Method for Determining the Attitude of Near-Earth Space Vehicles under Strong Sky Background Conditions

Abstract

A method for determining the attitude of a near-earth space vehicle under strong sky background conditions belongs to the technical field of autonomous attitude determination of near-earth space vehicles. The present invention aims at the problem that the attitude of the vehicle cannot be effectively obtained due to the weak star detection ability and small number of detections of short-wave infrared star sensors in the near-earth space under strong sky background conditions during the day. It includes: solving the singular value of the total vector set in the vehicle coordinate system from the total vector set in the vehicle coordinate system; solving the singular value of each total vector set in the north-east-earth coordinate system from the total vector set in the north-east-earth coordinate system; solving the set of target star unit vectors corresponding to the minimum absolute difference between the two singular values; forming a target vector set by the set of target star unit vectors in the north-east-earth coordinate system, the solar unit vector in the north-east-earth coordinate system, and the zenith unit vector in the north-east-earth coordinate system; and finally solving the optimal attitude matrix of the vehicle and calculating the three-axis attitude angles of the vehicle. The present invention is used for the autonomous determination of the attitude of near-earth space vehicles.

Description

Technical Field

[0001] The present invention relates to a method for determining the attitude of a near-earth space vehicle under strong sky background conditions, and belongs to the technical field of autonomous attitude determination of near-earth space vehicles. Background Art

[0002] A star sensor is the optical instrument with the highest attitude measurement accuracy on spacecraft so far. It mainly consists of an optical system, an image sensor, and a control and data processing circuit. The image sensor captures the starry sky image pointed by the optical axis, extracts the position information of star points through signal processing, then finds the matching observed stars in the navigation star library through a star map recognition algorithm, and finally calculates the three-axis attitude of the vehicle using the direction vector information of these matching star pairs. Due to the influence of the complex atmospheric environment, the star sensor is difficult to work effectively near the ground. In recent years, with the continuous development of star-inertial integrated navigation technology and short-wave infrared imaging technology, the near-earth space short-wave infrared star sensor that can be applied to ships, tanks, airplanes, etc. has become a current research hotspot. It can update and calibrate the output attitude of the inertial navigation system, and can even complete autonomous attitude determination independently of the inertial navigation system, greatly improving its navigation accuracy and reliability.

[0003] If we want to realize the attitude solution of the vehicle within the atmosphere, at least 3 stars that can be detected by the star sensor are required. The strong sky background radiation during the day will reduce the signal-to-noise ratio of star detection. Therefore, the near-earth space short-wave infrared star sensor generally adopts an optical design scheme with a small field of view and a large aperture to ensure its high star sensitivity ability; considering the limited installation space of the vehicle or platform where the star sensor is located, the focal length and aperture of the optical system of the designed near-earth space short-wave infrared star sensor should not be too large to ensure its light weight and small volume. In addition, the direct sunlight and cloud occlusion will also interfere with the star imaging, that is, when the optical axis direction of the star sensor is within the sun avoidance angle or the field of view is covered by clouds, it will cause a serious decline in the star detection ability of the system. Therefore, it is difficult to ensure that the number of stars that can be detected by the near-earth space short-wave infrared star sensor is not less than 3 under any optical axis direction. Summary of the Invention

[0004] Aiming at the problem that the attitude of the vehicle cannot be effectively obtained due to the weak star detection ability and small number of detected stars of the near-earth space short-wave infrared star sensor under strong sky background conditions during the day, the present invention provides a method for determining the attitude of a near-earth space vehicle under strong sky background conditions.

[0005] A method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to the present invention includes:

[0006] Step 1: Obtain the set of stellar unit vectors in the body coordinate system, the solar unit vector in the body coordinate system based on the all-sky polarization angle, and the zenith unit vector in the body coordinate system based on the all-sky polarization angle, form the set of total vectors in the body coordinate system, and solve for the singular values of the set of total vectors in the body coordinate system;

[0007] Step 2: Obtain multiple sets of stellar unit vectors in the north-east-down coordinate system, the solar unit vector in the north-east-down coordinate system, and the zenith unit vector in the north-east-down coordinate system, form multiple sets of total vectors in the north-east-down coordinate system, and solve for the singular values of each set of total vectors in the north-east-down coordinate system;

[0008] Step 3: Calculate the absolute difference between the singular values of the set of total vectors in the body coordinate system and the singular values of each set of total vectors in the north-east-down coordinate system. When the absolute difference is the smallest, the set of stellar unit vectors in the north-east-down coordinate system is used as the target set of stellar unit vectors in the north-east-down coordinate system;

[0009] Step 4: Combine the target set of stellar unit vectors in the north-east-down coordinate system with the solar unit vector in the north-east-down coordinate system and the zenith unit vector in the north-east-down coordinate system to form the target vector set;

[0010] Step 5: Transpose each target vector in the target vector set and multiply it by the corresponding vector in the set of total vectors in the body coordinate system respectively, then sum them up to obtain the intermediate matrix, and then perform singular value decomposition on the intermediate matrix to obtain the optimal attitude matrix of the body;

[0011] Step 6: Calculate the three-axis attitude angles of the body according to the optimal attitude matrix of the body.

[0012] According to the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention,

[0013] The set of total vectors in the body coordinate system in Step 1 is denoted as M b :

[0014] In the formula, S b is the set of stellar unit vectors in the body coordinate system, is the stellar unit vector of the k-th star in the body coordinate system, k is the total number of stellar vectors, and b is the body coordinate system;

[0015] is the solar unit vector in the body coordinate system based on the all-sky polarization angle, and aop represents the all-sky polarization angle image;

[0016] is the zenith unit vector in the body coordinate system based on the all-sky polarization angle.

[0017] The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to the present invention is based on the solar unit vector in the vehicle coordinate system based on the all-sky polarization angle and the zenith unit vector in the vehicle coordinate system based on the all-sky polarization angle The acquisition method is as follows:

[0018] Use an all-sky polarimeter to obtain an all-sky polarization degree image, and obtain the solar unit vector in the vehicle coordinate system based on the all-sky polarization degree from the all-sky polarization degree image dop represents the all-sky polarization degree image;

[0019] Use an all-sky polarimeter to obtain an all-sky polarization angle image, and obtain two sets of unit vectors from the all-sky polarization angle image; combine the solar unit vector in the vehicle coordinate system based on the all-sky polarization degree Distinguish the two sets of unit vectors into the solar unit vector in the vehicle coordinate system based on the all-sky polarization angle and the zenith unit vector in the vehicle coordinate system based on the all-sky polarization angle

[0020] According to the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention, the singular value of the total vector set in the vehicle coordinate system obtained in step one is Σ b :

[0021]

[0022] In the formula represents the i-th singular value in the vehicle coordinate system; i is the total number of singular values.

[0023] According to the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention, in step two, k stars are selected multiple times from the short-wave infrared navigation star catalog with the field of view size of the star sensor as the constraint condition. The star unit vector sets of the k stars selected each time in the north-east-earth coordinate system are represented as j represents the j-th star, j = 1, 2,..., k; n represents the north-east-earth coordinate system;

[0024] Each total vector set in the north-east-earth coordinate system is represented as

[0025]

[0026] In the formula S n is the solar unit vector in the north-east-earth coordinate system, and Z n is the zenith unit vector in the north-east-earth coordinate system;

[0027] Solve the singular value of each total vector set in the north-east-earth coordinate system as

[0028]

[0029] It represents the i-th singular value in the vehicle coordinate system.

[0030] According to the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention, the set of unit vectors of stars S in the vehicle coordinate system b is a k×3-dimensional matrix, and the value of k is not less than 1;

[0031] The unit vector of the sun in the vehicle coordinate system based on the degree of polarization of the entire sky is a 1×3-dimensional matrix, which is obtained by using the Fuzzy-C-Mean clustering algorithm in the degree-of-polarization image of the entire sky;

[0032] The unit vector of the sun in the vehicle coordinate system based on the polarization angle of the entire sky and the unit vector of the zenith in the vehicle coordinate system based on the polarization angle of the entire sky are both 1×3-dimensional matrices; the two sets of unit vectors obtained from the polarization angle image of the entire sky are obtained from the two common intersection points of the polarization angle contour lines in the polarization angle image of the entire sky.

[0033] According to the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention, the total vector set in the vehicle coordinate system is denoted as M b , which is a (k + 2)×3-dimensional matrix;

[0034] The set of unit vectors of stars in the north-east-earth coordinate system is denoted as which is a k×3-dimensional matrix;

[0035] The total vector set in the north-east-earth coordinate system is a (k + 2)×3-dimensional matrix. The unit vector of the sun S in the north-east-earth coordinate system n is obtained from the astronomical almanac, and the unit vector of the zenith Z in the north-east-earth coordinate system n is [0 0 -1].

[0036] According to the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention, the absolute difference between singular values in step three is denoted as D j :

[0037]

[0038] The set of unit vectors of target stars in the north-east-earth coordinate system is denoted as C n , which is a k×3-dimensional matrix;

[0039] The target vector set is denoted as M n :

[0040] Mn = [C n ; S n ; Z n .

[0041] According to the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention, the method for obtaining the optimal attitude matrix of the vehicle in step five is as follows:

[0042] Calculate the intermediate matrix X:

[0043]

[0044] where is the g-th vector in the total vector set M b in the vehicle coordinate system, is the g-th target vector in the target vector set M n ;

[0045] The relationship between b and M

[0046]

[0047] The relationship between n and M

[0048]

[0049] M b The relationship between n and M

[0050]

[0051] where is the attitude matrix:

[0052]

[0053] where θ represents the pitch angle of the vehicle, φ represents the roll angle of the vehicle, and ψ represents the yaw angle of the vehicle;

[0054] Perform equivalent corresponding substitution on the elements in the attitude matrix :

[0055]

[0056] The optimal attitude matrix of the vehicle is expressed as A:

[0057]

[0058] where U represents the left singular matrix and V represents the right singular matrix,

[0059] U, V T The relationship with the intermediate matrix X is:

[0060]

[0061] In the formula, Σ represents the singular value.

[0062] According to the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention, the calculation method of the three-axis attitude angles of the vehicle is:

[0063]

[0064] Advantages of the present invention: The method of the present invention jointly uses short-wave infrared stars and sky polarization characteristics for attitude determination of near-earth space vehicles. It can ensure the effective output of three-axis attitudes even under the condition that only a single star is detected by the star sensor. The method of the present invention has strong adaptability to the strong sky background radiation environment during the day and can be used for attitude acquisition of vehicles or platforms such as ships, tanks, and airplanes, improving their navigation accuracy and reliability.

[0065] The method of the present invention improves the navigation robustness and stability of near-earth space vehicles and can provide a theoretical basis and technical support for the engineering application of short-wave infrared star sensors on tanks, ships, and airplanes in near-earth space. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 is a flowchart of the method for determining the attitude of a near-earth space vehicle under strong sky background conditions of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0067] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0068] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0069] Next, the present invention will be further described in conjunction with the accompanying drawings and specific embodiments, but it is not a limitation of the present invention.

[0070] DETAILED DESCRIPTION OF THE INVENTION I. In combination with Figure 1 As shown, the present invention provides a method for determining the attitude of a near-earth space vehicle under strong sky background conditions, including

[0071] Step 1: Obtain the set of stellar unit vectors in the vehicle coordinate system, the solar unit vector in the vehicle coordinate system based on the all-sky polarization angle, and the zenith unit vector in the vehicle coordinate system based on the all-sky polarization angle, form the set of total vectors in the vehicle coordinate system, and solve the singular values of the set of total vectors in the vehicle coordinate system;

[0072] Step 2: Obtain multiple sets of stellar unit vectors in the north-east-down coordinate system, the solar unit vector in the north-east-down coordinate system, and the zenith unit vector in the north-east-down coordinate system, form multiple sets of total vectors in the north-east-down coordinate system, and solve the singular values of each set of total vectors in the north-east-down coordinate system;

[0073] Step 3: Calculate the absolute difference between the singular values of the set of total vectors in the vehicle coordinate system and the singular values of each set of total vectors in the north-east-down coordinate system. When the absolute difference is the smallest, the set of stellar unit vectors in the north-east-down coordinate system is used as the target set of stellar unit vectors in the north-east-down coordinate system;

[0074] Step 4: Combine the target set of stellar unit vectors in the north-east-down coordinate system with the solar unit vector in the north-east-down coordinate system and the zenith unit vector in the north-east-down coordinate system to form a target vector set;

[0075] Step 5: Transpose each target vector in the target vector set and multiply it with the corresponding vector in the set of total vectors in the vehicle coordinate system respectively, then sum them to obtain an intermediate matrix, and then perform singular value decomposition on the intermediate matrix to obtain the optimal attitude matrix of the vehicle;

[0076] Step 6: Calculate the three-axis attitude angles of the vehicle according to the optimal attitude matrix of the vehicle.

[0077] In addition to the intensity attribute, the daytime sky background also has a significant polarization pattern, including the all-sky polarization degree and the all-sky polarization angle. Some relatively stable polarization characteristics are contained in the all-sky polarization pattern. For example, the polarization degree at the position of the sun in the all-sky polarization degree is 0; any two contour lines in the all-sky polarization angle intersect at the position of the sun and the position of the zenith. The sun and the zenith can be equivalently regarded as stars and further used for solving the attitude of the vehicle. Even under the condition that only one bright star can be detected by the short-wave infrared star sensor in near-earth space in this embodiment, the real-time and effective output of the vehicle attitude information can be ensured.

[0078] Further, the set of total vectors in the vehicle coordinate system in Step 1 is represented as M b :

[0079]

[0080] In the formula, S b is the set of stellar unit vectors in the vehicle coordinate system. The stellar image is obtained by using the short-wave infrared star sensor in near-earth space, and the set of stellar unit vectors S in the vehicle coordinate system is obtained from the stellar image b ; is the unit vector of the k-th star in the vehicle coordinate system, where k is the total number of star vectors and b is the vehicle coordinate system;

[0081] is the unit vector of the sun in the vehicle coordinate system based on the all-sky polarization angle, and aop represents the all-sky polarization angle image;

[0082] is the unit vector of the zenith in the vehicle coordinate system based on the all-sky polarization angle.

[0083] In this embodiment, M b can be further expressed as:

[0084]

[0085] In the formula is the (k + 2)-th vector in the total vector set in the vehicle coordinate system.

[0086] The unit vector of the sun in the vehicle coordinate system based on the all-sky polarization angle and the unit vector of the zenith in the vehicle coordinate system based on the all-sky polarization angle are obtained as follows:

[0087] Use an all-sky polarimeter to obtain an all-sky polarization degree image, and obtain the unit vector of the sun in the vehicle coordinate system based on the all-sky polarization degree from the all-sky polarization degree image dop represents the all-sky polarization degree image;

[0088] Use an all-sky polarimeter to obtain an all-sky polarization angle image, and obtain two sets of unit vectors from the all-sky polarization angle image; Combine the unit vector of the sun in the vehicle coordinate system based on the all-sky polarization degree Distinguish the two sets of unit vectors as the unit vector of the sun in the vehicle coordinate system based on the all-sky polarization angle and the unit vector of the zenith in the vehicle coordinate system based on the all-sky polarization angle Among them, the two sets of unit vectors are the unit vector of the sun in the vehicle coordinate system based on the all-sky polarization angle and the unit vector of the zenith in the vehicle coordinate system based on the all-sky polarization angle However, it cannot be specifically determined in the all-sky polarization angle image and needs to be combined with to further determine.

[0089] The singular value of the total vector set in the vehicle coordinate system obtained in step one is Σ b :

[0090]

[0091] In the formula It represents the i-th singular value in the body coordinate system; i is the total number of singular values.

[0092] Furthermore, in step two, with the field of view of the star sensor as the constraint condition, k stars are selected multiple times from the short-wave infrared navigation star catalog. The set of unit vectors of the k stars selected each time in the north-east-down coordinate system is expressed as j represents the j-th star, j = 1, 2, ……, k; n represents the north-east-down coordinate system;

[0093] The total vector set in each north-east-down coordinate system is expressed as

[0094]

[0095] In the formula, S n is the unit vector of the sun in the north-east-down coordinate system, and Z n is the unit vector of the zenith in the north-east-down coordinate system;

[0096] Solve the total vector set in each north-east-down coordinate system, and the singular values are

[0097]

[0098] It represents the i-th singular value in the body coordinate system.

[0099] In this embodiment, the set of unit vectors of the stars in the body coordinate system S b is a k×3-dimensional matrix, and the value of k is not less than 1;

[0100] The unit vector of the sun in the body coordinate system based on the all-sky polarization degree is a 1×3-dimensional matrix, which is obtained by using the Fuzzy-C-Mean clustering algorithm in the all-sky polarization degree image;

[0101] The unit vector of the sun in the body coordinate system based on the all-sky polarization angle and the unit vector of the zenith in the body coordinate system based on the all-sky polarization angle are both 1×3-dimensional matrices; the two sets of unit vectors obtained from the all-sky polarization angle image are obtained from the two common intersection points of the polarization angle contour lines in the all-sky polarization angle image.

[0102] The total vector set in the body coordinate system is expressed as M b , which is a (k + 2)×3-dimensional matrix;

[0103] The set of unit vectors of the stars in the north-east-down coordinate system is expressed as which is a k×3-dimensional matrix;

[0104] The total vector set in the north-east-down coordinate system is a (k + 2)×3 dimensional matrix, and the solar unit vector S in the north-east-down coordinate system n is obtained from the astronomical almanac, and the zenith unit vector Z in the north-east-down coordinate system n is [0 0 -1].

[0105] Furthermore, the absolute difference between the singular values in step three is denoted as D j :

[0106]

[0107] The set of target star unit vectors in the north-east-down coordinate system is denoted as C n , which is a k×3 dimensional matrix;

[0108] The set of target vectors is denoted as M n :

[0109] M n = [C n ; S n ; Z n .

[0110] In this embodiment, M n can be further expressed as:

[0111]

[0112] where is the (k + 2)-th vector in the set of target vectors.

[0113] The method for obtaining the optimal attitude matrix of the carrier in step five is:

[0114] Calculate the intermediate matrix X:

[0115]

[0116] where is the g-th vector in the set of total vectors M in the carrier coordinate system b , is the g-th target vector in the set of target vectors M n ;

[0117] The relationship between b and M

[0118]

[0119] The relationship between n and M

[0120]

[0121] M b The relationship with M n is as follows:

[0122]

[0123] In the formula is the attitude matrix:

[0124]

[0125] In the formula, θ represents the pitch angle of the carrier, φ represents the roll angle of the carrier, and ψ represents the yaw angle of the carrier;

[0126] Perform equivalent corresponding substitution on the elements in the attitude matrix :

[0127]

[0128] The optimal attitude matrix of the carrier is expressed as A:

[0129]

[0130] In the formula, U represents the left singular matrix, V represents the right singular matrix,

[0131] U, V T The relationship with the intermediate matrix X is as follows:

[0132]

[0133] In the formula, Σ represents the singular value.

[0134] Finally, the calculation method of the carrier's three-axis attitude angles is:

[0135]

[0136] Although the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not depart from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can be used in other described embodiments.

Claims

1. A method for determining the attitude of a near-earth space vehicle under strong sky background conditions, characterized in that including, Step 1: Obtain the set of stellar unit vectors in the vehicle coordinate system, the solar unit vector in the vehicle coordinate system based on the full-sky polarization angle, and the zenith unit vector in the vehicle coordinate system based on the full-sky polarization angle, form the total vector set in the vehicle coordinate system, and solve the singular values of the total vector set in the vehicle coordinate system; Step 2: Obtain multiple sets of stellar unit vectors in the north-east-down coordinate system, the solar unit vector in the north-east-down coordinate system, and the zenith unit vector in the north-east-down coordinate system, form multiple total vector sets in the north-east-down coordinate system, and solve the singular values of each total vector set in the north-east-down coordinate system; Step 3: Calculate the absolute difference between the singular values of the total vector set in the vehicle coordinate system and the singular values of each total vector set in the north-east-down coordinate system. When the absolute difference is the smallest, the set of stellar unit vectors in the north-east-down coordinate system is used as the target set of stellar unit vectors in the north-east-down coordinate system; Step 4: Combine the target set of stellar unit vectors in the north-east-down coordinate system with the solar unit vector in the north-east-down coordinate system and the zenith unit vector in the north-east-down coordinate system to form the target vector set; Step 5: Transpose each target vector in the target vector set and multiply it with the corresponding vector in the total vector set in the vehicle coordinate system respectively, then sum them to obtain the intermediate matrix, and then perform singular value decomposition on the intermediate matrix to obtain the optimal attitude matrix of the vehicle; Step 6: Calculate the three-axis attitude angles of the vehicle according to the optimal attitude matrix of the vehicle.

2. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 1, characterized in that In step one, the total vector set in the carrier coordinate system is represented as M b : where S b is the set of unit vectors of stars in the vehicle coordinate system, is the unit vector of the k-th star in the vehicle coordinate system, k is the total number of star vectors, and b is the vehicle coordinate system; is the solar unit vector in the carrier coordinate system based on the all-sky polarization angle, and aop represents the all-sky polarization angle image; is the zenith unit vector in the carrier coordinate system based on the all-sky polarization angle.

3. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 2, characterized in that Solar unit vector in the vehicle coordinate system based on the full-sky polarization angle and zenith unit vector in the vehicle coordinate system based on the full-sky polarization angle are obtained by the following method: Obtain the all-sky polarization degree image using an all-sky polarimeter, and obtain the solar unit vector in the carrier coordinate system based on the all-sky polarization degree from the all-sky polarization degree image dop represents the all-sky polarization degree image; Obtain the all-sky polarization angle image using an all-sky polarimeter, and obtain two sets of unit vectors from the all-sky polarization angle image; combine the solar unit vector in the carrier coordinate system based on the all-sky polarization degree Distinguish the two sets of unit vectors into the solar unit vector in the carrier coordinate system based on the all-sky polarization angle and the zenith unit vector in the carrier coordinate system based on the all-sky polarization angle 4. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 3, characterized in that The singular values of the total vector set in the carrier coordinate system obtained in Step 1 are Σ b : where represents the i-th singular value in the carrier coordinate system; i is the total number of singular values.

5. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 4, characterized in that In step 2, k stars are selected multiple times from the short-wave infrared navigation star catalog with the field of view size of the star sensor as the constraint condition. The set of unit vectors of the k stars selected each time in the north-east-earth coordinate system is expressed as j represents the j-th star, j = 1, 2,..., k; n represents the north-east-earth coordinate system; The total vector set in each northeast local coordinate system is expressed as where S n is the solar unit vector in the north-east local coordinate system, and Z n is the zenith unit vector in the north-east local coordinate system; Solve the total vector set in each north-east local coordinate system The singular value of Denote the \(i\)-th singular value in the carrier coordinate system.

6. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 5, characterized in that The set of unit vectors of stars S in the vehicle coordinate system b is a k×3 dimensional matrix, and the value of k is not less than 1; Solar unit vector in the carrier coordinate system based on the degree of polarization of the entire sky It is a 1×3 dimensional matrix obtained by using the Fuzzy-C-Mean clustering algorithm in the degree-of-polarization image of the entire sky; Solar unit vector in the vehicle coordinate system based on the full-sky polarization angle and zenith unit vector in the vehicle coordinate system based on the full-sky polarization angle are both 1×3-dimensional matrices; the two sets of unit vectors obtained from the full-sky polarization angle image are obtained by finding the two common intersection points of the polarization angle contour lines in the full-sky polarization angle image.

7. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 6, characterized in that The total vector set in the carrier coordinate system is expressed as M b , which is a (k + 2)×3-dimensional matrix; The set of stellar unit vectors in the North-East coordinate system is expressed as which is a k×3 dimensional matrix; Total vector set in the north-east-down coordinate system is a (k + 2)×3 dimensional matrix. The solar unit vector S in the north-east-down coordinate system n is obtained from the astronomical almanac. The zenith unit vector Z in the north-east-down coordinate system n is [0 0 -1].

8. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 7, characterized in that The absolute difference between the singular values in Step 3 is denoted as D j : Express the set of unit vectors of the target star in the northeast geodetic coordinate system as C n , which is a k×3 dimensional matrix; Represent the target vector set as M n : M n = [C n ; S n ; Z n .

9. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 8, characterized in that The method for obtaining the optimal attitude matrix of the vehicle in Step 5 is: Calculate the intermediate matrix X: In the formula is the total vector set M in the carrier coordinate system b the g-th vector in it, is the target vector set M n the g-th target vector in it; The relationship with M b is as follows: The relationship with M n is as follows: M b The relationship with M n is as follows: In the formula is the attitude matrix: where θ represents the pitch angle of the vehicle, φ represents the roll angle of the vehicle, and ψ represents the yaw angle of the vehicle; Perform equivalent corresponding replacement on the elements in the attitude matrix : The optimal attitude matrix of the vehicle is expressed as A: where U represents the left singular matrix and V represents the right singular matrix, U, V T The relationship with the intermediate matrix X is as follows: where Σ represents the singular value.

10. The method for determining the attitude of a near-earth space vehicle under strong sky background conditions according to claim 9, characterized in that, The calculation method of the three-axis attitude angles of the vehicle is:

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