Ground station coverage analysis method under dynamic pointing based on satellite orbit

Abstract

The invention provides a dynamic pointing ground station coverage analysis method based on a satellite orbit, and the method comprises the steps: determining a ground station position vector and a maximum off-axis angle value of a satellite antenna under an earth-fixed system; calculating an arc section of the satellite transit ground station under the condition of meeting the minimum elevation angle of the ground station; constructing a satellite body coordinate system according to the satellite position and speed information; determining a satellite pointing vector under a satellite body coordinate system; converting the satellite pointing vector to an earth-fixed system; calculating a satellite pointing vector and a satellite pointing ground station included angle; and calculating a visible time window of the satellite to the ground station under the dynamic side-sway condition of the satellite. In combination with information such as satellite orbit data and attitude pointing, a mapping relation between a satellite body coordinate system and an earth-fixed system is established, data such as ground station position and elevation angle constraint are comprehensively considered, an included angle between a satellite pointing vector and a satellite-ground station vector is calculated, and the visibility of a satellite to a ground station is judged. The method is simple in process, easy to implement and high in precision, meets the requirements of ground station scheduling, tracking optimization and coverage analysis in various satellite task plans, and further can be applied to dynamic coverage analysis of agile satellites and ground targets.

Description

Technical Field

[0001] This invention relates to the field of satellite mission planning, and in particular to a method for ground station coverage analysis based on dynamic pointing of satellite orbit. Background Technology

[0002] Existing methods for calculating satellite visibility to ground stations mainly fall into two categories: geometric methods and dynamic pointing analysis methods. The geometric method primarily determines the presence of obstructions based on the line of sight between the satellite and the ground station, then calculates the satellite's projected trajectory on the ground and its coverage radius. However, this method neglects the Earth's non-spherical characteristics and the effects of orbital perturbations, making it unsuitable for complex satellite pointing dynamics and complex constellation systems.

[0003] In the pointing dynamic analysis method, since the changes in satellite pointing attitude need to be considered, the direction and size of the satellite field cone need to be determined based on the satellite antenna field of view. Therefore, it is necessary to acquire satellite attitude adjustment data in real time, and the calculation is complex due to the analytical geometric method. Summary of the Invention

[0004] To address the above problems, this invention provides a method for dynamic pointing-down ground station coverage analysis based on satellite orbits, characterized by comprising:

[0005] Determine the ground station position vector and the maximum off-axis angle of the satellite antenna under the Earth-fixed system;

[0006] Calculate the time period during which the satellite passes over the ground station while satisfying the minimum elevation angle of the ground station;

[0007] Construct a satellite coordinate system based on satellite position and velocity information;

[0008] Determine the satellite pointing vector in the satellite's body coordinate system;

[0009] Convert the satellite pointing vector to the Earth-fixed system;

[0010] Calculate the angle between the satellite pointing vector and the satellite pointing to the ground station; and

[0011] Record the time period during which the included angle is less than the maximum off-axis angle of the satellite antenna within the time period when the satellite passes over the ground station, and denote it as the satellite visible time window.

[0012] In one embodiment of the present invention, the ground station position vector is p, that is, the position vector from the Earth's center to the ground station;

[0013] The maximum off-axis angle of the satellite antenna is μ. The satellite is visible when the angle between the satellite pointing vector and the satellite pointing to the ground station is less than the maximum off-axis angle of the satellite antenna.

[0014] In another embodiment of the present invention, the step of calculating the time period of satellite transit over ground stations includes:

[0015] Calculate the arc of the satellite passing over the ground station windows[t0, t1], that is, the arc trajectory of the satellite completing the entry and exit of the ground station within the time period [t0, t1].

[0016] Where t0 is the time when the satellite enters the ground station, t1 is the time when the satellite leaves the ground station, and [t0, t1] is the time period.

[0017] In another embodiment of the present invention, the step of constructing the satellite body coordinate system includes:

[0018] The z-axis points towards the Earth's center, denoted as s. z ;

[0019] The x-axis points in the direction of the tangent to the satellite orbit, denoted as s. x ;as well as

[0020] The y-axis direction is determined using the right-hand rule, denoted as s. y ;

[0021] The satellite position and velocity information is (r, v), which represents the satellite's position and velocity in the Earth-fixed system at time t.

[0022] In another embodiment of the present invention, the satellite pointing vector is s θ =(s x s y s z )×R X ×a, where a is the satellite's pointing direction in the satellite's body coordinate system when the satellite has not swayed; R X This is the rotation matrix when the satellite rotates around the x-axis.

[0023] In another embodiment of the present invention, the satellite pointing vector under the Earth-fixed system is e = R. BCS ×s θ , where R BCS This is the transformation matrix for vectors in the satellite body coordinate system to the Earth-fixed coordinate system.

[0024] In another embodiment of the present invention, the included angle is Where pr is the target vector of the satellite pointing to the ground station in the Earth-fixed system at time t, pr = pr.

[0025] In another embodiment of the present invention, when |ρ|≤μ, the satellite is visible to the ground station, where μ is the maximum off-axis angle of the satellite antenna.

[0026] In another embodiment of the present invention, the step of calculating the visible time window further includes:

[0027] Calculate the angle between the satellite pointing vector and the satellite pointing to the ground station when the satellite pointing changes within the time window [t0, t1].

[0028] The time period during which the included angle |ρ|≤μ is determined is denoted as the satellite visibility time window.

[0029] This invention establishes a mapping relationship between the satellite's coordinate system and the Earth-fixed coordinate system by combining satellite orbit data and attitude pointing information. By comprehensively considering data such as ground station location and elevation constraints, it calculates the angle between the satellite pointing vector and the satellite-ground station vector, thereby determining the satellite's visibility to the ground station. This method is simple, easy to implement, and highly accurate, meeting the needs of ground station scheduling, tracking optimization, and coverage analysis in various satellite mission planning. Furthermore, it can be applied to dynamic coverage analysis of agile satellites and ground targets. Attached Figure Description

[0030] Figure 1 A schematic diagram showing the angle between the satellite pointing vector and the satellite pointing to the ground station in one embodiment of the present invention is shown;

[0031] Figure 2 A corresponding parameter table is shown in one embodiment of the present invention;

[0032] Figure 3 This diagram illustrates a simulation of various parameters when the satellite's pointing direction is tilted 30 degrees in one embodiment of the present invention.

[0033] Figure 4 A simulation diagram of various parameters is shown in one embodiment of the present invention when the satellite is pointing towards the Earth's center. Detailed Implementation

[0034] In the following description, the invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more specific details or with other alternatives and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure the inventive points of the invention. Similarly, for illustrative purposes, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of embodiments of the invention. However, the invention is not limited to these specific details.

[0035] Furthermore, it should be understood that the embodiments shown in the accompanying drawings are illustrative and not necessarily drawn to scale. In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not explicitly or implicitly suggest that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In this specification, references to "an embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing throughout this specification does not necessarily refer to the same embodiment in all instances.

[0037] Figure 1 A schematic diagram showing the angle between the satellite pointing vector and the satellite pointing to the ground station in one embodiment of the present invention is shown.

[0038] In one embodiment of the present invention, a satellite body coordinate system is defined using satellite position and velocity data. Within this coordinate system, the vector s pointing to the satellite is calculated when the satellite rotates θ around the x-axis. θ Then, the satellite pointing vector e in the Earth-fixed system is obtained. Based on the satellite pointing vector pr in the Earth-fixed system, as follows... Figure 1 As shown, pr = pr. Further calculations are performed to obtain the angle ρ between the satellite pointing vector and the satellite pointing vector to the ground station. When ρ satisfies the off-axis angle constraint, i.e., |ρ|≤μ, it indicates that the satellite is visible to the ground station. This yields the satellite's visible time period to the ground station. The maximum off-axis angle μ of the satellite antenna is a fixed value, known before calculating the satellite's visible time window.

[0039] like Figure 1 As shown, the angle ρ between the satellite pointing vector e and the satellite pointing vector pr to the ground station can be seen intuitively.

[0040] Figure 2 A table of corresponding parameters is shown in one embodiment of the present invention.

[0041] The simulated orbital data in one embodiment of the present invention will be described below.

[0042] like Figure 2As shown, in this embodiment, the semi-major axis is 6912.09 km; the eccentricity e is 0; the orbital inclination (degrees) is 97.4919°; the right ascension of the ascending node is 273.601°; the argument of perigee is 211.125°; and the mean perigee angle is 319.138°. The given ground station coordinates are (24.19, 55.68, 0.2464), with latitude and longitude in degrees and altitude in kilometers. The minimum elevation angle of the ground station is 5°, and the off-axis angle range of the satellite antenna is |μ|≤67.5°.

[0043] Based on the above data, simulations were performed to obtain the following: within the time window when the satellite enters the ground station, that is, within the arc segment where the elevation angle of the ground station relative to the satellite satisfies the minimum elevation angle of the ground station, when the satellite's pointing direction swings θ around the x-axis, at any time t, the angle between the satellite pointing vector to the ground station and the satellite pointing vector is Roll (ρ), the elevation angle of the ground station is Azimuth, and the lateral swing angle of the satellite relative to the ground station is Yaw.

[0044] Depend on Figure 1 It can be seen that when the satellite passes over the ground station, Roll = Yaw + θ.

[0045] Figure 3 A simulation diagram of various parameters is shown in one embodiment of the present invention when the satellite pointer is tilted 30 degrees to the side.

[0046] In this embodiment, the satellite pointing direction swings 30 degrees around the x-axis. Within the satellite's transit time, the angle between the satellite pointing vector to the ground station and the satellite pointing vector rolls. Figure 3 As shown by the blue curve, the elevation angle (Azimuth) of the ground station is... Figure 3 As shown by the green curve, the satellite points to the ground station via the vector Yaw. Figure 3 As shown by the red curve in the middle.

[0047] Depend on Figure 3 It can be seen that when the elevation angle Azimuth of the ground station is at its maximum,

[0048] Roll(min)=31.10086580449132,

[0049] Yaw(min)=1.500865949638646,

[0050] At this point, Roll = Yaw + θ holds true.

[0051] Figure 4 A simulation diagram of various parameters is shown in one embodiment of the present invention when the satellite is pointing towards the Earth's center.

[0052] In this embodiment, the satellite pointing direction swings 0 degrees around the x-axis, and the angle between the satellite pointing vector to the ground station and the satellite pointing vector is Roll, as shown below. Figure 4 As shown by the blue curve, the elevation angle (Azimuth) of the ground station is... Figure 4 As shown by the green curve; the angle Yaw between the satellite pointing vector to the ground station and the satellite pointing vector, as shown in the figure. Figure 4 As shown by the red curve in the middle.

[0053] As shown in the diagram, Roll and Yaw now completely overlap.

[0054] contrast Figure 3 and Figure 4 This demonstrates that the satellite's arrival time window changes when its pointing direction changes. Changes in the satellite's orbital position and velocity, as well as ground station information, also alter the satellite's visibility to the ground station. The simulation results show that the calculation error of the angle between the satellite pointing vector to the ground station and the satellite pointing vector is less than 0.001 arcseconds, indicating that this method has high calculation accuracy and is suitable for analyzing ground station coverage under dynamically changing satellite pointing conditions.

[0055] In summary, this invention calculates the angle between the satellite pointing vector and the satellite pointing vector towards the ground station based on high-precision satellite orbit data and satellite pointing attitude. Then, based on the maximum angle constraint of the satellite antenna roll axis, it calculates the arc segment within the satellite arc segment that satisfies the minimum elevation angle of the ground station, allowing the satellite antenna to cover the ground station. This scheme calculates a more accurate satellite transit arc segment. Furthermore, based on the characteristics of satellite motion, this scheme uses simple spatial vector operations, eliminating the need to calculate the antenna field-of-view cone coverage area, making the scheme itself simple and easy to implement. Moreover, considering the omnidirectional dynamic adjustment characteristics of satellite antenna pointing, it is not only suitable for traditional ground station coverage calculations but can also be efficiently applied to the dynamic analysis of coverage between agile satellites and ground targets.

[0056] 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 for analyzing ground station coverage based on dynamic pointing of satellite orbits, characterized in that, include: Determine the ground station position vector and the maximum off-axis angle of the satellite antenna under the Earth-fixed system; Calculate the time period during which the satellite passes over the ground station while satisfying the minimum elevation angle of the ground station; Construct a satellite coordinate system based on satellite position and velocity information; Determine the satellite pointing vector in the satellite's body coordinate system; Convert the satellite pointing vector to the Earth-fixed system; Calculate the angle between the satellite pointing vector and the satellite pointing to the ground station; as well as Record the time period during which the included angle is less than the maximum off-axis angle of the satellite antenna within the time period when the satellite passes over the ground station, and denote it as the satellite visible time window.

2. The ground station coverage analysis method based on dynamic pointing of satellite orbit as described in claim 1, characterized in that, The ground station position vector is p, which is the position vector from the Earth's center to the ground station; The maximum off-axis angle of the satellite antenna is μ. The satellite is visible when the angle between the satellite pointing vector and the satellite pointing to the ground station is less than the maximum off-axis angle of the satellite antenna.

3. The ground station coverage analysis method based on dynamic pointing of satellite orbit as described in claim 1, characterized in that, The steps for calculating the time period of satellite transit over ground stations include: Calculate the arc of the satellite passing over the ground station windows[t0,t1], that is, the arc trajectory of the satellite completing the entry and exit of the ground station within the time period [t0,t1]. Where t0 is the time when the satellite enters the ground station, t1 is the time when the satellite leaves the ground station, and [t0, t1] is the time period.

4. The ground station coverage analysis method based on dynamic pointing of satellite orbit as described in claim 1, characterized in that, The steps for constructing the satellite body coordinate system include: The z-axis points towards the Earth's center, denoted as s. z ; The x-axis points in the direction of the tangent to the satellite orbit, denoted as s. x ;as well as The y-axis direction is determined using the right-hand rule, denoted as s. y ; The satellite position and velocity information is (r,v), which represents the satellite's position and velocity in the Earth-fixed system at time t.

5. The ground station coverage analysis method based on dynamic pointing of satellite orbit as described in claim 1, characterized in that, The satellite pointing vector is s θ =(s x ,s y ,s z )×R X ×a, where a is the satellite's pointing direction in the satellite's body coordinate system when the satellite has not swayed; R X This is the rotation matrix when the satellite rotates around the x-axis.

6. The method for dynamic pointing-down ground station coverage analysis based on satellite orbit as described in claim 1, characterized in that, The satellite pointing vector in the Earth-fixed system is e = R BCS ×s θ , where R BCS This is the transformation matrix for vectors in the satellite body coordinate system to the Earth-fixed coordinate system.

7. The method for dynamic pointing-down ground station coverage analysis based on satellite orbit as described in claim 1, characterized in that, The included angle is Where pr is the target vector of the satellite pointing to the ground station in the Earth-fixed system at time t, pr = pr.

8. The method for dynamic pointing-down ground station coverage analysis based on satellite orbit as described in claim 7, characterized in that, When |ρ|≤μ, the satellite is visible to the ground station, where μ is the maximum off-axis angle of the satellite antenna.

9. The method for dynamic pointing-down ground station coverage analysis based on satellite orbit as described in claim 1, characterized in that, The step of calculating the visible time window also includes: Calculate the angle between the satellite pointing vector and the satellite pointing to the ground station when the satellite pointing changes within the time window [t0,t1]. The time period during which the included angle |ρ|≤μ is determined is denoted as the satellite visibility time window.

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