A method, apparatus, and storage medium for calculating the optical properties of a spacecraft surface.

Abstract

This invention provides a method, apparatus, and storage medium for calculating the optical properties of a spacecraft surface. The method includes: Step 1, analyzing the optical properties of the micro / nano structures on the spacecraft surface to obtain the absorbance of the surface micro / nano structures; Step 2, obtaining new material information of the spacecraft surface elements; Step 3, performing element-based processing on the complex surface of the spacecraft to obtain the spacecraft element normal and solar vector information in the J2000 coordinate system; Step 4, performing hidden surface removal judgment on the solar vector and element normal to obtain effective element information; Step 5, calculating the optical scattering characteristics of the effective elements to obtain the optical cross-sectional area of ​​the elements; Step 6, summing the optical cross-sectional areas of all elements to obtain the overall optical cross-sectional area of ​​the spacecraft, and calculating the apparent magnitude to obtain the optical properties of the spacecraft. This invention has the advantage of high calculation accuracy and can achieve accurate calculation of the optical properties of the spacecraft surface.

Description

Technical Field

[0001] This invention relates to the field of aerospace optics, and in particular to a method, apparatus, and storage medium for calculating the optical properties of spacecraft surfaces. Background Technology

[0002] With the continuous development of on-orbit detection technology, current spacecraft on-orbit detection has evolved into a comprehensive detection system encompassing radar, optics, infrared, and laser technologies. Especially for high-orbit, high-value spacecraft, the primary detection threat is optical detection. Therefore, research on the optical scattering characteristics and optical design of high-orbit satellites is of great strategic significance for detecting enemy high-value satellites, concealing our own capabilities, penetrating enemy space optical detection and surveillance systems, seizing space superiority, and ensuring national security.

[0003] Spacecraft optical technology refers to a comprehensive set of techniques employed to reduce the detectability of spacecraft by visible light. The aim is to minimize the probability of interception by enemy detection systems or significantly shorten their detection range, thereby improving the spacecraft's survivability. There are three main types of spacecraft optical techniques: configuration (reducing the optical cross-section, OCS, to lower the probability of detection); materials (coating with optical absorbing coatings or installing optical absorbing materials); and maneuvering (adjusting attitude to prevent sunlight from reflecting in the observation direction). Attitude maneuvering, however, is highly dependent on the platform's capabilities and has significant limitations. Current research primarily focuses on configuration and materials.

[0004] However, current research on the scattering characteristics of spacecraft is limited and mostly focuses on macroscopic optical properties, neglecting the influence of spacecraft surface structures on the optical properties of the spacecraft itself. This results in inaccurate modeling of the optical properties of spacecraft surfaces. Therefore, existing technologies lack an algorithm for evaluating the optical properties of spacecraft surfaces that can accurately calculate the optical properties of spacecraft and achieve effective performance evaluation. Summary of the Invention

[0005] Objective of the Invention: The technical problem to be solved by this invention is to address the shortcomings of existing technologies by providing a method for calculating the optical properties of spacecraft surfaces. This method enables the calculation and analysis of the optical properties of spacecraft, significantly improving the accuracy of performance evaluation and achieving precise modeling of the optical properties of spacecraft surfaces. To achieve the above objective, this invention adopts the following technical solution:

[0006] A method for calculating the optical properties of a spacecraft surface includes the following steps:

[0007] Step 1: Analyze the optical properties of the micro / nano structures on the spacecraft surface using the finite-difference time-domain method to obtain the absorbance A of the surface micro / nano structures. bs ;

[0008] Step 2: Measure the absorbance A of the surface micro / nano structure.bs By multiplying the coefficients, the material information fr of the spacecraft is assigned, resulting in the new material information of the spacecraft surface elements as (1-A). bs )fr;

[0009] Step 3: Perform surface segmentation on the complex surface of the spacecraft, such as by segmenting the surface using 3Dmax, and obtain the spacecraft surface normal and solar vector information in the J2000 coordinate system through coordinate system transformation.

[0010] Step 4: Perform hidden surface removal judgment on the solar vector and the surface element normal to obtain the effective surface element information;

[0011] Step 5: Calculate the optical scattering characteristics of the effective surface element to obtain the optical cross-sectional area of ​​the surface element;

[0012] Step 6: Sum the optical cross-sectional areas of all surface elements to obtain the overall optical cross-sectional area of ​​the spacecraft, and calculate the apparent magnitude to obtain the optical characteristics of the spacecraft.

[0013] In step 1, the analysis of the optical properties of the micro / nano structures on the spacecraft surface includes performing three-dimensional modeling of the micro / nano structures in optical property analysis software (such as FDTD Solutions) and calculating the absorbance A of the surface micro / nano structures using the finite-time difference method. bs .

[0014] In step 3, by reading the OBJ format file obtained by the surface segmentation software (such as 3Dmax), the surface material information after adding microstructure absorbance and the surface normal information in the system are obtained. Then, based on the six roots of the spacecraft orbit, the position vector information of the spacecraft at each moment is obtained by recursively deriving the orbital dynamics equation, and the rotation matrix from the system to the J2000 coordinate system is obtained, thereby obtaining the surface normal and solar vector information in the J2000 coordinate system.

[0015] Step 4 includes:

[0016] First, self-occlusion is determined using the vector method to initially filter the effective surface elements; the self-occlusion determination criteria include:

[0017] The angle between the solar vector and the surface element normal is greater than 90°, meaning that sunlight does not illuminate the surface element;

[0018] If the angle between the observation vector and the surface element normal is greater than 90°, it means the detector did not observe any surface element.

[0019] If a face element meets either of the above two conditions, it is determined to be an invalid face element and deleted. Then, the remaining face elements are judged to be mutually occluded according to the Z-buffer hidden surface removal algorithm to obtain the final valid face elements. The judgment condition is: under the same line of sight, the face element with the largest depth value is the valid face element.

[0020] Step 5 includes: calculating the optical cross section (OCS) S of the surface element using the following formula. ocs :

[0021]

[0022] Among them, f r A is the bidirectional reflection distribution function of the surface element; bs dA represents the light absorption rate of the surface microstructure. k Let θ be the area of ​​the k-th facet, and n represent the total number of facets; i θ is the incident zenith angle, which is the angle between the solar vector and the surface element normal vector N; r The zenith angle is the angle between the observation vector and the surface element normal vector N. For the observation azimuth angle, i.e., the solar vector I and the observation vector D in the surface element dA k The angle between the downward projections I' and D';

[0023] f r The calculation formula is shown in (4):

[0024]

[0025] Where ρ d ρ is the diffuse reflectance coefficient of the material; s α is the specular reflection coefficient of the material; α is the mirror index; cosθ i The introduced diffuse reflection term is used to adjust the reflection intensity of the mirror; β is the angle between the observation direction and the mirror reflection direction, β=min{π / 2,β}; the intermediate parameter a>0 is used to adjust the intensity of the Fresnel phenomenon; the intermediate parameter b>0 is used to adjust the increase and decrease rate of the mirror reflection component.

[0026] Step 6 includes: using the Sun as a reference, given that the Sun's apparent magnitude is -26.74, then after obtaining S... ocs Then, the apparent magnitude m is:

[0027]

[0028] Where R is the distance from the observation point to the space target.

[0029] The present invention also provides a device for calculating the optical properties of a spacecraft surface, comprising:

[0030] The absorbance calculation module is used to analyze the optical properties of micro / nano structures on the spacecraft surface using the finite-difference time-domain method, and to obtain the absorbance A of the surface micro / nano structures. bs ;

[0031] The surface element material information calculation module is used to calculate the absorbance A of the surface micro / nano structure. bs By multiplying the coefficients, the material information fr of the spacecraft is assigned, resulting in the new material information of the spacecraft surface elements as (1-A). bs )fr;

[0032] The surface element processing module is used to perform surface element processing on the complex surface of the spacecraft. Through coordinate system transformation, it obtains the spacecraft surface element normal and solar vector information in the J2000 coordinate system.

[0033] The effective surface element information acquisition module is used to perform hidden surface removal judgment on the solar vector and the surface element normal to obtain the effective surface element information;

[0034] The surface element optical cross-sectional area calculation module is used to calculate the optical scattering characteristics of effective surface elements and obtain the surface element optical cross-sectional area.

[0035] The optical characteristics calculation module for spacecraft is used to accumulate the optical cross-sectional areas of all surface elements to obtain the overall optical cross-sectional area of ​​the spacecraft, and to calculate the apparent magnitude to obtain the optical characteristics of the spacecraft.

[0036] The present invention also provides a storage medium storing a computer program or instructions, which, when the computer program or instructions are run, implement the aforementioned method for calculating the optical properties of a spacecraft surface.

[0037] The beneficial effects of this invention are:

[0038] Currently, there is limited research on the optics of high-orbit spacecraft. This invention proposes a method for calculating the optical properties of spacecraft surfaces, which comprehensively considers the overall and surface characteristics of the spacecraft. It achieves modeling of optical scattering characteristics across macro and micro scales, and provides more accurate solutions for the optical properties of spacecraft, thus providing a design basis for the subsequent design of high-orbit optical spacecraft. Attached Figure Description

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0040] Figure 1 This is a flowchart of the method of the present invention.

[0041] Figure 2a This is a diagram showing the effect of the height parameter of the V-groove array structure on absorbance.

[0042] Figure 2b This is a diagram showing the influence of the V-groove array structure base parameters on absorbance.

[0043] Figure 2c This is a diagram showing the effect of the periodic parameters of the V-groove array structure on absorbance.

[0044] Figure 3 This is a schematic diagram of the optical cross-sectional area variation of a surface element.

[0045] Figure 4 This is a schematic diagram for determining effective surface element occlusion.

[0046] Figure 5a This is a schematic diagram of the simulated spacecraft model and its coordinate system.

[0047] Figure 5b This is a comparison chart of simulation results for the optical cross-sectional area of ​​a spacecraft.

[0048] Figure 5c This is a comparison chart of spacecraft magnitude simulation results. Detailed Implementation

[0049] This invention proposes a method for calculating the optical properties of a spacecraft surface, the process of which is as follows: Figure 1 As shown, this invention significantly improves the accuracy of performance evaluation by enabling the calculation and analysis of the optical properties of spacecraft, and achieves precise modeling of the optical properties of spacecraft surfaces.

[0050] The specific process of this invention includes:

[0051] 1. The optical properties of the surface are analyzed using the finite-difference time-domain method to calculate its absorbance. The optical focus is on the visible light band. In this embodiment, the wavelength range is 400nm-800nm, and the light source type is a plane wave. Some results are shown below. Figure 2a , Figure 2b , Figure 2c As shown.

[0052] 2. Reconstructing the 3D model of the spacecraft and obtaining the material and normal information of the surface elements. In this embodiment, the 3D model of the spacecraft is divided into surface elements by 3Dmax and exported as OBJ format. Then, the surface element information of the spacecraft is read by MATLAB to realize model reconstruction and information acquisition.

[0053] 3. Solar Vector Acquisition: Solar vector information within the orbital system can be calculated using spacecraft orbital information. In this embodiment, the spacecraft model is as follows: Figure 5aAs shown, XYZ represents the spacecraft's intrinsic system. The six orbital coordinates of the spacecraft are set to [42166257, 0, 0, 0, 0, 0], corresponding to the semi-major axis, eccentricity, orbital inclination, right ascension of the ascending node, perigee depression angle, and true anomaly angle, respectively. The observation vector coincides with the Z-axis direction of the spacecraft's intrinsic system ([0, 0, 1]), which is the sub-satellite point of the observation station on the equator. Considering the periodic change of the solar vector within a day, the simulation duration is set to 48 hours with a step size of 0.5 hours; the epoch times are [2020, 9, 10, 0, 0, 0, 0], corresponding to year, month, day, hour, minute, second, and microsecond, respectively. The spacecraft's three axes are stable relative to the Earth's three axes, meaning that the coordinates of the intrinsic system coincide with the coordinates of the orbital system. Therefore, the solar vector under the orbital system is also the solar vector under the intrinsic system. If there are attitude maneuvers, the orbital solar vector can be easily projected onto the intrinsic system through the attitude matrix.

[0054] 4. Valid Element Judgment: This involves determining whether an element is occluded. Occluded elements are invalid and should be discarded during calculation. Occlusion includes both self-occlusion and mutual occlusion. Self-occlusion is determined by whether an element is exposed to sunlight, such as... Figure 4 As shown in the figure on the left, i is the incident solar vector and n is the normal vector of the surface element. The occlusion determination uses a vector-based method, as shown in formula (1):

[0055] i·n>0 (1)

[0056] Mutual occlusion means determining whether face A is occluded by face B, such as... Figure 4 As shown in the figure on the right, the mutual occlusion situation is relatively complex. The Z-buffer algorithm, a hidden surface removal algorithm in computer graphics, is used for judgment, as shown in formula (2):

[0057] z = max{z(x,y)|(x,y)∈l} (2)

[0058] In the formula, z represents the depth value of the surface element, l is the line-of-sight vector, and max indicates that the surface element with the largest depth value is taken as the effective surface element.

[0059] 5. Calculation of Optical Cross Section (OCS): The OCS of a space target depends only on the target's surface characteristics, geometry, size, solar vector, and observation vector. These relationships are as follows: Figure 3 As shown, xyz is the J2000 coordinate system, detector represents the detector, dA represents the surface element, and the calculation formula is shown in formula (3):

[0060]

[0061] Where f r A is the bidirectional reflectance distribution function (BRDF) of a surface element, which is a function describing the surface material properties;bs dA represents the light absorption rate of the surface microstructure. k Let θ be the area of ​​the k-th element; i θ is the incident zenith angle, which is the angle between the solar vector and the surface element normal vector N; r The zenith angle is the angle between the observation vector and the surface element normal vector N. For the observation azimuth angle, i.e., the solar vector I and the observation vector D in the surface element dA k The angle between the lower projections I' and D'.

[0062] In OCS calculations, the selection of the bidirectional reflection distribution function (BRDF) model for the surface element is crucial. Here, the improved Phong model for Fresnel reflection is adopted, as shown in Equation (4):

[0063]

[0064] Where ρ d ρ is the diffuse reflectance coefficient of the material; s α is the specular reflection coefficient of the material; α is the mirror index; cosθ i A modified diffuse reflection term is introduced to adjust the reflection intensity of the mirror; β is the angle between the observation direction and the mirror reflection direction, β = min{π / 2, β}; a > 0 to adjust the intensity of the Fresnel effect; b > 0 to adjust the rate of increase and decrease of the specular reflection component. The overall OCS of the simulated spacecraft is as follows: Figure 5b As shown, by comparing the effects of adding or not adding surface structures, it is found that the overall optical properties of the spacecraft differ significantly depending on whether or not surface structures are added. Therefore, the optical property analysis of surface micro- and nano-structures is necessary.

[0065] 6. Calculation of overall optical characteristics: Combining formulas (3) and (4), the overall optical cross-sectional area S of the spacecraft can be calculated. ocs And calculate the apparent magnitude using formula (5), with the Sun as a reference. Given that the Sun's apparent magnitude is -26.74, then obtain S... ocs Subsequently, its apparent magnitude is:

[0066]

[0067] Where R is the distance from the observation point to the space target. From formula (5), it can be seen that the larger the apparent magnitude, the dimmer the target; the smaller the apparent magnitude, the brighter the target. Finally, the optical characteristics of the spacecraft are obtained. The equivalent apparent magnitude of the simulated spacecraft is as follows: Figure 5c As shown, it can be seen that the spacecraft before and after the additional structure differs by 5 magnitudes.

[0068] This embodiment also provides a spacecraft surface optical property calculation device, including:

[0069] The absorbance calculation module is used to analyze the optical properties of micro / nano structures on the spacecraft surface using the finite-difference time-domain method, and to obtain the absorbance A of the surface micro / nano structures. bs ;

[0070] The surface element material information calculation module is used to calculate the absorbance A of the surface micro / nano structure. bs By multiplying the coefficients, the material information fr of the spacecraft is assigned, resulting in the new material information of the spacecraft surface elements as (1-A). bs )fr;

[0071] The surface element processing module is used to perform surface element processing on the complex surface of the spacecraft. Through coordinate system transformation, it obtains the spacecraft surface element normal and solar vector information in the J2000 coordinate system.

[0072] The effective surface element information acquisition module is used to perform hidden surface removal judgment on the solar vector and the surface element normal to obtain the effective surface element information;

[0073] The surface element optical cross-sectional area calculation module is used to calculate the optical scattering characteristics of effective surface elements and obtain the surface element optical cross-sectional area.

[0074] The optical characteristics calculation module for spacecraft is used to accumulate the optical cross-sectional areas of all surface elements to obtain the overall optical cross-sectional area of ​​the spacecraft, and to calculate the apparent magnitude to obtain the optical characteristics of the spacecraft.

[0075] This embodiment also provides a storage medium storing a computer program or instructions, which, when executed, implements the aforementioned method for calculating the optical properties of a spacecraft surface.

[0076] Those skilled in the art will clearly understand that the technical solutions in the embodiments of the present invention can be implemented using computer programs and their corresponding general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of computer programs, i.e., software products. These computer program software products can be stored in a storage medium and include several instructions to cause a device containing a data processing unit (which may be a personal computer, server, microcontroller, MUU, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0077] This invention provides a method, apparatus, and storage medium for calculating the optical properties of a spacecraft surface. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for calculating the optical properties of a spacecraft surface, characterized in that, Includes the following steps: Step 1: Analyze the optical properties of the micro / nano structures on the spacecraft surface using the finite-difference time-domain method to obtain the absorbance A of the surface micro / nano structures. bs ; Step 2: Measure the absorbance A of the surface micro / nano structure. bs By multiplying the coefficients, the material information fr of the spacecraft is assigned, resulting in the new material information of the spacecraft surface elements as (1-A). bs )fr; Step 3: Perform surface element processing on the complex surface of the spacecraft, and obtain the spacecraft surface element normal and solar vector information in the J2000 coordinate system through coordinate system transformation; Step 4: Perform hidden surface removal judgment on the solar vector and the surface element normal to obtain the effective surface element information; Step 5: Calculate the optical scattering characteristics of the effective surface element to obtain the optical cross-sectional area of ​​the surface element; Step 5 includes: calculating the optical cross-sectional area of ​​the surface element using the following formula. : ， Among them, f r A is the bidirectional reflection distribution function of the surface element; bs dA represents the light absorption rate of the surface microstructure. k Let θ be the area of ​​the k-th facet, and n represent the total number of facets; i θ is the incident zenith angle, which is the angle between the solar vector and the surface element normal vector N; r The zenith angle is the angle between the observed vector and the surface element normal vector N; φ is the azimuth angle, which is the angle between the solar vector I and the observed vector D on surface element dA. k The angle between the downward projections I' and D'; f r The calculation formula is as follows: ， in denoted as the diffuse reflectance coefficient of the material; denoted as the specular reflectance coefficient of the material; This is a mirror index; The introduced diffuse reflection correction term is used to adjust the reflection intensity of the mirror; β is the angle between the observation direction and the mirror reflection direction, β = min{π / 2, β}; the intermediate parameter a > 0 is used to adjust the intensity of the Fresnel phenomenon; the intermediate parameter b > 0 is used to adjust the increase and decrease rate of the specular reflection component. Step 6: Sum the optical cross-sectional areas of all surface elements to obtain the overall optical cross-sectional area of ​​the spacecraft, and calculate the apparent magnitude to obtain the optical characteristics of the spacecraft.

2. The method according to claim 1, characterized in that, In step 1, the analysis of the optical properties of the micro / nano structures on the spacecraft surface includes performing three-dimensional modeling of the micro / nano structures in optical property analysis software and calculating the absorbance A of the surface micro / nano structures using the finite-time difference method. bs .

3. The method according to claim 2, characterized in that, In step 3, by reading the OBJ format file obtained by the surface segmentation software, the surface material information after adding microstructure absorbance and the surface normal information of the system are obtained. Then, based on the six orbital roots of the spacecraft, the position vector information of the spacecraft at each moment is obtained by recursively deriving the orbital dynamics equation, and the rotation matrix from the system to the J2000 coordinate system is obtained, thereby obtaining the surface normal and solar vector information in the J2000 coordinate system.

4. The method according to claim 3, characterized in that, Step 4 includes: First, self-occlusion is determined using the vector method to initially filter the effective surface elements; the self-occlusion determination criteria include: The angle between the solar vector and the surface element normal is greater than 90°, meaning that sunlight does not illuminate the surface element; If the angle between the observation vector and the surface element normal is greater than 90°, it means the detector did not observe any surface element. If a face element meets either of the above two conditions, it is determined to be an invalid face element and deleted. Then, the remaining face elements are judged to be mutually occluded according to the Z-buffer hidden surface removal algorithm to obtain the final valid face elements. The judgment condition is: under the same line of sight, the face element with the largest depth value is the valid face element.

5. The method according to claim 4, characterized in that, Step 6 includes: using the Sun as a reference, given that the Sun's apparent magnitude is -26.74, then after obtaining S... ocs Then, the apparent magnitude m is: ， Where R is the distance from the observation point to the space target.

6. A spacecraft surface optical property calculation device based on the method described in any one of claims 1 to 5, characterized in that, include: The absorbance calculation module is used to analyze the optical properties of micro / nano structures on the spacecraft surface using the finite-difference time-domain method, and to obtain the absorbance A of the surface micro / nano structures. bs ; The surface element material information calculation module is used to calculate the absorbance A of the surface micro / nano structure. bs By multiplying the coefficients, the material information fr of the spacecraft is assigned, resulting in the new material information of the spacecraft surface elements as (1-A). bs )fr; The surface element processing module is used to perform surface element processing on the complex surface of the spacecraft. Through coordinate system transformation, it obtains the spacecraft surface element normal and solar vector information in the J2000 coordinate system. The effective surface element information acquisition module is used to perform hidden surface removal judgment on the solar vector and the surface element normal to obtain the effective surface element information; The surface element optical cross-sectional area calculation module is used to calculate the optical scattering characteristics of effective surface elements and obtain the surface element optical cross-sectional area. The optical characteristics calculation module for spacecraft is used to accumulate the optical cross-sectional areas of all surface elements to obtain the overall optical cross-sectional area of ​​the spacecraft, and to calculate the apparent magnitude to obtain the optical characteristics of the spacecraft.

7. A storage medium, characterized in that, It stores a computer program or instructions that, when executed, implement the method as described in any one of claims 1 to 5.

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