Focal plane polarization remote sensing instrument in-orbit relative radiation calibration method and device

Abstract

The invention discloses a focal plane polarization remote sensing instrument on-orbit relative radiation calibration method and device, and belongs to the technical field of remote sensing instrument on-orbit radiation calibration. The method comprises the steps that a uniform target is selected as a calibration scene, and an instrument to be calibrated is controlled to perform multiple times of imaging on a target area under the condition of different yaw angles in an attitude maneuver mode; then, carrying out preprocessing such as dark current correction on the obtained remote sensing data, and then calculating a mean value of multiple observation data of each wave band and each pixel under the condition of different yaw angles; on the basis, a vector radiation measurement model of the focal plane polarization remote sensing instrument is combined, and the on-orbit relative radiation response coefficient of the focal plane polarization remote sensing instrument is obtained through a data fitting method. The method has the main advantages that on-orbit relative radiometric calibration of the focal plane polarization remote sensing instrument is completely autonomous based on attitude maneuver control of a load or a satellite, and an on-orbit calibrator, a ground reference datum and a reference remote sensing instrument are not needed.

Description

Technical Field

[0001] This invention belongs to the field of on-orbit radiometric calibration technology for remote sensing instruments, specifically relating to an on-orbit relative radiometric calibration method and apparatus for a focal plane polarization remote sensing instrument. Background Technology

[0002] Polarization remote sensing technology can detect more dimensions of target information and is widely used in atmospheric environment monitoring, climate change research, and other fields. It has also attracted increasing attention due to its excellent performance in atmospheric correction and camouflage identification. Focused plane polarization remote sensing instruments achieve polarization resolution by etching pixel-level micro-polarization devices on the detector using photolithography. Each pixel has a different polarization direction, and the Stokes vector of the incident light is finally solved by combining adjacent 2×2 pixels. Compared with traditional time-division, amplitude-division, and aperture-division polarization instruments, focused plane polarization detectors have significant advantages in terms of weight reduction, miniaturization, and detection efficiency. Therefore, focused plane polarization remote sensing instruments have enormous application prospects in commercial aerospace and other fields.

[0003] In-orbit relative radiometric calibration of optical remote sensing instruments is crucial for ensuring the long-term quality of their on-orbit data. The relative radiometric response characteristics between pixels of an optical instrument are jointly affected by the optical lens and detector. Due to factors such as severe vibrations during satellite launch and significant differences between laboratory and on-orbit environments, the on-orbit relative radiometric response characteristics of the instrument differ greatly from laboratory calibration results. In-orbit calibration is necessary to obtain the relative response coefficients of the optical remote sensing instrument during its on-orbit operation. Commonly used in-orbit relative radiometric calibration methods are based on in-orbit calibrators, uniform ground calibration fields, or reference remote sensing instruments. These methods are mature and effective for traditional instruments that only measure scalar radiometric data. However, for focal plane polarization remote sensing instruments, the polarization characteristics of the target scene are unknown, and the polarization direction of each pixel is different, causing a traditional uniform target to become a non-uniform target when detected by pixels with different polarization directions.

[0004] To address the inapplicability of traditional on-orbit relative radiometric calibration methods in the application of focal plane polarization remote sensing instruments, there is an urgent need to propose new on-orbit calibration techniques. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for on-orbit relative radiometric calibration of a focal plane polarization remote sensing instrument, comprising:

[0007] S1. Construct a vector radiation measurement model for a focal plane polarization remote sensing instrument. The construction process comprehensively considers the radiation and polarization characteristics of the optical lens and the focal plane polarization array.

[0008] S2, based on attitude maneuvering, collects on-orbit relative radiometric calibration data;

[0009] S3, perform observation data preprocessing;

[0010] S4, perform on-orbit relative response coefficient calibration.

[0011] An on-orbit relative radiometric calibration device for a focal plane polarization remote sensing instrument includes:

[0012] The vector radiation measurement model construction module constructs a vector radiation measurement model for a focal plane polarization remote sensing instrument. The construction process comprehensively considers the radiation and polarization characteristics of the optical lens and the focal plane polarization array.

[0013] The data acquisition module acquires on-orbit relative radiometric calibration data based on attitude maneuvers;

[0014] The data preprocessing module performs preprocessing of the observation data;

[0015] The calibration module performs on-orbit relative response coefficient calibration.

[0016] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the on-orbit relative radiometric calibration method for a focal plane polarization remote sensing instrument.

[0017] A non-transitory computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the on-orbit relative radiometric calibration method for a focal plane polarization remote sensing instrument.

[0018] The present invention has the following beneficial effects:

[0019] 1. This invention achieves on-orbit relative radiometric calibration by combining uniform ground target observation data obtained under different yaw angles in orbit with the vector radiometric measurement model of a focal plane polarization remote sensing instrument and using a data fitting method. This can solve the problem of on-orbit relative radiometric calibration of focal plane polarization remote sensing instruments.

[0020] 2. This invention acquires observation data of uniform natural targets at different yaw angles through satellite or instrumental maneuvering imaging, achieving fully autonomous on-orbit relative radiometric calibration without the need for on-orbit calibrators, reference remote sensing instruments, ground-based measured benchmarks, etc.

[0021] 3. This invention only requires observing uniform natural targets under different yaw angles to achieve on-orbit relative radiometric calibration of a split-focus plane polarization remote sensing instrument. It can autonomously plan calibration tasks globally according to on-orbit calibration requirements, achieve on-orbit relative radiometric calibration at high frequency, and improve the long-term effectiveness of the instrument's on-orbit remote sensing data. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of the on-orbit relative radiometric calibration method for the focal plane polarization remote sensing instrument of the present invention.

[0023] Figure 2 A schematic diagram of the coordinate system used when constructing the instrument's vector radiation measurement model;

[0024] Figure 3 The figure shows the measured results of the relative response coefficient of the instrument calibrated in the laboratory based on a large-aperture integrating sphere uniform light source.

[0025] Figure 4 The relative response coefficients are calibrated by the on-orbit relative radiometric calibration method under different error sources; among them, (a) is the calibration result diagram of the relative response coefficient under ideal conditions, (b) is the calibration result diagram of the relative response coefficient under 1% random measurement error, (c) is the calibration result diagram of the relative response coefficient under 0.1° random yaw angle error, and (d) is the calibration result diagram of the relative response coefficient under 1% random error in the incident light Stokes vector;

[0026] Figure 5 shows the relative difference between the on-orbit calibration relative response coefficient and the laboratory measured reference relative response coefficient. (a) is the comparison result under ideal conditions, (b) is the comparison result under 1% random measurement error, (c) is the comparison result under 0.1° random yaw angle error, and (d) is the comparison result under 1% random error in the incident light Stokes vector. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The specific technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0029] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the protection scope of the present invention.

[0030] This invention proposes an on-orbit relative radiometric calibration method for a focal plane polarization remote sensing instrument. Based on attitude maneuver control, it achieves autonomous on-orbit relative radiometric calibration without relying on an on-orbit calibrator, reference remote sensing instrument, or ground-based measured benchmark, thus enabling high-frequency, long-term autonomous on-orbit calibration.

[0031] This embodiment uses a certain type of polarization remote sensing instrument as an example to provide an on-orbit relative radiometric calibration method for a focal plane polarization remote sensing instrument. The implementation process is described in [link to implementation details]. Figure 1 It consists of four steps, specifically including:

[0032] S1. Constructing a vector radiation measurement model for a focal plane polarization remote sensing instrument requires comprehensive consideration of the radiation and polarization characteristics of the optical lens and the focal plane polarization array.

[0033] The instrument image size is 1024×1024, and the pixel detection direction is set to... , , , ;

[0034] in, Let be the row coordinates of the pixel on the image plane. represents the column coordinates of the pixel on the image plane.

[0035] Its coordinate system is as follows Figure 2 As shown, the image coordinate system is... The axis is along the direction of increasing detector rows, in the image coordinate system. The axis is along the direction of increasing detector column; the local coordinate system of the instrument pixels. The axis is defined as the local coordinate system of the instrument pixel along the meridional direction of the optical system. The axis is defined as the direction along the sagittal arc of the optical system; Let be the polarization direction of the incident light, and let be the polarization azimuth angle in the local coordinate system of the pixel. , For pixels The corresponding azimuth angle in the image coordinate system , , , The azimuth angle for the detection of four adjacent pixels.

[0036] The vector radiometric measurement model of the focal plane polarization remote sensing instrument is as follows:

[0037] ;

[0038] in, Stokes vector of incident light In the instrument band Pixel The response value on the screen; circular polarization components are usually not considered in remote sensing applications; , , For the parameters of the Stokes vector, The intensity of the incident light. , For the linearly polarized component of the incident light, The polarization degree of the incident light. The polarization azimuth angle of the incident light; For instrument bands The absolute radiative response coefficient; The relative response coefficient of the instrument; The Mueller matrix of the focal plane polarization array; For the Muller matrix of optical lenses; Dark current represents the inherent response value of each pixel in the instrument under conditions of no light source illumination.

[0039] The model is described in detail below:

[0040] (1) Instrument band absolute radiation response coefficient Represented as:

[0041] ;

[0042] in, For the instrument at a known brightness of Under unbiased light source incidence, the response value of a specific reference pixel in the instrument's central field of view. and The ratio of .

[0043] (2) The relative response coefficient of the instrument Represented as:

[0044] ;

[0045] in, For each pixel of the instrument at a brightness of Under the condition of unbiased uniform light source incidence, the response values ​​of each pixel Compared with absolute radiometric calibration pixel response value The relative differences are shown in the measured results of the instrument's relative response coefficient, calibrated in the laboratory using a large-aperture integrating sphere uniform light source. Figure 3 As shown.

[0046] (3) Mueller matrix of focal plane polarization array Represented as:

[0047] ;

[0048] The Mueller matrix represents the polarization characteristics of each pixel in the focal plane polarization detector, and each pixel is characterized by an extinction ratio of... Incompletely linearly polarized devices, and This represents the transmittance along two orthogonal principal axes. Represents a pixel Azimuth angle in the instrument coordinate system Represents a pixel The deviation angle in the instrument coordinate system Indicates in pixel The angle of analysis in the local coordinate system.

[0049] (4) Muller matrix of optical lenses Represented as:

[0050] ;

[0051] The Mueller matrix takes into account the lens's initial deviation. , and These represent the transmittance of s-rays (light with polarization perpendicular to the incident plane) and p-rays (light with polarization parallel to the incident plane), respectively, neglecting the small-scale depolarization and phase delay effects.

[0052] Combining the parameters from (1) to (4) above, the vector radiation measurement model can be obtained as follows:

[0053] .

[0054] S2, based on attitude maneuvering, collects on-orbit relative radiation calibration data. The specific steps are as follows:

[0055] S2.1, pre-select uniform targets as candidate calibration scenarios, such as uniform natural targets like deserts and oceans as calibration sites;

[0056] S2.2, In the selected target area, an uncalibrated focal plane polarization remote sensing instrument is used to image the target and collect multiple frames of data;

[0057] S2.3, adjust the yaw angle of the split-plane polarization remote sensing instrument to sample at small angle intervals within the range of 0-180°, and repeat S2.2.

[0058] S3. Perform observation data preprocessing, including dark current correction for all measurement data, and then calculate the average value of multiple acquisitions of data for each band and each pixel under the same yaw angle after dark current correction. The calculation formula is as follows:

[0059] ;

[0060] in, and These represent the yaw angles at positions 1 and 2 respectively. The frame number and the total number of frames collected at any given time. The yaw angle number is The instrument frame number is , band At that time, like a pixel The response value.

[0061] S4. Perform on-orbit relative response coefficient calibration. The specific steps are as follows:

[0062] S4.1, referring to the vector radiation measurement model in S1, set the fitting equation. :

[0063] ;

[0064] in, , , , , These are the parameters in the fitting equation; is the independent variable of the function, representing the yaw sampling angle.

[0065] S4.2, for pixels ,according to Combined with the fitting equation of S4.1 With yaw angle as the independent variable, the corresponding For the dependent variable, parameters are obtained using data fitting methods. .

[0066] S4.3, based on the parameters obtained in step 4.2 Combining the vector radiation measurement model of S1, the absolute radiation response coefficient is calculated. The relative response coefficient in orbit and incident light intensity Intermediate process parameters formed together :

[0067] .

[0068] S4.4, For all pixels of the full-image plane, repeat steps S4.1-4.3.

[0069] S4.5, using intermediate process parameters for each pixel. Divide by the intermediate process parameters of the absolute radiometric calibration reference pixel Obtain the final on-orbit relative response coefficients :

[0070] .

[0071] Based on simulation data, calibration results of the relative response coefficients were obtained under ideal conditions, 1% random measurement error, 0.1° random angle error, and 1% random error of the incident Stokes vector. Figure 4 As shown; Figure 4 (a) is the calibration result of the relative response coefficient under ideal conditions. Figure 4 (b) is a graph showing the calibration results of the relative response coefficients under a 1% random measurement error. Figure 4 (c) is the calibration result of the relative response coefficient under a random yaw angle error of 0.1°. Figure 4 (d) is the calibration result of the relative response coefficient with 1% random error in the incident light Stokes vector. By comparing the calibration result shown in Figure 4 with... Figure 3 Compared to the instrument relative response coefficient calibrated using a large-aperture integrating sphere uniform light source, the laboratory results are as follows: Figure 5 The comparison results are shown. Figure 5 To determine the relative difference between the on-orbit calibrated relative response coefficient and the laboratory-measured reference relative response coefficient, Figure 5 (a) is a comparison result under ideal conditions. Figure 5 (b) shows the comparison results under the condition of 1% random measurement error. Figure 5 (c) shows the comparison results under the condition of a random yaw angle error of 0.1°. Figure 5 Figure (d) shows the comparison results under the condition of 1% random error in the incident light Stokes vector. The results show that the present invention can achieve high-precision on-orbit calibration of the relative response coefficient under various interference conditions.

[0072] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented 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. The embodiments of the present invention can be implemented using various computer languages.

[0073] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. 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 illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0074] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0075] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0076] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0077] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0078] The above description is merely an embodiment of the present invention and does not limit the scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the protection scope of the present invention.

[0079] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. An on-orbit relative radiometric calibration method for a focal plane polarimetric remote sensing instrument, characterized in that, Comprising: S1, constructing a vector radiometric measurement model of the focal plane polarization remote sensing instrument, the construction process considering the radiation and polarization characteristics of the optical lens and the focal plane polarization array comprehensively; S2, collecting on-orbit relative radiometric calibration data based on attitude maneuvering; S3, performing observation data preprocessing; S4, performing on-orbit relative response coefficient calibration.

2. The method of on-orbit relative radiometric calibration of a focal plane polarimetric remote sensing instrument according to claim 1, wherein, In S1, the vector radiometric measurement model constructed is: ； where is the incident light Stokes vector is the absolute radiometric response coefficient of the instrument waveband , pixel is the response value on the pixel; the circular polarization component is usually not considered in remote sensing applications; , , is the parameter of the Stokes vector, is the intensity of the incident light, , is the linear polarization component of the incident light, is the degree of polarization of the incident light, is the polarization azimuth angle of the incident light; is the absolute radiometric response coefficient of the instrument waveband ; is the relative response coefficient of the instrument; is the Mueller matrix of the focal plane polarimetric array; is the Mueller matrix of the optical lens; is the dark current, representing the intrinsic response value of each pixel of the instrument in the absence of light source illumination.

3. The method of on-orbit relative radiometric calibration of a focal plane polarimetric remote sensing instrument according to claim 2, wherein, In S1, the parts of the vector radiometric measurement model are described as follows: (1) Instrument waveband Absolute radiometric response coefficient is expressed as: ； wherein, the ratio of the response value of the central field of view of the instrument for a known luminance of an unpolarized light source incident on the instrument to the response value of the specific reference pixel of the central field of view of the instrument for a known luminance of and the ratio of the response value of the central field of view of the instrument for a known luminance of (2) Relative response factor of the instrument is represented as: ； wherein, is the relative difference between the response value of each pixel of the instrument under the incidence of an unbiased uniform light source with luminance and the response value of the absolute radiometric calibration pixel ; (3) Mueller matrix of focal plane polarimetric array is represented as: ； Mueller matrix of a focal plane polarimetric array For characterizing the polarimetric properties of each pixel of a focal plane polarimetric detector, each pixel is characterized as an incomplete linear polarizing device with an extinction ratio , and representing the transmittance in the direction of the two orthogonal principal axes, representing the azimuth angle of the pixel in the instrument coordinate system, representing the angle of depolarization of the pixel in the instrument coordinate system, representing the angle of depolarization in the local coordinate system of the pixel ; (4) Mueller matrix of an optical lens is represented as: ； Mueller matrix of an optical lens Considering the degree of polarization of the lens , and Ts and Tp represent the transmittance of s and p light, respectively, neglecting the very small depolarization and phase delay effects. Combining , , and results in a vector radiative transfer model: 。 4. The on-orbit relative radiometric calibration method of a focal plane polarimetric remote sensing instrument according to claim 1, wherein S2 Comprising: S2.1, selecting a uniform natural target as a candidate calibration scene in advance; S2.2, imaging the target using the focal plane polarization remote sensing instrument to be calibrated in the selected target area, and collecting multiple frames of data; S2.3, adjusting the yaw angle of the focal plane polarization remote sensing instrument in the range of 0-180° at small angle intervals, and repeating S2.

2.

5. The method of on-orbit relative radiometric calibration of a focal plane polarimetric remote sensing instrument according to claim 1, wherein, S3 includes: dark current correction to all measurement data, and then calculating the average value of each wave band and each pixel under the same yaw angle after dark current correction : ； wherein, and respectively represent the frame number and the total frame number of data collected at the yaw angle index , is the response value of the pixel at the yaw angle index , the instrument frame number , and the wave band .

6. The on-orbit relative radiometric calibration method of a focal plane polarimetric remote sensing instrument according to claim 5, wherein S4 Comprising: S4.1, set up the fitting equation with reference to the vector radiance transfer model of S1 : ； wherein , , , , are parameters in the fitting equation; is the argument of the function, representing each yaw sampling angle; S4.2, for each pixel , according to , the fitting equation of S4.1 , with the yaw angle as the independent variable, the corresponding as the dependent variable, the data fitting method is used to obtain the parameters ; S4.3, the parameters obtained according to S4.2 , in combination with the vector radiance transfer model of S1, calculate the intermediate process parameters , the on-orbit relative response coefficient , and the incident light intensity ;​ ； S4.4, repeating S4.1-4.3 for all pixels of the full image plane; S4.5, using the intermediate process parameters of each pixel Divide by the intermediate process parameter of the absolute radiometric calibration reference pixel Obtain the final on-orbit relative response coefficients .

7. The method of on-orbit relative radiometric calibration of a focal plane polarimetric remote sensing instrument according to claim 6, wherein, In step 4.5, the final on-track relative response coefficient is: 。 8. An on-orbit relative radiometric calibration device for a focal plane polarimetric remote sensing instrument, characterized in that, Comprising: A vector radiometric measurement model construction module, which constructs a vector radiometric measurement model of the focal plane polarization remote sensing instrument, the construction process considering the radiation and polarization characteristics of the optical lens and the focal plane polarization array comprehensively; A data acquisition module, which collects on-orbit relative radiometric calibration data based on attitude maneuvering; A data preprocessing module, which performs observation data preprocessing; A calibration module, which performs on-orbit relative response coefficient calibration.

9. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to implement the steps of the on-orbit relative radiometric calibration method of the focal plane polarization remote sensing instrument according to any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the on-orbit relative radiometric calibration method of the focal plane polarization remote sensing instrument according to any one of claims 1 to 7.

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