An ultra-low orbit space-based guided ground measurement, control and tracking method and system

Abstract

The present invention relates to an ultra-low orbit space-based guided ground tracking and control method and system. The method comprises the following steps: S1, obtaining single-point positioning data of an aircraft, determining whether ephemeris departure has occurred, and if so, executing step S2; S2, performing orbit extrapolation based on the single-point positioning data; S3, correcting the orbit extrapolation result based on an autonomous orbit control strategy, and obtaining predicted orbit data for ephemeris calculation; S4, calculating the station address and tracking time required for the next tracking and control based on the predicted orbit data; S5, determining whether the difference between the tracking and control time for the next tracking and control and the current time is less than a set threshold, and if so, executing step S6; S6, calculating the pitch angle and azimuth angle required for the next tracking and control, integrating the predicted orbit data, tracking and control time, pitch angle, and azimuth angle, and transmitting a short message based on the station address. Compared with existing technologies, the present invention has the advantages of achieving efficient tracking and eliminating the need for large-scale blind scanning and acquisition.

Description

Technical Field

[0001] The present invention belongs to the field of ultra-low orbit technology, and in particular relates to an ultra-low orbit space-based guided ground measurement, control and tracking method and system. Background Art

[0002] After launching into orbit, ultra-low-orbit spacecraft often face challenges with ground-based orbit determination due to the constant need for orbit maintenance. (Normal ground-based orbit determination requires four to five consecutive orbits without orbital control, resulting in highly accurate orbit prediction.) Without ground-based orbit determination, tracking by ground-based TT&C antennas often presents challenges. Ground-based tracking relies on calculated ephemeris, elevation, and azimuth for initial acquisition. The ground-based equipment has a field of view of approximately 5°, corresponding to a 250km ultra-low orbit. At an elevation of 3°, the range is approximately 1500km, and at 5°, the acceptable error is only 65km. Maintaining a single orbit at a 250km ultra-low orbit requires a speed of 72m / s, resulting in a controlled position of approximately 200km per orbit. Even with the support of domestic measurement stations, the longest TT&C interval is six orbits or more, making accurate estimation impossible. This results in the inability to complete basic satellite TT&C tasks, potentially leading to irreparable damage to the ultra-low-orbit spacecraft.

[0003] Currently, orbit determination for satellites with orbit control is often performed using propulsion strategies. However, this method suffers from low accuracy and is impractical when propulsion strategies are implemented autonomously onboard. When satellites are autonomously controlling their orbits and orbit prediction is unavailable on the ground, how ground stations can accurately track satellites remains a pressing technical challenge.

[0004] Existing patent CN103178895B discloses an inter-satellite measurement and control method for a satellite mobile communications constellation. This method utilizes three GEO satellites to perform measurement and control on LEO satellites within their respective fields of view. The three GEO satellites include a master GEO satellite and two slave GEO satellites. The GEO satellites receive uploaded measurement and control instructions and transmit them directly or via the two slave GEO satellites to the corresponding LEO satellites. The two slave GEO satellites and the master GEO satellite then downlink the received measurement and control information from the LEO satellite via the master GEO satellite. However, the related prior art does not propose a ground-based measurement and control tracking method that is primarily space-based. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide an ultra-low orbit space-based dominated ground measurement and control tracking method and system that can achieve efficient tracking and does not require large-scale blind scanning capture.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for ultra-low orbit space-based guided ground tracking and measurement includes the following steps:

[0008] S1. Obtain the single point positioning data of the aircraft and determine whether ephemeris departure occurs. If so, execute step S2; if not, return to step S1;

[0009] S2. performing orbit extrapolation based on the single point positioning data;

[0010] S3. Correct the orbit extrapolation result based on the autonomous orbit control strategy to obtain the predicted orbit data for ephemeris calculation;

[0011] S4. Calculating the station location and tracking time required for the next tracking and control based on the predicted orbit data;

[0012] S5. Determine whether the difference between the measurement and control time of the next measurement and control tracking and the current time is less than a set threshold. If so, execute step S6; if not, return to step S4;

[0013] S6. Calculate the pitch angle and azimuth angle required for the next measurement, control and tracking, integrate the predicted orbit data, measurement and control time, pitch angle and azimuth angle, and send a short message according to the station address.

[0014] Furthermore, the station address required for the next measurement, control and tracking is obtained based on a preset on-board ground station address database.

[0015] Furthermore, the predicted orbit data includes time and six orbit numbers.

[0016] Furthermore, the station address required for the next measurement, control and tracking is calculated as follows:

[0017] According to the predicted orbit data, the corresponding WGS84 coordinate system orbit information is obtained, and the vector RSi pointing from the i-th ground station to the aircraft in the WGS84 coordinate system is calculated. If there exists |RSi| <R max , it is determined that the aircraft enters the i-th ground station, and then the station address required for the next measurement, control and tracking is determined.

[0018] Furthermore, if there are multiple ground stations satisfying |RSi| <R max , then the ground station with the highest priority or the ground station with the longest entry time is selected to determine the station site required for the next measurement, control and tracking.

[0019] Furthermore, the calculation formulas for the pitch angle and azimuth angle of the ground station are as follows:

[0020] θ=asin(RSi e (3) / |RSi|)

[0021] Φ=atan2(RSi e (2),RSi e (1)

[0022] Among them, θ is the pitch angle, Φ is the azimuth angle, RSi e RSi is the vector pointing from the ground station to the aircraft in the northeast celestial coordinate system. e =[RSi e (1),RSi e (2),RSi e (3)], RSi is the vector from the ground station to the aircraft in the WGS84 coordinate system, and |RSi| is the modulus of RSi.

[0023] Furthermore, the short message is sent using Beidou short message sending.

[0024] Furthermore, when performing the orbit extrapolation, the points of each minute within the prediction time period are calculated sequentially during the initialization phase, and after the initialization phase is completed, calculations are performed according to the points after the prediction time period.

[0025] The present invention also provides a computer-readable storage medium, comprising one or more programs for execution by one or more processors of an electronic device, wherein the one or more programs include instructions for executing the ultra-low orbit space-based dominated ground measurement, control and tracking method as described above.

[0026] The present invention also provides an ultra-low orbit space-based dominant ground measurement, control and tracking system, comprising a space-based main body and a ground measurement station, wherein:

[0027] The space-based subject obtains the predicted orbit data, tracking time, pitch angle and azimuth angle based on the steps of the ultra-low orbit space-based dominant ground tracking and control method described above, and sends the data to the ground station with the corresponding station address via a short message;

[0028] The ground station is used to realize the measurement, control and tracking of the target space-based body on the ground.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention proposes a ground measurement, control and tracking method dominated by space-based systems, which can enable ground equipment to track the aircraft while the propulsion strategy is autonomously completed on board, thus achieving ground measurement and control support for ultra-low-orbit satellites with high precision.

[0031] 2. The present invention uses the spacecraft to complete single-point positioning by itself, combined with the orbit control strategy for prediction, and calculates the ephemeris based on the station situation, thereby realizing ground station tracking based on on-orbit autonomous orbit control. It provides a feasible method for efficient ground station tracking for spacecraft such as ultra-low-orbit spacecraft that require high-frequency orbital maneuvers and on-board autonomous orbit control, without the need for large-scale blind scanning and capture, and has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the internal information flow of the aircraft measurement, control and prediction system in the present invention;

[0033] Figure 2 This is a schematic diagram of the space-ground information flow for measurement, control and forecasting in the present invention;

[0034] Figure 3 Flowchart of the measurement and control method of the present invention;

[0035] Figure 4 The diagram is a schematic diagram showing the calculation principle of the longest distance in the ephemeris corresponding to the elevation angle of the ground station in an embodiment of the present invention. E is the radius of the earth, H is the altitude of the satellite orbit;

[0036] Figure 5 Schematic diagram of the calculation principle of the azimuth and elevation angles required by the ground station in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0038] Example 1

[0039] This embodiment provides an ultra-low orbit space-based guided ground tracking and control method, which uses space-based guidance to calculate the sites required for the next ground tracking and control, as well as the elevation and azimuth angles required for site tracking. Within a set time range before tracking, the predicted orbital conditions and the elevation and azimuth angles required for tracking are transmitted via real-time communication means such as Beidou short messages, thereby achieving ground tracking and control of the target spacecraft. Figure 1 As shown, the method is run in a space-based subject, i.e., a satellite (aircraft, spacecraft), and includes the following steps:

[0040] S1. Obtain the single-point positioning data of the aircraft and determine whether ephemeris departure occurs. If so, execute step S2; if not, return to step S1.

[0041] S2. Orbit extrapolation based on single-point positioning data.

[0042] When the aircraft's orbit is frequently controlled, the onboard GNSS orbit determination often fails to converge. Therefore, the aircraft is normally in the GNSS positioning state. This embodiment triggers the above process based on the ephemeris output. After the ephemeris is output, single-point positioning data is output, and real-time single-point positioning data extrapolation is performed to form predicted orbit data.

[0043] In this embodiment, orbital extrapolation is implemented using existing orbital extrapolation methods, such as numerical integration and analytical methods. During the prediction process, during the initialization phase, calculations are performed sequentially for each minute within the prediction time period. After the initialization phase is complete, calculations are performed for points after the prediction time period. The prediction time period can be set to 15 minutes.

[0044] S3. Based on the autonomous orbit control strategy, the orbit extrapolation result is corrected according to the orbital dynamics to obtain the predicted orbit data for ephemeris calculation.

[0045] S4. Calculate the station address and tracking time required for the next tracking based on the predicted orbit data. In this embodiment, the station address required for the next tracking is obtained based on a preset onboard ground station address database.

[0046] S5. Determine whether the difference between the measurement and control time of the next measurement and control tracking and the current time is greater than a set threshold. If so, execute step S6; if not, return to step S4.

[0047] In this embodiment, the threshold is set to 15 minutes.

[0048] S6. Calculate the pitch angle and azimuth angle required for the next measurement, control and tracking, integrate the predicted orbit data, measurement and control time, pitch angle and azimuth angle, and send a short message according to the station address.

[0049] In this embodiment, after initialization is completed, the process of calculating the ephemeris based on the predicted orbit data is specifically as follows:

[0050] The WGS84 coordinate system parameters of the station are annotated, such as [rx1, ry1, rz1, minimum elevation angle 1] and [rx1, ry2, rz3, minimum elevation angle 2]. The WGS84 coordinate system orbit [Rx, Ry, Rz, H] 15 minutes later is obtained through the onboard orbit prediction. In this embodiment, the onboard orbit prediction adopts the existing conventional algorithm. The vector RSi pointing to the satellite from the i-th ground station in the WGS84 coordinate system is calculated as [Rx-rxi, Ry-ryi, Rz-rzi], and the modulus of the distance vector RSi, that is, the distance scalar between each ground station and the satellite, is calculated. For the predicted orbit 15 minutes later, the distance calculation is performed for all stations, and the distance method is used for screening. When |RSi| <R max When you enter the country, R maxis the longest distance in the ephemeris corresponding to the ground station elevation angle, which can be obtained by using the cosine theorem, such as Figure 4 As shown, record T1, and further refine the entry time. Extrapolate to 1s interval between T1-1min and T1 to get a more accurate T1. Then calculate the exit time. Extrapolate the exit time from T1 for 1 minute. When |RSi|>R max Stop and record T2. You can further refine the departure time and extrapolate it to 1s intervals between T2-1min and T2 to obtain a more accurate T2.

[0051] When multiple stations enter at the same time, the ground station with the highest priority / the station with the longest entry time is selected for use.

[0052] Calculate the azimuth and elevation angles required by the ground station at T1 time, and convert the coordinate system of RSi to the Northeast Sky coordinate system (ENU) used by the ground station.

[0053] RSi e =R efi *RSi

[0054] Among them, R efi is the transformation matrix from the WGS84 coordinate system of the i-th ground station to the Northeast Sky coordinate system, which is calculated as follows:

[0055]

[0056] Where loni is the longitude of the i-th ground station, and lati is the latitude of the i-th ground station.

[0057] like Figure 5 As shown, the azimuth and elevation angles required for the ground station are calculated as follows:

[0058] Azimuth Φ=atan2(RSi e (2),RSi e (1));

[0059] Pitch angle θ = asin(RSi e (3) / |RSi|).

[0060] In the above-mentioned ground measurement, control and tracking method dominated by space-based systems, orbit prediction is carried out through the space-based main body, namely the satellite, based on orbit control and on-board orbit data (the source is not limited to GNSS orbit determination and orbit recursion). The ephemeris for the next measurement, control and tracking is calculated in the form of the station address, and the station address, time, and corresponding elevation and azimuth angles required for the next measurement, control and tracking are output. At the same time, the orbit (including time and six orbit numbers) predicted for the next measurement, control and tracking and the ephemeris are sent to the ground through real-time communication interfaces such as Beidou short messages. The ground dispatches the ground measurement and control equipment for tracking based on the above information to achieve normal measurement and control of the target spacecraft.

[0061] The spacecraft to which the above method of the present invention is applicable has high orbit control requirements and should have real-time communication means such as Beidou short messages for downlinking small amounts of data required for measurement, control and tracking. It is particularly suitable for spacecraft in ultra-low orbit continuous flight. Among them, the present invention does not limit the specific communication link form (such as microwave communication, laser communication), specific flight orbit style (such as low-inclination orbit, polar orbit), specific orbit control strategy (such as low-thrust continuous, multi-pulse), specific orbit extrapolation method (such as numerical integration method, analytical method). The present invention does not limit the type of spacecraft to which the spacecraft is related.

[0062] The scope of application of this method must meet the following basic conditions:

[0063] 1) The spacecraft needs to have real-time communication interfaces such as BeiDou short messages;

[0064] 2) The spacecraft needs to have the computing capability to independently calculate ephemeris;

[0065] The following constraints must be met when using the method:

[0066] 1) The ground measurement and control system allows tracking directly based on the tracking requirements provided by the satellite party;

[0067] 2) The ground measurement and control system allows tracking input to be provided 15 minutes in advance;

[0068] 3) The spacecraft should avoid making major adjustments to its orbital control strategy after sending forecast information to the ground system.

[0069] If the above method is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program code.

[0070] Example 2

[0071] This embodiment provides an ultra-low orbit aircraft 1, which is a space-based main body. Figure 1 As shown, it includes an orbit determination module 11, a prediction calculation module 12, a short message transceiver antenna 13 and a GNSS receiving antenna 14, wherein the orbit determination module 11 is connected to the prediction calculation module 12 and the GNSS receiving antenna 14 respectively, and is used to receive single-point positioning data and send it to the prediction calculation module 12. The prediction calculation module 12 and the short message transceiver antenna 13 are used to carry out real-time single-point positioning data extrapolation based on the single-point positioning data to form predicted orbit data, and send it to the ground measurement and control system 2 through the short message transceiver antenna 13. The ground measurement and control system 2 tracks the target aircraft based on the received data.

[0072] The prediction calculation module 12 is triggered to work when the ephemeris is out of the range. The specific working process includes:

[0073] Step 1: Determine the real-time orbital situation based on the real-time single-point positioning data, generate an autonomous orbital control strategy based on the real-time orbital situation, and during the operation of the spacecraft based on the autonomous orbital control strategy, perform corrections on the predicted orbital data in combination with the autonomous orbital control strategy to form orbital data for calculating ephemeris;

[0074] Step 2: Calculate the ephemeris of the ground station (preset on the satellite) based on the predicted orbit data, calculate the station address and tracking time required for the next tracking, and determine the difference between the tracking time and the current time. If the difference is ≥15 minutes, do not proceed to the next step and return to step 1. If the difference is <15 minutes, further calculate and output the station address, tracking time, and corresponding elevation and azimuth angles required for the next tracking.

[0075] Step 3: The orbit (including time, six orbit numbers) and ephemeris of the next measurement, control and tracking are sent down in real time through the short message transceiver antenna 13. The onboard process ends and waits for the next ephemeris to be sent out.

[0076] like Figure 2 As shown, the ultra-low orbit aircraft 1 and the ground measurement and control system 2 are connected in communication through several Beidou systems 3.

[0077] Example 3

[0078] This embodiment provides an ultra-low orbit space-based dominated ground measurement, control and tracking system, including a space-based body and a ground measurement station, wherein the space-based body obtains predicted orbit data, measurement and control time, pitch angle and azimuth angle based on the steps of the ultra-low orbit space-based dominated ground measurement, control and tracking method as described in Example 1, and sends them to the ground measurement station with the corresponding station address via a short message; the ground measurement station is used to implement measurement, control and tracking of the target space-based body on the ground.

[0079] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for ultra-low orbit space-based ground tracking and measurement, characterized in that: The following steps are involved: S1. Obtain the single point positioning data of the aircraft and determine whether ephemeris departure occurs. If so, execute step S2; if not, return to step S1; S2. performing orbit extrapolation based on the single point positioning data; S3. Correct the orbit extrapolation result based on the autonomous orbit control strategy to obtain the predicted orbit data for ephemeris calculation; S4. Calculating the station location and tracking time required for the next tracking and control based on the predicted orbit data; S5. Determine whether the difference between the measurement and control time of the next measurement and control tracking and the current time is less than a set threshold. If so, execute step S6; if not, return to step S4; S6. Calculate the pitch angle and azimuth angle required for the next measurement, control and tracking, integrate the predicted orbit data, measurement and control time, pitch angle and azimuth angle, and send a short message according to the station address.

2. The ultra-low orbit space-based guided ground tracking method according to claim 1, characterized in that: The station address required for the next measurement, control and tracking is obtained based on a preset on-board ground station address database.

3. The ultra-low orbit space-based guided ground tracking method according to claim 1, characterized in that: The predicted orbit data includes time and six orbit numbers.

4. The ultra-low orbit space-based guided ground tracking method according to claim 1, characterized in that: The station address required for the next measurement, control and tracking is calculated as follows: According to the predicted orbit data, the corresponding WGS84 coordinate system orbit information is obtained, and the vector RSi pointing from the i-th ground station to the aircraft in the WGS84 coordinate system is calculated. If there exists |RSi| <R max , it is determined that the aircraft enters the i-th ground station, and then the station address required for the next measurement, control and tracking is determined.

5. The ultra-low orbit space-based guided ground tracking and measurement method according to claim 4, characterized in that: If there are multiple ground stations satisfying |RSi| <R max , then the ground station with the highest priority or the ground station with the longest entry time is selected to determine the station site required for the next measurement, control and tracking.

6. The ultra-low orbit space-based guided ground tracking method according to claim 1, characterized in that: The calculation formulas for the pitch angle and azimuth angle of the ground station are as follows: θ=and(RSi e (3) / |RSi|) Φ=atan2(RSi e (2),RSi e (1)) Among them, θ is the pitch angle, Φ is the azimuth angle, RSi e RSi is the vector pointing from the ground station to the aircraft in the northeast celestial coordinate system. e =[RSi e (1),RSi e (2),RSi e (3)], RSi is the vector from the ground station to the aircraft in the WGS84 coordinate system, and |RSi| is the modulus of RSi.

7. The ultra-low orbit space-based guided ground tracking method according to claim 1, characterized in that: The short message is sent using Beidou short message sending.

8. The ultra-low orbit space-based guided ground tracking and measurement method according to claim 1, characterized in that: When performing the orbit extrapolation, the points of each minute within the prediction time period are calculated in sequence during the initialization phase, and after the initialization phase is completed, calculations are performed according to the points after the prediction time period.

9. A computer-readable storage medium, characterized in that It includes one or more programs for execution by one or more processors of an electronic device, and the one or more programs include instructions for executing the ultra-low orbit space-based dominated ground measurement, control and tracking method as described in any one of claims 1-8.

10. An ultra-low orbit space-based ground-based tracking and measurement system, characterized in that: It includes space-based entities and ground stations, among which: The space-based subject obtains predicted orbit data, tracking time, pitch angle and azimuth angle based on the steps of the ultra-low orbit space-based dominated ground tracking and control method according to any one of claims 1 to 8, and sends them to the ground station with the corresponding station address through a short message; The ground station is used to realize the measurement, control and tracking of the target space-based body on the ground.

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