Absolute radiometric calibration method, device, equipment and medium for optical satellites under low ocean brightness based on marine pseudo-invariant field

Abstract

The present invention relates to a method, device, equipment and medium for absolute radiation calibration of optical satellites under low ocean brightness based on a pseudo-invariant field at sea, and belongs to the technical field of on-orbit absolute radiation calibration. The method determines a pseudo-invariant field at sea with stable water and atmospheric optical characteristics from calibrated optical satellite ocean observation data, calculates its water-leaving radiance through the chlorophyll a concentration of the pseudo-invariant field at sea, and theoretically calculates the zenith radiance, providing a data source for absolute radiation calibration of the satellite to be calibrated, thereby completing the calibration. The present invention explores the potential of pseudo-invariant fields at sea in supplementing traditional radiation calibration methods, breaks away from the data source limitations of fixed, single ocean optical buoy MOBY sites, increases the data volume, coverage area and acquisition frequency of effective calibration data, provides a guarantee for the continuity of optical satellite observation missions, and can use multiple calibration sources to achieve rapid and accurate calibration of optical satellites, significantly improving the efficiency of marine optical satellite calibration.

Description

Technical Field

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

[0002] Maintaining the long-term stability and consistency of the radiometric characteristics of optical satellite sensors is crucial for accurately obtaining optical remote sensing products. Although some optical satellites are equipped with onboard calibration systems to track changes in instrument radiometric characteristics due to significant environmental variations and optical degradation, further corrections using field-measured data are still necessary to eliminate residual errors in onboard radiometric calibration and systematic biases in atmospheric correction algorithms. Optical sensors without onboard calibration systems require even more stable and accurate in-situ data to support their calibration. In other words, in-situ data is essential for calibration.

[0003] Currently, calibration of ocean targets is typically performed using the Marine Optical Buoy (MOBY). Managed by the National Oceanic and Atmospheric Administration (NOAA) since late 1996, MOBY is located approximately 20 kilometers west of Lanai, Hawaii. MOBY's site selection and instrument configuration are based on specific requirements, enabling it to provide high-quality in-situ measurement data to support radiometric calibration of a variety of optical satellite sensors. However, using MOBY's in-situ measurement sites for radiometric calibration presents the following challenges:

[0004] (1) There are few effective radiation calibration coefficients. Due to the strict matching standards between field measurements and synchronous satellite observations (such as observation time intervals and observation geometry restrictions), coupled with frequent solar flares and cloud cover, the effective matching data that MOBY can provide for a single optical satellite sensor each year is limited. For example, considering the bad sea conditions and instrument failures, there are few matching points between field measurements and satellite observations. Even with daily satellite observations, only about 20 sets of radiation calibration coefficients can be obtained. Therefore, it may take 2 to 3 years to obtain stable radiation calibration coefficients using only MOBY sites;

[0005] (2) It relies heavily on on-site measurement data. With more than two decades of operation, MOBY's measurement quality has been declining. Its regular update frequency has gradually decreased in recent years, and it is often difficult to obtain valid measurement data during certain time periods. This has seriously affected the temporal continuity and calibration accuracy of the radiometric calibration of optical satellite sensors. At the same time, as a field measurement site managed by NASA, MOBY may face the possibility of data being unavailable in the future, which will have a serious impact on satellite calibration (especially for domestic satellite sensors).

[0006] In summary, marine optical satellite calibration has technical problems such as low calibration efficiency due to low frequency of effective field data acquisition, small data volume and difficulty in data acquisition. Summary of the Invention

[0007] In view of this, embodiments of the present invention provide a method, device, equipment and medium for absolute radiation calibration of optical satellites under low ocean brightness based on a pseudo-invariant field at sea to solve the above technical problems.

[0008] In a first aspect, a method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a pseudo-invariant field at sea is provided, the method comprising:

[0009] selecting first observation data of the ocean from a calibrated optical satellite, and comparing a parameter in the first observation data with a preset threshold to determine a pseudo-invariant field at sea;

[0010] The chlorophyll a concentration of the pseudo-invariant field at sea is used as a single input of a bio-optical model to obtain a 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;

[0011] The top-of-atmosphere radiance is calculated based on the target water-leaving radiance theory, and then the absolute radiation calibration coefficient of the optical satellite to be calibrated is determined in combination with the digital value actually observed by the optical satellite to be calibrated, thereby completing the absolute radiation calibration of the optical satellite to be calibrated.

[0012] In a second aspect, a device for absolute radiometric calibration of an optical satellite under low ocean brightness based on a pseudo-invariant field at sea is provided, the device comprising:

[0013] a calibration field determination module, configured to select first ocean observation data from a calibrated optical satellite, and compare parameters in the first observation data with a preset threshold to determine a pseudo-invariant field at sea;

[0014] a target parameter acquisition module, configured to use the chlorophyll a concentration of the pseudo-invariant field at sea as a single input of a bio-optical model to obtain a hyperspectral water-leaving radiance, and to convolve the hyperspectral water-leaving radiance with the spectral response function of the optical satellite to be calibrated as a target water-leaving radiance;

[0015] The target satellite calibration module is used to calculate the top-of-atmosphere radiance based on the target water-leaving radiance theory, and then determine the absolute radiation calibration coefficient of the optical satellite to be calibrated in combination with the digital value actually observed by the optical satellite to be calibrated, so as to complete the absolute radiation calibration of the optical satellite to be calibrated.

[0016] In a third aspect, an embodiment of the present invention provides a computer device, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method for absolute radiation calibration of optical satellites under low brightness in the ocean based on a pseudo-invariant field at sea is implemented as described in the first aspect.

[0017] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the method for absolute radiation calibration of optical satellites under low brightness in the ocean based on a pseudo-invariant field at sea as described in the first aspect is implemented.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention determines a pseudo-invariant field at sea, representing the optical properties of water and atmosphere with a stable variation pattern, based on ocean observation data from a calibrated optical satellite. The chlorophyll-a concentration of the pseudo-invariant field at sea is used as a single input to a bio-optical model to obtain a hyperspectral water-leaving radiance. The target water-leaving radiance required for calibration is obtained by combining the spectral response function of the optical satellite to be calibrated. Furthermore, the theoretically predicted top-of-atmosphere radiance is determined. The absolute radiometric calibration coefficient is then obtained by combining the actual digital values ​​observed by the optical satellite to be calibrated to complete the calibration. The present invention explores the potential of the pseudo-invariant field at sea to supplement traditional radiometric calibration methods, breaking away from the limitations of existing calibration methods imposed by a single ocean optical buoy (MOBY) station. This increases the coverage area of ​​effective calibration data, provides more data for calibration without requiring high construction and maintenance costs, and significantly increases the data update frequency compared to existing ocean optical buoy MOBY stations, ensuring the continuity of remote sensing observation missions for optical satellite sensors. Ultimately, based on multiple calibration sources capable of providing calibration data at high frequency, rapid and accurate calibration of optical satellites can be achieved, significantly improving the efficiency of marine optical satellite calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a schematic diagram of an application environment of an optical satellite absolute radiometric calibration method under low ocean brightness based on a pseudo-invariant field at sea, provided in the first embodiment of the present invention;

[0022] Figure 2This is a flow chart of a method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a pseudo-invariant field at sea, provided in accordance with the first embodiment of the present invention;

[0023] Figure 3 1 is a schematic diagram of a sequence of chlorophyll a concentration changes at different time scales in the pseudo-invariant field OPIS-INP in the sea during a known period of time provided by the first embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of a sequence of chlorophyll a concentration changes at different time scales in the pseudo-invariant field OPIS-NPP over sea during a known period of time provided by the first embodiment of the present invention;

[0025] Figure 5 1 is a schematic diagram of a sequence of chlorophyll a concentration changes at different time scales in the pseudo-invariant field OPIS-SPP over sea during a known period of time provided by the first embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of a sequence of chlorophyll a concentration changes at different time scales in the pseudo-invariant field OPIS-NAP over the sea during a known period of time provided by the first embodiment of the present invention;

[0027] Figure 7 This is a time series diagram of the absolute radiation calibration coefficients obtained based on MOBY station data and offshore pseudo-invariant field data provided in the comparative example of the present invention;

[0028] Figure 8 This is a schematic structural diagram of an optical satellite absolute radiometric calibration device under low ocean brightness based on a pseudo-invariant field at sea, provided in a third embodiment of the present invention;

[0029] Figure 9 This is a structural diagram of a computer device provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0030] The overall concept of the present invention is:

[0031] With the help of high-precision optical satellites that have completed absolute radiometric calibration, the optical properties of global ocean areas are analyzed through long-term observation data. Regions with low temporal variability and high spatial uniformity that can accurately characterize the interannual variations in ocean optical properties are selected as the required offshore pseudo-invariant fields (OPIS). The determined offshore pseudo-invariant fields are used as the calibration fields for the satellites to be calibrated. The water surface radiation of the calibration fields is estimated based on the bio-optical model. Specifically, the chlorophyll a (Chla) concentration of the offshore pseudo-invariant fields is used to obtain the water-leaving radiance used for calibration. This provides a data source for the absolute radiometric calibration of the satellites to be calibrated, breaks away from the limitations of a fixed, single data source, increases the amount of calibration data and the acquisition frequency, and achieves efficient calibration of ocean optical satellite sensors and land optical satellite sensors with ocean observation capabilities.

[0032] In the following description, specific details such as particular system structures and techniques are provided for purposes of illustration, not limitation, to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0033] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0034] It will also be understood that the term "and / or" used in the present description and appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0035] As used in the present specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0036] In addition, in the description of the present specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0037] References to "one embodiment" or "some embodiments" in the present specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present invention. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0038] Embodiments of the present invention can acquire and process relevant data based on artificial intelligence technology. Artificial Intelligence (AI) refers to the theories, methods, techniques, and application systems that use digital computers or machines controlled by digital computers to simulate, extend, and expand human intelligence, perceive the environment, acquire knowledge, and use that knowledge to achieve optimal results.

[0039] Fundamental AI technologies generally include sensors, dedicated AI chips, cloud computing, distributed storage, big data processing, operating / interaction systems, and mechatronics. AI software technologies primarily encompass computer vision, robotics, biometrics, speech processing, natural language processing, and machine learning / deep learning.

[0040] It should be understood that the order of execution of the steps in the following embodiments does not necessarily mean the order in which they are executed. The order in which each process is executed should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0041] In order to illustrate the technical solution of the present invention, specific embodiments are provided below.

[0042] The first embodiment of the present invention provides an optical satellite absolute radiometric calibration method under low ocean brightness based on a pseudo-invariant field at sea, which can be applied in the following situations: Figure 1 The application environment includes, but is not limited to, PDAs, desktop computers, laptops, ultra-mobile personal computers (UMPCs), netbooks, cloud-based terminal devices, and personal digital assistants (PDAs). The server can be implemented as a standalone server or a server cluster consisting of multiple servers. Sensing devices include, but are not limited to, calibrated optical satellites and those awaiting calibration.

[0043] The above absolute radiation calibration method can be specifically applied to Figure 1The client in the figure, 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 execute the corresponding task, a corresponding task log will be generated, and the above task log can be collected through the API. The above absolute radiation calibration method can also be specifically applied to the server in Figure 1. The computer device corresponding to the server is connected to the corresponding database, rule base, etc. to obtain the corresponding data in the database. The above computer device can also be connected to the client to collect data and control instructions sent by the client user. In addition, the above absolute radiation calibration method can also be specifically applied to Figure 1 Sensing devices in.

[0044] See also Figure 2 , is a flow chart of a method for absolute radiometric calibration of an optical satellite under low ocean brightness based on a pseudo-invariant field at sea, provided in the first embodiment of the present invention. The absolute radiometric calibration method may include the following steps:

[0045] Step S101 : selecting first observation data of the ocean from a calibrated optical satellite, and comparing parameters in the first observation data with a preset threshold to determine a pseudo-invariant field at sea.

[0046] In order to provide stable and reliable calibration data to the optical satellite to be calibrated over a long period of time, this embodiment first selects a water color satellite sensor with global ocean observation capabilities and good calibration accuracy (such as MODIS-Aqua) as the calibrated optical satellite. To ensure data stability and reliability, the earth observation data product of the calibrated optical satellite over a long time series is 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 of each band (R rs ), reference band aerosol optical depth ( τ 869), Ångström index (AE), coefficient of variation (CV), blue-green band ratio (BGR) and clear sky rate (CSR), etc.

[0047] Among them, the coefficient of variation gives the regional stability of each band, the blue-green band ratio indicates the cleanliness of the water in the area, and a higher clear sky rate can provide more effective matches. This embodiment selects the parameters in the first observation data based on whether the parameters in the first observation data are related to the temporal variability, spatial uniformity and interannual variation of the ocean optical properties of the ocean area, and completes the determination of the pseudo-invariant field at sea with the selected parameters and the corresponding parameter constraints set for the parameters. The operator can flexibly set specific parameter items and parameter constraints according to the above-mentioned parameter selection principles. As an example, this embodiment uses the parameters and parameter constraints in Table 1 below to complete the screening of the pseudo-invariant field at sea, where the symbol μ and <> respectively indicate the mean and standard deviation of the parameters.

[0048] Table 1 Target parameters and thresholds for determining the offshore pseudo-invariant field

[0049]

[0050] This embodiment specifically uses a calibrated optical satellite to obtain earth observation data products over the long time series from July 2002 to December 2016 as the first observation data, and uses the contents of Table 1 to determine four ocean pseudo-invariant fields as shown in Table 2 below. These fields are located in the Indian Ocean (OPIS-INP), North Pacific Ocean (OPIS-NPP), South Pacific Ocean (OPIS-SPP), and North Atlantic Ocean (OPIS-NAP), respectively. The specific ranges and central longitudes and latitudes of the four determined ocean pseudo-invariant fields are shown in Table 2 below.

[0051] Table 2 Determined location information of offshore pseudo-invariant field areas

[0052]

[0053] Step S102: Using the chlorophyll a concentration of the pseudo-invariant field at sea as a single input of a bio-optical model to obtain a hyperspectral water-leaving radiance, and using 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.

[0054] In this embodiment, the chlorophyll a (Chla) concentration of the selected pseudo-invariant field at sea is used as the single input of the bio-optical model to construct a hyperspectral water-off-radiance, and the subsequent absolute radiation calibration process is implemented based on the obtained hyperspectral water-off-radiance.

[0055] Figures 3 to 6 The Chla concentration variation series of the four offshore pseudo-invariant fields OPIS-INP, OPIS-NPP, OPIS-SPP and OPIS-NAP at different time scales from July 2002 to December 2016 are shown in turn. Specifically, Figures 3 to 6 Sub-graphs (a), (b), and (c) in each figure respectively show the daily, 8-day average, and monthly average sampling results of Chla concentration. The discrete points are the Chla concentration data observed by satellite, i.e., the sampling values, and the curves represent the Chla concentration change curves at different time scales fitted based on the Chla concentration data observed by satellite.

[0056] 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 characteristics of stable changes, which can provide a stable data basis for subsequent absolute radiation calibration.

[0057] In a preferred embodiment, the Chla concentration of the pseudo-invariant field at sea is determined by constructing a stable variation model of the Chla concentration in each pseudo-invariant field at sea based on the Chla concentration data of each pseudo-invariant field at sea in the above-mentioned earth observation data product. Specifically, it can be determined by Fourier function. concentration: ,in, 、 、 as well as are all fixed parameters obtained by fitting, and the variables Represents the number of days from the specified date. This model can provide simulated Chla concentrations by inputting a specified calibration time, providing data support for subsequent calibration. Specifically, the Chla concentration calculation formula can be used to determine the steadily varying Chla concentration in the pseudo-invariant field at sea based on the time of the satellite data to be calibrated. This steadily varying Chla concentration is then used as the single input to the bio-optical model to obtain the hyperspectral water-leaving radiance.

[0058] The bio-optical model may directly adopt an existing model, such as the OC series model. This embodiment does not specifically limit the bio-optical model, and the operator may select it according to specific needs.

[0059] In a preferred embodiment, the Chla concentration is used as the single input of the bio-optical model to obtain the hyperspectral water-off radiance, specifically including: first, using existing algorithms (such as Gaussian decomposition method, absorption coefficient decomposition model and backscattering coefficient model, LightGBM model under machine learning, etc.) to calculate the total absorption coefficient from the Chla concentration a and the total backscatter coefficient b b , and then through the total absorption coefficient a and the total backscatter coefficient b b Calculating subsurface remote sensing reflectivity r rs : ,in, as well as Both represent fitting coefficients.

[0060] Afterwards, further r rs Converted into remote sensing reflectivity above sea surface :

[0061] ,in, represents the water surface-atmosphere transmittance, Indicates the bidirectional correction factor, which is preferred in this embodiment. , .

[0062] Finally, the hyperspectral Converted to hyperspectral water-leaving radiance :

[0063] ,in, represents the extraterrestrial solar irradiance corresponding to the optical satellite to be calibrated, represents the solar zenith angle, Indicates the atmospheric diffuse transmittance in the sensor detection band of the optical satellite to be calibrated.

[0064] The water-leaving radiance of the obtained hyperspectral By convolving it with the spectral response function of the optical satellite sensor to be calibrated, the target water-leaving radiance corresponding to the optical satellite sensor to be calibrated can be obtained. , which serves as an important basis for the subsequent absolute radiation calibration process. represents the sensor detection band of the optical satellite to be calibrated. The spectral response function of the sensor of the optical satellite to be calibrated can be determined based on the observation data of the pseudo-invariant field of the optical satellite to be calibrated at sea. The target water-leaving radiance specifically refers to the water-leaving radiance of the band corresponding to the payload to be calibrated of the optical satellite to be calibrated.

[0065] Step S103, calculating the top-of-atmosphere radiance according to the target water-leaving radiance theory, and then determining the absolute radiation calibration coefficient of the optical satellite to be calibrated in combination with the digital value actually observed by the optical satellite to be calibrated, thereby completing the absolute radiation calibration of the optical satellite to be calibrated.

[0066] The absolute radiation calibration of the optical satellite is completed by the absolute radiation calibration coefficient. The absolute radiation calibration coefficient of the optical satellite sensor to be calibrated is determined by the top-of-atmosphere radiance corresponding to the optical satellite to be calibrated obtained by theoretical calculation and the digital value actually observed by the optical satellite sensor to be calibrated.

[0067] The digital values ​​actually observed by the optical satellite sensor to be calibrated can usually be obtained through the Level-1A data of the satellite sensor, while the top-of-atmosphere radiance corresponding to the optical satellite to be calibrated needs to be calculated based on the target water-leaving radiance theory: ,in, represents the top-of-atmosphere radiance, Indicates the sensor detection band of the optical satellite to be calibrated, represents the Rayleigh scattering contribution corresponding to the optical satellite to be calibrated, represents the aerosol scattering contribution corresponding to the optical satellite to be calibrated, represents the radiation contribution of the Rayleigh-aerosol coupling effect corresponding to the optical satellite to be calibrated, It represents the diffuse transmittance of the sensor observation path from the sea surface to the satellite on the standard optical satellite. represents the radiation contribution of the white-hat scattering of the sea surface corresponding to the optical satellite to be calibrated, represents the direct transmittance of the atmosphere at the optical satellite. represents the contribution of the solar flare corresponding to the optical satellite to be calibrated, represents the target's water-leaving radiance, represents the gas absorption along the solar zenith, represents the gas absorption along the satellite's viewing path.

[0068] By combining sea surface atmospheric pressure data and observation geometry information, the Rayleigh scattering contribution of a specific satellite can be calculated based on the Rayleigh lookup table of the sensor to be calibrated. Based on the aerosol type (the pseudo-invariant field area at sea is all marine aerosol) and aerosol optical depth, the aerosol contribution can be derived through the atmospheric correction process. and Finally, combining the reconstructed hyperspectral And synchronized atmospheric parameters, the top of the atmosphere radiance can be calculated by theoretical simulation .

[0069] Based on the obtained top-of-atmosphere radiance , combined with the digital value actually observed by the optical satellite to be calibrated, the absolute radiation calibration coefficient of the optical satellite sensor to be calibrated can be calculated by the formula :

[0070]

[0071] in, Indicates the digital value of the top of the atmosphere actually observed by the sensor. is the radiance at the top of the atmosphere.

[0072] According to the obtained absolute radiation calibration coefficient of the optical satellite sensor to be calibrated, the absolute radiation calibration of the optical satellite sensor to be calibrated can be completed, and the purpose of absolute radiation calibration of the optical satellite under low brightness of the ocean can be achieved by using the determined marine pseudo-invariant field.

[0073] The present invention also provides a second embodiment. In this embodiment, before completing step S102 and executing step S103, the following steps are further included:

[0074] The second observation data of the optical satellite to be calibrated in the pseudo-invariant field at sea is obtained. According to the latitude and longitude information in the second observation data, the optical satellite to be calibrated and the pseudo-invariant field at sea are spatially matched point-to-point with a preset spatial threshold. The second observation data is filtered according to the observation geometry of the optical satellite to be calibrated. The filtered second observation data is obtained and used to theoretically calculate the top-of-atmosphere radiance.

[0075] Specifically include:

[0076] 1) Acquisition of satellite observation data to be calibrated

[0077] Obtain second observation data of the optical satellite sensor to be calibrated in the pseudo-invariant field area at sea determined above. The second observation data includes, but is not limited to, top of atmosphere observation digital values ​​in each band, latitude and longitude information, observation geometry information (including solar zenith angle and azimuth, satellite observation zenith angle and azimuth, and relative azimuth), mask identification information, spectral response function, and auxiliary data (sea surface atmospheric pressure, wind speed, relative humidity, and water vapor content, etc.). These data are mainly used in the atmospheric correction process of the optical satellite sensor to be calibrated.

[0078] 2) Region matching data extraction

[0079] After determining the second observation data, the latitude and longitude information of the optical satellite to be calibrated in the second observation data is used to perform point-to-point spatial matching between the optical satellite to be calibrated and the maritime pseudo-invariant field using a preset spatial threshold. To improve the accuracy of absolute radiometric calibration, the following principles need to be followed during the matching process:

[0080] Spatial matching principle: After obtaining the latitude and longitude, observation geometry and top-of-atmosphere observation data of the sensor to be calibrated in a large range of the offshore pseudo-invariant field area, point-to-point spatial matching is performed between the sensor and the center position of the offshore pseudo-invariant field. A preset spatial threshold of 0.01° is set, and the closest pixel point within the threshold range is obtained through matrix operation as the matching point between the two. Duplicate matching points are eliminated, and only one-to-one cases and related matching parameters are retained, thereby completely matching 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 radiation calibration coefficient.

[0081] The value of the preset spatial threshold is determined based on the spatial resolution of the MODIS-Aqua sensor used in determining the offshore pseudo-invariant field, that is, the spatial resolution of the calibrated optical satellite. Based on the 1 km spatial resolution of the MODIS-Aqua sensor, the corresponding preset spatial threshold is set to 0.01°. Furthermore, the actual spatial resolution of the sensor on the optical satellite to be calibrated must also be considered. If the actual spatial resolution of the sensor on the optical satellite to be calibrated is lower than that of MODIS-Aqua, then if the preset spatial threshold is too small, the sensor resolution of the optical satellite to be calibrated will not meet the preset spatial threshold requirement, thus affecting spatial matching. Therefore, the preset spatial threshold needs to be adjusted based on the actual spatial resolution of the sensor on the optical satellite to be calibrated. In other words, the lower resolution of the optical satellite to be calibrated and the resolution of the calibrated optical satellite must be considered to determine the value of the preset spatial threshold.

[0082] Observation geometry restriction principle: Before performing absolute radiometric calibration of the sensor to be calibrated with the marine pseudo-invariant field, the sensor's observation geometry must be considered and restricted. In other words, the sensor's observation data (secondary observation data) must be filtered based on the observation geometry. For example, for the solar zenith angle, the matching data must be within 60°, and for the satellite observation zenith angle, the matching data must be within 40°.

[0083] Finally, the second observation data after screening is obtained after spatial matching.

[0084] 3) Effective pixel screening

[0085] To further improve calibration accuracy, after matching the latitude and longitude of the sensor to be calibrated with the maritime pseudo-invariant field, this embodiment optionally uses pixel mask information from the observation data (second observation data) of the optical satellite sensor to be calibrated to screen the filtered second observation data for valid matching pixels, eliminating invalid pixels such as those caused by clouds, flares, and pixels with excessively large observation angles. Finally, valid matching pixels are determined to obtain the second observation data after secondary screening.

[0086] By removing invalid pixels from the matching pixels using mask information, some influencing factors can be eliminated during the absolute radiometric calibration process, further improving the absolute radiometric calibration accuracy of the optical satellite to be calibrated. After removing invalid pixels, the above-mentioned top of atmosphere radiance is calculated in the actual calculation. and The effective pixel filtering can be directly processed as 0, because after the effective pixel screening, the retained data is not affected by solar flares and sea surface white caps. Therefore, effective pixel screening can also reduce the amount of calculation in the calibration process to a certain extent and improve calibration efficiency.

[0087] To verify the effectiveness of the present invention, based on the above embodiments of the present invention, the satellite absolute radiation calibration results are compared using the following comparative examples.

[0088] This comparative example selected the optical satellite sensor VIIRS carried on SNPP as the payload to be calibrated, and calculated its radiometric calibration coefficients under two radiometric calibration methods. One method uses the traditional calibration station MOBY to provide on-site measurement data; the other method uses the four marine pseudo-invariant fields determined in the embodiments of the present invention to provide simulated data as input.

[0089] Through the above two radiation calibration methods, the following results were obtained in the time range from January 2012 to December 2014: Figure 7 The time series of the absolute radiation calibration coefficient is shown in FIG. 1 , and the absolute radiation calibration coefficient is normalized for the convenience of analysis and comparison.

[0090] Among them, the VIIRS-SNPP bands involved in the calibration are 410 nm, 443 nm, 486 nm, 551 nm, and 671 nm. Figure 7 Sub-figures (a) to (e) in the figure show the absolute radiometric calibration coefficients at the 410 nm, 443 nm, 486 nm, 551 nm, and 671 nm bands, respectively. The black dots represent the absolute radiometric calibration results corresponding to the offshore pseudo-invariant field, the red dots represent the absolute radiometric calibration results corresponding to the MOBY site, and the black and red solid lines represent the average values ​​of the two absolute radiometric calibration result datasets, respectively.

[0091] 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 below 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 below and Figure 7 It can be seen that the absolute radiation calibration coefficients corresponding to the offshore pseudo-invariant field are stable at the first three wavelengths and very close to the average value, while the absolute radiation calibration coefficients corresponding to the MOBY site at the last two wavelengths show slightly larger variations. Therefore, compared with the existing method of completing absolute radiation calibration based on the MOBY site, the method of completing absolute radiation calibration based on the offshore pseudo-invariant field has enhanced the stability of the obtained absolute radiation calibration coefficients, and the higher calibration frequency can significantly shorten the calibration time.

[0092] Table 3 Comparison of radiation calibration coefficients obtained based on offshore pseudo-invariant field simulation data and field measurement data at the MOBY station

[0093]

[0094] From the comparison of the results of the two radiometric calibration methods, the following preliminary conclusions can be drawn: First, the radiometric calibration method based on the offshore pseudo-invariant field shows good consistency in the numerical values ​​of the calibration coefficients compared with the radiometric calibration method based on the field measurement station. The average absolute percentage difference (MAPE) between each band can be kept within 5%, indicating that the calibration accuracy of the present invention is similar to that of the traditional calibration method, demonstrating the effectiveness of the present method. Second, after using the four offshore pseudo-invariant fields proposed in the present invention in the radiometric calibration calculation, the number of valid calibration coefficient groups increased from 36 to 114 within the three-year study period. The four offshore pseudo-invariant fields provided 78 more valid calibration results for the sensors to be calibrated. This enables the accumulation of absolute radiometric calibration coefficients to be achieved more quickly, thereby providing accurate business products more quickly. It also shows that the calibration method of the present invention has important application value and practical significance.

[0095] In summary, the present invention first completes the determination of the pseudo-invariant field at sea, and then uses the pseudo-invariant field at sea to achieve the purpose of absolute radiometric calibration of optical satellite sensors under low-brightness conditions at sea. Compared with the existing technology, it has the following beneficial effects:

[0096] (1) As a universal method, the present invention can utilize optical satellite sensors with high radiometric calibration accuracy, long time span, and large spatial coverage to analyze and determine the pseudo-invariant field at sea with stable variation characteristics, thereby being applied to the on-orbit absolute radiometric calibration of sensors.

[0097] (2) Compared with the traditional radiometric calibration method based on field measurement sites, the present invention can effectively increase the frequency of on-orbit absolute radiometric calibration, saving a large amount of manpower and material resources required for field measurements. At the same time, it helps newly launched sensors quickly obtain a large number of initial calibration coefficients, thereby helping the sensors to provide stable data products as soon as possible;

[0098] (3) This invention introduces the pseudo-invariant field at sea into the on-orbit absolute radiometric calibration of the sensor. Compared with the pseudo-invariant field on land under high brightness, it provides radiometric calibration conditions under low brightness scenes, providing important data support for the absolute radiometric calibration of the sensor under low gain state.

[0099] (4) The radiometric calibration method for low-brightness scenarios based on a pseudo-invariant field at sea provided by this invention is a method for constructing hyperspectral off-water radiance. Therefore, it can be applied to the absolute radiometric calibration of all optical satellite sensors capable of ocean observation, and has excellent applicability. Furthermore, this method is not limited to sensors already in orbit; it is also applicable to optical satellite sensors that have not yet been launched and meet the ocean observation conditions, thus having both practical and future significance.

[0100] Furthermore, the method of the present invention combines the generation of marine pseudo-invariant field simulation data with optical satellite sensor observation data, forming a matching and calibration program that combines data matching and on-orbit absolute radiometric calibration. By implementing the method of the present invention, continuous data matching and radiometric calibration are achieved, thereby continuously tracking and correcting the changes in the sensor's radiometric performance during on-orbit operation. The accumulated long-term calibration sequence of each sensor also provides data support for analyzing the overall change trend of the instrument. Furthermore, the present invention's method for absolute radiometric calibration of optical satellites under low-light conditions based on a marine pseudo-invariant field is a universal method that can provide an absolute radiometric calibration method under low-light conditions for marine optical satellite sensors and terrestrial optical satellite sensors with ocean observation capabilities, including but not limited to domestic ocean color satellite sensors such as COCTS-HY1C / D and CZI-HY1C / D, mainstream international ocean color satellite sensors such as MODIS-Terra / Aqua, VIIRS-SNPP / NOAA, OLCI-Sentinel3, and OCI-PACE, and terrestrial optical satellite sensors such as OLI-Landsat8 / 9 and MSI-Sentinel2.

[0101] Corresponding to the method of the above embodiment, Figure 8 This figure shows a block diagram of an apparatus for absolute radiometric calibration of optical satellites under low-brightness conditions at sea, based on a pseudo-invariant field at sea, according to a third embodiment of the present invention. This apparatus is applied to a computer device, which is connected to a target database via a pre-defined application programming interface (API). When the target database is driven to execute a task, a corresponding task log is generated, which can be collected via the API. For ease of illustration, only the portions relevant to this embodiment of the present invention are shown.

[0102] See also Figure 8 , the absolute radiation calibration device comprises:

[0103] The calibration field determination module 31 is configured to select first ocean observation data from a calibrated optical satellite and compare a parameter in the first observation data with a preset threshold to determine a pseudo-invariant field at sea;

[0104] a target parameter acquisition module 32 for using the chlorophyll a concentration of the pseudo-invariant field at sea as a single input of a bio-optical model to obtain a hyperspectral water-leaving radiance, and convolving the hyperspectral water-leaving radiance with the spectral response function of the optical satellite to be calibrated as a target water-leaving radiance;

[0105] The target satellite calibration module 33 is used to calculate the top-of-atmosphere radiance based on the target water-leaving radiance theory, and then determine the absolute radiation calibration coefficient of the optical satellite to be calibrated in combination with the digital value actually observed by the optical satellite to be calibrated, thereby completing the absolute radiation calibration of the optical satellite to be calibrated.

[0106] Optionally, the above device further includes:

[0107] The data matching and screening module is configured to perform the following after obtaining the target water-leaving radiance and before theoretically calculating the top-of-atmosphere radiance:

[0108] Second observation data of the optical satellite to be calibrated in the pseudo-invariant field at sea is obtained, and based on the latitude and longitude information in the second observation data, the optical satellite to be calibrated and the pseudo-invariant field at sea are spatially matched point-to-point with a preset spatial threshold, and the second observation data is filtered according to the observation geometry of the optical satellite to be calibrated, and the top-of-atmosphere radiance is theoretically calculated based on the filtered second observation data.

[0109] Optionally, a data matching and screening module may include:

[0110] The preset spatial threshold determination unit is configured to limit the preset spatial threshold to be determined according to a lower resolution between the resolution of the optical satellite to be calibrated and the resolution of the calibrated optical satellite.

[0111] Optionally, the data matching and screening module further includes:

[0112] The pixel secondary screening unit is configured to perform the following after obtaining the filtered second observation data and before theoretically calculating the top-of-atmosphere radiance:

[0113] The pixels of the filtered second observation data are filtered using the mask information of the pixels in the second observation data to obtain the second observation data after secondary filtering and used for theoretically calculating the top-of-atmosphere radiance.

[0114] Optionally, the target parameter acquisition module 32 includes:

[0115] Chlorophyll a concentration calculation unit, used to determine the chlorophyll a concentration through Fourier function :

[0116]

[0117] in, 、 、 as well as are all fixed parameters obtained by fitting. Indicates the number of days from the specified date.

[0118] Optionally, the target parameter acquisition module 32 further includes:

[0119] A hyperspectral water-leaving radiance acquisition unit, used to limit the obtained hyperspectral water-leaving radiance, includes:

[0120] Determine the total absorption coefficient based on the chlorophyll a concentration and the total backscatter coefficient , and then calculate the remote sensing reflectivity under the sea surface :

[0121]

[0122] in, as well as All represent fitting coefficients;

[0123] Will Converted into remote sensing reflectivity above sea surface :

[0124]

[0125] in, represents the water surface-atmosphere transmittance, represents the bidirectional correction factor;

[0126] Then Converted to hyperspectral water-leaving radiance :

[0127]

[0128] in, represents the extraterrestrial solar irradiance corresponding to the optical satellite to be calibrated, represents the solar zenith angle, Indicates the atmospheric diffuse transmittance in the sensor detection band of the optical satellite to be calibrated.

[0129] Optionally, the target satellite calibration module 33 includes:

[0130] Theoretical prediction of the top of the atmosphere radiance acquisition unit, used to limit the top of the atmosphere radiance for:

[0131]

[0132] in, represents the sensor detection band of the optical satellite to be calibrated, represents the Rayleigh scattering contribution corresponding to the optical satellite to be calibrated, represents the aerosol scattering contribution corresponding to the optical satellite to be calibrated, represents the radiation contribution of the Rayleigh-aerosol coupling effect corresponding to the optical satellite to be calibrated, represents the diffuse transmittance of the sensor observation path from the sea surface to the satellite on the optical satellite to be calibrated, represents the radiation contribution of the sea surface white-hat scattering corresponding to the optical satellite to be calibrated, represents the direct atmospheric transmittance at the optical satellite to be calibrated, represents the contribution of the solar flare corresponding to the optical satellite to be calibrated, represents the target's water-leaving radiance, represents the gas absorption along the solar zenith, represents the gas absorption along the satellite's viewing path.

[0133] It should be noted that the information interaction, execution process and other contents between the above modules are based on the same concept as the embodiment of the method of the present invention. Their specific functions and technical effects can be found in the method embodiment part and will not be repeated here.

[0134] Figure 9 This is a schematic diagram of the structure of a computer device provided in the fourth embodiment of the present invention. Figure 9 As shown, the computer device of this embodiment includes: at least one processor ( Figure 9 Only one is shown), a memory, and a computer program stored in the memory and executable on at least one processor, wherein when the processor executes the computer program, the steps in any of the above-mentioned embodiments of the method for absolute radiation calibration of an optical satellite under low brightness in the ocean based on a pseudo-invariant field at sea are implemented.

[0135] The computer device may include, but is not limited to, a processor and a memory. It will be understood by those skilled in the art that Figure 9 This is merely 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 a combination of certain components, or different components.

[0136] The processor may be a CPU, other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0137] Memory includes readable storage media, internal memory, and the like. Internal memory can be the internal memory of a computer device, providing an environment for the operation of the operating system and computer-readable instructions stored in the readable storage medium. The readable storage medium can be the computer device's hard drive. In other embodiments, it can also be an external storage device, such as a plug-in hard drive, a Smart Media Card (SMC), a Secure Digital (SD) card, or a flash memory card. Furthermore, memory can include both the computer device's internal storage unit and external storage devices. Memory is used to store the operating system, application programs, boot loaders, data, and other programs, such as the program code of computer programs. Memory can also be used to temporarily store data that has been output or is about to be output.

[0138] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, 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. The functional units and modules in the embodiment 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-mentioned 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 the functional units and modules are only for the convenience of distinguishing each other and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned device can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here. 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 this understanding, the present invention can implement all or part of the process steps in the above-mentioned method embodiments by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When executed by a processor, the computer program can implement the steps of the above-mentioned method embodiments. The computer program includes computer program code, which can be in source code form, object code form, executable file, or some intermediate form. Computer-readable media can include at least: any entity or device capable of carrying computer program code, recording media, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signals, telecommunications signals, and software distribution media. Examples include USB flash drives, removable hard drives, magnetic disks, or optical disks. In some jurisdictions, based on legislation and patent practice, computer-readable media cannot be electric carrier signals or telecommunications signals.

[0139] The present invention may implement all or part of the processes in the above-mentioned method embodiments, and may also be completed through a computer program product. When the computer program product runs on a computer device, the computer device can implement the steps in the above-mentioned method embodiments when executing the computer program product.

[0140] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0141] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0142] In the embodiments provided by the present invention, it should be understood that the disclosed apparatus / computer equipment and methods can be implemented in other ways. For example, the apparatus / computer equipment embodiments described above are merely illustrative. For example, the division of modules or units is merely a logical function division. In actual implementation, there may be other division methods, such as 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 mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0143] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0144] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A method for absolute radiometric calibration of optical satellites under low ocean brightness conditions based on a pseudo-invariant field at sea, characterized in that: The method comprises: selecting first observation data of the ocean from a calibrated optical satellite, and comparing a parameter in the first observation data with a preset threshold to determine a pseudo-invariant field at sea; The chlorophyll a concentration of the pseudo-invariant field at sea is used as a single input of a bio-optical model to obtain a 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; Calculating the top-of-atmosphere radiance based on the target water-leaving radiance theory, and then determining the absolute radiometric calibration coefficient of the optical satellite to be calibrated in combination with the digital value actually observed by the optical satellite to be calibrated, thereby completing the absolute radiometric calibration of the optical satellite to be calibrated; After obtaining the target water-leaving radiance and before theoretically calculating the top-of-atmosphere radiance, the method further includes: Acquiring second observation data of the optical satellite to be calibrated in the pseudo-invariant field at sea, performing point-to-point spatial matching between the optical satellite to be calibrated and the pseudo-invariant field at sea using a preset spatial threshold based on latitude and longitude information in the second observation data, and filtering the second observation data based on the observation geometry of the optical satellite to be calibrated, and theoretically calculating the top-of-atmosphere radiance using the filtered second observation data; The point-to-point spatial matching includes: performing point-to-point spatial matching on the optical satellite to be calibrated and the center position of the pseudo-invariant field at sea, obtaining the closest pixel point within the preset spatial threshold range as the matching point between the two through matrix operation, and eliminating duplicate matching points.

2. The method for absolute radiometric calibration of optical satellites under low ocean brightness based on a pseudo-invariant field at sea according to claim 1, characterized in that: The preset spatial threshold is determined according to a lower resolution between the resolution of the optical satellite to be calibrated and the resolution of the calibrated optical satellite.

3. The method for absolute radiometric calibration of optical satellites under low ocean brightness based on a pseudo-invariant field at sea according to claim 1 or 2, characterized in that: After obtaining the filtered second observation data and before theoretically calculating the top-of-atmosphere radiance, the method further includes: The pixels of the filtered second observation data are filtered using the mask information of the pixels in the second observation data to obtain the second observation data after secondary filtering and used for theoretically calculating the top-of-atmosphere radiance.

4. The method for absolute radiometric calibration of optical satellites under low ocean brightness based on a pseudo-invariant field at sea according to claim 1, characterized in that: The chlorophyll a concentration was determined by Fourier function ： ,in, 、 、 as well as are all fixed parameters obtained by fitting. Indicates the number of days from the specified date.

5. The method for absolute radiometric calibration of optical satellites under low ocean brightness based on a pseudo-invariant field at sea according to claim 1 or 4, characterized in that: The method of obtaining the hyperspectral water-leaving radiance comprises: Determine the total absorption coefficient based on the chlorophyll a concentration and the total backscatter coefficient , and then calculate the remote sensing reflectivity under the sea surface : ,in, as well as are fitting coefficients; Converted into remote sensing reflectivity above sea surface : ,in, represents the water surface-atmosphere transmittance, Represents the bidirectional correction factor; then Converted to hyperspectral water-leaving radiance : ,in, represents the extraterrestrial solar irradiance corresponding to the optical satellite to be calibrated, represents the solar zenith angle, Indicates the atmospheric diffuse transmittance in the sensor detection band of the optical satellite to be calibrated.

6. The method for absolute radiometric calibration of optical satellites under low ocean brightness based on a pseudo-invariant field at sea according to claim 1, characterized in that: Top-of-atmosphere radiance for: ,in, represents the sensor detection band of the optical satellite to be calibrated, represents the Rayleigh scattering contribution corresponding to the optical satellite to be calibrated, represents the aerosol scattering contribution corresponding to the optical satellite to be calibrated, represents the radiation contribution of the Rayleigh-aerosol coupling effect corresponding to the optical satellite to be calibrated, represents the diffuse transmittance of the sensor observation path from the sea surface to the satellite on the optical satellite to be calibrated, represents the radiation contribution of the sea surface white-hat scattering corresponding to the optical satellite to be calibrated, represents the direct atmospheric transmittance at the optical satellite to be calibrated, represents the contribution of the solar flare corresponding to the optical satellite to be calibrated, represents the target's water-leaving radiance, represents the gas absorption along the solar zenith, represents the gas absorption along the satellite's viewing path.

7. An optical satellite absolute radiation calibration device under low ocean brightness based on a pseudo-invariant field at sea, characterized in that: The device comprises: a calibration field determination module, configured to select first ocean observation data from a calibrated optical satellite, and compare parameters in the first observation data with a preset threshold to determine a pseudo-invariant field at sea; a target parameter acquisition module, configured to use the chlorophyll a concentration of the pseudo-invariant field at sea as a single input of a bio-optical model to obtain a hyperspectral water-leaving radiance, and to convolve the hyperspectral water-leaving radiance with the spectral response function of the optical satellite to be calibrated as a target water-leaving radiance; a target satellite calibration module, configured to calculate the top-of-atmosphere radiance based on the target water-leaving radiance theory, and then determine the absolute radiometric calibration coefficient of the optical satellite to be calibrated in combination with the digital value actually observed by the optical satellite to be calibrated, thereby completing the absolute radiometric calibration of the optical satellite to be calibrated; After obtaining the target water-leaving radiance and before theoretically calculating the top-of-atmosphere radiance, the method further includes: Acquiring second observation data of the optical satellite to be calibrated in the pseudo-invariant field at sea, performing point-to-point spatial matching between the optical satellite to be calibrated and the pseudo-invariant field at sea using a preset spatial threshold based on latitude and longitude information in the second observation data, and filtering the second observation data based on the observation geometry of the optical satellite to be calibrated, and theoretically calculating the top-of-atmosphere radiance using the filtered second observation data; The point-to-point spatial matching includes: performing point-to-point spatial matching on the optical satellite to be calibrated and the center position of the pseudo-invariant field at sea, obtaining the closest pixel point within the preset spatial threshold range as the matching point between the two through matrix operation, and eliminating duplicate matching points.

8. 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, the optical satellite absolute radiation calibration method under low ocean brightness based on the marine pseudo-invariant field is implemented as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for absolute radiation calibration of an optical satellite under low ocean brightness based on a pseudo-invariant field at sea is implemented as described in any one of claims 1 to 6.

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