Satellite tracking imaging method for dynamic target

Abstract

The application discloses a satellite tracking imaging method for a dynamic target, and the method is characterized in that: according to discrete position information of the dynamic target, a curve fitting algorithm is used to perform curve fitting on the position information, so as to obtain a continuous function of the target position information about time, and then, in combination with position information of the satellite, the target attitude and the target angular velocity of the satellite tracking target at a current control time can be obtained. The application uses the discrete position information of the dynamic target to perform high-precision and high-stability tracking on the dynamic target, improves the definition of satellite camera tracking imaging for the dynamic target, and has practical significance for a satellite ground dynamic target tracking imaging task.

Description

Technical Field

[0001] This invention relates to a satellite tracking and imaging method for dynamic targets. Background Technology

[0002] When a satellite camera tracks and images a moving target, the satellite control system needs to maintain high accuracy to ensure the target is centered in the field of view and high stability to ensure clear imaging. Currently, satellites typically track targets that are stationary relative to the ground or moving slowly, and the target attitude input, i.e., the target's spatial position information, is a fixed value or a continuously slowly varying value relative to the Earth's fixed frame. However, existing tracking methods are no longer suitable for tracking moving targets, mainly for the following reasons:

[0003] 1. The spatial position information of dynamic targets acquired by satellites is generally discrete, and the time interval between acquisitions of target information is uneven. This results in the satellite attitude control system using inaccurate target position information within the control cycle, leading to low tracking accuracy.

[0004] 2. The spatial position information of dynamic targets acquired by satellites is generally discrete, and the time interval between acquisitions of target information is uneven. The position and velocity information obtained by differential analysis of discrete position information will amplify the noise of the position information and affect the stability of satellite tracking.

[0005] 3. The spatial position information of dynamic targets acquired by satellites often contains invalid data. After the position information is updated, the satellite attitude during the tracking process will change significantly, resulting in imaging interruption.

[0006] 4. Due to the above three reasons, the target angular velocity and target attitude data are not at the same moment when the satellite tracks the dynamic target, resulting in tracking deviation and low tracking stability. Summary of the Invention

[0007] The purpose of this invention is to provide a satellite tracking and imaging method for dynamic targets, which can perform high-precision and high-stability tracking of dynamic targets and improve the clarity of satellite camera tracking and imaging of dynamic targets.

[0008] To achieve the above objectives, a satellite-based tracking and imaging method for dynamic targets includes the following steps:

[0009] Step S1: Project the vector pointing from the Earth's center to the target into the J2000 inertial coordinate system using the least squares method. Perform curve fitting to obtain Continuous function with respect to time

[0010] Step S2, for Find the first and second derivatives to obtain the first derivative of the projection of the geocentric vector pointing towards the target into the J2000 inertial coordinate system. and second derivative

[0011] Step S3: Use the obtained first derivative And the projection of the geocentric vector pointing to the satellite in the inertial coordinate system. and its derivative Calculate the target attitude q of the satellite tracking target at the current control moment. i→m ;

[0012] Step S4: Use the obtained first derivative and second derivative And the projection of the geocentric vector pointing to the satellite in the inertial coordinate system. and its derivative Calculate the target angular velocity ω of the satellite tracking target at the current control moment. mi .

[0013] Step S1 includes: calculating the projection of the vector pointing from the Earth's center to the target in the J2000 inertial coordinate system using the least squares method. In and Fitted curve of a continuous function with respect to time;

[0014] by For example, use the 5 most recent valid data points. and in, These are the most recent valid data points. The timestamps corresponding to the five data points are t(1), t(2), t(3), t(4), and t(5). The current time is represented by T0. The timestamps are processed as follows:

[0015] T(5)=t(5)-INT(t(5))+1

[0016] T(4)=t(4)-INT(t(5))+1

[0017] T(3)=t(3)-INT(t(5))+1

[0018] T(2)=t(2)-INT(t(5))+1

[0019] T(1)=t(1)-INT(t(5))+1

[0020] In the formula, the function INT is the integer function that truncates positive numbers.

[0021] Let Bh For a 5×3 space array, C h D is a 5×1 vector. h If the vector is 3×1, then:

[0022] B h (j,1)=T(j) 0

[0023] B h (j,2)=T(j) 1

[0024] B h (j,3)=T(j) 2

[0025]

[0026] j = 1, 2, 3, 4, 5

[0027]

[0028] The three coefficients of the quadratic equation are:

[0029] a h =D h (1)

[0030] b h =D h (2)

[0031] c h =D h (3)

[0032] Then at the current moment for:

[0033]

[0034] Similarly, we can obtain and

[0035] Step S2 includes:

[0036] Will Taking the derivative with respect to T0, we get:

[0037]

[0038]

[0039] Similarly, we can obtain and Ultimately obtainable and

[0040] Step S3 includes:

[0041] The projection of the satellite's pointing vector towards the target in the J2000 inertial coordinate system. m←s for:

[0042]

[0043] in, It is the projection of the geocentric vector pointing to the satellite in the inertial coordinate system, obtained from the satellite's orbital parameters;

[0044] The projection ρ of the unit vector of the satellite pointing towards the target in the J2000 inertial coordinate system m←s for:

[0045]

[0046] The velocity vector projected onto the J2000 inertial coordinate system by the unit vector of the satellite pointing towards the target. for:

[0047]

[0048]

[0049] in, It is the derivative of the vector pointing from the Earth's center to the satellite projected in the inertial coordinate system, obtained from the satellite's orbital parameters;

[0050] When a satellite tracks a target, the optical axis of the satellite's payload, i.e., the Zb axis, is oriented as ρ. m←s Yb axis and ρ m←s and If the planes formed are perpendicular, and the Xb-axis is determined using the right-hand rule, then...

[0051] i z =ρ m←s

[0052]

[0053] i x =i y ×i z

[0054] Among them, i x i y and i z This is the unit vector pointing to the three axes of the satellite's coordinate system;

[0055] Then the attitude cosine matrix of the inertial frame when the satellite is tracking the target is:

[0056]

[0057] In the formula, e x =[1;0;0],e y =[0;1;0],e z = [0; 0; 1];

[0058] The conversion formula from attitude transformation matrix to attitude quaternion can be derived from A. m←i Obtain the target attitude q of the satellite-tracked target at the current control time. i→m .

[0059] Step S4 includes:

[0060] make

[0061] Then ω mi =-[A m (yz); A m (zx); A m (xy)];

[0062] Among them, A m (yz) represents A m The second row and third column of the matrix, A m (zx) represents A m The third row and first column of the matrix, A m (xy) represents A m The first row and second column of the matrix;

[0063]

[0064]

[0065]

[0066]

[0067] in, and For i x i y and i z The derivative; R s It is the horizontal semi-major axis of the satellite orbit; mu is the geocentric gravitational constant, mu = 3.9860044m. 3 / s 2 .

[0068] This invention utilizes the discrete position information of dynamic targets to perform high-precision and high-stability tracking of dynamic targets, improving the clarity of satellite camera imaging of dynamic target tracking, and has practical significance for satellite-based ground dynamic target tracking imaging tasks. Detailed Implementation

[0069] This invention provides a satellite tracking and imaging method for dynamic targets. Based on the discrete position information of the dynamic target, a curve fitting algorithm is used to fit the position information to obtain a continuous function of the target position information with respect to time. Then, combined with the satellite's position information, the target attitude and target angular velocity at the current control moment can be obtained.

[0070] The satellite tracking and imaging method for dynamic targets provided by this invention specifically includes the following steps:

[0071] Step S1: Project the vector pointing from the Earth's center to the target into the J2000 inertial coordinate system using the least squares method. Perform curve fitting to obtain Continuous function with respect to time

[0072] The projections of the geocentric vector pointing towards the target in the J2000 inertial coordinate system are obtained using the least squares method. In and Fitted curve of a continuous function with respect to time;

[0073] by For example, use the 5 most recent valid data points. and in, These are the most recent valid data points. The timestamps corresponding to the five data points are t(1), t(2), t(3), t(4), and t(5). The current time is represented by T0. Since the current time is a relatively large value, the timestamps are processed as follows to reduce calculation errors:

[0074] T(5)=t(5)-INT(t(5))+1

[0075] T(4)=t(4)-INT(t(5))+1

[0076] T(3)=t(3)-INT(t(5))+1

[0077] T(2)=t(2)-INT(t(5))+1

[0078] T(1)=t(1)-INT(t(5))+1

[0079] In the formula, the function INT is the integer function that truncates positive numbers.

[0080] Let B h For a 5×3 space array, C h D is a 5×1 vector.h If the vector is 3×1, then:

[0081] B h (j,1)=T(j) 0

[0082] B h (j,2)=T(j) 1

[0083] B h (j,3)=T(j) 2

[0084]

[0085] j = 1, 2, 3, 4, 5

[0086]

[0087] The three coefficients of the quadratic equation are:

[0088] a h =D h (1)

[0089] b h =D h (2)

[0090] c h =D h (3)

[0091] Then at the current moment for:

[0092]

[0093] Similarly, we can obtain and

[0094] Step S2, for Find the first and second derivatives to obtain the first derivative of the projection of the geocentric vector pointing towards the target into the J2000 inertial coordinate system. and second derivative

[0095] Will Taking the derivative with respect to T0, we get:

[0096]

[0097]

[0098] Similarly, we can obtain and Ultimately obtainable and

[0099] Step S3: Use the obtained first derivative And the projection of the geocentric vector pointing to the satellite in the inertial coordinate system. and its derivative Calculate the target attitude q of the satellite tracking target at the current control moment. i→m ;

[0100] The projection of the satellite's pointing vector towards the target in the J2000 inertial coordinate system. m←s for:

[0101]

[0102] in, It is the projection of the geocentric vector pointing to the satellite in the inertial coordinate system, obtained from the satellite's orbital parameters;

[0103] The projection ρ of the unit vector of the satellite pointing towards the target in the J2000 inertial coordinate system m←s for:

[0104]

[0105] The velocity vector projected onto the J2000 inertial coordinate system by the unit vector of the satellite pointing towards the target. for:

[0106]

[0107]

[0108] in, It is the derivative of the vector pointing from the Earth's center to the satellite projected in the inertial coordinate system, obtained from the satellite's orbital parameters;

[0109] When a satellite tracks a target, the optical axis of the satellite's payload, i.e., the Zb axis, is oriented as ρ. m←s Yb axis and ρ m←s and If the planes formed are perpendicular, and the Xb-axis is determined using the right-hand rule, then...

[0110] i z =ρ m←s

[0111]

[0112] i x =i y ×i z

[0113] Among them, i x iy and i z This is the unit vector pointing to the three axes of the satellite's coordinate system;

[0114] Then the attitude cosine matrix of the inertial frame when the satellite is tracking the target is:

[0115]

[0116] In the formula, e x =[1;0;0],e y =[0;1;0],e z = [0; 0; 1];

[0117] The conversion formula from attitude transformation matrix to attitude quaternion can be derived from A. m←i Obtain the target attitude q of the satellite-tracked target at the current control time. i→m ;

[0118] Step S4: Use the obtained first derivative and second derivative And the projection of the geocentric vector pointing to the satellite in the inertial coordinate system. and its derivative Calculate the target angular velocity ω of the satellite tracking target at the current control moment. mi ;

[0119] make

[0120] Then ω mi =-[A m (yz); A m (zx); A m (xy)];

[0121] Among them, A m (yz) represents A m The second row and third column of the matrix, A m (zx) represents A m The third row and first column of the matrix, A m (xy) represents A m The first row and second column of the matrix;

[0122]

[0123]

[0124]

[0125]

[0126] in, and For i x i y and i z The derivative; R s It is the horizontal semi-major axis of the satellite orbit; mu is the geocentric gravitational constant, mu = 3.9860044m. 3 / s 2 .

[0127] Thus, the target attitude q at the current moment, required for satellite tracking of a dynamic target, can be obtained. i→m and target angular velocity ω mi .

[0128] This invention utilizes the discrete position information of dynamic targets to perform high-precision and high-stability tracking of dynamic targets, improving the clarity of satellite camera imaging of dynamic target tracking, and has practical significance for satellite-based ground dynamic target tracking imaging tasks.

[0129] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A satellite-based tracking and imaging method for dynamic targets, characterized in that, Includes the following steps: Step S1: Project the vector pointing from the Earth's center to the target into the J2000 inertial coordinate system using the least squares method. Perform curve fitting to obtain Continuous function with respect to time ; Step S2, for Find the first and second derivatives to obtain the first derivative of the projection of the geocentric vector pointing towards the target into the J2000 inertial coordinate system. and second derivative ; Step S3: Use the obtained first derivative And the projection of the geocentric vector pointing to the satellite in the inertial coordinate system. and its derivative Calculate the target attitude of the satellite-tracked target at the current control moment. ; Step S4: Use the obtained first derivative and second derivative And the projection of the geocentric vector pointing to the satellite in the inertial coordinate system. and its derivative Calculate the target angular velocity of the satellite tracking target at the current control moment. .

2. The satellite tracking and imaging method for dynamic targets as described in claim 1, characterized in that, Step S1 includes: calculating the projection of the vector pointing from the Earth's center to the target in the J2000 inertial coordinate system using the least squares method. In , and Fitted curve of a continuous function with respect to time; by For example, use the 5 most recent valid data points. , , , and ,in, These are the most recent valid data points. The timestamps corresponding to the 5 data points are: , , , and At the current moment This indicates that the timestamp will be processed as follows: In the formula, the function INT is the integer function that truncates positive numbers. make It is a 5×3 space array. It is a 5×1 vector. If the vector is 3×1, then: The three coefficients of the quadratic equation are: Then at the current moment for: ； Similarly, we can obtain and .

3. The satellite tracking and imaging method for dynamic targets as described in claim 2, characterized in that, Step S2 includes: Will about Differentiation yields: Similarly, we can obtain , , and Ultimately, we can obtain and .

4. The satellite tracking and imaging method for dynamic targets as described in claim 3, characterized in that, Step S3 includes: Projection of the satellite's pointing vector towards the target in the J2000 inertial coordinate system for: in, It is the projection of the geocentric vector pointing to the satellite in the inertial coordinate system, obtained from the satellite's orbital parameters; Projection of the unit vector of the satellite pointing towards the target in the J2000 inertial coordinate system for: The velocity vector projected onto the J2000 inertial coordinate system by the unit vector of the satellite pointing towards the target. for: in, It is the derivative of the projection of the geocentric vector pointing to the satellite onto the inertial coordinate system, obtained from the satellite orbital parameters; When a satellite tracks a target, the optical axis of the satellite's payload, i.e., the Zb axis, is oriented as follows: Yb axis and and If the planes formed are perpendicular, and the Xb-axis is determined using the right-hand rule, then... in, , and This is the unit vector pointing along the three axes of the satellite's own system when the satellite is tracking a target; Then the attitude cosine matrix of the inertial frame when the satellite is tracking the target is: In the formula, , , ; The conversion formula from attitude transformation matrix to attitude quaternion can be derived from... Obtain the target attitude of the satellite-tracked target at the current control moment. .

5. The satellite tracking and imaging method for dynamic targets as described in claim 4, characterized in that, Step S4 includes: make ; but ; in, express The second row and third column of the matrix, express The third row and first column of the matrix, express The first row and second column of the matrix; in, , and for , and The derivative; ; ; It is the horizontal semi-major axis of the satellite orbit; It is the gravitational constant. .

Images