An absolute radiometric calibration method for a spaceborne micro-light load and related equipment

Abstract

The embodiment of the application provides a kind of absolute radiation calibration method of spaceborne micro-light load and related equipment.Therein, method includes: the multiple point light sources of different light source imaging area are carried out respectively spaceborne micro-light load entrance pupil radiance calculation, obtain multiple entrance pupil radiance value;The pixel of each point light source corresponding multiple remote sensing image pixel brightness value is accumulated, and multiple remote sensing image pixel brightness value sum is obtained;Based on entrance pupil radiance value and remote sensing image pixel brightness value sum, determine the radiation calibration point corresponding to each point light source;Linear fitting is carried out to multiple radiation calibration points, and the calibration function after fitting is obtained, and the calibration coefficient is determined based on the calibration function after fitting.The absolute radiation calibration of spaceborne micro-light load can be realized in the way of multiple-point calibration, compared with the way of single-point calibration in prior art, the calibration accuracy can be improved, and the demand of high-precision radiation calibration and radiation performance monitoring of spaceborne micro-light load can be met.

Description

Technical Field

[0001] This invention relates to the field of absolute radiometric calibration technology, and in particular to an absolute radiometric calibration method and related equipment for spaceborne low-light payloads. Background Technology

[0002] Absolute radiometric calibration of spaceborne low-light payloads is achieved by fitting the relationship between the digital number (DN) luminance values ​​of remote sensing images and the radiance at the payload's entrance pupil, thereby obtaining absolute radiometric calibration coefficients. Current methods for absolute radiometric calibration of spaceborne low-light payloads mainly include two types: site-substitute calibration and active light source-based calibration. However, these two methods primarily employ single-point calibration, resulting in low calibration accuracy, which is insufficient to meet the requirements for high-precision radiometric calibration and radiometric performance monitoring of spaceborne low-light payloads. Summary of the Invention

[0003] The purpose of this invention is to provide an absolute radiometric calibration method and related equipment for spaceborne low-light payloads, which can achieve absolute radiometric calibration of spaceborne low-light payloads through multi-point calibration, thereby improving calibration accuracy. The specific technical solution is as follows:

[0004] This invention provides an absolute radiometric calibration method for spaceborne low-light payloads, comprising:

[0005] The radiance at the entrance pupil of multiple point light sources with different imaging areas was calculated for the spaceborne micro-light payload, and multiple radiance values ​​at the entrance pupil were obtained.

[0006] The brightness values ​​of the remote sensing image pixels corresponding to each point light source are summed to obtain the sum of the brightness values ​​of the remote sensing image pixels.

[0007] Based on the sum of the radiance value at the entrance pupil and the pixel radiance value of the remote sensing image, the radiometric calibration point corresponding to each point light source is determined.

[0008] Linear fitting is performed on multiple radiation calibration points to obtain a fitted calibration function, and calibration coefficients are determined based on the fitted calibration function.

[0009] Optionally, methods for calculating the radiance at the entrance pupil of a spaceborne low-light payload include:

[0010] The emitted radiance of the point light source is obtained when the point light source responds within the wavelength range of the spaceborne micro-light payload.

[0011] The effective brightness of the point light source is calculated based on the emitted radiance of the point light source and the imaging area of ​​the point light source.

[0012] The radiance at the entrance pupil of the spaceborne micro-light payload is calculated based on the effective brightness of the point light source, and the radiance value at the entrance pupil is obtained.

[0013] Optionally, calculating the effective brightness of the point light source based on the emitted radiance and the imaging area of ​​the point light source includes:

[0014] Based on the emitted radiance, scattering factor, and atmospheric transmittance of the point light source, the radiance of the point light source after atmospheric scattering and transmission is calculated.

[0015] The effective brightness of the point light source is calculated based on the radiance of the point light source after transmission, the imaging area of ​​the point light source, and the spatial projection area of ​​the spaceborne micro-light payload.

[0016] Optionally, the method for determining the scattering factor includes:

[0017] If the point light source is a Lambertian light source, the scattering factor is determined based on spherical albedo and surface reflectivity.

[0018] Optionally, the method for determining the atmospheric transmittance includes:

[0019] Acquire atmospheric profile data and aerosol content at the moment of transit of the spaceborne low-light payload;

[0020] The atmospheric profile data and the aerosol content are input into the atmospheric radiative transfer model to obtain the atmospheric transmittance.

[0021] Optionally, the step of calculating the radiance at the entrance pupil of the spaceborne low-light payload based on the effective brightness of the point light source to obtain the radiance value at the entrance pupil includes:

[0022] The effective brightness of the point light source and the background radiance are summed to obtain the radiance value at the entrance pupil.

[0023] The present invention also provides an absolute radiometric calibration system for a spaceborne low-light payload, comprising:

[0024] The entrance pupil radiance value calculation module is used to calculate the entrance pupil radiance of multiple point light sources with different imaging areas for spaceborne micro-light payloads, and obtain multiple entrance pupil radiance values.

[0025] The accumulation calculation module is used to accumulate the brightness values ​​of multiple remote sensing image pixels corresponding to each point light source to obtain the sum of the brightness values ​​of multiple remote sensing image pixels.

[0026] The radiometric calibration point determination module is used to determine the radiometric calibration point corresponding to each of the point light sources based on the sum of the radiance value at the entrance pupil and the pixel radiance value of the remote sensing image;

[0027] The calibration coefficient determination module is used to perform linear fitting on multiple radiation calibration points to obtain a fitted calibration function, and to determine the calibration coefficients based on the fitted calibration function.

[0028] Optionally, the entrance pupil radiance value calculation module includes:

[0029] A point light source emission radiance acquisition unit is used to acquire the emission radiance of the point light source when the point light source has a response in the wavelength range of the spaceborne micro-light payload.

[0030] An effective brightness calculation unit for a point light source is used to calculate the effective brightness of the point light source based on the emitted radiance of the point light source and the imaging area of ​​the point light source.

[0031] The entrance pupil radiance value calculation unit is used to calculate the entrance pupil radiance of the spaceborne micro-light payload based on the effective brightness of the point light source, and obtain the entrance pupil radiance value.

[0032] The present invention also provides a computer-readable storage medium storing a program that, when executed by a processor, implements the above-described absolute radiometric calibration method for spaceborne low-light payloads.

[0033] The present invention also provides an electronic device, comprising:

[0034] At least one processor, and at least one memory and bus connected to the processor;

[0035] The processor and the memory communicate with each other through the bus; the processor is used to call program instructions in the memory to execute the above-mentioned absolute radiometric calibration method for spaceborne low-light payloads.

[0036] This invention provides an absolute radiometric calibration method and related equipment for spaceborne low-light payloads. Multiple radiance values ​​at the entrance pupil are calculated using multiple point light sources with different imaging areas. Multiple radiometric calibration points are obtained based on the sum of the entrance pupil radiance values ​​and the pixel brightness values ​​of the remote sensing image. Linear fitting is then performed on these multiple calibration points to determine the calibration coefficients. Therefore, this invention enables absolute radiometric calibration of spaceborne low-light payloads using a multi-point calibration method. Compared to the single-point calibration method used in existing technologies, this improves calibration accuracy and meets the needs of high-precision radiometric calibration and radiometric performance monitoring for spaceborne low-light payloads.

[0037] Of course, any product or method implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A flowchart of the absolute radiometric calibration method for a spaceborne low-light payload provided in an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of the radiative transfer model of a point light source under moonless conditions provided in an embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of multi-point radiation calibration provided in an embodiment of the present invention;

[0042] Figure 4 This is a structural diagram of the absolute radiometric calibration system for a spaceborne low-light payload provided in an embodiment of the present invention;

[0043] Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] In the absolute radiometric calibration of spaceborne low-light payloads, if a site-substitute calibration method is used, this method is typically conducted under full moon conditions, which limits the frequency of absolute radiometric calibration. Furthermore, this method requires using a lunar irradiance model to simulate the radiance at the entrance pupil of the spaceborne low-light payload; therefore, its calibration accuracy cannot be further improved due to the uncertainties of the lunar irradiance model, making it difficult to meet the requirements for high-precision radiometric calibration and radiometric performance monitoring of spaceborne low-light payloads.

[0046] If an active light source-based calibration method is used, a self-illuminating active light source is typically used as the calibration ground object. By acquiring atmospheric parameters at the moment of transit of the spaceborne low-light payload, the upward radiance at the entrance pupil of the satellite payload is simulated, thereby achieving absolute radiometric calibration. However, the active light source-based absolute radiometric calibration method for spaceborne low-light payloads mainly focuses on single-point calibration in the low-resolution VIIRS DNB band, which cannot meet the full-spectrum coverage requirements of spaceborne low-light payloads.

[0047] Based on this, the present invention proposes an absolute radiometric calibration method for spaceborne low-light payloads. The method achieves absolute radiometric calibration of spaceborne low-light payloads through multi-point calibration, which can improve calibration accuracy, meet the requirements of high-precision radiometric calibration and radiometric performance monitoring of spaceborne low-light payloads, and also meet the requirements of full-spectrum coverage of spaceborne low-light payloads.

[0048] like Figure 1 As shown, the present invention provides an absolute radiometric calibration method for a spaceborne low-light payload, comprising:

[0049] Step 101: Calculate the radiance at the entrance pupil of multiple point light sources with different imaging areas for the spaceborne micro-light payload, and obtain multiple radiance values ​​at the entrance pupil.

[0050] To address the issue of low calibration accuracy when using single-point calibration, this invention utilizes multiple point light sources to calculate the radiance at the entrance pupil of the spaceborne micro-light payload. These point light sources can have different areas, and the imaging areas of different point light sources are different, resulting in different radiance values ​​at the entrance pupil obtained through the calculation of the radiance at the entrance pupil of the spaceborne micro-light payload.

[0051] Under lunar-less conditions, the radiation sources acquired by spaceborne low-light payloads are mainly natural and artificial light sources. In this case, the acquired remote sensing images of the low-light payload have a higher signal-to-noise ratio, better imaging quality, and are more conducive to the site-specific absolute radiometric calibration of the low-light payload. Therefore, this invention can perform absolute radiometric calibration of spaceborne low-light payloads under dark conditions (lunar-less or new moon). Figure 2 The diagram shows a radiative transfer model of a point light source under moonless conditions, as follows. Figure 2 As shown, the angle between the two dashed lines represents the field of view of satellite 21, the radiation path of light source 22, and the dotted dashed lines represent point source radiation, solid lines represent scattered radiation, and dotted dashed lines represent path radiation. Figure 2 It can be seen that the radiance at the entrance pupil of a spaceborne low-light payload mainly consists of two parts: the emission radiance of the surface light source and the background radiance.

[0052] As an optional implementation, a method for calculating the radiance at the entrance pupil of a spaceborne low-light payload includes:

[0053] The emitted radiance of the point light source is obtained when the point light source responds in all wavelength ranges of the spaceborne micro-light payload.

[0054] The effective brightness of a point light source is calculated based on its emitted radiance and its imaging area.

[0055] The radiance at the entrance pupil of the spaceborne low-light payload is calculated based on the effective brightness of the point light source, and the radiance value at the entrance pupil is obtained.

[0056] To meet the full-spectrum coverage requirement of spaceborne low-light payloads, point light sources must have a response within the spectral range of the spaceborne low-light payload, meaning that the emitted radiance of the point light source is not zero within the payload's spectral response range. Under this condition, the emitted radiance of the point light source is determined.

[0057] Optionally, the effective brightness of the point light source is calculated based on the emitted radiance and the imaging area of ​​the point light source, including:

[0058] Based on the emitted radiance, scattering factor, and atmospheric transmittance of the point source, the radiance of the point source after atmospheric scattering and transmission is calculated.

[0059] The effective brightness of the point light source is calculated based on the radiance of the point light source after transmission, the imaging area of ​​the point light source, and the spatial projection area of ​​the spaceborne micro-light payload.

[0060] The radiance of the point source after atmospheric scattering and transmission is calculated using the following formula:

[0061] L AS (θ)=M S ·L TS (θ)·T↑

[0062] In the formula, L AS (θ) represents the radiance of the point source after atmospheric scattering and transmission, M S is the scattering factor, and T↑ is the atmospheric upward transmittance.

[0063] Specifically, methods for determining the scattering factor include:

[0064] If the point source is a Lambertian source, the scattering factor is determined based on spherical albedo and surface reflectivity.

[0065] In practical applications, the scattering factor can be determined using the following formula:

[0066]

[0067] In the formula, s is the spherical albedo, and ρ is the surface reflectance.

[0068] Specifically, methods for determining atmospheric transmittance include:

[0069] Acquire atmospheric profile data and aerosol content at the moment of transit of the spaceborne low-light payload;

[0070] Atmospheric profile data and aerosol content are input into the atmospheric radiative transfer model to obtain atmospheric transmittance.

[0071] Optionally, the atmospheric profile data may include, but is not limited to, water vapor content, pressure, and temperature.

[0072] The effective luminance of a point light source can be calculated using the following formula:

[0073]

[0074] In the formula, L MS (θ) represents the effective luminance of the point light source, which is the effective luminance of the point light source considering the finite pixel size. It indicates the average value of the point light source radiance within the spatial projection range of a single probe element of the load. L AS (θ) represents the radiance of the point source after atmospheric scattering and transmission, A S Let A be the imaging area of ​​the point light source. DAS This represents the spatial projected area of ​​the spaceborne micro-light payload.

[0075] The radiance at the entrance pupil of a spaceborne low-light payload is calculated based on the effective brightness of a point source, yielding the radiance value at the entrance pupil, including:

[0076] The radiance value at the entrance pupil is obtained by summing the effective luminance of the point light source and the background radiance. The radiance value at the entrance pupil is then calculated using the following formula:

[0077] L S =L MS (θ)+L Backgound

[0078] In the formula, L S L is the radiance value at the entrance pupil. MS (θ) represents the effective brightness of the point light source, θ is the zenith angle observed by the satellite, and L Backgound This represents the background radiance.

[0079] Background radiation includes upward atmospheric radiation from light pollution, atmospheric glow, and downward atmospheric radiation that strikes the Earth's surface and reflects into space. Background radiation may also include lunar radiation, but the calibration light source of this invention operates under dark conditions (no moon or new moon), therefore the influence of lunar radiation is not considered.

[0080] In summary, the radiance value at the entrance pupil can be calculated using the following formula:

[0081]

[0082] The above formula shows that when the area A of the point light source is... S The spatial projected area A of the spaceborne micro-light payload DAS Point light source emitted radiance L TS When (θ) and atmospheric transmittance T↑ are known, absolute radiometric calibration of the low-light load can be achieved.

[0083] Step 102: Accumulate the brightness values ​​of the remote sensing image pixels corresponding to each point light source to obtain the sum of the brightness values ​​of the multiple remote sensing image pixels.

[0084] In the absence of a moon, each point light source in the remote sensing image corresponds to multiple pixels. The sum of the brightness values ​​of the remote sensing image pixels corresponding to each point light source is obtained to get the total DN value of each point light source. For example, the DN value of the i-th point light source illuminating the j-th pixel is DN. i，j Then the sum of the brightness values ​​of the remote sensing image pixels corresponding to the point light source is n is the number of pixels corresponding to this point light source.

[0085] Step 103: Based on the sum of the radiance value at the entrance pupil and the pixel radiance value of the remote sensing image, determine the radiometric calibration point corresponding to each point light source.

[0086] The x-axis of the radiometric calibration point represents the sum of the brightness values ​​of the remote sensing image pixels, and the y-axis represents the radiance value at the entrance pupil. For each point light source, there is a corresponding radiance value at the entrance pupil and a sum of the brightness values ​​of the remote sensing image pixels. By matching the radiance value at the entrance pupil and the brightness value of the remote sensing image pixels with the point light source, the radiometric calibration point of that point light source is obtained.

[0087] Step 104: Perform linear fitting on multiple radiation calibration points to obtain the fitted calibration function, and determine the calibration coefficients based on the fitted calibration function.

[0088] When using a sequence of point light sources with different point light source areas, the corresponding radiance L at the entrance pupil of the satellite payload... s This represents a series of values. After extracting the sum of the DN values ​​of the pixels corresponding to each point light source in the spaceborne low-light payload image data, multi-point radiometric calibration of the spaceborne low-light payload can be achieved through linear fitting.

[0089] The fitted scaling function is as follows:

[0090] L S =∑DN·Gain+Bias

[0091] In the formula, Gain is the gain in the scaling coefficients, and Bias is the bias in the scaling coefficients.

[0092] like Figure 3 The diagram shown is a schematic of multi-point radiometric calibration. Figure 3 The text provides three radiometric calibration points, with the x-coordinate of the first radiometric calibration point being... The vertical axis is L S1 The x-coordinate of the second radiation calibration point is The vertical axis is L S2 The x-coordinate of the i-th radiation calibration point is The vertical axis is L Si The straight line obtained through linear fitting is as follows: Figure 3 As shown.

[0093] This invention obtains the calibration coefficients Gain and Bias by linearly fitting multiple radiometric calibration points, thereby completing the absolute radiometric calibration of spaceborne low-light payloads.

[0094] The present invention can also adjust the size of the lamp array opening formed by multiple point light sources, increasing the lamp array opening when the spatial resolution is low and decreasing the lamp array opening when the spatial resolution is high, thereby achieving absolute radiometric calibration of spaceborne micro-light payloads with different spatial resolutions.

[0095] This invention also provides an absolute radiometric calibration system for spaceborne low-light payloads, such as... Figure 4 As shown, the system includes:

[0096] The entrance pupil radiance value calculation module 401 is used to calculate the entrance pupil radiance of multiple point light sources with different imaging areas for spaceborne micro-light payloads, and obtain multiple entrance pupil radiance values.

[0097] The accumulation calculation module 402 is used to accumulate the brightness values ​​of multiple pixels in the remote sensing image corresponding to each point light source to obtain the sum of the brightness values ​​of multiple remote sensing image pixels.

[0098] The radiometric calibration point determination module 403 is used to determine the radiometric calibration point corresponding to each point light source based on the sum of the radiance value at the entrance pupil and the pixel radiance value of the remote sensing image.

[0099] The calibration coefficient determination module 404 is used to perform linear fitting on multiple radiation calibration points to obtain the fitted calibration function, and to determine the calibration coefficients based on the fitted calibration function.

[0100] As an optional implementation, the entrance pupil radiance value calculation module 401 includes:

[0101] The point light source emission radiance acquisition unit is used to obtain the emission radiance of the point light source when the point light source has a response in the wavelength range of the spaceborne micro-light payload.

[0102] The effective brightness calculation unit for a point light source is used to calculate the effective brightness of the point light source based on the emitted radiance and the imaging area of ​​the point light source.

[0103] The entrance pupil radiance calculation unit is used to calculate the entrance pupil radiance of the spaceborne micro-light payload based on the effective radiance of the point light source, and obtain the entrance pupil radiance value.

[0104] The effective brightness calculation unit for a point light source is specifically used for:

[0105] Based on the emitted radiance, scattering factor, and atmospheric transmittance of the point light source, the radiance of the point light source after atmospheric scattering and transmission is calculated.

[0106] The effective brightness of the point light source is calculated based on the radiance of the point light source after transmission, the imaging area of ​​the point light source, and the spatial projection area of ​​the spaceborne micro-light payload.

[0107] Optionally, if the point light source is a Lambertian light source, the scattering factor is determined based on spherical albedo and surface reflectivity.

[0108] Optionally, atmospheric profile data and aerosol content are obtained at the moment of passage of the spaceborne low-light payload; the atmospheric profile data and aerosol content are input into the atmospheric radiative transfer model to obtain the atmospheric transmittance.

[0109] The radiance value calculation unit at the entrance pupil is specifically used for:

[0110] The effective brightness of the point light source and the background radiance are summed to obtain the radiance value at the entrance pupil.

[0111] This invention provides a computer-readable storage medium storing a program that, when executed by a processor, implements the aforementioned absolute radiometric calibration method for spaceborne low-light payloads.

[0112] This invention provides an electronic device, such as... Figure 5 As shown, the electronic device 50 includes at least one processor 501, and at least one memory 502 and a bus 503 connected to the processor 501; wherein the processor 501 and the memory 502 communicate with each other through the bus 503; the processor 501 is used to call program instructions in the memory 502 to execute the above-described absolute radiometric calibration method for spaceborne low-light payloads. The electronic device in this article may be a server, PC, PAD, mobile phone, etc.

[0113] This application also provides a computer program product, which, when executed on a data processing device, is adapted to perform the steps included in the above-described absolute radiometric calibration method for spaceborne low-light payloads.

[0114] This application is described with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0115] In a typical configuration, the device includes one or more processors (CPUs), memory, and a bus. The device may also include input / output interfaces, network interfaces, etc.

[0116] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, like read-only memory (ROM) or flash RAM, and memory includes at least one memory chip. Memory is an example of computer-readable media.

[0117] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0118] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0119] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0120] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0121] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. An absolute radiometric calibration method for a spaceborne low-light payload, characterized in that, include: The radiance at the entrance pupil of multiple point light sources with different imaging areas was calculated for the spaceborne micro-light payload, and multiple radiance values ​​at the entrance pupil were obtained. The methods for calculating the radiance at the entrance pupil of a spaceborne low-light payload include: The emitted radiance of the point light source is obtained when the point light source responds within the wavelength range of the spaceborne micro-light payload. Based on the emitted radiance, scattering factor, and atmospheric transmittance of the point light source, the radiance of the point light source after atmospheric scattering and transmission is calculated. The effective brightness of the point light source is calculated based on the radiance of the point light source after atmospheric scattering and transmission, the imaging area of ​​the point light source, and the spatial projection area of ​​the spaceborne micro-light payload. Based on the effective brightness of the point light source, the radiance at the entrance pupil of the spaceborne micro-light payload is calculated to obtain the radiance value at the entrance pupil. The brightness values ​​of the remote sensing image pixels corresponding to each point light source are summed to obtain the sum of the brightness values ​​of the remote sensing image pixels. Based on the sum of the radiance value at the entrance pupil and the pixel radiance value of the remote sensing image, the radiometric calibration point corresponding to each point light source is determined. Linear fitting is performed on multiple radiation calibration points to obtain a fitted calibration function, and calibration coefficients are determined based on the fitted calibration function.

2. The absolute radiometric calibration method for spaceborne low-light payloads according to claim 1, characterized in that, The method for determining the scattering factor includes: If the point light source is a Lambertian light source, the scattering factor is determined based on spherical albedo and surface reflectivity.

3. The absolute radiometric calibration method for spaceborne low-light payloads according to claim 1, characterized in that, The method for determining atmospheric transmittance includes: Acquire atmospheric profile data and aerosol content at the moment of transit of the spaceborne low-light payload; The atmospheric profile data and the aerosol content are input into the atmospheric radiative transfer model to obtain the atmospheric transmittance.

4. The absolute radiometric calibration method for spaceborne low-light payloads according to claim 1, characterized in that, The calculation of the radiance at the entrance pupil of the spaceborne micro-light payload based on the effective brightness of the point light source, to obtain the radiance value at the entrance pupil, includes: The effective brightness of the point light source and the background radiance are summed to obtain the radiance value at the entrance pupil.

5. An absolute radiometric calibration system for a spaceborne low-light payload, characterized in that, include: The entrance pupil radiance value calculation module is used to calculate the entrance pupil radiance of multiple point light sources with different imaging areas for spaceborne micro-light payloads, and obtain multiple entrance pupil radiance values. The entrance pupil radiance value calculation module includes: The point light source emission radiance acquisition unit is used to obtain the point light source emission radiance when the point light source has a response in the wavelength range of the spaceborne micro-light payload. The effective brightness calculation unit of the point light source is used to calculate the radiation brightness of the point light source after atmospheric scattering and transmission based on the emitted radiance, scattering factor and atmospheric transmittance of the point light source; and to calculate the effective brightness of the point light source based on the radiation brightness of the point light source after atmospheric scattering and transmission, the light source imaging area of ​​the point light source and the spatial projection area of ​​the spaceborne micro-light payload. The entrance pupil radiance value calculation unit is used to calculate the entrance pupil radiance of the spaceborne micro-light payload based on the effective brightness of the point light source, and obtain the entrance pupil radiance value. The accumulation calculation module is used to accumulate the brightness values ​​of multiple remote sensing image pixels corresponding to each point light source to obtain the sum of the brightness values ​​of multiple remote sensing image pixels. The radiometric calibration point determination module is used to determine the radiometric calibration point corresponding to each of the point light sources based on the sum of the radiance value at the entrance pupil and the pixel radiance value of the remote sensing image; The calibration coefficient determination module is used to perform linear fitting on multiple radiation calibration points to obtain a fitted calibration function, and to determine the calibration coefficients based on the fitted calibration function.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a program that, when executed by a processor, implements the absolute radiometric calibration method for a spaceborne low-light payload as described in any one of claims 1-4.

7. An electronic device, characterized in that, include: At least one processor, and at least one memory and bus connected to the processor; The processor and the memory communicate with each other via the bus; The processor is used to call program instructions in the memory to execute the absolute radiometric calibration method for a spaceborne low-light payload according to any one of claims 1-4.

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