Satellite-ground one-way distance correction method considering earth rotation

Abstract

The application provides an on-orbit satellite-ground one-way distance correction method considering the rotation of the earth, and the measuring equipment used comprises: an on-orbit satellite and a ground station; a distance correction module is added in the satellite-ground distance measuring system of the ground station, which comprises: a satellite-ground distance measuring model is established in the satellite-ground distance measuring system of the ground station without considering the rotation of the earth, and the satellite-ground distance without considering the influence factors of the rotation of the earth is obtained by using a relay ranging method; the projection of the displacement of the ground station along the satellite-ground connecting line caused by the rotation of the earth is calculated according to the rotation speed of the earth and the geographical latitude where the satellite-ground station is located; the asymmetric satellite-ground distance is corrected by using the projection distance correction, and high-precision satellite-ground one-way distance is obtained.

Description

Technical Field

[0001] This invention relates to the field of satellite orbit measurement technology, and in particular to a method for correcting the one-way distance between an on-orbit satellite and the ground, taking into account the Earth's rotation. Background Technology

[0002] In a transponder-based measurement system consisting of a satellite and a ground station, the ground station sends a ranging signal to the satellite. The satellite receives the signal and relays it. The ground station receives the relayed ranging signal, compares the phase difference between the transmitted and received signals, and calculates the two-way distance between the satellite and the ground station based on the signal transmission rate. This distance, along with the satellite's velocity, the ground station's antenna pointing direction, and atmospheric correction parameters, forms the basis for determining the satellite's orbit. The accuracy of the distance measurement results is crucial for achieving precise orbit determination of satellites in orbit.

[0003] Due to the relative motion between the satellite and the Earth, the spatial transmission paths of uplink and downlink signals are asymmetrical. During the satellite's approach to the ground station and its overhead pass, the uplink transmission distance is greater than the downlink transmission distance; conversely, during the satellite's overhead pass and its exit from the ground station, the uplink transmission distance is less than the downlink transmission distance. Transponder-based measurements cannot separate the unidirectional uplink and downlink distance values; the bidirectional ranging result must be divided by 2 to approximate the distance between the satellite and the ground station. This asymmetry in the uplink and downlink spatial distances between the satellite and the ground station causes measurement errors in the satellite-to-ground distance. Summary of the Invention

[0004] In view of the above, the purpose of this invention is to overcome the shortcomings of the prior art. A first aspect of this invention proposes a method for correcting the one-way distance between an on-orbit satellite and its ground station, taking into account the Earth's rotation. The measuring equipment used includes an on-orbit satellite and a ground station. A distance correction module is added to the satellite-to-ground distance measurement system of the ground station. The method includes the following steps:

[0005] Step 1: Establish a satellite-to-ground distance measurement model between the satellite ground station and the satellite in orbit in the ground station's satellite-to-ground distance measurement system without considering the Earth's rotation, and obtain the satellite-to-ground distance without considering the influence of the Earth's rotation using the transponder-based ranging method.

[0006] Step 2: Based on the Earth's rotation speed and the geographical latitude of the satellite ground station, calculate the projection of the displacement of the ground station caused by the Earth's rotation onto the line connecting the satellite and the ground.

[0007] Step 3: Use projection distance correction to correct the asymmetric satellite-to-ground distance to obtain a high-precision satellite-to-ground one-way distance.

[0008] As described in the first aspect of the present invention, step 1 includes:

[0009] Step 1.1: The ground station sends an uplink ranging signal to the satellite in orbit;

[0010] Step 1.2: After receiving the measurement signal, the on-orbit satellite completes signal synchronization, generates a downlink signal based on the frequency and phase of the uplink ranging signal, and forwards it to the ground station;

[0011] Step 1.3: The ground station completes the ranging signal synchronization and calculates the downlink measurement signal phase and the uplink measurement signal phase;

[0012] Step 1.4: Calculate the satellite-to-ground distance without considering the influence of Earth's rotation based on the downlink measurement signal phase, uplink measurement signal phase, and uplink measurement signal transmission speed.

[0013] As described in the first aspect of the present invention, the one-way spatial distance s between Earth and space, without considering the influence of Earth's rotation, is expressed by the following formula:

[0014]

[0015] Where f is the frequency of the ranging signal, c is the propagation speed of electromagnetic waves in space, and φ up2 It is the phase of the uplink measurement signal, φ up1 It is the downlink measurement signal phase.

[0016] As described in the first aspect of the present invention, step 2 includes the following sub-steps:

[0017] Step 2.1: Calculate the linear velocity of the ground station as the Earth rotates within one distance measurement cycle;

[0018] Step 2.2: Calculate the displacement of the ground station due to the Earth's rotation;

[0019] Step 2.3: Based on the azimuth and elevation angles of the on-orbit satellite relative to the ground station, the distance change of the ground station along the line connecting the satellite and the ground station due to the Earth's rotation can be calculated.

[0020] As described in the first aspect of the present invention, the distance change along the direction of the star-ground connection caused by the displacement of the ground station due to the Earth's rotation, obtained in step 3, is used to correct the star-ground distance calculated in step 1 without considering the influence of the Earth's rotation, thereby obtaining the one-way star-ground distance that takes into account the Earth's rotation correction.

[0021] As described in the first aspect of the present invention, the high-precision one-way distance between satellite and ground, taking into account the correction for the ground station's rotation with respect to the Earth's rotation, is expressed as follows:

[0022]

[0023] Where A is the azimuth angle, E is the elevation angle, and B is the geographical latitude of the ground station.

[0024] A second aspect of the present invention provides a satellite-to-ground distance measurement system for taking into account the one-way distance between an on-orbit satellite and the ground station, the measurement system comprising: an on-orbit satellite and a ground station; the ground station comprising a telemetry and control baseband processing module and a ground station monitoring module, the ground station monitoring module comprising: a time difference measurement monitoring and management unit; the telemetry and control baseband processing module comprising: a distance measurement unit and a distance correction module.

[0025] As described in the second aspect of the present invention, in the satellite-to-ground distance measurement system, the distance measurement unit calculates the satellite-to-ground distance without considering the influence of the Earth's rotation based on the downlink measurement signal phase, uplink measurement signal phase, and uplink measurement signal transmission speed obtained by the ground station, and forwards it to the time difference measurement monitoring and management unit and the distance correction module.

[0026] As described in the second aspect of the present invention, in the satellite-to-ground distance measurement system, the time difference measurement monitoring and management unit sends the latitude and longitude information of the ground station to the distance correction module. The distance correction module calculates the satellite-to-ground distance of the orbiting satellite considering the Earth's rotation based on the satellite-to-ground distance corrected without considering the influence of the Earth's rotation, the azimuth and elevation angles of the ground station, and the latitude and longitude information of the ground station.

[0027] The beneficial effects of this invention are as follows: the technical solution adopted is based on the principle of transponder ranging, and establishes a motion model of the satellite and ground station in the geocentric coordinate system. The displacement of the ground station generated by the Earth's rotation is used to correct the satellite-to-ground distance, thereby obtaining a high-precision one-way satellite-to-ground distance. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a model for measuring distances between stars and the Earth that does not consider the Earth's rotation.

[0029] Figure 2 This is a schematic diagram of a model for measuring distances between stars and the Earth that takes into account the Earth's rotation.

[0030] Figure 3 This is a schematic diagram illustrating the calculation of the rotation speed and displacement of a ground station as it rotates with the Earth.

[0031] Figure 4 This is a schematic diagram illustrating the calculation process of the unidirectional distance correction.

[0032] Figure 5 This is a schematic diagram of the composition of a distance measuring positive system. Detailed Implementation

[0033] A method for correcting the distance between an on-orbit satellite and the ground station that takes into account the Earth's rotation is provided, which is mainly used to eliminate ranging errors caused by the asymmetry of uplink and downlink signal transmission distances between the satellite and the ground station.

[0034] Based on the principle of the transponder ranging system, within a measurement cycle, after the satellite completes uplink ranging signal locking and generates downlink ranging signals to transmit to the ground, the satellite's motion state is independent of the satellite-to-ground distance measurement result. However, during the time the satellite's downlink signal reaches the ground station, the relative motion of the ground station relative to the satellite's position at the sampling time, caused by the Earth's rotation, becomes the main factor contributing to the asymmetry in uplink and downlink signal transmission delays. Therefore, taking the satellite's position at the time of transmitting the downlink measurement signal as a reference, the change in the ground station's distance relative to this reference is mainly caused by the Earth's rotation. Calculating this distance and then using the relationship between distance and signal transmission delay, the distance correction can be obtained. The specific implementation follows these steps:

[0035] Step 1: Establish a satellite-to-ground distance measurement model that does not consider Earth's rotation between the satellite ground station and the satellite in orbit, and obtain the satellite-to-ground distance without correcting for the influence of Earth's rotation based on the principle of transponder ranging.

[0036] Step 2: Based on the Earth's rotation speed and the geographical latitude of the satellite ground station, calculate the projection of the displacement of the ground station caused by the Earth's rotation onto the line connecting the satellite and the ground.

[0037] Step 3: Use projection distance correction to correct the asymmetric satellite-to-ground distance to obtain a high-precision satellite-to-ground one-way distance.

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] The first aspect of this invention proposes a method for correcting the one-way distance between an on-orbit satellite and its ground station, taking into account the Earth's rotation. The measurement equipment used includes an on-orbit satellite and a ground station. A distance correction module is added to the satellite-to-ground distance measurement system of the ground station. The method includes the following steps:

[0040] Step 1: Establish a satellite-to-ground distance measurement model between the satellite ground station and the satellite in orbit in the ground station's satellite-to-ground distance measurement system without considering the Earth's rotation, and obtain the satellite-to-ground distance without considering the influence of the Earth's rotation using the transponder-based ranging method.

[0041] Step 2: Based on the Earth's rotation speed and the geographical latitude of the satellite ground station, calculate the projection of the displacement of the ground station caused by the Earth's rotation onto the line connecting the satellite and the ground.

[0042] Step 3: Use projection distance correction to correct the asymmetric satellite-to-ground distance to obtain a high-precision satellite-to-ground one-way distance.

[0043] As described in the first aspect of the present invention, step 1 includes:

[0044] Step 1.1: The ground station sends an uplink ranging signal to the satellite in orbit;

[0045] Step 1.2: After receiving the measurement signal, the on-orbit satellite completes signal synchronization, generates a downlink signal based on the frequency and phase of the uplink ranging signal, and forwards it to the ground station;

[0046] Step 1.3: The ground station completes the ranging signal synchronization and calculates the downlink measurement signal phase and the uplink measurement signal phase;

[0047] Step 1.4: Calculate the satellite-to-ground distance without considering the influence of Earth's rotation based on the downlink measurement signal phase, uplink measurement signal phase, and uplink measurement signal transmission speed.

[0048] As described in the first aspect of the present invention, the one-way spatial distance s between Earth and space, without considering the influence of Earth's rotation, is expressed by the following formula:

[0049]

[0050] Where f is the frequency of the ranging signal, c is the propagation speed of electromagnetic waves in space, and φ up2 It is the phase of the uplink measurement signal, φ up1 It is the downlink measurement signal phase.

[0051] As described in the first aspect of the present invention, step 2 includes the following sub-steps:

[0052] Step 2.1: Calculate the linear velocity of the ground station as the Earth rotates within one distance measurement cycle;

[0053] Step 2.2: Calculate the displacement of the ground station due to the Earth's rotation;

[0054] Step 2.3: Based on the azimuth and elevation angles of the on-orbit satellite relative to the ground station, the distance change of the ground station along the line connecting the satellite and the ground station due to the Earth's rotation can be calculated.

[0055] As described in the first aspect of the present invention, the distance change along the direction of the star-ground connection caused by the displacement of the ground station due to the Earth's rotation, obtained in step 3, is used to correct the star-ground distance calculated in step 1 without considering the influence of the Earth's rotation, thereby obtaining the one-way star-ground distance that takes into account the Earth's rotation correction.

[0056] As described in the first aspect of the present invention, the high-precision one-way distance between satellite and ground, taking into account the correction for the ground station's rotation with respect to the Earth's rotation, is expressed as follows:

[0057]

[0058] Where A is the azimuth angle, E is the elevation angle, and B is the geographical latitude of the ground station.

[0059] A second aspect of the present invention provides a satellite-to-ground distance measurement system for taking into account the one-way distance between an on-orbit satellite and the ground station, the measurement system comprising: an on-orbit satellite and a ground station; the ground station comprising a telemetry and control baseband processing module and a ground station monitoring module, the ground station monitoring module comprising: a time difference measurement monitoring and management unit; the telemetry and control baseband processing module comprising: a distance measurement unit and a distance correction module.

[0060] As described in the second aspect of the present invention, in the satellite-to-ground distance measurement system, the distance measurement unit calculates the satellite-to-ground distance without considering the influence of the Earth's rotation based on the downlink measurement signal phase, uplink measurement signal phase, and uplink measurement signal transmission speed obtained by the ground station, and forwards it to the time difference measurement monitoring and management unit and the distance correction module.

[0061] As described in the second aspect of the present invention, in the satellite-to-ground distance measurement system, the time difference measurement monitoring and management unit sends the latitude and longitude information of the ground station to the distance correction module. The distance correction module calculates the satellite-to-ground distance of the orbiting satellite considering the Earth's rotation based on the satellite-to-ground distance corrected without considering the influence of the Earth's rotation, the azimuth and elevation angles of the ground station, and the latitude and longitude information of the ground station.

[0062] like Figure 1 As shown, a satellite-to-ground distance measurement model is established without considering Earth's rotation. Based on the transponder ranging principle, the ground station sends an uplink ranging signal. After receiving the measurement signal, the satellite synchronizes its signal and generates a downlink signal based on the frequency and phase of the uplink ranging signal, which is then relayed to the ground station. The ground station synchronizes the ranging signal and calculates the downlink measurement signal phase φ. up1 Phase φ of the uplink measurement signal up2 .

[0063] Considering the distance between the satellite and the ground station, the satellite signal, upon reaching the ground, experiences a spatial transmission delay. This spatial transmission distance is equivalent to the phase difference of the uplink measurement signal. The known uplink measurement signal rate is R. pn The one-way distance in space is:

[0064]

[0065] Where f is the frequency of the ranging signal and c is the speed of light (i.e., the transmission rate of electromagnetic waves in space). Multiplying by 1 / 2 here is to evenly distribute the two-way delay of the uplink and downlink signals to obtain the one-way distance.

[0066] like Figure 2As shown, considering the Earth's rotation, a satellite-to-ground distance measurement model is established in a geocentric coordinate system, which more closely approximates the actual state of satellite-to-ground distance measurement in orbit. During the satellite-to-ground distance measurement process, the Earth rotates, and the near-Earth satellite orbits the Earth under the influence of gravity. The distance between the satellite and the ground station lies only on the line connecting the satellite and the ground, also known as the radial distance.

[0067] According to the principle of transponder ranging, considering the ground station's rotation with the Earth, from the time the uplink ranging signal is sent until the satellite receives the uplink ranging signal, completes signal synchronization, and generates a downlink ranging signal to forward to the ground station, the displacement of the ground station due to the Earth's rotation within one measurement cycle results in a radial displacement of the ground station relative to the satellite. For the satellite, although it is in motion within one measurement cycle, the time corresponding to the satellite-to-ground distance within that cycle is the time when the satellite sends the downlink ranging signal, and is independent of the satellite's motion state before and after that moment. Therefore, when correcting for the space transmission distance, only the error caused by the Earth's rotation needs to be considered.

[0068] like Figure 3 As shown, to calculate the displacement of the ground station relative to the satellite along the latitude line caused by the Earth's rotation, the rotational velocity of the ground station is first obtained. The geographical latitude of the ground station is ∠B, the Earth's equatorial radius is 6378.130 km, the polar radius is 6356.752 km, and the average radius is 6356.470 km. The Earth's rotation period is 23 hours, 56 minutes, and 4 seconds, or 86164 seconds. The value of pi is taken as 3.142. The linear velocity ν of the ground station due to the Earth's rotation can be calculated using the following formula:

[0069] ν=2π(6356.4695·cosB) / 86164=463.5817cosB (2)

[0070] (2) In equation B, the latitude of the ground station is given. Using the principle that distance equals velocity multiplied by time, the time of the ground station's rotation within one distance measurement cycle is equal to the bidirectional transmission delay of the uplink and downlink measurement signals. According to formula (1), this time is...

[0071]

[0072] The displacement Δs of the ground station due to the Earth's rotation can be calculated:

[0073]

[0074] like Figure 4As shown, C represents the location of the ground station, and the plane where the ground station is located is the plane tangent to the Earth at the location of the ground station. O′ is the intersection of the line connecting the satellite in orbit and the Earth's center with the tangent plane. CO′ is the azimuth angle pointing from the ground station to the satellite, with true north as 0° and the clockwise angle being the azimuth angle ∠A. According to the definition of azimuth angle, CO′ is also the projection line of the satellite-ground connection CA onto the tangent plane, and the angle ∠E between the satellite-ground connection CA and CO′ is the elevation angle. After obtaining the displacement Δs of the ground station caused by the Earth's rotation, the change in distance Δs along the direction of the satellite-ground connection CA can be calculated based on the azimuth and elevation angles of the satellite relative to the ground station.

[0075] First, it is known that Δs is along the parallel of latitude, in the same direction as the Earth's rotation. Draw CO′⊥BO′ through point O′, BO′ intersects the parallel of latitude at point B. Draw BD⊥CD through point B. Since CO′ is the projection of the Earth-Satellite line CA onto the tangent plane, plane CO′A is perpendicular to the tangent plane, and the intersection of the two planes is CO′. Furthermore, since CO′⊥BO′, we know that BO′ is perpendicular to plane CO′A. In summary, the projection of s onto plane CO′A is s. CO′ Coinciding with CO′, s can be obtained from the following formula. co′ :

[0076]

[0077] (4) In the formula, A is the azimuth angle.

[0078] Because BD⊥CD and BO′ is perpendicular to plane CO′A, O′D⊥CA. Therefore, s will be placed in plane CO′A. CO′ By decomposing the data onto the star-to-ground line CA, we can obtain the component s of Δs along the star-to-ground line. CA :

[0079] s CA =s CO′ ·cos∠DCO′=s CO′ ·cosE=-Δs·sinAcosE (5)

[0080] (5) In the formula, E is the pitch angle.

[0081] The s obtained from equation (5) CA The two-way time delay correction is divided by 2 to obtain the one-way time delay correction. Using this to correct s in equation (1), we can obtain the high-precision one-way satellite-to-ground distance s′ that takes into account the correction of the ground station with the Earth's rotation:

[0082]

[0083] (6) The entire calculation process has taken into account that the direction of motion is positive from west to east and the direction of rotation of the angle is positive in the clockwise direction. The distance and speed involved in the calculation process can be calculated as scalars to simplify the calculation process.

[0084] Figure 5 The image shows a high-precision satellite-to-ground distance measurement system with the addition of a distance correction module. The distance measurement unit can output the satellite-to-ground one-way / two-way distance or φ. up1 φ up2 The angle measurement unit can output the antenna azimuth angle A and elevation angle E to the time difference correction module; the time difference measurement monitoring and management unit of the ground station provides the ground station coordinates to the time difference correction module, which includes the ground station latitude information B.

[0085] The above examples are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for correcting the one-way distance between an on-orbit satellite and the ground, taking into account the Earth's rotation, characterized in that, The measurement equipment used includes: on-orbit satellites and ground stations; a distance correction module is added to the satellite-to-ground distance measurement system of the ground station, and the method includes the following steps: Step 1: Establish a satellite-to-ground distance measurement model between the satellite ground station and the satellite in orbit in the ground station's satellite-to-ground distance measurement system without considering the Earth's rotation, and obtain the satellite-to-ground distance without considering the influence of the Earth's rotation using the transponder-based ranging method. Step 2: Based on the Earth's rotation speed and the geographical latitude of the satellite ground station, calculate the projection of the displacement of the ground station caused by the Earth's rotation onto the line connecting the satellite and the ground. Step 3: Use projection distance correction to correct the asymmetric satellite-to-ground distance and obtain a high-precision satellite-to-ground one-way distance. Step 2 includes the following sub-steps: Step 2.1: Calculate the linear velocity of the ground station as the Earth rotates within one distance measurement cycle; Step 2.2: Calculate the displacement of the ground station due to the Earth's rotation; Step 2.3: Based on the azimuth and elevation angles of the on-orbit satellite relative to the ground station, calculate the change in distance of the ground station along the line connecting the satellite and the ground station due to the Earth's rotation. Using the distance change along the star-ground connection direction caused by the displacement of the ground station due to the Earth's rotation obtained in step 3, the star-ground distance calculated in step 1 without considering the influence of the Earth's rotation is corrected to obtain the one-way star-ground distance considering the Earth's rotation correction. The high-precision one-way distance between satellite and ground, taking into account the correction for ground station rotation with the Earth's rotation, is expressed as: in, A For azimuth, E The pitch angle, B It is the geographical latitude of the ground station. This is the two-way delay correction amount. It is the phase of the uplink measurement signal. It is the downlink measurement signal phase. s This refers to the one-way spatial distance between Earth and space, without considering the influence of Earth's rotation. The frequency of the ranging signal, This refers to the propagation speed of electromagnetic waves in space.

2. The method as described in claim 1, characterized in that, Step 1 includes: Step 1.1: The ground station sends an uplink ranging signal to the satellite in orbit; Step 1.2: After receiving the measurement signal, the on-orbit satellite completes signal synchronization, generates a downlink signal based on the frequency and phase of the uplink ranging signal, and forwards it to the ground station; Step 1.3: The ground station completes the ranging signal synchronization and calculates the downlink measurement signal phase and the uplink measurement signal phase; Step 1.4: Calculate the satellite-to-ground distance without considering the influence of Earth's rotation based on the downlink measurement signal phase, uplink measurement signal phase, and uplink measurement signal transmission speed.

3. The method as described in claim 2, characterized in that, The unidirectional spatial distance *s* between Earth and space, without considering the influence of Earth's rotation, is expressed by the following formula: 。

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