Radiometric cross-calibration method for optical remote sensing satellites based on stable radiation sources

Abstract

The present invention relates to a radiometric cross-calibration method for optical remote sensing satellites based on a stable radiation source, comprising the following steps: a. calibrating the optical remote sensing satellite using an onboard blackbody to obtain a calibration coefficient; b. calculating the radiometric value of the stable radiation source based on the calibration coefficient; c. repeating steps (a) and (b) to obtain a series of calibration coefficients and radiometric values; and d. selectively performing radiometric correction based on the decay of the optical remote sensing satellite's radiometric measurement performance. The present invention can achieve stable calibration of the absolute radiometric reference of an optical remote sensing satellite on orbit, providing support for the quantitative processing and application of remote sensing data.

Description

Technical Field

[0001] The invention relates to a radiation cross-calibration method for an optical remote sensing satellite based on a stable radiation source. Background Art

[0002] Radiometric calibration is a crucial task for on-orbit optical remote sensing satellites. Its primary objective is to calibrate the radiometric measurement capabilities of onboard optical cameras and achieve single-satellite or multi-satellite radiometric calibration. In existing technologies, calibration is typically accomplished using methods such as onboard blackbodies and ground-based calibration fields. However, due to atmospheric influences, it is difficult to directly use ground-based calibration fields to calibrate onboard optical cameras in specific optical spectral bands. Furthermore, onboard blackbodies are subject to performance degradation and detector performance degradation, making it difficult to calibrate the absolute radiometric reference of remote sensing satellites. Therefore, achieving accurate multi-satellite cross-radiometric calibration is an urgent challenge in the field of radiometric calibration. Summary of the Invention

[0003] The purpose of the present invention is to provide an optical remote sensing satellite radiation cross-calibration method based on a stable radiation source.

[0004] To achieve the above-mentioned object of the invention, the present invention provides a method for optical remote sensing satellite radiation cross-calibration based on a stable radiation source, comprising the following steps:

[0005] a. Use the onboard blackbody to calibrate the optical remote sensing satellite and obtain the calibration coefficient;

[0006] b. Calculate the radiation value of the stable radiation source according to the calibration coefficient;

[0007] c. Repeat steps (a) and (b) to obtain a series of calibration coefficients and radiation values;

[0008] d. Selectively perform radiation correction based on the decay of the radiation measurement performance of the optical remote sensing satellite.

[0009] According to one aspect of the present invention, in step (a), the calibration coefficient slope K of the camera linear response is obtained based on the two-point calibration method. i and intercept B i ;

[0010] Here, i represents the i-th calibration based on the onboard blackbody after the satellite enters orbit.

[0011] According to one aspect of the present invention, in step (b), two or more stable radiation sources are observed to obtain the original image grayscale value DN of the stable radiation source. n,j , and use the calibration coefficient slope K closest to the observation time of the stable radiation source i and intercept B iCalculate the radiation value E of a stable radiation source n,j , as follows:

[0012] E n,j =K i ·DN n,j +B i ;

[0013] Where n=1, 2, 3… represents the nth observation of a stable radiation source.

[0014] According to one aspect of the present invention, in step (d), when the performance of the radiation measurement of the optical remote sensing satellite decays When it is greater than the set threshold η0, radiation correction is performed;

[0015] Among them, E 1,j It represents the radiation value of the j-th stable radiation source calculated based on the first calibration coefficient.

[0016] According to one aspect of the present invention, the following formula is established in step (d):

[0017] ΔK m ·DN n,j +ΔB m =E 1,j -E n,j ;

[0018] Where ΔK m and ΔB m is the calibration correction coefficient, m=1,2,3… represents the mth radiation correction.

[0019] According to one aspect of the present invention, a matrix form is used to use the observation results of the stable radiation source to calculate the calibration correction coefficient ΔK based on the least square method. m and ΔB m The calculation is as follows:

[0020] Assume DK = E, calculate K = (D T D) -1 D T E;

[0021] in,

[0022] According to one aspect of the present invention, in step (d), the calibration correction coefficient ΔK is obtained. m and ΔB m Then, using K i +ΔK m and B i +ΔB mCalculate the radiation values ​​of the target and background.

[0023] The device includes a storage medium, a processor, and a computer program stored in the storage medium and capable of running on the processor. When the processor executes the program, an optical remote sensing satellite radiation cross-calibration method based on a stable radiation source is implemented.

[0024] According to the present invention, ground-based vacuum calibration, on-orbit blackbody calibration, and on-orbit stellar calibration are combined to achieve on-orbit cross-radiometric calibration for optical remote sensing satellites. This approach first establishes a payload radiation benchmark by leveraging the minimal blackbody performance decay observed on both the ground and satellite during initial orbit. Then, through regular observation of stable radiation sources such as stars and monitoring performance decay, the blackbody calibration deviation is corrected. This allows for stable correction of the absolute radiation benchmark for the optical remote sensing satellite on-orbit, thus supporting the quantitative processing and application of remote sensing data. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The flowchart schematically shows a method for cross-calibration of optical remote sensing satellite radiation based on a stable radiation source according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0027] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0028] The optical remote sensing satellite radiation cross-calibration method based on a stable radiation source of the present invention is completed based on a mature two-point calibration method after obtaining the ground vacuum internal and external calibration results of the optical remote sensing satellite and assuming that the camera radiation response is a linear response.

[0029] See also Figure 1 This method first calibrates an optical remote sensing satellite using an onboard blackbody to obtain calibration coefficients. The radiometric value of a stable radiation source is then calculated based on these calibration coefficients. These steps are then repeated periodically to obtain a series of calibration coefficients and radiometric values. Finally, radiometric corrections are selectively applied based on the degradation of the optical remote sensing satellite's radiometric measurement performance.

[0030] In the present invention, at the initial stage of the optical remote sensing satellite launch, the onboard blackbody is used for calibration. The calibration coefficient slope K1 and intercept B1 of the camera linear response are obtained based on the two-point calibration method, thereby completing the first on-orbit calibration of the optical remote sensing satellite based on the onboard blackbody. At this time, at least two stable radiation sources (such as stars, etc.) should be observed in time, and the original image grayscale value DN is obtained based on the calibration coefficient slope K1 and intercept B1. 1,j , and then use the K1 and B1 coefficients to calculate the radiation value information E of the radiation source 1,j =K1·DN 1,j +B1. Among them, E 1,j It represents the radiation value calculated by the j-th stable radiation source based on the first calibration coefficient, which is also recorded as the true value of the radiation value.

[0031] Therefore, in the future, when optical remote sensing satellites are in orbit, on-board black bodies can be used to conduct regular on-orbit calibration, and a series of corresponding calibration coefficients can be obtained using the two-point calibration method. In addition, since the performance of black bodies decays on orbit, each calibration based on on-board black bodies will obtain different calibration coefficients. Therefore, the present invention uses the subscript i (i = 1, 2, 3 ...) to mark them, and records them as the slope K i and intercept B i Among them, i is the i-th calibration based on the onboard blackbody after the satellite enters orbit. At the same time, during this period, it is also necessary to regularly observe two or more stable radiation sources to obtain a series of original image grayscale values ​​of the stable radiation sources, recorded as DN n,j After that, the slope of the calibration coefficient K closest to the observation time of the stable radiation source can be used i and intercept B i Calculate the radiation value E of a stable radiation source n,j , as follows:

[0032] E n,j =K i ·DN n,j +B i ;

[0033] Here, n=1, 2, 3, ... represents the nth stable radiation source observation. In addition, the duration / number of the regular on-orbit calibration and stable radiation source observation in the present invention can be selected according to actual needs.

[0034] After completing the above steps of the present invention, the n,j With E 1,j Specifically, when the performance of the optical remote sensing satellite on-orbit radiation measurement decays, When it is greater than a certain set threshold η0 (not greater than 0.1, but can be adjusted according to engineering requirements), radiation correction is required.

[0035] In the present invention, the following formula is first established:

[0036] ΔK m ·DN n,j +ΔB m =E 1,j -E n,j ;

[0037] Where ΔK m and ΔB m is the calibration correction coefficient, m=1,2,3… represents the mth radiation correction.

[0038] The present invention adopts matrix form to express, utilizes the observation results of two or more stable radiation sources (j≥2), and then uses the least square method to correct the calibration coefficient ΔK m and ΔB m Specifically, let DK = E, and calculate K = (D T D) - 1 D T E;

[0039] in,

[0040] The calibration correction coefficient ΔK is obtained according to the above method m and ΔB m After that, the calibration coefficient can be corrected and the corrected calibration coefficient is K i +ΔK m and B i +ΔB m The corrected calibration coefficients are then used to calculate the radiation values ​​of the target and background to reduce the characteristic errors of the target and background radiation in practical applications and improve the measurement accuracy of the target and background radiation.

[0041] The following is a simulation of the on-orbit radiation calibration performance of an optical remote sensing satellite using a calibration method according to one embodiment of the present invention, as shown in Table 1 below:

[0042] First observation Second observation deviation Correction results Segment 1 0.0037 0.0029 21.6％ 0.0037 Segment 2 0.0039 0.0038 2.56％ 0.0039 Segment 3 0.0055 0.0040 27.2％ 0.0055

[0043] Table 1 Observation and correction results of the same star by optical remote sensing satellite

[0044] In this way, the simulation results show that this method can be used to effectively monitor the changes in the camera's on-orbit radiation performance. In addition, by establishing the above-mentioned correction model, the deviations caused by the attenuation of the on-board blackbody and detector performance can be effectively corrected, thereby achieving the unification of multi-star radiation benchmarks (i.e., multi-star cross-radiation calibration).

[0045] The device of the present invention includes a storage medium, a processor, and a computer program stored in the storage medium and executable on the processor. When the processor executes the program, the method of the present invention is implemented.

[0046] The above description is merely one embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for cross-calibration of optical remote sensing satellite radiation based on a stable radiation source, comprising the following steps: a. Use the onboard blackbody to calibrate the optical remote sensing satellite and obtain the calibration coefficient; b. Calculate the radiation value of the stable radiation source according to the calibration coefficient; c. Repeat steps (a) and (b) to obtain a series of calibration coefficients and radiation values; d. Selectively perform radiometric corrections based on the degradation of the radiometric performance of optical remote sensing satellites; In the step (d), the following formula is established: ΔK m ·DN n,j +ΔB m =E 1,j -E n,j ; Where ΔK m and ΔB m is the calibration correction coefficient, m=1,2,3…means the mth radiation correction, DN n,j Represents the original image grayscale value of the stable radiation source, E 1,j It represents the radiation value of the jth stable radiation source calculated based on the first calibration coefficient; In matrix form, using the observation results of stable radiation source, the calibration correction coefficient ΔK is calculated based on the least square method. m and ΔB m The calculation is as follows: Assume DK = E, calculate K = (D T D) -1 D T E; in, Get the calibration correction coefficient ΔK m and ΔB m Then, using K i +ΔK m and B i +ΔB m Calculate the radiation values ​​of the target and background.

2. The method according to claim 1, characterized in that In step (a), the calibration coefficient slope K of the camera linear response is obtained based on the two-point calibration method. i and intercept B i ; Here, i represents the i-th calibration based on the onboard blackbody after the satellite enters orbit.

3. The method according to claim 2, characterized in that In step (b), two or more stable radiation sources are observed to obtain the original image grayscale value DN of the stable radiation source. n,j , and use the calibration coefficient slope K closest to the observation time of the stable radiation source i and intercept B i Calculate the radiation value E of a stable radiation source n,j , as follows: E n,j =K i ·DN n,j +B i ; Where n=1, 2, 3… represents the nth observation of a stable radiation source.

4. The method according to claim 3, characterized in that In step (d), when the performance of the radiometric measurement of the optical remote sensing satellite decays When it is greater than the set threshold η0, radiation correction is performed; Among them, E 1,j It represents the radiation value of the j-th stable radiation source calculated based on the first calibration coefficient.

5. A device comprising a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, wherein: When the processor executes the program, the method according to any one of claims 1 to 4 is implemented.

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