Distributed InSAR satellite distance direction space synchronization on-orbit test method and system

Abstract

The invention provides a distributed InSAR (Interferometric Synthetic Aperture Radar) satellite distance direction space synchronization on-orbit test method and system. The method comprises the following steps: acquiring echo data of the same region of a tropical rainforest by adopting a one-transmitting double-receiving mode; imaging the tropical rainforest SAR echoes of the main and auxiliary satellites respectively to obtain SAR images of the main and auxiliary satellites; obtaining a main satellite distance direction beam pointing test result RP02 and an auxiliary satellite distance direction beam pointing test result RP12; a distance direction pointing test result RP01 in a primary satellite ground test stage, and a distance direction pointing test result RP11 in an auxiliary satellite ground test stage; judging whether the RP01-RP02 and the RP11-RP12 exceed a threshold or not, and selecting a test sample pair which is in a threshold range at the same time; calculating a distance direction space synchronization test result; and calculating a plurality of groups of test sample results, averaging each group of calculation values, further reducing the random error, and obtaining a final test result.

Description

Technical Field

[0001] This invention relates to the field of aerospace systems technology, and more specifically, to a distributed InSAR satellite range-oriented space-synchronous on-orbit testing method and system. Background Technology

[0002] Interferometric Synthetic Aperture Radar (InSAR) is an important remote sensing method for acquiring high-precision ground elevation models (DSMs). It utilizes two SAR antennas distributed along the vertical flight path to observe the same area from different perspectives. The two complex SAR images are then interferometrically processed to calculate the slant range difference between the phase centers of the primary and secondary radar antennas and the target, thereby obtaining the DSM of the observed area. Distributed satellite InSAR systems mount two SAR antennas on two satellites flying in formation to simultaneously observe the Earth. This overcomes the problems of temporal decoherence and low baseline accuracy faced by repeated-pass InSAR, enabling the acquisition of high-precision DSMs. Since the SAR transmitting and receiving antennas are located on different satellite platforms, to achieve single-satellite SAR imaging and InSAR interferometry, the transmitting and receiving antenna beams must simultaneously cover the same ground illumination area. This spatial synchronization of the dual-satellite SAR beams ensures that the secondary satellite receives sufficient echo energy and maintains good coherence with the primary satellite.

[0003] Patent application document CN112327262A discloses a distributed InSAR satellite SAR beam pointing consistency on-orbit calibration method and system, which solves the problem of on-orbit calibration of dual-satellite pointing consistency in self-transmitting and self-receiving mode. In contrast, this invention adopts a dual-satellite one-transmitting and two-receiving mode for range-direction space synchronous on-orbit testing. The two have significant differences in application direction and technical approach.

[0004] Patent application document CN112346028A discloses a method and system for on-orbit testing of azimuth direction space synchronization of distributed InSAR satellites, which solves the problem of on-orbit testing of azimuth direction beam pointing of two satellites in the self-transmitting and self-receiving mode of distributed InSAR satellite systems. In contrast, this invention adopts the dual-satellite one-transmitting and dual-receiving mode for range direction space synchronization on-orbit testing. The two have significant differences in application direction and technical approach.

[0005] Patent application document CN119087368A discloses a high-precision and rapid calibration method for satellite SAR beam pointing based on echo data, which solves the calibration problem of SAR beam pointing for single-satellite systems. In contrast, this invention adopts a dual-satellite, one-transmitter, two-receiver mode for range-direction space synchronous on-orbit testing. The two methods differ significantly in their application direction, applicable scope, and technical approach.

[0006] Patent application CN119644269A discloses a spaceborne SAR beam pointing calibration method based on antenna installation deviation and differential beam image characteristics, which solves the calibration problem of SAR beam pointing for single-satellite systems. In contrast, this invention uses a dual-satellite, one-transmit, two-receive mode for range-direction space synchronous on-orbit testing. The two methods differ significantly in their application direction, applicable scope, and technical approach.

[0007] Analysis of the Impact of InSAR Space Synchronization on System Performance Based on Satellite Formation, Journal of Wuhan University (Information Science Edition), 200710. Main differences: This invention primarily addresses the problem of on-orbit testing methods for range-oriented space synchronization under a unified transmit / receive mode in distributed InSAR binary star systems, while this paper mainly demonstrates the requirements of InSAR elevation measurement for space synchronization under formation conditions and analyzes the impact of space synchronization on the elevation measurement accuracy and resolution of the InSAR system. There are significant differences in application direction, applicable scope, and technical approach.

[0008] Interferometric SAR Satellite Formation Beam Synchronization Method, China Space Science and Technology, 201005. Main differences: This invention primarily addresses the problem of on-orbit testing methods for range-direction space synchronization under a unified transmit / receive mode in distributed InSAR binary star systems, while this paper mainly proposes an engineering implementation approach for beam synchronization through satellite formation attitude guidance. There are significant differences in application direction, applicable scope, and technical approach.

[0009] A Practical Space Synchronization Method for Satellite-Aircraft Bistatic SAR, Journal of Electronics and Information Technology, 200806. Main Differences: This invention primarily addresses the problem of on-orbit testing methods for range-direction space synchronization under a unified transmit / receive mode in distributed InSAR binary systems, while this paper mainly proposes a space synchronization approach for beam pointing on satellite and aircraft transceiver platforms. There are significant differences in application direction, applicable scope, and technical approach. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the purpose of this invention is to provide a distributed InSAR satellite range-oriented space synchronization on-orbit testing method and system.

[0011] The distributed InSAR satellite range-oriented space synchronization on-orbit testing method provided by the present invention includes:

[0012] Step 1: The two satellites adopt a one-transmit, two-receive working mode to acquire radar echo data of the same ground target area; the one-transmit, two-receive working mode is: the main satellite transmits radar wave signals to the ground target area, and the main satellite and the auxiliary satellite simultaneously receive radar echo signals from the same ground target area; Step 2: Perform imaging processing on the radar echo data received by the primary satellite and the secondary satellite respectively to obtain the primary satellite SAR image and the secondary satellite SAR image; Step 3: Based on the primary satellite SAR image and the secondary satellite SAR image, obtain the primary satellite's on-orbit range beam pointing test result RP02 and the secondary satellite's on-orbit range beam pointing test result RP12, respectively; Step 4: Obtain the distance-direction pointing test result RP01 obtained by the primary star during the ground test phase, and the distance-direction pointing test result RP11 obtained by the secondary star during the ground test phase; Step 5: Based on RP01, RP02, RP11, and RP12, determine and screen the validity of the test samples; Step 6: Based on the filtered valid test sample data, calculate the range-direction space synchronization test results of the distributed InSAR satellite dual-satellite system; Step 7: Calculate the results of multiple test samples, average the calculated values ​​of each group to further reduce random error, and obtain the final test results.

[0013] Preferably, step 3 includes: using the azimuth modulus averaging method to calculate the average power value along the range direction for the acquired SAR image, and fitting the radiation pattern curve to obtain the SAR range radiation pattern on-orbit test results; wherein, the highest gain point of the primary satellite radiation pattern is the range beam pointing test result RP02, and the highest gain point of the secondary satellite radiation pattern is the range beam pointing test result RP12.

[0014] Preferably, in step 4, RP01 is the ground test range direction obtained by the main satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase; RP11 is the ground test range direction obtained by the auxiliary satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase.

[0015] Preferably, step 5 includes: determining whether |RP01-RP02| and |RP11-RP12| exceed a preset threshold, and selecting test sample pairs where |RP01-RP02| and |RP11-RP12| are both within the preset threshold range.

[0016] Preferably, in step 6, the range-direction space synchronization test result is calculated using the formula |RP12-RP02| / RW×100%, where RW is the range-direction beamwidth of the main star.

[0017] The distributed InSAR satellite range-oriented space-synchronous on-orbit testing system provided by the present invention includes: Module M1: The dual satellites adopt a one-transmit, two-receive working mode to acquire radar echo data of the same ground target area; the one-transmit, two-receive working mode is: the main satellite transmits radar wave signals to the ground target area, and the main satellite and the auxiliary satellite simultaneously receive radar echo signals from the same ground target area; Module M2: Performs imaging processing on the radar echo data received by the primary satellite and the secondary satellite respectively to obtain primary satellite SAR image and secondary satellite SAR image; Module M3: Based on the primary satellite SAR image and the secondary satellite SAR image, acquire the primary satellite's on-orbit range beam pointing test result RP02 and the secondary satellite's on-orbit range beam pointing test result RP12, respectively; Module M4: Acquires the range-pointing test result RP01 obtained by the primary satellite during the ground testing phase, and the range-pointing test result RP11 obtained by the secondary satellite during the ground testing phase; Module M5: Based on RP01, RP02, RP11 and RP12, it performs test sample validity assessment and screening; Module M6: Based on the filtered valid test sample data, calculate the range-direction space synchronization test results of the distributed InSAR satellite dual-satellite system; Module M7: Calculates the results of multiple test samples, averages the calculated values ​​of each group to further reduce random errors, and obtains the final test results.

[0018] Preferably, the module M3 includes: using the azimuth modulus averaging method to calculate the average power value along the range direction for the acquired SAR image, and fitting the radiation pattern curve to obtain the SAR range radiation pattern on-orbit test results; wherein, the highest gain point of the primary satellite radiation pattern is the range beam pointing test result RP02, and the highest gain point of the secondary satellite radiation pattern is the range beam pointing test result RP12.

[0019] Preferably, in module M4, RP01 is the ground test range direction obtained by the main satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase and calculated; RP11 is the ground test range direction obtained by the auxiliary satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase and calculated.

[0020] Preferably, module M5 includes: determining whether |RP01-RP02| and |RP11-RP12| exceed a preset threshold, and selecting test sample pairs where |RP01-RP02| and |RP11-RP12| are simultaneously within the preset threshold range.

[0021] Preferably, in module M6, the range-direction space synchronization test result is calculated using the formula |RP12-RP02| / RW×100%, where RW is the range-direction beamwidth of the main star.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) The dual satellites of this invention adopt a one-to-two-receive mode and work simultaneously, which is less affected by the error of the test scenario, has higher test accuracy, and can effectively save time and cost. (2) The present invention has an on-orbit test data validity check function, which can filter out invalid data caused by changes in terrain and landform by setting a threshold, thereby improving the validity and reliability of the test algorithm. Attached Figure Description

[0023] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 A flowchart illustrating the processing steps of a distributed InSAR satellite range-oriented space-synchronous on-orbit testing method; Figure 2 Schematic diagram of a unified transmit / receive working mode for distributed InSAR binary systems; Figure 3a and Figure 3b A schematic diagram of a distributed InSAR primary and secondary satellite image transmission and reception system. Figure 4a and Figure 4b This is a schematic diagram of the on-orbit test results of the primary and secondary satellites. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0025] Example 1 like Figure 1 This invention provides a method for on-orbit testing of distributed InSAR satellite range-direction space synchronization, comprising the following steps: Step 1: Distributed InSAR dual satellites use a one-transmit, two-receive mode to acquire echo data from the same area in the tropical rainforest; Step 2: Image the SAR echoes of the tropical rainforest from the primary and secondary satellites respectively to obtain SAR images of the primary and secondary satellites; Step 3: Primary star range-direction beam pointing test result RP02, secondary star range-direction beam pointing test result RP12; Step 4: Range pointing test result RP01 during the primary satellite ground test phase; Range pointing test result RP11 during the secondary satellite ground test phase. Step 5: Determine whether |RP01-RP02| and |RP11-RP12| exceed the threshold, and select test sample pairs where |RP01-RP02| and |RP11-RP12| are both within the threshold range; Step 6: The distance-to-space synchronization test result is |RP12-RP02| / RW×100%; Step 7: Calculate the results of multiple test samples, average the calculated values ​​of each group to further reduce random error, and obtain the final test results.

[0026] In step 1, this method is applicable to distributed InSAR satellite dual-satellite systems, with close-range formation flight in orbit, such as... Figure 2 As shown, the primary satellite transmits radar waves to the ground target area, while the secondary satellite simultaneously receives the radar echoes—a dual-receiver mode. When both satellites fly over a tropical rainforest region simultaneously, they use this dual-receiver mode to acquire echo data from the same area within the rainforest.

[0027] In step 2, the SAR echoes of the tropical rainforest from the primary and secondary satellites are imaged separately to obtain SAR images of the primary and secondary satellites. A schematic diagram of the primary and secondary satellite images is shown below. Figure 3a and Figure 3b As shown.

[0028] In steps 3 and 4, the power statistics include: a first average power value along the distance direction and a second average power value along the distance direction.

[0029] In step 3, the acquired SAR image is averaged along the azimuth direction to calculate the average power value along the range direction, and the SAR range direction SAR curve is fitted to obtain the on-orbit test results. The highest gain point of the primary satellite SAR is the range direction beam pointing test result RP02, and the highest gain point of the secondary satellite SAR is the range direction beam pointing test result RP12.

[0030] In step 3, the mathematical expression for the first average power value along the distance direction is:

[0031] Wherein, P1(i) is the average power value of the i-th column of the range direction of the SAR image, that is, the average power value along the first range direction, N is the number of points in the azimuth direction of the SAR image, and f1(i,k) is the power sampling value of the i-th column of the range direction and the k-th row of the azimuth direction of the SAR image; the SAR beam pointing corresponding to the maximum value in the P1(i) curve (i.e. the radiation pattern amplitude curve) is the range beam pointing test result.

[0032] In step 4, the primary satellite acquires measured data of the SAR antenna pattern during the ground-based anechoic chamber test phase and calculates the range direction RP01 for the ground test. The secondary satellite acquires measured data of the SAR antenna pattern during the ground-based anechoic chamber test phase and calculates the range direction RP11 for the ground test. A schematic diagram of the primary and secondary satellite test results is shown below. Figure 4a and Figure 4b As shown.

[0033] Preferably, in step 4, the mathematical expression for the second average power value along the distance direction is:

[0034] Wherein, P2(i) is the average power value of the i-th column in the range direction of the SAR ground test sample, that is, the average power value along the second range direction, N is the number of azimuth points in the SAR ground test sample, and f2(i,k) is the power sampling value of the i-th column in the range direction and the k-th row in the azimuth direction of the SAR ground test sample; the SAR beam pointing corresponding to the maximum value in the P2(i) curve (i.e. the amplitude curve of the SAR pattern) is the range beam pointing test result.

[0035] In step 5, it is determined whether |RP01-RP02| and |RP11-RP12| exceed the threshold, and test sample pairs where |RP01-RP02| and |RP11-RP12| are both within the threshold range are selected. The threshold value is related to the SAR operating frequency band, satellite attitude control accuracy, and product manufacturing level, and can be selected by the user according to the actual situation.

[0036] In step 6, the distance-to-space synchronization test result is |RP12-RP02| / RW×100%.

[0037] In step 7, multiple sets of test sample results are calculated, and the average of the calculated values ​​of each set is taken to further reduce random errors and obtain the final test results.

[0038] Example 2 This invention provides a distributed InSAR satellite range-oriented space-synchronous on-orbit testing system, comprising: Module M1: The dual satellites adopt a one-transmit, two-receive working mode to acquire radar echo data of the same ground target area; the one-transmit, two-receive working mode is: the main satellite transmits radar wave signals to the ground target area, and the main satellite and the auxiliary satellite simultaneously receive radar echo signals from the same ground target area; Module M2: Performs imaging processing on the radar echo data received by the primary satellite and the secondary satellite respectively to obtain primary satellite SAR image and secondary satellite SAR image; Module M3: Based on the primary satellite SAR image and the secondary satellite SAR image, acquire the primary satellite's on-orbit range beam pointing test result RP02 and the secondary satellite's on-orbit range beam pointing test result RP12, respectively; Module M4: Acquires the range-pointing test result RP01 obtained by the primary satellite during the ground testing phase, and the range-pointing test result RP11 obtained by the secondary satellite during the ground testing phase; Module M5: Based on RP01, RP02, RP11 and RP12, it performs test sample validity assessment and screening; Module M6: Based on the filtered valid test sample data, calculate the range-direction space synchronization test results of the distributed InSAR satellite dual-satellite system; Module M7: Calculates the results of multiple test samples, averages the calculated values ​​of each group to further reduce random errors, and obtains the final test results.

[0039] The module M3 includes: using the azimuth modulus averaging method to calculate the average power value along the range direction for the acquired SAR image, and fitting the radiation pattern curve to obtain the on-orbit test results of the SAR range radiation pattern; wherein, the highest gain point of the primary satellite radiation pattern is the range beam pointing test result RP02, and the highest gain point of the secondary satellite radiation pattern is the range beam pointing test result RP12.

[0040] In module M4, RP01 is the ground test range direction obtained by the main satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase; RP11 is the ground test range direction obtained by the auxiliary satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase.

[0041] The module M5 includes: determining whether |RP01-RP02| and |RP11-RP12| exceed a preset threshold, and selecting test sample pairs where |RP01-RP02| and |RP11-RP12| are both within the preset threshold range.

[0042] In module M6, the range-direction space synchronization test result is calculated using the formula |RP12-RP02| / RW×100%, where RW is the range-direction beamwidth of the main star.

[0043] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0044] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A distributed InSAR satellite range-oriented space-synchronous on-orbit testing method, characterized in that, include: Step 1: The two satellites adopt a one-transmit, two-receive working mode to acquire radar echo data of the same ground target area; The one-to-two-receive working mode is as follows: the main satellite transmits radar wave signals to the ground target area, and the main satellite and the auxiliary satellite simultaneously receive radar echo signals from the same ground target area. Step 2: Perform imaging processing on the radar echo data received by the primary satellite and the secondary satellite respectively to obtain the primary satellite SAR image and the secondary satellite SAR image; Step 3: Based on the primary satellite SAR image and the secondary satellite SAR image, obtain the primary satellite's on-orbit range beam pointing test result RP02 and the secondary satellite's on-orbit range beam pointing test result RP12, respectively; Step 4: Obtain the distance-direction pointing test result RP01 obtained by the primary star during the ground test phase, and the distance-direction pointing test result RP11 obtained by the secondary star during the ground test phase; Step 5: Based on RP01, RP02, RP11, and RP12, determine and screen the validity of the test samples; Step 6: Based on the filtered valid test sample data, calculate the range-direction space synchronization test results of the distributed InSAR satellite dual-satellite system; Step 7: Calculate the results of multiple test samples, average the calculated values ​​of each group to further reduce random error, and obtain the final test results.

2. The distributed InSAR satellite range-oriented space-synchronous on-orbit testing method according to claim 1, characterized in that, Step 3 includes: using the azimuth modulus averaging method to calculate the average power value along the range direction for the acquired SAR image, and fitting the radiation pattern curve to obtain the on-orbit test results of the SAR range radiation pattern; wherein, the highest gain point of the primary satellite radiation pattern is the range beam pointing test result RP02, and the highest gain point of the secondary satellite radiation pattern is the range beam pointing test result RP12.

3. The distributed InSAR satellite range-oriented space-synchronous on-orbit testing method according to claim 1, characterized in that, In step 4, RP01 is the ground test range direction obtained by the main satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase; RP11 is the ground test range direction obtained by the auxiliary satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase.

4. The distributed InSAR satellite range-oriented space-synchronous on-orbit testing method according to claim 1, characterized in that, Step 5 includes: determining whether |RP01-RP02| and |RP11-RP12| exceed a preset threshold, and selecting test sample pairs where |RP01-RP02| and |RP11-RP12| are both within the preset threshold range.

5. The distributed InSAR satellite range-oriented space-synchronous on-orbit testing method according to claim 1, characterized in that, In step 6, the range-direction space synchronization test result is obtained by calculating the formula |RP12-RP02| / RW×100%, where RW is the range-direction beamwidth of the main star.

6. A distributed InSAR satellite range-oriented space-synchronous on-orbit testing system, characterized in that, include: Module M1: The dual satellites adopt a one-transmit, two-receive working mode to acquire radar echo data of the same ground target area; The one-to-two-receive working mode is as follows: the main satellite transmits radar wave signals to the ground target area, and the main satellite and the auxiliary satellite simultaneously receive radar echo signals from the same ground target area. Module M2: Performs imaging processing on the radar echo data received by the primary satellite and the secondary satellite respectively to obtain primary satellite SAR images and secondary satellite SAR images; Module M3: Based on the primary satellite SAR image and the secondary satellite SAR image, acquire the primary satellite's on-orbit range beam pointing test result RP02 and the secondary satellite's on-orbit range beam pointing test result RP12, respectively; Module M4: Acquires the range-pointing test result RP01 obtained by the primary satellite during the ground testing phase, and the range-pointing test result RP11 obtained by the secondary satellite during the ground testing phase; Module M5: Based on RP01, RP02, RP11 and RP12, it performs test sample validity assessment and screening; Module M6: Based on the filtered valid test sample data, calculate the range-direction space synchronization test results of the distributed InSAR satellite dual-satellite system; Module M7: Calculates the results of multiple test samples, averages the calculated values ​​of each group to further reduce random errors, and obtains the final test results.

7. The distributed InSAR satellite range-oriented space-synchronous on-orbit test system according to claim 6, characterized in that, The module M3 includes: using the azimuth modulus averaging method to calculate the average power value along the range direction for the acquired SAR image, and fitting the radiation pattern curve to obtain the on-orbit test results of the SAR range radiation pattern; wherein, the highest gain point of the primary satellite radiation pattern is the range beam pointing test result RP02, and the highest gain point of the secondary satellite radiation pattern is the range beam pointing test result RP12.

8. The distributed InSAR satellite range-oriented space-synchronous on-orbit test system according to claim 6, characterized in that, In module M4, RP01 is the ground test range direction obtained by the main satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase; RP11 is the ground test range direction obtained by the auxiliary satellite from the measured SAR antenna pattern data acquired during the ground anechoic chamber test phase.

9. The distributed InSAR satellite range-oriented space-synchronous on-orbit test system according to claim 6, characterized in that, The module M5 includes: determining whether |RP01-RP02| and |RP11-RP12| exceed a preset threshold, and selecting test sample pairs where |RP01-RP02| and |RP11-RP12| are both within the preset threshold range.

10. The distributed InSAR satellite range-oriented space-synchronous on-orbit test system according to claim 6, characterized in that, In module M6, the range-direction space synchronization test result is calculated using the formula |RP12-RP02| / RW×100%, where RW is the range-direction beamwidth of the main star.

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