etc. The computer-readable medium can at least include: any entity or device capable of carrying the computer program code, recording medium, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium. For example, a USB flash drive, a mobile hard disk, a magnetic disk or an optical disc, etc. In some jurisdictions, according to legislation and patent practice, the computer-readable medium cannot be an electrical carrier signal and a telecommunication signal.

[0085] All or part of the processes in the above method embodiments of the present invention can also be completed by a computer program product. When the computer program product runs on a computer device, the computer device can be made to execute the steps in the above method embodiments.

[0086] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0087] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0088] In the embodiments provided by the present invention, it should be understood that the disclosed device / computer equipment and method can be implemented in other ways. For example, the device / computer equipment embodiments described above are merely illustrative. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of devices or units can be in electrical, mechanical or other forms.

[0089] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. An absolute radiometric calibration method for optical satellites under low brightness in the ocean based on the marine pseudo-invariant field, characterized in that, The method includes: Selecting the first observation data of the ocean by a calibrated optical satellite, and comparing the parameters in the first observation data with a preset threshold to determine a marine pseudo-invariant field; Taking the chlorophyll a concentration of the marine pseudo-invariant field as a single input of a bio-optical model to obtain the hyperspectral water-leaving radiance, and taking the convolution of the hyperspectral water-leaving radiance and the spectral response function of the optical satellite to be calibrated as the target water-leaving radiance; Theoretically calculating the top-of-atmosphere radiance according to the target water-leaving radiance, and then combining the digital values actually observed by the optical satellite to be calibrated to determine the absolute radiometric calibration coefficient of the optical satellite to be calibrated, thereby completing the absolute radiometric calibration of the optical satellite to be calibrated.

2. The method for absolute radiometric calibration of an optical satellite under low marine brightness based on a marine pseudo-invariant field according to claim 1, wherein Before obtaining the target water-leaving radiance and before theoretically calculating the top-of-atmosphere radiance, it further includes: Obtaining the second observation data of the optical satellite to be calibrated in the marine pseudo-invariant field, according to the longitude and latitude information in the second observation data, performing point-to-point spatial matching between the optical satellite to be calibrated and the marine pseudo-invariant field with a preset spatial threshold, and screening the second observation data according to the observation geometry of the optical satellite to be calibrated, and theoretically calculating the top-of-atmosphere radiance with the screened second observation data.

3. The method for absolute radiometric calibration of an optical satellite under low marine brightness based on a marine pseudo-invariant field according to claim 2, characterized in that The preset spatial threshold is determined according to the lower resolution of the resolution of the optical satellite to be calibrated and the resolution of the calibrated optical satellite.

4. The method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a marine pseudo-invariant field according to claim 2 or 3, characterized in that, Before obtaining the screened second observation data and before theoretically calculating the top-of-atmosphere radiance, it further includes: Screening the pixels of the screened second observation data through the mask information of the pixels in the second observation data to obtain the second observation data after secondary screening and use it for theoretically calculating the top-of-atmosphere radiance.

5. The method for absolute radiometric calibration of an optical satellite under low brightness in the ocean based on a marine pseudo-invariant field according to claim 1, wherein Determine the chlorophyll a concentration through Fourier functions : , where , , and are all fixed parameters obtained by fitting, represents the number of days starting from the specified date.

6. The method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a marine pseudo-invariant field according to claim 1 or 5, characterized in that The obtaining of the hyperspectral water-leaving radiance includes: determining the total absorption coefficient according to the chlorophyll a concentration and the total backscattering coefficient , and then calculating the remote sensing reflectance below the sea surface : , where and both represent fitting coefficients; converting into the remote sensing reflectance above the sea surface : , where represents the water-atmosphere transmittance, represents the bidirectional correction factor; and then converting into the hyperspectral water-leaving radiance : , where represents the extra-terrestrial solar irradiance corresponding to the to-be-calibrated optical satellite, represents the solar zenith angle, represents the atmospheric diffuse transmittance under the sensor detection band of the to-be-calibrated optical satellite.

7. The method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a marine pseudo-invariant field according to claim 1, wherein The top-of-atmosphere radiance is as follows: ， Among them, represents the sensor detection band of the to-be-calibrated optical satellite, represents the Rayleigh scattering contribution corresponding to the to-be-calibrated optical satellite, represents the aerosol scattering contribution corresponding to the to-be-calibrated optical satellite, represents the radiation contribution of the Rayleigh-aerosol coupling effect corresponding to the to-be-calibrated optical satellite, represents the diffuse transmittance of the sensor observation path from the sea surface to the satellite on the to-be-calibrated optical satellite, represents the radiation contribution of the sea surface whitecap scattering corresponding to the to-be-calibrated optical satellite, represents the atmospheric direct transmittance at the to-be-calibrated optical satellite, represents the contribution of the solar flare corresponding to the to-be-calibrated optical satellite, represents the target water-leaving radiance, represents the gas absorption along the solar zenith, represents the gas absorption along the satellite viewing path.

8. An absolute radiometric calibration device for optical satellites under low ocean brightness based on a pseudo-invariant field at sea, characterized in that, The device includes: A calibration field determination module, configured to select the first observation data of the ocean by a calibrated optical satellite, and compare the parameters in the first observation data with a preset threshold to determine a marine pseudo-invariant field; A target parameter acquisition module, configured to take the chlorophyll a concentration of the marine pseudo-invariant field as a single input of a bio-optical model to obtain the hyperspectral water-leaving radiance, and take the convolution of the hyperspectral water-leaving radiance and the spectral response function of the optical satellite to be calibrated as the target water-leaving radiance; A target satellite calibration module, configured to theoretically calculate the top-of-atmosphere radiance according to the target water-leaving radiance, and then combine the digital values actually observed by the optical satellite to be calibrated to determine the absolute radiometric calibration coefficient of the optical satellite to be calibrated, thereby completing the absolute radiometric calibration of the optical satellite to be calibrated.

9. A computer device, characterized in that, The computer device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the method for absolute radiometric calibration of an optical satellite under low brightness of the ocean based on a marine pseudo-invariant field according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the method for absolute radiometric calibration of an optical satellite under low brightness of the ocean based on a marine pseudo-invariant field according to any one of claims 1 to 7.

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