Ultra-low orbit space-based dominant ground measurement and control tracking method and system

Abstract

The invention relates to an ultra-low orbit space-based dominant ground measurement and control tracking method and system, and the method comprises the following steps: S1, obtaining the single-point positioning data of an aircraft, judging whether ephemeris exit occurs or not, and if yes, executing the step S2; s2, orbit extrapolation is carried out based on single-point positioning data; s3, correcting an orbit extrapolation result based on an autonomous orbit control strategy, and obtaining predicted orbit data for ephemeris calculation; s4, calculating and obtaining the site and the measurement and control time required by the next measurement and control tracking based on the predicted orbit data; s5, judging whether the difference between the measurement and control time of the next measurement and control tracking and the current time is smaller than a set threshold value or not, and if yes, executing the step S6; and S6, calculating a pitch angle and an azimuth angle required by next measurement and control tracking, integrating the predicted orbit data, the measurement and control time, the pitch angle and the azimuth angle, and carrying out short message transmission according to the site. Compared with the prior art, the method has the advantages that efficient tracking can be achieved, and large-range blind scanning and capturing are not needed.

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 dominated ground measurement, control and tracking method and system. Background Art

[0002] After the ultra-low orbit vehicle is launched into orbit, due to the normalization of its orbit maintenance, ground orbit determination is often unable to be carried out in normal circumstances (under normal circumstances, ground orbit determination requires continuous measurement of 4 to 5 orbits without orbit control of the satellite for orbit determination prediction, with high accuracy). In the absence of ground orbit determination, ground measurement and control antenna tracking often has problems. Ground equipment tracking relies on the calculated ephemeris, elevation and azimuth for initial capture. The field of view angle of the ground equipment is about 5°, corresponding to a 250km ultra-low orbit. At an elevation of 3°, the distance is about 1500km, and at 5°, the acceptable error is only 65km. The control requirement for maintaining a single orbit of a 250km ultra-low orbit is 72m / s, and the control position of one orbit reaches about 200km. With the support of domestic measurement stations, the longest measurement and control interval reaches more than 6 orbits, which cannot be accurately estimated, resulting in the inability to complete the basic task of satellite measurement and control, which can easily cause irreparable losses to ultra-low orbit vehicles.

[0003] At present, in the face of orbit determination problems with orbit control, prediction based on propulsion strategies is a common method used on the ground, but this method has low accuracy and is not operational when the propulsion strategy is completed autonomously on the satellite. When the satellite conducts autonomous orbit control and the ground cannot predict the orbit, how the ground station can accurately track the satellite is a technical problem that needs to be solved in this field.

[0004] The existing patent CN103178895B discloses an inter-satellite measurement and control method for a satellite mobile communication constellation, which uses three GEO satellites to measure and control LEO satellites within their respective fields of view; the three GEO satellites include a master GEO satellite and two slave GEO satellites; the GEO satellite obtains the uploaded measurement and control instructions and sends them directly or through the two slave GEO satellites to the corresponding LEO satellite; the two slave GEO satellites and the master GEO satellite transmit the received measurement and control information of the LEO satellite through the master GEO satellite. However, the related prior art does not propose a ground measurement and control tracking method dominated by 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 and capture.

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

[0007] An ultra-low orbit space-based ground measurement, control and tracking method comprises the following steps:

[0008] S1, obtain the single point positioning data of the aircraft, determine whether the ephemeris exit 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 address and tracking time required for the next tracking 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 the 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 orbital 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, the points after the prediction time period are calculated.

[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 ground measurement, control and tracking system, including a space-based main body and a ground measurement station, wherein:

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

[0028] The ground station is used to implement measurement, control and tracking of the target space-based entity 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 satellites, which can realize the measurement, control and tracking of the aircraft by ground equipment when the propulsion strategy is completed autonomously on the satellite, and realize the ground measurement and control guarantee of ultra-low orbit satellites with high precision.

[0031] 2. The present invention realizes ground station tracking based on on-orbit autonomous orbit control by using the spacecraft itself to complete single-point positioning in combination with the orbit control strategy for prediction, and calculates the ephemeris in combination with the station situation, thereby providing a feasible method for efficient ground station tracking for ultra-low orbit spacecraft and other spacecraft that require high-frequency orbital maneuvers and on-board autonomous orbital control, and does not require large-scale blind scanning capture, with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the internal information flow of the aircraft measurement, control and prediction in the present invention;

[0033] Figure 2 This is a schematic diagram of the information flow of the sky, earth and measurement and forecasting in the present invention;

[0034] Figure 3 is a flow chart of the measurement and control method of the present invention;

[0035] Figure 4 1 is a 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 The figure is a schematic diagram of the calculation principle of the azimuth and elevation angles required by the ground station in the embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with 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 ground tracking and control method, which uses space-based as the leading factor to calculate the sites required for the next ground tracking and control as well as the elevation and azimuth required for site tracking. Within a set time range before tracking, the predicted orbital conditions and the elevation and azimuth required for tracking are transmitted through real-time communication means such as Beidou short messages, so as to achieve 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 orbit control of the aircraft is relatively frequent, the onboard GNSS orbit determination often cannot converge. Therefore, the aircraft is normally in the GNSS positioning state. This embodiment triggers the above process based on the ephemeris exit. After the ephemeris exits, the single-point positioning data is output, and the real-time single-point positioning data is extrapolated to form the predicted orbit data.

[0043] In this embodiment, orbital extrapolation is implemented using existing orbital extrapolation methods, such as numerical integration method, analytical method, etc. During the prediction process, the points of each minute in the prediction time period are calculated in sequence in the initialization stage, and the points after the prediction time period are calculated after the initialization stage. 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 orbit dynamics to obtain the predicted orbit data for ephemeris calculation.

[0045] S4. Calculate and obtain 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 on-board 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 performing ephemeris calculation based on the predicted orbit data is specifically as follows:

[0050] The parameters of the station wgs84 coordinate system are annotated, such as [rx1, ry1, rz1, minimum elevation angle 1], [rx1, ry2, rz3, minimum elevation angle 2], and the wgs84 coordinate system orbit [Rx, Ry, Rz, H] after 15 minutes is obtained through the on-board orbit prediction. In this embodiment, the on-board orbit prediction adopts the existing conventional algorithm; calculate the vector RSi=[Rx-rxi, Ry-ryi, Rz-rzi] pointing to the satellite from the i-th ground station in the wgs84 coordinate system, and calculate the modulus value of the distance vector RSi, that is, the distance scalar between each ground station and the satellite. For the predicted orbit after 15 minutes, 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 elevation angle of the ground station, and the calculation method can be obtained by using the cosine theorem, such as Figure 4 As shown, record T1, and further refine the entry time. Refine and extrapolate to 1s interval between T1-1min and T1 to obtain a more accurate T1. Then calculate the exit time. The exit time is extrapolated from T1 for 1 minute. When |RSi|>R max Stop and record T2. You can further refine the exit time by refining and extrapolating 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 Northeastern Sky coordinate system (ENU) used by the ground station.

[0053] R 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, and 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 by the ground station are calculated as follows:

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

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

[0060] In the above-mentioned ground measurement, control and tracking method dominated by space-based, the orbit is predicted by the space-based entity, i.e. the satellite, based on orbit control and on-board orbit data (the source is not limited to GNSS orbit determination and orbit recursion), and the ephemeris of the next measurement, control and tracking is calculated in the form of 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 that fly continuously in ultra-low orbits. 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), and 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 autonomously 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;

[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, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform 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 codes.

[0070] Example 2

[0071] This embodiment provides an ultra-low orbit aircraft 1, which is a space-based subject. 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 respectively connected to the prediction calculation module 12 and the GNSS receiving antenna 14, for receiving single-point positioning data and sending it to the prediction calculation module 12, the prediction calculation module 12 and the short message transceiver antenna 13, for carrying out real-time single-point positioning data extrapolation according to the single-point positioning data, forming predicted orbit data, and sending it to the ground measurement and control system 2 through the short message transceiver antenna 13, and the ground measurement and control system 2 tracks the target aircraft according to the received sent data.

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

[0073] Step 1: determine the real-time orbit situation based on the real-time single-point positioning data, generate an autonomous orbit control strategy based on the real-time orbit situation, and during the operation of the aircraft based on the autonomous orbit control strategy, correct the predicted orbit data in combination with the autonomous orbit control strategy to form orbit data for calculating the 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 it is ≥15 minutes, do not proceed to the next step and return to step 1. If it 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, and the on-board 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] The present embodiment provides an ultra-low orbit space-based dominated ground measurement, control and tracking system, comprising a space-based body and a ground 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 a ground station with a corresponding station address via a short message; the ground station is used to realize measurement, control and tracking of the target space-based body on the ground.

[0079] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined 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, determine whether the ephemeris exit 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 address and tracking time required for the next tracking 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 the 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 ground-based tracking method according to claim 1 is 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 ground-based tracking method according to claim 1 is characterized in that: The predicted orbit data includes time and six orbital numbers.

4. The ultra-low orbit space-based ground-based tracking method according to claim 1 is 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 method according to claim 4 is 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 elevation 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 ground-based tracking method according to claim 1 is characterized in that: The short message sending adopts Beidou short message sending.

8. The ultra-low orbit space-based ground-based tracking 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 sequentially during the initialization phase, and after the initialization phase is completed, the points after the prediction time period are calculated.

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 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, measurement and control time, pitch angle and azimuth angle based on the steps of the ultra-low orbit space-based dominant ground measurement and control tracking method as described in any one of claims 1 to 8, and sends them to the ground measurement station with the corresponding station address through a short message; The ground station is used to implement measurement, control and tracking of the target space-based entity on the ground.

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