Real-time compensation method for drift angle of tracking imaging satellite for ground dynamic target

Abstract

The application provides a method for real-time compensation of the drift angle of a satellite for tracking and imaging a dynamic target on the ground, and the method is based on the geographic position information of the target on the ground and the conversion relationship among the inertial system, the earth-fixed system and the satellite-to-earth coordinate system, and solves a three-axis attitude calculation method for real-time compensation of the drift angle of the satellite when tracking and imaging the dynamic target on the ground. The application can improve the definition of the observation and tracking and imaging of the satellite camera on the ground, and has practical significance for the tracking and imaging of the dynamic target on the ground by the satellite.

Description

Technical Field

[0001] This invention relates to the field of satellite yaw angle compensation technology, and in particular to a method for real-time yaw angle compensation of a satellite for tracking and imaging dynamic ground targets. Background Technology

[0002] When a satellite camera tracks and images a ground target, the discrepancy between the camera's push-broom direction and the target's movement direction caused by the Earth's rotation can lead to image blurring. Compensation is needed for the angle between these two directions, known as the yaw angle. Existing methods provide a yaw angle calculation model for satellite imaging of a nadir point with zero attitude on all three axes relative to the Earth. However, this calculation method is no longer applicable when the satellite tracks dynamic targets, mainly for the following reasons:

[0003] 1) When a satellite is tracking a dynamic ground target, the satellite's three-axis attitude in the Earth coordinate system is not zero. The existing yaw angle calculation model is only applicable to the case where the satellite has zero attitude relative to the Earth coordinate system (tracking the nadir point).

[0004] 2) When a satellite is tracking a dynamic ground target, its three-axis attitude relative to the Earth system is time-varying. Therefore, it is necessary to use the satellite's current three-axis attitude information to perform on-orbit real-time calculation and compensation of the yaw angle.

[0005] 3) The diversity and unpredictability of the motion characteristics of ground targets may cause drastic changes in the three-axis attitude during satellite tracking, which in turn causes drastic changes in the yaw angle that the satellite needs to compensate for, thus affecting the satellite attitude control system. Summary of the Invention

[0006] The purpose of this invention is to provide a real-time compensation method for the yaw angle of a satellite that tracks and images dynamic ground targets. When a satellite tracks and images dynamic ground targets, it can improve the clarity of the satellite camera's Earth observation and target tracking imaging, which is of practical significance for the satellite's ground dynamic target tracking and imaging mission.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A method for real-time compensation of drift angle for satellites tracking and imaging dynamic ground targets includes the following steps:

[0009] S1. Based on the longitude, latitude, and altitude information of the ground dynamic target, calculate the projection of the vector pointing from the geocenter to the target in the J2000 inertial coordinate system and the WGS84 Earth-Fixed system. and And the velocity vector of the target in the WGS84 ground-fixed coordinate system and the J2000 inertial coordinate system. and

[0010] S2. When calculating the projection ρ of the unit vector of the satellite pointing towards the target in the J2000 inertial coordinate system, when the satellite is tracking a dynamic target. m←s The velocity vector of the projection of the satellite's pointing vector towards the target into the J2000 inertial coordinate system is expressed as:

[0011] S3. When calculating the direction of the three axes of the satellite's body coordinate system when tracking a dynamic target, the unit vector i pointing in the J2000 inertial coordinate system. x i y i z ;

[0012] S4. Calculate the attitude cosine matrix A of the satellite body coordinate system when the J2000 inertial coordinate system is tracking the target. m←i ;

[0013] S5. Calculate the attitude cosine matrix A of the satellite's body coordinate system when the satellite is tracking the target from the Earth coordinate system. m←o Thus, the magnitude of the deflection angle is obtained.

[0014] Optionally, S1 further includes:

[0015] Projection of the geocentric vector pointing to the target in the WGS84 geosolid system Calculate as follows:

[0016]

[0017] In the formula, r m The local radius of the target point is calculated as follows:

[0018]

[0019] Projection of the geocentric vector pointing to the target in the J2000 inertial coordinate system Calculate as follows:

[0020]

[0021] In the formula, λ m γ m h m These are the target's geographical longitude, geographical latitude, and geographical elevation, respectively; R e f e These are the Earth's equatorial radius and Earth's oblateness, respectively; A i←g This is the attitude transformation matrix from the WGS84 ground-fixed frame to the J2000 inertial frame;

[0022] The velocity vector of the target in the WGS84 ground-fixed coordinate system and the J2000 inertial coordinate system and Calculate using the following formula:

[0023]

[0024]

[0025] In the formula, These are the derivatives of the target's geographical longitude, geographical latitude, and geographical elevation, respectively. This is the derivative of the attitude transformation matrix from the WGS84 ground-fixed frame to the J2000 inertial coordinate system.

[0026] Optionally, S2 further includes:

[0027] The projection of the satellite-to-target vector in the J2000 inertial coordinate system is represented as l. m←s ,but

[0028]

[0029] The projection ρ of the unit vector pointing from the satellite to the target in the J2000 inertial coordinate system m←s Calculate using the following formula:

[0030]

[0031] Projecting the vector pointing from the satellite to the target into the J2000 inertial coordinate system m←s The velocity vector is represented as l m←s ,but

[0032]

[0033] In the formula, and These are the projections of the geocentric vector pointing to the satellite and its derivative in the J2000 inertial coordinate system.

[0034] Optionally, S3 further includes:

[0035] When a satellite tracks a moving target, the pointing unit vector i of the three axes of the satellite's body coordinate system in the J2000 inertial coordinate system. x i y i z Calculate using the following formula:

[0036] i z =ρ m←s

[0037]

[0038] i x =i y ×i z.

[0039] Optionally, S4 further includes:

[0040] The attitude cosine matrix A of the satellite's body coordinate system when the J2000 inertial coordinate system is aligned with the target being tracked by the satellite. m←i Calculate using the following formula:

[0041]

[0042] In the formula, e x =[1;0;0],e y =[0;1;0],e z =[0; 0; 1].

[0043] Optionally, S5 further includes:

[0044] The attitude cosine matrix A of the satellite body coordinate system when the satellite is tracking the target from the Earth coordinate system. m←o Calculate using the following formula:

[0045] A m←o =A m←i A i←o

[0046] In the formula, A i←o This is the coordinate transformation matrix from the satellite's Earth-based coordinate system to the J2000 inertial coordinate system.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] This invention proposes a real-time yaw angle compensation method for satellites tracking and imaging dynamic ground targets. By utilizing the geographical location information of the ground target and the transformation relationships between the inertial frame, the Earth-fixed frame, and the satellite-to-Earth coordinate system, a three-axis attitude calculation method is derived to compensate for the yaw angle during real-time satellite tracking and imaging of dynamic ground targets. This method can improve the clarity of satellite camera Earth observation and target tracking imaging, and has practical significance for satellite-based ground dynamic target tracking and imaging missions. Attached Figure Description

[0049] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the drawings described below are one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0050] Figure 1 The flowchart illustrates a method for real-time compensation of the drift angle of a satellite used for tracking and imaging dynamic targets on the ground, as provided by this invention. Detailed Implementation

[0051] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the solution proposed by the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of the present invention. Please refer to the drawings to make the objectives, features, and advantages of the present invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the present invention, should still fall within the scope of the technical content disclosed in the present invention.

[0052] As described in the background section, the yaw angle caused by the Earth's rotation, where the camera's push-broom direction is inconsistent with the target's movement direction, leads to blurred satellite imaging, thus requiring yaw angle compensation. Existing methods provide yaw angle calculation models when the satellite images a nadir point and has a zero attitude across the Earth's three axes. However, these methods are no longer applicable when the satellite tracks dynamic targets. This invention proposes a real-time yaw angle compensation method for satellites tracking and imaging dynamic ground targets. By utilizing the geographical location information of the ground target and the transformation relationships between the inertial frame, the Earth-fixed frame, and the satellite-to-Earth coordinate system, a three-axis attitude calculation method for real-time yaw angle compensation is derived when the satellite tracks and images moving ground targets. This method can improve the clarity of satellite camera Earth observation and target tracking imaging, and has practical significance for satellite-based ground dynamic target tracking and imaging tasks.

[0053] like Figure 1 As shown, the present invention provides a method for real-time compensation of the drift angle of a satellite tracking and imaging dynamic ground targets, comprising the following steps:

[0054] S1. Based on the longitude, latitude, and altitude information of the ground dynamic target, calculate the projection of the vector pointing from the geocenter to the target in the J2000 inertial coordinate system and the WGS84 Earth-Fixed system. and And the velocity vector of the target in the WGS84 ground-fixed coordinate system and the J2000 inertial coordinate system. and

[0055] S2. When calculating the projection ρ of the unit vector of the satellite pointing towards the target in the J2000 inertial coordinate system, when the satellite is tracking a dynamic target. m←s The velocity vector of the projection of the satellite's pointing vector towards the target into the J2000 inertial coordinate system is expressed as:

[0056] S3. When calculating the direction of the three axes of the satellite's body coordinate system when tracking a dynamic target, the unit vector i pointing in the J2000 inertial coordinate system. x i y i z ;

[0057] S4. Calculate the attitude cosine matrix A of the satellite body coordinate system when the J2000 inertial coordinate system is tracking the target. m←i ;

[0058] S5. Calculate the attitude cosine matrix A of the satellite's body coordinate system when the satellite is tracking the target from the Earth coordinate system. m←o Thus, the magnitude of the deflection angle is obtained.

[0059] This invention is based on the coordinate transformation matrix from the WGS84 Earth-fixed frame to the J2000 inertial frame, the coordinate transformation matrix from the satellite-to-Earth coordinate system to the inertial frame, and the projection of the geocentric vector pointing to the satellite and its derivative in the inertial coordinate system. and By combining the position parameters of the ground target with the satellite's position parameters, the three-axis attitude in the inertial frame when the satellite is tracking the target is calculated. At this time, the yaw angle of the satellite in the Earth coordinate system is the real-time drift angle. First, the following spatial vector information needs to be obtained.

[0060] (1) Calculate the projection of the vector pointing from the Earth's center to the target in the J2000 inertial coordinate system.

[0061] Projection of the geocentric vector pointing to the target in the WGS84 geofixed coordinate system Calculate as follows:

[0062]

[0063] In the formula, r m The local radius of the target point (the distance from the center of the earth without considering geographical elevation) is calculated as follows:

[0064]

[0065] get,

[0066]

[0067] In the formula, λ m γ m h m These are the target's geographical longitude, geographical latitude, and geographical elevation, respectively; R e f e These are the Earth's equatorial radius and Earth's oblateness, respectively; A i←gThis is the attitude transformation matrix from the WGS84 ground-fixed frame to the J2000 inertial frame;

[0068] (2) Calculate the velocity vector of the target in the WGS84 ground-fixed coordinate system and the J2000 inertial coordinate system. and

[0069]

[0070]

[0071] In the formula, These are the derivatives of the target's geographical longitude, geographical latitude, and geographical elevation, respectively. The derivative of the attitude transformation matrix from the WGS84 ground-fixed frame to the J2000 inertial frame;

[0072] (3) Coordinate transformation matrix A from WGS84 Earth-Fixed Frame to J2000 Inertial Frame i←g and its derivative The coordinate transformation matrix A from the satellite's Earth coordinate system to its inertial system. i←o It can be obtained from the satellite's orbital parameters.

[0073] This invention calculates the three-axis attitude and yaw angle when a satellite tracks a target using its line of sight through the following steps:

[0074] (1) The projection of the satellite-to-target vector in the J2000 inertial coordinate system is represented as l m←s ,

[0075]

[0076] The projection ρ of the unit vector pointing from the satellite to the target in the J2000 inertial coordinate system m←s

[0077]

[0078] (2) Project the vector pointing from the satellite to the target into the J2000 inertial coordinate system. m←s The velocity vector is represented as l m←s ,but

[0079]

[0080] (3) When a satellite tracks a moving target, the satellite's camera line of sight, i.e., Z... b The axis points to the target, and the pointing vector is ρ. m←s To ensure that the push-broom direction of the satellite camera's line of sight aligns with the target's movement direction, the Y-axis of the satellite's own system... b axis and ρ m←s and -lm←s The plane they form is perpendicular. The satellite's X-axis. b The axis is determined by the right-hand rule.

[0081] i z =ρ m←s

[0082]

[0083] i x =i y ×i z

[0084] In the formula, i x i y i z The pointing unit vector of this system in the inertial frame when the satellite tracks the target.

[0085] (4) The attitude cosine matrix of the system when the inertial frame tracks the satellite target is:

[0086]

[0087] In the formula, e x =[1;0;0],e y =[0;1;0],e z =[0; 0; 1].

[0088] (5) The Earth attitude quaternion q of the satellite in the inertial frame at this time is obtained by the calculation method of mutual conversion between attitude cosine matrix and attitude quaternion. i→o .

[0089] A m←o =A m←i A i←o

[0090] A i←o This is the coordinate transformation matrix from the satellite's Earth-based coordinate system to its inertial system;

[0091] Coordinate transformation matrix A from satellite-to-Earth coordinate system to inertial system i←o This allows us to obtain the satellite's three-axis attitude angles in the Earth-oriented coordinate system; this transformation is a basic mathematical transformation. The Z-axis angle of the satellite in the Earth-oriented coordinate system, i.e., the yaw angle, is the real-time drift angle.

[0092] At this point, the push-broom direction of the satellite camera's line of sight is aligned with the target's movement direction, and the drift angle is compensated in real time when the satellite tracks and images dynamic targets on the ground.

[0093] 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 method for real-time compensation of the drift angle of a satellite tracking and imaging dynamic ground targets, characterized in that, Includes the following steps: S1. Based on the longitude, latitude, and altitude information of the ground dynamic target, calculate the projection of the vector pointing from the geocenter to the target in the J2000 inertial coordinate system. The projection of the geocentric vector pointing to the target in the WGS84 geofixed system and the velocity vector of the target in the WGS84 geofixed system The velocity vector of the target in the J2000 inertial coordinate system S2. When calculating the projection ρ of the unit vector of the satellite pointing towards the target in the J2000 inertial coordinate system, when the satellite is tracking a dynamic target. m←s The velocity vector of the projection of the satellite's pointing vector towards the target onto the J2000 inertial coordinate system is expressed as l. m←s ; S3. When calculating the direction of the three axes of the satellite's body coordinate system when tracking a dynamic target, the unit vector i pointing in the J2000 inertial coordinate system. x i y i z ; S4. Calculate the attitude cosine matrix A of the satellite body coordinate system when the J2000 inertial coordinate system is tracking the target. m←i ; S5. Calculate the attitude cosine matrix A of the satellite's body coordinate system when the satellite is tracking the target from the Earth coordinate system. m←o The Earth attitude quaternion q of the satellite in the J2000 inertial frame at this time o→m Thus, the magnitude of the deflection angle is obtained.

2. The method for real-time compensation of the drift angle of a satellite tracking and imaging ground dynamic targets as described in claim 1, characterized in that, S1 further includes: Projection of the geocentric vector pointing to the target in the WGS84 geosolid system Calculate as follows: In the formula, r m The local radius of the target point is calculated as follows: Projection of the geocentric vector pointing to the target in the J2000 inertial coordinate system Calculate as follows: In the formula, λ m γ m h m These are the target's geographical longitude, geographical latitude, and geographical elevation, respectively; R e f e These are the Earth's equatorial radius and Earth's oblateness, respectively; A i←g This is the attitude transformation matrix from the WGS84 ground-fixed frame to the J2000 inertial frame; The velocity vector of the target in the WGS84 ground-fixed coordinate system and the J2000 inertial coordinate system and Calculate using the following formula: In the formula, These are the derivatives of the target's geographical longitude, geographical latitude, and geographical elevation, respectively. This is the derivative of the attitude transformation matrix from the WGS84 ground-fixed frame to the J2000 inertial coordinate system.

3. The method for real-time compensation of the drift angle of a satellite tracking and imaging ground dynamic targets as described in claim 1, characterized in that, S2 further includes: The projection of the satellite-to-target vector in the J2000 inertial coordinate system is represented as l. m←s ,but The projection ρ of the unit vector pointing from the satellite to the target in the J2000 inertial coordinate system m←s Calculate using the following formula: Projecting the vector pointing from the satellite to the target into the J2000 inertial coordinate system m←s The velocity vector is represented as but In the formula, and These are the projections of the geocentric vector pointing to the satellite and its derivative in the J2000 inertial coordinate system.

4. The method for real-time compensation of drift angle for tracking and imaging satellites of dynamic ground targets as described in claim 3, characterized in that, The S3 further includes: When a satellite tracks a moving target, the pointing unit vector i of the three axes of the satellite's body coordinate system in the J2000 inertial coordinate system. x i y i z Calculate using the following formula: I z =ρ m←s i x =i y ×i z 。 5. The method for real-time compensation of drift angle for tracking and imaging satellites of dynamic ground targets as described in claim 1, characterized in that, The S4 further includes: The attitude cosine matrix A of the satellite's body coordinate system when the J2000 inertial coordinate system is aligned with the target being tracked by the satellite. m←i Calculate using the following formula: In the formula, e x =[1;0;0],e y =[0;1;0],e z =[0; 0; 1].

6. The method for real-time compensation of drift angle for tracking and imaging satellites of dynamic ground targets as described in claim 1, characterized in that, The S5 further includes: The attitude cosine matrix A of the satellite body coordinate system when the satellite is tracking the target from the Earth coordinate system. m←o Calculate using the following formula: A m←o =A m←i A i←o In the formula, A i←o This is the coordinate transformation matrix from the satellite's Earth-based coordinate system to the J2000 inertial coordinate system.

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