Geosynchronous orbit SAR echo simulation method and device based on Beidou satellite

Abstract

The present invention discloses a method and device for simulating the geosynchronous orbit SAR echo of a Beidou satellite, which is used to improve the authenticity and reliability of the echo simulation data. The method includes: obtaining Beidou satellite ephemeris data by the ionosphere monitoring device, calculating the STEC value and VTEC value of the Beidou satellite observation path; determining the candidate synchronous orbit satellite code; obtaining the ephemeris data within the available time period of the selected satellite, the STEC value of the selected satellite line of sight direction corresponding to the available time period, and the VTEC value of the ionosphere monitoring device point; determining the typical value of VTEC time variation, extracting a group of satellite ephemeris data corresponding to the typical value, and the STEC data of the selected satellite line of sight direction; using the extracted satellite ephemeris data as the satellite platform orbit data source, and using the extracted STEC data of the selected satellite line of sight direction as the ionosphere data source; performing geosynchronous orbit SAR echo simulation, as well as imaging simulation and imaging quality evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of synthetic aperture radar data processing, and in particular to a method and device for simulating geosynchronous orbit SAR echoes based on Beidou satellites. Background Art

[0002] Spaceborne synthetic aperture radar (SAR) echo signal simulation is the basis for estimating and evaluating the system and imaging performance in the SAR system design phase. Since spaceborne SAR echo signals are closely related to satellite platforms and space environment, spaceborne SAR echo signal simulation usually consists of four parts: satellite platform simulation, radar system simulation, target model simulation, and space environment simulation. Figure 1 In the process of spaceborne SAR simulation demonstration, it is necessary to isolate and locate the impact of satellite platform and space environment on radar system performance. Therefore, the satellite platform data and space environment data introduced into the spaceborne SAR echo signal simulation must be authentic and reliable.

[0003] Geosynchronous orbit SAR refers to a synthetic aperture radar system based on an inclined geosynchronous orbit satellite at an altitude of 36,000 km. Compared with low-orbit SAR, the synthetic aperture time of geosynchronous orbit SAR is very long, and the influence of satellite orbit perturbation characteristics and ionosphere TEC fast-changing characteristics on SAR echo signals cannot be ignored. The current geosynchronous orbit SAR echo simulation based on satellite platform model simulation and ionosphere model simulation has the following shortcomings:

[0004] (1) The orbital perturbations of geosynchronous satellites are affected by many factors and have great randomness. It is difficult to accurately simulate the orbital perturbation characteristics of geosynchronous SAR within a long synthetic aperture time by mathematical models. Even small orbital perturbations will cause non-negligible distortion of geosynchronous SAR echo data.

[0005] (2) The characteristics of the ionosphere are quantitatively described by TEC (Total Electron Content). The impact of the ionosphere on the SAR signal is determined by the line-of-sight TEC (STEC) on the observation path. In SAR signal simulation, only by introducing STEC in the satellite line-of-sight direction can the reliability and authenticity of the ionosphere data be guaranteed to the greatest extent. Even semi-physical simulation based on the conversion of ionosphere data measured on other paths cannot truly reflect the ionosphere characteristics in the line-of-sight direction within the long synthetic aperture time of the geosynchronous orbit SAR satellite. Summary of the invention

[0006] In view of this, the present invention provides a method and device for simulating geosynchronous orbit SAR echo based on Beidou satellite, taking the geosynchronous orbit satellite in the Beidou constellation as the target satellite (geosynchronous orbit SAR satellite), taking the actual ephemeris data of the Beidou geosynchronous orbit satellite as the orbit data source for echo data simulation, and taking the ionospheric STEC data directly measured by the dual-frequency signal transmitted by the Beidou satellite as the ionospheric data source in the echo data simulation, so that the orbit data and ionospheric data in the geosynchronous orbit satellite SAR echo data simulation are both measured data, effectively improving the authenticity and reliability of the echo simulation data.

[0007] In order to solve the above technical problems, the present invention is implemented as follows.

[0008] A method for simulating geosynchronous orbit SAR echo based on Beidou satellite, comprising:

[0009] Step S01: An ionosphere monitoring device with a Beidou satellite signal receiving function is deployed on the ground, wherein the ionosphere monitoring device can display a Beidou satellite constellation diagram, output Beidou satellite ephemeris data, and calculate a slant TEC (STEC) value and a vertical TEC (VTEC) value;

[0010] Step S02: performing an ionospheric data acquisition test, wherein the ionospheric monitoring device acquires Beidou satellite ephemeris data, calculates the STEC value of the Beidou satellite line of sight direction and the VTEC value of the ionospheric monitoring device point;

[0011] Step S03: Based on the Beidou satellite constellation diagram, determine the candidate synchronous orbit satellite code from the Beidou satellite constellation;

[0012] Step S04: selecting an unprocessed satellite from the candidate synchronous orbit satellite codes as the selected satellite; obtaining the ephemeris data within the available time period of the selected satellite and the STEC value of the line of sight direction of the selected satellite and the VTEC value of the ionospheric monitoring equipment point corresponding to the available time period according to the length of the geosynchronous orbit SAR synthetic aperture time;

[0013] Step S05: Calculate the derivative of the VTEC values ​​in all the available time periods to obtain a VTEC time-varying variable, and determine num VTEC time-varying typical values ​​based on the VTEC time-varying variable, num≥3; initialize the number of iterations i=1;

[0014] Step S06: for the ith typical value, extracting a set of satellite ephemeris data corresponding to the ith typical value and STEC data of the selected satellite line of sight direction;

[0015] Step S07: based on the extracted set of satellite ephemeris data corresponding to the i-th typical value and the STEC data in the selected satellite line of sight direction, the extracted satellite ephemeris data is used as the satellite platform orbit data source, and the extracted STEC data in the selected satellite line of sight direction is used as the ionospheric data source;

[0016] Step S08: Based on the satellite platform orbit data source and the ionosphere data source, perform geosynchronous orbit SAR echo simulation, imaging simulation, and imaging quality evaluation; assign i to i+1;

[0017] Step S09: if i>num, the selected satellite is marked as processed, and the process goes to S10; if not, the process goes to step S6;

[0018] Step S10: If all satellites corresponding to the candidate synchronous orbit satellite codes have been processed, the method ends; if not, proceed to step S04.

[0019] Preferably, in step S03, the code of the geosynchronous orbit satellite is randomly selected from the constellation diagram.

[0020] Preferably, in step S05, based on the VTEC time-varying variable, num VTEC time-varying typical values ​​are determined, wherein the typical values ​​at least include a maximum value, a median value and a minimum value.

[0021] Preferably, the step S06, for the ith typical value, extracting a set of satellite ephemeris data corresponding to the ith typical value and STEC data of the selected satellite line of sight direction, comprises:

[0022] For the i-th typical value, the corresponding observation time is found from the VTEC time variable, and then the STEC data of a certain time period is intercepted from the STEC data in the line of sight direction of the selected satellite with the observation time as the center, and the satellite ephemeris data of the same time period as STEC is intercepted from the selected satellite ephemeris data, and the length of the time period is at least greater than the length of the synthetic aperture time of the geosynchronous orbit SAR.

[0023] The present invention provides a geosynchronous orbit SAR echo simulation device based on Beidou satellite, the device comprising:

[0024] Configuration module: configured as an ionosphere monitoring device with Beidou satellite signal receiving function deployed on the ground, the ionosphere monitoring device can display Beidou satellite constellation diagram, output Beidou satellite ephemeris data, calculate slant TEC (STEC) value, and vertical TEC (VTEC) value;

[0025] Data acquisition module: configured to perform an ionospheric data acquisition test, wherein the ionospheric monitoring device acquires Beidou satellite ephemeris data, calculates the STEC value of the Beidou satellite line of sight direction and the VTEC value of the ionospheric monitoring device point;

[0026] A candidate synchronous orbit satellite determination module is configured to determine the candidate synchronous orbit satellite code from the Beidou satellite constellation based on the Beidou satellite constellation diagram;

[0027] The first data acquisition module is configured to select an unprocessed satellite from the candidate synchronous orbit satellite codes as the selected satellite; obtain the ephemeris data within the available time period of the selected satellite and the STEC value of the line of sight direction of the selected satellite and the VTEC value of the ionospheric monitoring equipment point corresponding to the available time period according to the length of the geosynchronous orbit SAR synthetic aperture time;

[0028] The data processing module is configured to obtain the derivative of the VTEC values ​​in all the available time periods to obtain the VTEC time-varying variables, and determine num VTEC time-varying typical values ​​based on the VTEC time-varying variables, num≥3; and initialize the number of iterations i=1;

[0029] A second data acquisition module: configured to extract, for an i-th typical value, a set of satellite ephemeris data corresponding to the i-th typical value and STEC data of the selected satellite line of sight direction;

[0030] A third data acquisition module is configured to use the extracted satellite ephemeris data as a satellite platform orbit data source and the extracted STEC data in the selected satellite line of sight direction as an ionospheric data source based on the extracted set of satellite ephemeris data corresponding to the i-th typical value and the STEC data in the selected satellite line of sight direction;

[0031] Simulation module: configured to perform geosynchronous orbit SAR echo simulation, imaging simulation, and imaging quality evaluation based on the satellite platform orbit data source and ionosphere data source; assign i to i+1;

[0032] The first judgment module is configured to trigger the second judgment module if i>num, the selected satellite is marked as processed, and if not, the second data acquisition module is triggered;

[0033] The second judgment module is configured to trigger the first data acquisition module if the satellites corresponding to the candidate synchronous orbit satellite codes have all been processed; if not,

[0034] Preferably, the candidate synchronous orbit satellite determination module randomly selects the code of the geosynchronous orbit satellite from the constellation diagram.

[0035] Preferably, the data processing module determines num VTEC time-varying typical values ​​based on the VTEC time-varying variable, wherein the typical values ​​at least include a maximum value, a median value and a minimum value.

[0036] Preferably, for the i-th typical value, extracting a set of satellite ephemeris data corresponding to the i-th typical value and STEC data of the selected satellite line of sight direction comprises:

[0037] For the i-th typical value, the corresponding observation time is found from the VTEC time variable, and then the STEC data of a certain time period is intercepted from the STEC data in the line of sight direction of the selected satellite with the observation time as the center, and the satellite ephemeris data of the same time period as STEC is intercepted from the selected satellite ephemeris data, and the length of the time period is at least greater than the length of the synthetic aperture time of the geosynchronous orbit SAR.

[0038] Beneficial effects:

[0039] (1) The method provided by the present invention introduces the actual orbit data of the geosynchronous orbit satellite in the Beidou system into the geosynchronous orbit SAR echo simulation, which can truly reflect the impact of the orbit perturbation of the geosynchronous orbit satellite on the echo data;

[0040] (2) The present invention introduces the ionosphere data in the satellite line of sight direction obtained by the ionosphere observation experiment into the geosynchronous orbit SAR echo simulation, which can truly reflect the impact of the ionosphere time variation on the satellite observation path on the echo data.

[0041] (3) The present invention uses the geosynchronous orbit satellite in the BeiDou satellite constellation as a reference satellite, uses ionospheric observation equipment to carry out ionospheric data acquisition experiments, and directly introduces the acquired geosynchronous orbit satellite ephemeris data and STEC data in the satellite line of sight direction into the geosynchronous orbit SAR echo data simulation, thereby improving the authenticity and reliability of the simulation.

[0042] (4) The present invention can generate geosynchronous orbit SAR echoes under different orbits and ionospheric states by acquiring ephemeris data of different satellites and ionospheric data with different time-varying characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a structural block diagram of geosynchronous orbit SAR echo simulation in the prior art;

[0044] Figure 2 This is a structural block diagram of the geosynchronous orbit SAR echo simulation proposed by the present invention;

[0045] Figure 3 It is a schematic diagram of the flow of the geosynchronous orbit SAR echo simulation method of the Beidou satellite of the present invention;

[0046] Figure 4 The present invention is a structural block diagram of the geosynchronous orbit SAR echo simulation device of the Beidou satellite. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0048] like Figure 3 As shown, the present invention provides a method for simulating geosynchronous orbit SAR echoes of Beidou satellites, the method comprising the following steps:

[0049] Step S01: An ionosphere monitoring device with a Beidou satellite signal receiving function is deployed on the ground, wherein the ionosphere monitoring device can display a Beidou satellite constellation diagram, output Beidou satellite ephemeris data, and calculate a slant TEC (STEC) value and a vertical TEC (VTEC) value;

[0050] Step S02: performing an ionospheric data acquisition test, wherein the ionospheric monitoring device acquires Beidou satellite ephemeris data, calculates the STEC value of the Beidou satellite line of sight direction and the VTEC value of the ionospheric monitoring device point;

[0051] Step S03: Based on the Beidou satellite constellation diagram, determine the candidate synchronous orbit satellite code from the Beidou satellite constellation;

[0052] Step S04: selecting an unprocessed satellite from the candidate synchronous orbit satellite codes as the selected satellite; obtaining the ephemeris data within the available time period of the selected satellite and the STEC value of the line of sight direction of the selected satellite and the VTEC value of the ionospheric monitoring equipment point corresponding to the available time period according to the length of the geosynchronous orbit SAR synthetic aperture time;

[0053] Step S05: Calculate the derivative of the VTEC values ​​in all the available time periods to obtain a VTEC time-varying variable, and determine num VTEC time-varying typical values ​​based on the VTEC time-varying variable, num≥3; initialize the number of iterations i=1;

[0054] Step S06: for the ith typical value, extracting a set of satellite ephemeris data corresponding to the ith typical value and STEC data of the selected satellite line of sight direction;

[0055] Step S07: based on the extracted set of satellite ephemeris data corresponding to the i-th typical value and the STEC data in the selected satellite line of sight direction, the extracted satellite ephemeris data is used as the satellite platform orbit data source, and the extracted STEC data in the selected satellite line of sight direction is used as the ionospheric data source;

[0056] Step S08: Based on the satellite platform orbit data source and the ionosphere data source, perform geosynchronous orbit SAR echo simulation, imaging simulation, and imaging quality evaluation; assign i to i+1;

[0057] Step S09: if i>num, the selected satellite is marked as processed, and the process goes to S10; if not, the process goes to step S6;

[0058] Step S10: If all satellites corresponding to the candidate synchronous orbit satellite codes have been processed, the method ends; if not, proceed to step S04.

[0059] Furthermore, the method is based on Figure 2 The geosynchronous orbit SAR echo simulation system shown is implemented.

[0060] The step S03, determining the candidate synchronous orbit satellite code from the Beidou satellite constellation, includes: the Beidou satellite constellation map will display the code of each satellite, wherein the code of the geosynchronous orbit satellite is different from the code of the low-orbit satellite, and the code of the geosynchronous orbit satellite is randomly selected from the constellation map.

[0061] The step S05 is to determine num VTEC time-varying typical values ​​based on the VTEC time-varying value, wherein the typical values ​​at least include a maximum value, a median value, and a minimum value.

[0062] The step S06, for the ith typical value, extracting a set of satellite ephemeris data corresponding to the ith typical value and STEC data of the selected satellite line of sight direction, comprises:

[0063] For the i-th typical value, the corresponding observation time is found from the VTEC time variable, and then the STEC data of a certain time period is intercepted from the STEC data in the line of sight direction of the selected satellite with the observation time as the center, and the satellite ephemeris data of the same time period as STEC is intercepted from the selected satellite ephemeris data, and the length of the time period is at least greater than the length of the synthetic aperture time of the geosynchronous orbit SAR.

[0064] The present invention also provides a Beidou satellite geosynchronous orbit SAR echo simulation device, such as Figure 4 As shown, the device comprises:

[0065] Configuration module: configured as an ionosphere monitoring device with Beidou satellite signal receiving function deployed on the ground, the ionosphere monitoring device can display Beidou satellite constellation diagram, output Beidou satellite ephemeris data, calculate slant TEC (STEC) value, and vertical TEC (VTEC) value;

[0066] Data acquisition module: configured to perform an ionospheric data acquisition test, wherein the ionospheric monitoring device acquires Beidou satellite ephemeris data, calculates the STEC value of the Beidou satellite line of sight direction and the VTEC value of the ionospheric monitoring device point;

[0067] A candidate synchronous orbit satellite determination module is configured to determine the candidate synchronous orbit satellite code from the Beidou satellite constellation based on the Beidou satellite constellation diagram;

[0068] The first data acquisition module is configured to select an unprocessed satellite from the candidate synchronous orbit satellite codes as the selected satellite; obtain the ephemeris data within the available time period of the selected satellite and the STEC value of the line of sight direction of the selected satellite and the VTEC value of the ionospheric monitoring equipment point corresponding to the available time period according to the length of the geosynchronous orbit SAR synthetic aperture time;

[0069] The data processing module is configured to obtain the derivative of the VTEC values ​​in all the available time periods to obtain the VTEC time-varying variables, and determine num VTEC time-varying typical values ​​based on the VTEC time-varying variables, num≥3; and initialize the number of iterations i=1;

[0070] A second data acquisition module: configured to extract, for an i-th typical value, a set of satellite ephemeris data corresponding to the i-th typical value and STEC data of the selected satellite line of sight direction;

[0071] A third data acquisition module is configured to use the extracted satellite ephemeris data as a satellite platform orbit data source and the extracted STEC data in the selected satellite line of sight direction as an ionospheric data source based on the extracted set of satellite ephemeris data corresponding to the i-th typical value and the STEC data in the selected satellite line of sight direction;

[0072] Simulation module: configured to perform geosynchronous orbit SAR echo simulation, imaging simulation, and imaging quality evaluation based on the satellite platform orbit data source and ionosphere data source; assign i to i+1;

[0073] The first judgment module is configured to trigger the second judgment module if i>num, the selected satellite is marked as processed, and if not, the second data acquisition module is triggered;

[0074] The second judgment module is configured to trigger the first data acquisition module if the satellites corresponding to the candidate synchronous orbit satellite codes have all been processed; if not,

[0075] The above specific embodiments only describe the design principle of the present invention. The shapes and names of the components in the description may be different and are not limited. Therefore, those skilled in the art in the field of the present invention may modify or replace the technical solutions recorded in the above embodiments; and these modifications and replacements do not deviate from the creative purpose and technical solutions of the present invention and should all fall within the protection scope of the present invention.

Claims

1. A method for simulating geosynchronous orbit SAR echoes based on Beidou satellite, characterized in that: include: Step S01: An ionosphere monitoring device with a Beidou satellite signal receiving function is deployed on the ground, wherein the ionosphere monitoring device can display a Beidou satellite constellation diagram, output Beidou satellite ephemeris data, and calculate a slant TEC value, namely, a STEC value, and a vertical TEC value, namely, a VTEC value; Step S02: performing an ionospheric data acquisition test, wherein the ionospheric monitoring device acquires Beidou satellite ephemeris data, calculates the STEC value of the Beidou satellite line of sight direction and the VTEC value of the ionospheric monitoring device point; Step S03: Based on the Beidou satellite constellation diagram, determine the candidate synchronous orbit satellite code from the Beidou satellite constellation; Step S04: selecting an unprocessed satellite from the candidate synchronous orbit satellite codes as a selected satellite; According to the length of the geosynchronous orbit SAR synthetic aperture time, the ephemeris data within the available time period of the selected satellite and the STEC value of the line of sight direction of the selected satellite and the VTEC value of the ionospheric monitoring device point corresponding to the available time period are obtained; Step S05: Calculate the derivative of the VTEC values ​​in all the available time periods to obtain a VTEC time-varying variable, and determine num VTEC time-varying typical values ​​based on the VTEC time-varying variable, num≥3; initialize the number of iterations i=1; Step S06: for the ith typical value, extracting a set of satellite ephemeris data corresponding to the ith typical value and STEC data of the selected satellite line of sight direction; Step S07: based on the extracted set of satellite ephemeris data corresponding to the i-th typical value and the STEC data in the selected satellite line of sight direction, the extracted satellite ephemeris data is used as the satellite platform orbit data source, and the extracted STEC data in the selected satellite line of sight direction is used as the ionospheric data source; Step S08: Based on the satellite platform orbit data source and the ionosphere data source, geosynchronous orbit SAR echo simulation, imaging simulation, and imaging quality evaluation are performed; Assign i to i+1; Step S09: if i>num, the selected satellite is marked as processed, and the process goes to S10; If not, proceed to step S6; Step S10: If all satellites corresponding to the candidate synchronous orbit satellite codes have been processed, the method ends; if not, proceed to step S04.

2. The method according to claim 1, characterized in that The step S03 randomly selects the code of the geosynchronous orbit satellite from the constellation diagram.

3. The method according to claim 2, characterized in that The step S05 is to determine num VTEC time-varying typical values ​​based on the VTEC time-varying value, wherein the typical values ​​at least include a maximum value, a median value, and a minimum value.

4. The method according to claim 3, characterized in that The step S06, for the ith typical value, extracting a set of satellite ephemeris data corresponding to the ith typical value and STEC data of the selected satellite line of sight direction, comprises: For the i-th typical value, the corresponding observation time is found from the VTEC time variable, and then the STEC data of a certain time period is intercepted from the STEC data in the line of sight direction of the selected satellite with the observation time as the center, and the satellite ephemeris data of the same time period as STEC is intercepted from the selected satellite ephemeris data, and the length of the time period is at least greater than the length of the synthetic aperture time of the geosynchronous orbit SAR.

5. A geosynchronous orbit SAR echo simulation device based on Beidou satellite, characterized in that: include: Configuration module: configured as an ionosphere monitoring device with Beidou satellite signal receiving function deployed on the ground, the ionosphere monitoring device can display Beidou satellite constellation diagram, output Beidou satellite ephemeris data, calculate oblique TEC, i.e. STEC value, and vertical TEC, i.e. VTEC value; Data acquisition module: configured to perform an ionospheric data acquisition test, wherein the ionospheric monitoring device acquires Beidou satellite ephemeris data, calculates the STEC value of the Beidou satellite line of sight direction and the VTEC value of the ionospheric monitoring device point; A candidate synchronous orbit satellite determination module is configured to determine the candidate synchronous orbit satellite code from the Beidou satellite constellation based on the Beidou satellite constellation diagram; A first data acquisition module: configured to select an unprocessed satellite from the candidate synchronous orbit satellite codes as a selected satellite; According to the length of the geosynchronous orbit SAR synthetic aperture time, the ephemeris data within the available time period of the selected satellite and the STEC value of the line of sight direction of the selected satellite and the VTEC value of the ionospheric monitoring device point corresponding to the available time period are obtained; The data processing module is configured to obtain the derivative of the VTEC values ​​in all the available time periods to obtain the VTEC time-varying variables, and determine num VTEC time-varying typical values ​​based on the VTEC time-varying variables, num≥3; and initialize the number of iterations i=1; A second data acquisition module: configured to extract, for an i-th typical value, a set of satellite ephemeris data corresponding to the i-th typical value and STEC data of the selected satellite line of sight direction; A third data acquisition module is configured to use the extracted satellite ephemeris data as a satellite platform orbit data source and the extracted STEC data in the selected satellite line of sight direction as an ionospheric data source based on the extracted set of satellite ephemeris data corresponding to the i-th typical value and the STEC data in the selected satellite line of sight direction; Simulation module: configured to perform geosynchronous orbit SAR echo simulation, imaging simulation, and imaging quality evaluation based on the satellite platform orbit data source and ionosphere data source; Assign i to i+1; The first judgment module is configured to trigger the second judgment module if i>num, the selected satellite is marked as processed, and if not, the second data acquisition module is triggered; The second judgment module is configured to trigger the first data acquisition module if the satellites corresponding to the candidate synchronous orbit satellite codes have all been processed; if not, 6. The device according to claim 5, characterized in that The candidate synchronous orbit satellite determination module randomly selects the code of the geosynchronous orbit satellite from the constellation diagram.

7. The device according to claim 6, characterized in that The data processing module determines num VTEC time-varying typical values ​​based on the VTEC time-varying value, wherein the typical values ​​at least include a maximum value, a median value, and a minimum value.

8. The device according to claim 7, characterized in that For the i-th typical value, extracting a set of satellite ephemeris data corresponding to the i-th typical value and STEC data of the selected satellite line of sight direction, including: For the i-th typical value, the corresponding observation time is found from the VTEC time variable, and then the STEC data of a certain time period is intercepted from the STEC data in the line of sight direction of the selected satellite with the observation time as the center, and the satellite ephemeris data of the same time period as STEC is intercepted from the selected satellite ephemeris data, and the length of the time period is at least greater than the length of the synthetic aperture time of the geosynchronous orbit SAR.

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