Low earth orbit satellite transit azimuth and elevation angle detection method

Abstract

This invention discloses a method for detecting the azimuth and elevation angles of a low-Earth orbit (LEO) satellite transit, belonging to the field of satellite communication technology. The method includes the following steps: obtaining the satellite coordinates and communication time differences for three consecutive two-way communications between a ground terminal and a LEO satellite; calculating the distance between the ground terminal and the satellite at the three communication times based on the communication time differences; calculating the ground terminal coordinates in the geocentric coordinate system based on the satellite coordinates and the calculated three distances at the three communication times; and calculating the elevation and azimuth angles of the satellite relative to the ground terminal using a vector method based on the satellite coordinates and ground terminal coordinates at the time of the last communication.

Description

Technical Field

[0001] This invention belongs to the field of satellite communication technology, and in particular relates to a method for detecting the azimuth and elevation angles of low-orbit satellites passing over the area. Background Technology

[0002] During communication between low-Earth orbit satellites and ground equipment, the azimuth and elevation angles of the satellite change in real time due to its rapid movement relative to the ground terminal. If the ground equipment uses a fixed antenna, its maximum radiation gain direction is fixed, and communication performance is optimal only when the satellite passes in that direction; at other times, the gain decreases, affecting communication quality. To improve communication performance, existing technologies typically use a server to pre-push the real-time elevation and azimuth angles of the satellite's passage. The ground equipment then uses a mechanical turntable to drive the antenna rotation or uses a phased array antenna to dynamically adjust the beam direction to achieve real-time tracking of the satellite. These methods rely on pre-acquired satellite orbit parameters and passage forecast information and require a stable communication link between the ground terminal and the backend server to ensure the real-time nature and accuracy of the angle data. Figure 1 As shown.

[0003] However, existing technologies have the following problems in practical applications: First, whether it's turntable tracking or phased array beam control, it's essential to ensure that the ground antenna coordinate system and the satellite angle information pushed by the backend are strictly consistent in the zero-degree direction; otherwise, tracking accuracy will significantly decrease. For moving ground terminals (such as vehicle-mounted, ship-mounted, or handheld devices), their attitude and position are constantly changing. Even if the satellite's transit angle information is obtained in advance, it cannot be guaranteed that the antenna's maximum gain direction is accurately pointing towards the satellite. Second, this method requires a stable and continuous communication connection between the terminal and the server backend to obtain satellite transit time and angle data, which increases the system's dependence on the communication link. Furthermore, for third-party satellite systems, transit angle information may be confidential data that the terminal cannot obtain, causing traditional tracking schemes to fail. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for detecting the azimuth and elevation angles of low-orbit satellites passing over the area, thereby resolving the issues present in the prior art.

[0005] To achieve the above objectives, the present invention provides a method for detecting the azimuth and elevation angles of a low-orbit satellite transit, comprising: Obtain the satellite coordinates and communication time difference of three consecutive two-way communications between the ground terminal and the low-Earth orbit satellite; The distance between the ground terminal and the satellite at the three communication times is calculated based on the communication time difference; Based on the satellite coordinates at the three communication times and the three calculated distances, the coordinates of the ground terminal in the geocentric-ground-fixed coordinate system are calculated. Based on the satellite coordinates at the last communication time and the ground terminal coordinates, the elevation and azimuth angles of the satellite relative to the ground terminal are calculated using the vector method.

[0006] Optionally, the process of obtaining the satellite coordinates and communication time difference for three consecutive two-way communications between the ground terminal and the low-Earth orbit satellite includes: The ground terminal sends a transmission signal to the receiving satellite, and the receiving satellite returns a reply signal based on the transmission signal. The satellite coordinates and satellite signal processing time difference are obtained based on the response signal analysis. The total time difference is recorded based on the transmission time of the transmitted signal and the reception time of the response signal.

[0007] Optionally, the process of calculating the distance between the ground terminal and the satellite at the three communication times based on the communication time difference includes: Subtract the satellite signal processing time difference from the total time difference to obtain the electromagnetic wave space transmission time difference; The distance is obtained by multiplying the time difference of electromagnetic wave spatial transmission by the speed of light.

[0008] Optionally, the process of solving the ground terminal coordinates in the geocentric-geostatic coordinate system includes: constructing three spherical equations with the satellite coordinate positions at the three communication times as the center and the corresponding three distances as the radii; and solving the three spherical equations simultaneously to obtain the ground terminal coordinates.

[0009] Optionally, the process of calculating the satellite's elevation angle relative to the ground terminal using the vector method includes: Using the line vector connecting the ground terminal and the origin of the geocentric coordinate system as the normal vector, construct a plane passing through the ground terminal; Calculate the vector connecting the satellite position and the ground terminal at the time of the last communication. Calculate the angle between the vector and the normal vector; The pitch angle is obtained by subtracting the included angle from 90 degrees.

[0010] Optionally, the process of calculating the azimuth using the vector method includes: The first plane is constructed using the line vector connecting the origin of the geocentric coordinate system to the ground terminal and the line vector connecting the origin to the Z-axis. Calculate the projection point of the satellite position at the time of the last communication onto the plane passing through the ground terminal and with the vector of the line connecting the ground terminal and the origin as the normal vector; Calculate the line vector connecting the projection point and the ground terminal; The azimuth angle is obtained by calculating the angle between the connecting vector and the first plane.

[0011] Optionally, during the three consecutive two-way communications, the satellite coordinates of the three communications are the satellite's location at three different times during the continuous transit.

[0012] The present invention also provides a computer, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described thereon.

[0013] The present invention also provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described thereon.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: This invention does not rely on a server to push satellite transit angle information, nor does it require strict alignment between the ground antenna coordinate system and the pushed data. It is applicable to fixed or mobile terminals, significantly reducing system deployment and alignment requirements. At the same time, it can independently complete terminal positioning and transit angle calculation using only the time difference of the two-way communication signal between the ground terminal and the low-orbit satellite and the coordinate information broadcast by the satellite itself, without the need to maintain a stable communication link with the server. Furthermore, since it does not require prior acquisition of satellite transit time and angle information, it can still achieve accurate antenna pointing control even for third-party or classified satellite systems that cannot obtain transit data, demonstrating good versatility and autonomy. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram illustrating satellite transit and ground terminal communication according to an embodiment of the present invention; Figure 2 This is a model diagram of the satellite overpass position and the relative position of the terminal in an embodiment of the present invention; Figure 3 This is a diagram illustrating the communication process between a satellite and a ground terminal according to an embodiment of the present invention; Figure 4 This is a diagram showing the elevation and azimuth angles of the satellite relative to the terminal, as well as an auxiliary planar model, according to an embodiment of the present invention. Figure 5 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0018] Example 1 like Figure 5 As shown, this invention is based on the fact that when a low-Earth orbit satellite communicates with ground equipment, the relative position elevation and azimuth angles are in real-time relative motion. By using the signal time difference from the ground equipment to the satellite and back, the distance between the satellite and the ground terminal at that moment can be calculated. This process is then repeated to calculate the distances between the satellite and the ground terminal for three consecutive satellites within a very short period of time. Moreover, each time the satellite returns a signal, it carries real-time position information to the terminal. Therefore, a geometric model is established to calculate the coordinate position of the ground terminal. The elevation and azimuth angles of the satellite relative to the ground terminal equipment are further calculated using the vector method, thereby controlling the ground terminal antenna to point the maximum gain radiation direction toward the satellite, thus improving communication performance.

[0019] like Figure 2 As shown, this embodiment provides a method for detecting the azimuth and elevation angles of a low-orbit satellite transit. First, the satellite coordinates and communication time differences of three consecutive two-way communications between the ground terminal and the low-orbit satellite are obtained. The communication time differences include the satellite signal processing time difference and the total time difference. Then, the distance between the ground terminal and the satellite at the three communication times is calculated based on the communication time differences.

[0020] The coordinate system in the figure is a geocentric coordinate system, where A is the location of the communication terminal on the Earth's surface, and the coordinates of point K are (x0, y0, z0). P1, P2, and P3 are the satellite coordinates at three simultaneous communication moments between the terminal and the satellite. Since the terminal can obtain the satellite's coordinates transmitted to it in real time each time it communicates with the satellite, the satellite coordinates at the three communication moments are known as follows: P1 (x1, y1, z1), P2 (x2, y2, z2), and P3 (x3, y3, z3). Taking the communication process between terminal K and the satellite at point P1 in the first moment as an example, calculate the distance L1 between P1 and point K. Figure 3The diagram illustrates the communication process. Terminal K sends a signal at time t1, which is received by the satellite at time t2. After processing by the satellite, a reply signal is sent back at time t3, along with its own coordinates and the signal processing time difference TA = t3 - t2, to the ground terminal K. The terminal receives the signal at time t4 and processes it to obtain the satellite's coordinates at that communication time. The coordinates of point P1 are (x1, y1, z1), which are known. The total time difference between the transmission and reception of the signal is TB = t4 - t1, completing the first two-way communication between the terminal and the satellite. Therefore, the electromagnetic wave spatial transmission time difference from terminal K to satellite P1 is TP1 = (TB - TA) / 2. The speed of electromagnetic wave transmission, approximately the speed of light, is c = 3 × 10⁻¹⁰. 8 (meters / second), so the distance between the terminal at point K and the satellite at point P1 is L1 = c × TP1.

[0021] Similarly, the spatial transmission time difference of the electromagnetic wave signal during the second communication between the ground terminal and the satellite can be calculated as TP2. The distance between the satellite's location P2 and the terminal's K point can be calculated as L2 = c × TP2. The spatial transmission time difference of the electromagnetic wave signal during the third communication between the ground terminal and the satellite can be calculated as TP3. The distance between the satellite's location P2 and the terminal's K point can be calculated as L3 = c × TP3. Therefore, after these three communications, the terminal can know the coordinates of the satellite and the relative distances L1, L2, and L3 between the satellite and the terminal's K point. Based on this satellite distance and coordinate information, the following equation can be established to calculate the coordinate position of the terminal's K point: [Specific calculation formula follows]. (x0-x1) 2 +(y0-y1) 2 +(z0-z1) 2 =L1 2 (1) (x0-x2) 2 +(y0-y2) 2 +(z0-z2) 2 =L2 2 (2) (x0-x3) 2 +(y0-y3) 2 +(z0-z3) 2 =L3 2 (3) The results obtained by combining the above formulas are as follows: x0=[1 / 2 (x1 2 -x2 2 +y1 2 -y2 2 +z1 2 -z2 2 +L2 2 -L12 )-(y1-y2)y0-(z1-z2)z0] / (x1-x2) (4) y0={1 / 2 (x1 2 -x3 2 +y1 2 -y3 2 +z1 2 -z3 2 +L3 2 -L1 2 ) (x1-x2)-1 / 2 (x1-x3) (1 / 2 (x1 2 -x2 2 +y1 2 -y2 2 +z1 2 -z2 2 +L2 2 -L1 2 ))+[(x1-x3) (z1-z2)-(x1-x2) (z1-z3)] z0} / [(x1-x3) (y1-y2)-(x1-x2) (y1-y3)] (5) Substituting the calculation results of formulas (4) and (5) with respect to x0 and y0 into formula (1), we obtain the calculation result of z0. The simplified quadratic equation expression is: A z0 2 +B z0 + C = 0, where A, B, and C are coefficients obtained from x1, y1, z1, x2, y2, z2, x3, y3, z3, L1, L2, and L3 through complex algebraic operations. According to the quadratic formula, we have: z0=[-B±(B 2 -4AC) 0.5 ] / 2A (6) Therefore, by finding the result of z0 and substituting z0 into formulas (4) and (5), the results of x0 and y0 can be calculated.

[0022] Based on the above method, given the coordinates of three consecutive points P1, P2, and P3 of the satellite within three extremely short time intervals, and the distances L1, L2, and L3 between the terminal and the three points of the satellite calculated by the terminal based on the communication time difference, the position of the terminal's coordinate point K (x0, y0, z0) can be deduced. Based on this information, the elevation angle and azimuth angle of the last position P3 of the satellite relative to the terminal's point K can be calculated.

[0023] The process of calculating the elevation angle of a satellite relative to a ground terminal using the vector method includes: constructing a plane passing through the ground terminal using the vector of the line connecting the ground terminal and the origin of the geocentric coordinate system as the normal vector; calculating the vector of the line connecting the satellite position and the ground terminal at the last communication time; calculating the angle between the vector and the normal vector; and subtracting the angle from 90 degrees to obtain the elevation angle.

[0024] The process of calculating the azimuth using the vector method includes: constructing a first plane using the line vector connecting the origin of the geocentric coordinate system and the ground terminal, and the line vector connecting the origin and the Z-axis; calculating the projection point of the satellite position at the last communication time onto the plane passing through the ground terminal and with the line vector connecting the ground terminal and the origin as the normal vector; calculating the line vector connecting the projection point and the ground terminal; and calculating the angle between the line vector and the first plane to obtain the azimuth.

[0025] The specific implementation process of calculating the elevation and azimuth angles of a satellite relative to a ground terminal using the vector method includes: According to the geocentric coordinate system, the vector connecting the origin (the Earth's center) and the terminal point K is: =(x0,y0,z0), in vector form Draw a perpendicular line to the perpendicular line A plane M is defined, and this plane M passes through point K. A vector is then used to connect the satellite's location P3 with the terminal point K. Therefore, vector The angle between the satellite and plane M is the elevation angle of the satellite at point P3 relative to the ground terminal point K. According to the point-normal form equation, the equation of plane M is x0(x-x0)+y0(y-y0)+z0(z-z0)=0. The simplified equation is: x0x+y0y+z0z=x0 2 +y0 2 +z0 2 (7) Therefore vector The angle α between the vector and plane M is equal to 90 degrees minus the vector. Normal vector to plane M The included angle, vector with vector The included angle ψ = arccos[| · | / (| || Based on the coordinates of point P3, point K, and the origin O, substituting them into the formula, we get ψ=arccos{|(x3-x0)x0+(y3-y0)y0+(z3-z0)x0| / {[(x3-x0)x0]} 2 +(y3-y0) 2 +(z3-z0) 2 ] 0.5 +(x0 2 +y0 2 +z0 2 ) 0.5}}, and 0°<ψ<90°, therefore: α = 90° - ψ (8) Then, based on the Earth-centered coordinate system, the azimuth angle of the satellite at point P3 relative to the terminal point K is calculated. The vector connecting the origin (the Earth's center) and the terminal point K is... =(x0,y0,z0), draw a vector connecting the origin to the Z-axis of the coordinate system. =(0,0,z d ), in vector and projects Construct a plane N, and then take the foot of the satellite's perpendicular from point P3 onto the aforementioned plane M as point PD3. Connect PD3 with the terminal point K to form a vector. ,so The angle between P3 and plane N is the azimuth angle β of the satellite at point P3 relative to the ground terminal point K. Therefore, we first need to calculate the coordinates (x, y) of the projection point of point P3 onto plane M, i.e., the perpendicular point PD3. PD3 ,y PD3 ,z PD3 The specific calculation method is based on the normal vector of plane M. =(x0,y0,z0), so x PD3 =x3+tx0(9) y PD3 =y3+ty0(10) z PD3 =z3+tz0(11) Substituting the above equation into the plane equation (7) of plane M, the value of t is calculated as follows: t=[(x0 2 +y0 2 +z0 2 -x3x0-y3y0-z3z0) / (x0 2 +y0 2 +z0 2 )] (12) Substituting the result of t (12) into the above equations (9) and (11), we can obtain the coordinates of point PD3 (x). PD3 ,y PD3 ,z PD3 The result of ).

[0026] According to the vector =(x0,y0,z0), vector =(0,0,z d ),vector = (x PD3 -x0,y PD3 -y0,z PD3 -z0) calculate vector The method for calculating the angle β between the plane and N is to take a normal vector of plane N. =(x Q ,y Q ,z Q ),vector The angle β with plane N is 90° - vector with vector Given the included angle ω, we obtain the following formula: (13) x Q = (14) y Q = (15) z Q =0 (16) Therefore, β = 90° - arccos[| · | / (| || |)]) (17) By combining formulas (13) and (17), the final elevation angle β of the satellite at point P3 and terminal point K can be calculated.

[0027] The above patented solution can calculate the elevation and azimuth angles of the last point of the satellite relative to the terminal based on the three communication information between the satellite and the terminal in a very short period of time, using vector and plane equations. This allows the ground terminal to adjust the maximum gain radiation direction of its antenna to point to the calculated azimuth, thereby improving the communication performance between the terminal and the satellite. Furthermore, by continuously calculating multiple sets of data from the three communication information between the satellite and the terminal, it is possible to ensure that the terminal antenna is always pointing to the azimuth of the satellite in real time.

[0028] This invention can calculate the coordinates of a ground terminal based solely on the coordinates of three points and the communication time difference during the transit of a single low-Earth orbit satellite. The invention utilizes the projection points and vectors of satellite coordinates onto a plane to calculate the real-time elevation and azimuth angles of the ground terminal relative to the transit of a single satellite.

[0029] As a specific implementation method of this embodiment, the model is established using 3D modeling software as shown above. Figure 2 As shown, the relevant parameters are substituted into formulas (1)-(17) for calculation to determine the rationality of the derivation of the pitch angle and azimuth angle of the technical solution of the present invention.

[0030] For example, given that the coordinates of three consecutive points P1 (49.88, 17.59, 49.88), P2 (50.28, 15.12, 50.28), and P3 (50.63, 12.62, 50.63) are used for communication between the satellite and the ground terminal, and the distances between the satellite and the ground terminal for the three communications are L1=29.46, L2=30.52, and L3=31.71 respectively, the coordinates of the terminal point K are calculated as (54.23, 25.27, 21.81) according to formulas (4)-(6). Substituting the coordinates of point K into formulas (7)-(14) in Section 5, the final calculated azimuth angle α of the satellite at point P3 relative to the terminal point K is 3.11°, while the actual model value is 3.15°, and the elevation angle β is 18.35°, while the actual model value is 18.32°. The calculation error of this invention is ±0.4°, which fully meets the usage requirements. Figure 4 The figure shown is a diagram of the elevation and azimuth angles of the satellite relative to the terminal and an auxiliary planar model according to an embodiment of the present invention.

[0031] Based on the above model verification, the calculation method is confirmed to be accurate and the patented solution is reasonable and effective.

[0032] The present invention also provides a computer, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described thereon.

[0033] The present invention also provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described thereon.

[0034] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for detecting the azimuth and elevation angles of a low-orbit satellite transit, characterized in that, Includes the following steps: The satellite coordinates and communication time differences of three consecutive two-way communications between the ground terminal and the low-Earth orbit satellite are obtained. The communication time difference includes the satellite signal processing time difference and the total time difference. The distance between the ground terminal and the satellite at the three communication times is calculated based on the communication time difference; Based on the satellite coordinates at the three communication times and the three calculated distances, the coordinates of the ground terminal in the geocentric-ground-fixed coordinate system are calculated. Based on the satellite coordinates at the last communication time and the ground terminal coordinates, the elevation and azimuth angles of the satellite relative to the ground terminal are calculated using the vector method.

2. The method for detecting the azimuth and elevation angles of a low-orbit satellite transit according to claim 1, characterized in that, The process of obtaining the satellite coordinates and communication time difference of three consecutive two-way communications between the ground terminal and the low-Earth orbit satellite includes: The ground terminal sends a transmission signal to the receiving satellite, and the receiving satellite returns a reply signal based on the transmission signal. The satellite coordinates and satellite signal processing time difference are obtained based on the response signal analysis. The total time difference is recorded based on the transmission time of the transmitted signal and the reception time of the response signal.

3. The method for detecting the azimuth and elevation angles of a low-orbit satellite transit according to claim 2, characterized in that, The process of calculating the distance between the ground terminal and the satellite at the three communication times based on the communication time difference includes: Subtract the satellite signal processing time difference from the total time difference to obtain the electromagnetic wave space transmission time difference; The distance is obtained by multiplying the time difference of electromagnetic wave spatial transmission by the speed of light.

4. The method for detecting the azimuth and elevation angles of a low-orbit satellite transit according to claim 1, characterized in that, The process of calculating the ground terminal coordinates in the geocentric-geostatic coordinate system includes: constructing three spherical equations with the satellite coordinate positions at the three communication times as the center and the corresponding three distances as the radii; and solving the three spherical equations simultaneously to obtain the ground terminal coordinates.

5. The method for detecting the azimuth and elevation angles of a low-orbit satellite transit according to claim 1, characterized in that, The process of calculating the satellite's elevation angle relative to the ground terminal using the vector method includes: Using the line vector connecting the ground terminal and the origin of the geocentric coordinate system as the normal vector, construct a plane passing through the ground terminal; Calculate the vector connecting the satellite position and the ground terminal at the time of the last communication. Calculate the angle between the vector and the normal vector; The pitch angle is obtained by subtracting the included angle from 90 degrees.

6. The method for detecting the azimuth and elevation angles of a low-orbit satellite transit according to claim 5, characterized in that, The process of calculating the azimuth using the vector method includes: The first plane is constructed using the line vector connecting the origin of the geocentric coordinate system to the ground terminal and the line vector connecting the origin to the Z-axis. Calculate the projection point of the satellite position at the time of the last communication onto the plane passing through the ground terminal and with the vector of the line connecting the ground terminal and the origin as the normal vector; Calculate the line vector connecting the projection point and the ground terminal; The azimuth angle is obtained by calculating the angle between the connecting vector and the first plane.

7. The method for detecting the azimuth and elevation angles of a low-orbit satellite transit according to claim 1, characterized in that, During the three consecutive two-way communications, the satellite coordinates of the three communications represent the satellite's location at three different moments during the continuous transit.

8. A computer comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in claim 1.

9. A storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in claim 1.

Images