Calculation method for earth observation target point position of satellite load and remote sensing satellite applied to calculation method

Abstract

The invention relates to the technical field of satellite observation, and provides a method for calculating the position of an earth observation target point of a satellite load and a remote sensing satellite applied to the method. The method comprises the following steps: calculating the position and speed (r, v) of a satellite under an earth-fixed coordinate system at a te moment according to satellite orbit data predicted on the satellite; constructing a satellite motion coordinate system according to the working mode information of the satellite, and determining the relationship among the earth-fixed coordinate system, the satellite motion coordinate system and the satellite load; when the side swing angle theta of the satellite is fixed, calculating the direction se of a satellite load in an earth-fixed coordinate system, and determining the position of a ground target point corresponding to the side swing angle theta of the satellite; and calculating the geographic position (delta, lambda) of the ground target point according to the geometrical relationship between the satellite load and the ground target point under the earth-fixed coordinate system. The method is simple and easy to implement, occupation of satellite resources can be effectively reduced, observation task planning of various types of remote sensing satellites can be met when the method is applied to the remote sensing satellites, and the method can be well suitable for the remote sensing satellites with narrow imaging breadth and high resolution.

Description

Technical Field

[0001] This invention generally relates to the field of satellite observation technology. Specifically, this invention relates to a method for calculating the location of Earth observation target points using a satellite payload and its application in remote sensing satellites. Background Technology

[0002] In the process of planning observation missions for remote sensing satellites, it is necessary to calculate the positions of ground target points corresponding to the satellite payload. Existing technologies are usually based on planar analytical geometry methods for calculation, which have the problem of complex calculation processes and often ignore the influence of the Earth's oblateness, resulting in poor calculation accuracy. Therefore, they are not suitable for planning satellite observation missions with narrow imaging swaths and high resolution. Summary of the Invention

[0003] To at least partially solve the aforementioned problems in the prior art, this invention proposes a method for calculating the location of Earth observation target points using a satellite payload, characterized by comprising the following steps:

[0004] Based on the satellite orbit data predicted by the satellite, calculate t e The position and velocity (r, v) of the satellite in the ground-fixed coordinate system at any given time;

[0005] Construct a satellite motion coordinate system based on the satellite's operating mode information, and determine the relationship between the Earth-fixed coordinate system, the satellite motion coordinate system, and the satellite payload;

[0006] When the satellite's side-slip angle θ is fixed, calculate the pointing s of the satellite payload in the Earth-fixed coordinate system. e And determine the location of the ground target point corresponding to the satellite's side swing angle θ; and

[0007] Based on the geometric relationship between the satellite payload and the ground target point in the Earth-fixed coordinate system, the geographical location (δ, λ) of the ground target point is calculated, where δ represents longitude and λ represents latitude.

[0008] In one embodiment of the present invention, it is specified that the x-axis of the satellite motion coordinate system points to the satellite velocity direction e. x The z-axis points to the Earth's center e. z y-axis direction e y Determined by the right-hand criterion, it is expressed as follows:

[0009]

[0010] In one embodiment of the present invention, determining the relationship between the Earth-fixed coordinate system, the satellite motion coordinate system, and the satellite payload includes expressing the orientation e0 of the satellite payload in the satellite motion coordinate system as follows:

[0011] e0 = (0, 0, 1)T .

[0012] In one embodiment of the present invention, when the satellite's side-slip angle θ is fixed, the pointing direction s of the satellite payload in the Earth-fixed coordinate system is calculated. e It can be expressed as the following formula:

[0013] s e =(e x e y e z )·R X (θ)·e0

[0014] Among them, R x (θ) represents the matrix of the lateral swing angle θ of the rotation around the X-axis of the satellite's motion coordinate system.

[0015] In one embodiment of the present invention, determining the location of the ground target point corresponding to the satellite side swing angle θ includes:

[0016] Considering the Earth's oblateness and setting the Earth's altitude to 0, the satellite payload points in the direction s in the Earth-fixed coordinate system. e Intersecting the Earth's surface, the position of the ground target point corresponding to the satellite's side tilt angle θ is represented as (δ, λ, 0).

[0017] In one embodiment of the present invention, calculating the geographical location (δ, λ) of the ground target point based on the geometric relationship between the satellite payload and the ground target point in the Earth-fixed coordinate system includes the following steps:

[0018] Determine the rectangular coordinates R of the ground target point in the Earth-fixed coordinate system;

[0019] The geometric relationship between the satellite payload and the ground target point is expressed as Rr = s e ;as well as

[0020] Based on the geometric relationship between the satellite payload and the ground target point, a system of equations is established to calculate the geographical location (δ, λ) of the ground target point.

[0021] In one embodiment of the present invention, the method for calculating the location of the Earth observation target point of the satellite payload further includes:

[0022] Calculate the location of the ground target point corresponding to the edge of the satellite's swath width based on the half field of view ±△θ of the satellite payload.

[0023] The present invention also proposes a remote sensing satellite that calculates the location of Earth observation target points of the satellite payload according to the method described above in order to plan observation missions.

[0024] This invention offers at least the following advantages: It proposes a method for calculating the location of Earth observation target points on a satellite payload. This method calculates the location of Earth observation target points based on high-precision predicted orbit and attitude information, combined with the satellite's designed operating mode (i.e., the payload is under a defined side-swing angle), and taking into account the Earth's oblateness. The target point location calculated using this method is more consistent with reality and has higher accuracy. Because this method uses simple vector operations, it does not require consideration of complex planar geometry problems as in traditional methods, thus offering advantages in simplicity and ease of implementation, effectively reducing the occupation of onboard resources. When applied to remote sensing satellites, this method can meet the needs of various types of remote sensing satellite observation mission planning and is well-suited for remote sensing satellites with narrow imaging swaths and high resolution. Attached Figure Description

[0025] To further illustrate the advantages and other features of the various embodiments of the present invention, a more specific description of the embodiments of the present invention will be presented with reference to the accompanying drawings. It is understood that these drawings depict only typical embodiments of the invention and are therefore not intended to limit its scope. In the drawings, identical or corresponding parts will be indicated by the same or similar reference numerals for clarity.

[0026] Figure 1 The diagram illustrates a flowchart of a method for calculating the location of an Earth observation target point for a satellite payload according to an embodiment of the present invention.

[0027] Figure 2 This diagram illustrates the direction of the satellite payload's Earth observation target point under a satellite side-swing condition in one embodiment of the present invention.

[0028] Figure 3 A schematic diagram of the elevation angle of a satellite's 24-hour predicted orbit relative to a given ground target point is shown in one embodiment of the present invention. Detailed Implementation

[0029] It should be noted that the components in the various figures may be shown exaggeratedly for illustrative purposes and are not necessarily to scale. In each figure, the same reference numerals are used for components that are identical or have the same function.

[0030] In this invention, unless otherwise specified, "arranged on," "arranged above," and "arranged on" do not exclude the possibility of an intermediate element between them. Furthermore, "arranged on or above" merely indicates the relative positional relationship between two components, and in certain cases, such as when the product orientation is reversed, it can also be converted to "arranged below or under," and vice versa.

[0031] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0032] In this invention, unless otherwise specified, the quantifiers “a” and “one” do not exclude scenarios involving multiple elements.

[0033] It should also be noted that, in the embodiments of the present invention, only a portion of the components or parts may be shown for clarity and simplicity. However, those skilled in the art will understand that, under the teachings of the present invention, necessary components or parts can be added as needed for specific scenarios. Furthermore, unless otherwise stated, features in different embodiments of the present invention can be combined with each other. For example, a feature in the second embodiment can replace a corresponding or functionally identical or similar feature in the first embodiment, and the resulting embodiment will also fall within the scope of disclosure or description of this application.

[0034] It should also be noted that, within the scope of this invention, the terms "same," "equal," and "equal to" do not imply that the two values ​​are absolutely equal, but rather allow for a certain reasonable margin of error. In other words, the terms also encompass "substantially the same," "substantially equal," and "substantially equal to." Similarly, in this invention, the directional terms "perpendicular to," "parallel to," etc., also encompass the meanings of "substantially perpendicular to" and "substantially parallel to."

[0035] Furthermore, the numbering of the steps in the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps may be executed in different orders.

[0036] This invention establishes the relationship between the satellite's motion coordinate system, payload coordinate system, and Earth-fixed coordinate system based on the satellite's predicted orbit and attitude information, combined with on-orbit observation mode information. The method is clear, easy to implement, and highly accurate. Using the WGS-84 reference ellipsoid, it takes into account the Earth's oblateness. Based on high-precision orbit information, it calculates the location of the ground target point corresponding to the payload under lateral tilt conditions. This method can meet the planning needs of various types of remote sensing satellite observation missions and is well-suited for remote sensing satellites with narrow imaging swaths and high resolution.

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] Figure 1 This diagram illustrates a flowchart of a method for calculating the location of an Earth observation target point using a satellite payload, according to one embodiment of the present invention. Figure 1 As shown, the method includes the following steps:

[0039] Step 101: Calculate t based on the satellite orbit data predicted by the satellite. e The position and velocity (r, v) of the satellite in the Earth-fixed coordinate system at any given time.

[0040] Step 102: Construct a satellite motion coordinate system based on the satellite's working mode information, and determine the relationship between the Earth-fixed coordinate system, the satellite motion coordinate system, and the satellite payload.

[0041] Step 103: When the satellite's side-slip angle θ is fixed, calculate the pointing s of the satellite payload in the Earth-fixed coordinate system. e And determine the location of the ground target point corresponding to the satellite's side swing angle θ.

[0042] Step 104: Calculate the geographical location (δ, λ) of the ground target point based on the geometric relationship between the satellite payload and the ground target point in the Earth-fixed coordinate system, where δ represents longitude and λ represents latitude.

[0043] The steps of this method are explained in detail below.

[0044] First, based on the satellite orbit data predicted on-board, the time t is calculated. e The position and velocity (r, v) of the satellite in the time-ground-fixed coordinate system.

[0045] Furthermore, based on the satellite's operating mode information, a satellite motion coordinate system is defined, with the x-axis pointing in the direction of the satellite's velocity e. x The z-axis points to the Earth's center e. z y-axis direction e y Determined by the right-hand criterion, it is expressed as follows:

[0046]

[0047] Furthermore, based on the satellite's position and velocity (r, v) in the Earth-fixed coordinate system and the satellite's motion coordinate system, the relationship between the Earth-fixed coordinate system, the satellite's motion coordinate system, and the payload coordinate system is determined, and the direction e0 of the satellite payload in the satellite's motion coordinate system is expressed as follows:

[0048] e0 = (0, 0, 1) T .

[0049] Furthermore, given the satellite's side tilt angle θ, the pointing direction s of the satellite payload in the Earth-fixed coordinate system can be calculated. e It can be expressed as the following formula:

[0050] s e =(e x e y e z )·R X (θ)·e0

[0051] Among them, R X (θ) represents the matrix of the lateral swing angle θ of the rotation around the X-axis of the satellite's motion coordinate system.

[0052] Furthermore, let the position of the ground target point corresponding to the satellite side swing angle θ be (δ, λ, 0), and calculate the rectangular coordinates R of the ground target point in the Earth-fixed coordinate system.

[0053] Furthermore, a system of equations is established based on the geometric relationships in the Earth-fixed coordinate system, and the geographical locations δ and λ of the ground target points are calculated. The geometric relationships in the Earth-fixed coordinate system can be expressed as follows:

[0054]

[0055] Furthermore, by substituting the payload half-field of view ±△θ into steps 101 to 106, the position of the ground target point corresponding to the edge of the satellite's swath is calculated.

[0056] In one embodiment of the present invention, a remote sensing satellite is also proposed, which calculates the location of the Earth observation target point of the satellite payload according to the method to plan the observation mission.

[0057] In this invention, a satellite motion coordinate system is first defined according to the satellite observation mode. The relationship between the satellite's Earth observation payload and the satellite motion coordinate system, as well as the relationship between the satellite motion coordinate system and the Earth-fixed coordinate system, are then established. Subsequently, the Earth-direction s of the payload under the condition of satellite side-slip θ is calculated. e Considering the Earth's oblateness, let the Earth's height be 0, and let s be... e The point of intersection with the Earth's surface is (δ, λ, 0), and the rectangular coordinates of the ground target point are R. Figure 2 This diagram illustrates the orientation of the satellite payload towards the Earth observation target point under a satellite side-swing condition, according to one embodiment of the present invention. Figure 2 The geometric relationship shown indicates that the direction of the satellite payload's Earth observation target point is Rr, and theoretically Rr = s e Therefore, a system of two linear equations in two variables is established to solve for the geographical location δ and λ of the ground point. The above method takes into account the Earth's oblateness and the satellite's design mode, and uses high-precision predicted orbits for calculation. Therefore, it has higher calculation accuracy and is more consistent with reality compared to existing technologies.

[0058] In one embodiment of the present invention, predicted orbit data from STK simulation is used for illustration. First, given the initial conditions, the orbital elements of the satellite at epoch 2025.1.10h are shown in Table 1.

[0059] Table 1

[0060] semi-long shaft Eccentricity e track inclination Right ascension of ascending node Perimeter Argument Plane near point angle 6928.14km 0 97.5976° 78.3996° 0 0

[0061] Furthermore, the geodetic coordinates of the ground target point are given as (24.233, 55.3, 0), where latitude and longitude are in degrees and geodetic height is in meters.

[0062] Based on the simulation data above, calculate the time t at which the satellite passes over the ground target point. e =7.0747h(am), when the satellite sideswedges to point to the given ground target point (24.233, 55.3, 0), the corresponding sideswedge angle is -5.209° (in the satellite motion coordinate system). Figure 3 A schematic diagram illustrating the elevation angle of a satellite's 24-hour predicted orbit relative to a given ground target point is shown in one embodiment of the present invention. Figure 3 In this context, a negative value indicates that the satellite is not visible relative to a given ground target point, meaning the satellite is below the ground plane. When t... e At 7.0747h, the satellite's elevation angle relative to the ground point is at its maximum.

[0063] Given t e The orbital position and velocity at any given time, along with the lateral tilt angle information, can be used to calculate the corresponding ground target point position. The calculation results were verified based on the simulation experiments above. The lateral tilt angle deviation is less than 1.5 arcseconds, and for a ground-orbiting satellite at an altitude of 1000 kilometers, the ground target point position error is less than 8 meters, indicating that this method can meet the planning requirements of high-precision remote sensing satellite observation missions.

[0064] Although various embodiments of the invention have been described above, it should be understood that they are presented by way of example only and not as limitations. It will be apparent to those skilled in the art that various combinations, modifications, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the breadth and scope of the invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A method of calculating a position of a point of observation on the ground of a satellite payload, characterized in that, The method comprises the following steps: According to the predicted satellite orbit data on the satellite, the position and velocity (r, v) of the satellite in the geocentric coordinate system at time t are calculated. e According to the predicted satellite orbit data on the satellite, the position and velocity (r, v) of the satellite in the geocentric coordinate system at time t are calculated. constructing a satellite motion coordinate system according to the working mode information of the satellite, and determining the relationship among the earth-fixed coordinate system, the satellite motion coordinate system and the satellite payload; When the satellite's yaw angle θ is fixed, the pointing s of the satellite payload in the earth-fixed coordinate system is calculated e and the ground target point position corresponding to the satellite's yaw angle θ is determined; and calculating the geographical position (δ, λ) of the ground target point according to the geometric relationship between the satellite payload and the ground target point in the earth-fixed coordinate system, wherein δ represents longitude and λ represents latitude.

2. The method of claim 1, wherein the satellite payload is a synthetic aperture radar (SAR) payload. The x-axis of the satellite motion coordinate system points in the direction of the satellite velocity e x The z-axis of the satellite motion coordinate system points in the direction of the Earth's center e z The y-axis of the satellite motion coordinate system e y is determined by the right-hand rule and is expressed as follows:

3. The method of claim 2, wherein the satellite payload is a synthetic aperture radar (SAR) payload. The determination of the relationship among the earth-fixed coordinate system, the satellite motion coordinate system and the satellite payload comprises representing the pointing direction e0 of the satellite payload in the satellite motion coordinate system as the following formula: e0＝(0，0，1) T 。 4. The method of claim 3, wherein the satellite payload is a synthetic aperture radar (SAR) payload. When the satellite's yaw angle θ is fixed, the satellite payload's pointing s in the earth-fixed coordinate system is calculated e and is expressed as follows: s e = (e x , e y , e z ) · R X (θ) · e0 wherein R X (0) denotes a matrix that rotates the side-slip angle θ around the X-axis of the satellite moving coordinate system.

5. The method of claim 4, wherein the satellite payload is a synthetic aperture radar (SAR) payload. The determination of the ground target point position corresponding to the satellite yaw angle θ comprises: Considering the oblateness of the Earth and setting the height of the Earth to 0, the pointing s of the satellite payload in the Earth-fixed coordinate system e Intersecting the surface of the Earth, where the satellite yaw angle Θ corresponds to a ground target point position expressed as (δ, λ, 0).

6. The method of calculating the position of a point of observation on the Earth's surface of a satellite payload according to claim 5, characterized in that, The calculation of the geographical position (δ, λ) of the ground target point according to the geometric relationship between the satellite payload and the ground target point in the earth-fixed coordinate system comprises the following steps: determining the rectangular coordinates R of the ground target point in the earth-fixed coordinate system; representing a geometric relationship between the satellite payload and the ground target point as R - r = s e ; and establishing an equation group according to the geometric relationship between the satellite payload and the ground target point, and calculating the geographical position (δ, λ) of the ground target point.

7. The method of claim 6, wherein the satellite payload is a synthetic aperture radar (SAR) payload. Further comprising: calculating the ground target point position corresponding to the width edge of the satellite according to the half field angle ±△θ of the satellite payload.

8. A remote sensing satellite, characterized in that, The method for calculating the ground observation target point position of the satellite payload according to any one of claims 1-7 is used to calculate the ground observation target point position of the satellite payload for observation task planning.

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