SAR satellite system sensitivity on-orbit test method and system

Abstract

The invention provides an SAR satellite system sensitivity on-orbit test method and system, and the method comprises the steps: S1, selecting a target region, and compiling a satellite load instruction packet; s2, enabling a satellite to start up for imaging according to the satellite load instruction packet, and obtaining SAR echo data of the target area; s3, generating an SAR image according to the SAR echo data; and S4, calculating according to the SAR image to obtain a power statistical value, and further obtaining a system sensitivity test result of the satellite. The method can be used for the on-orbit test of the sensitivity index of the SAR satellite system, and aims at a traditional test method which needs to be started twice to respectively record echo and noise data.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of space system, in particular, relates to a SAR satellite system sensitivity on-orbit test method and system. More particularly, it relates to a satellite overall design and load on-orbit test method. BACKGROUND

[0002] Synthetic Aperture Radar, SAR for short, is a kind of all-weather and all-day active ground observation equipment, which can observe the ground all day long and all weather, and plays a huge role in natural resources, earthquakes, disaster reduction, forestry and national defense. At present, SAR satellites usually have multiple imaging modes, among which the most important working modes are strip and spotlight modes. The strip mode is shown in Figure 2 , and the spotlight mode is shown in Figure 3 .

[0003] SAR satellite system sensitivity represents the observation ability of the SAR system to weak and small targets, and reflects the lower limit of the weak and small target signals that the SAR system itself can detect, which is an important indicator of SAR system engineering development. Due to the large number of wave positions of SAR satellite strip / spotlight mode, the system sensitivity indicators of each wave position are different, and during on-orbit test, it is usually necessary to test all wave position system sensitivity, so the test work of this indicator becomes one of the longest projects in on-orbit test time, which greatly affects the time of forming satellite on-orbit capability.

[0004] Under the prior art, SAR satellite system sensitivity test needs two starts to record echo and noise data respectively. Since the SAR satellite system sensitivity test needs two starts to record echo and noise data under the prior art, the state of the satellite in terms of temperature, attitude, etc. is different, and it is difficult to represent the test results under the same time condition.

[0005] In recent years, satellite users have increasingly urgent requirements for the timeliness of SAR satellite system sensitivity on-orbit test.

[0006] Patent document CN107271995A discloses a system sensitivity optimization design method based on beam pointing adjustment, which mainly solves the problem of on-orbit test method of SAR satellite system sensitivity, but does not solve the problem of system sensitivity optimization design.

[0007] Patent document CN119439159A discloses a method for determining the aperture of a SAR antenna in medium and high orbits based on full-orbit traversal analysis, which solves the problem of on-orbit test method of SAR satellite system sensitivity, but does not solve the problem of design method of SAR antenna aperture.

[0008] Patent document CN114662273A discloses a micro-nano satellite SAR antenna overall design method, which solves the on-orbit test method problem of SAR satellite system sensitivity, but fails to solve the problem of micro-nano satellite SAR antenna size integration design.

[0009] Patent document CN112684448A discloses a spaceborne SAR wave position calculation and generation method and system for multi-parameter combination, which mainly solves the on-orbit test method problem of SAR satellite system sensitivity, but fails to solve the SAR system parameter design problem.

[0010] Research on the influence of spaceborne SAR system sensitivity on ship classification, Electronic Design Engineering, 202306. The scheme does not solve the on-orbit test method problem of SAR satellite system sensitivity, but mainly solves the problem of different SAR image ship classification accuracy under different spaceborne SAR system sensitivities.

[0011] Sensitivity test and analysis of spaceborne radiometer receiving calibration system, Terahertz Science and Electronic Information Journal, 201606. The scheme does not solve the on-orbit test method problem of SAR satellite system sensitivity, but mainly solves the problem of verifying whether the spaceborne radiometer meets the observation requirements.

[0012] Patent document CN118376849B discloses a spaceborne SAR high-efficiency multi-beam range direction pattern on-orbit test method, which shortens the on-orbit test acceptance time and increases the effective service life of the satellite, but fails to solve the on-orbit test method problem of SAR satellite system sensitivity.

[0013] In summary, this problem needs to be solved urgently. SUMMARY

[0014] In view of the defects in the prior art, the purpose of the present application is to provide a SAR satellite system sensitivity on-orbit test method and system.

[0015] According to the SAR satellite system sensitivity on-orbit test method provided by the present application, the following steps are included:

[0016] Step S1: selecting a target area, preparing a satellite payload instruction package;

[0017] Step S2: starting the satellite to image according to the satellite payload instruction package, and acquiring SAR echo data of the target area;

[0018] Step S3: generating a SAR image according to the SAR echo data;

[0019] Step S4: calculating the power statistical value according to the SAR image, and then obtaining the system sensitivity test result of the satellite.

[0020] Preferably, in the step S1, the target area is able to be covered by the test wave position of the satellite, and the target area comprises a tropical rainforest of a water body.

[0021] Preferably, in the step S2, the imaging comprises strip imaging and spotlight imaging.

[0022] In the step S4, the power statistical value comprises a first average power value along a distance direction and a second average power value along the distance direction.

[0023] Preferably, in the step S4, the first average power value along the distance direction is mathematically expressed as:

[0024]

[0025] wherein P1(i) is an average power value of an i-th column along a distance direction of a panoramic image, i.e. the first average power value along the distance direction, N is a point number of an azimuth direction of the panoramic image, f1(i, k) is a power sampling value of an i-th column along the distance direction and a k-th row along an azimuth direction of the panoramic image;

[0026] The second average power value along the distance direction is mathematically expressed as:

[0027]

[0028] wherein P2(j) is an average power value of a j-th column along a distance direction of a water body image, i.e. the second average power value along the distance direction, M is a point number of an azimuth direction of the water body image, f2(j, l) is a power sampling value of a j-th column along the distance direction and a l-th row along an azimuth direction of the water body image; and I represents a row number.

[0029] The mathematical expression of the system sensitivity is:

[0030]

[0031] wherein NEσ 0 represents the system sensitivity, and the unit is dB; represents an average power of a water body, and the unit is dB, L is a point number of the water body along the distance direction; min(P1(i)) represents an average minimum power value of the panoramic image along the distance direction, and the unit is dB; and P3 represents an average backscattering coefficient of a test area, and the P3 value of a tropical rainforest area is -7dB to -6.5dB.

[0032] According to the present application, a SAR satellite system sensitivity on-orbit test system is provided, which comprises:

[0033] Module M1: selecting a target area and compiling a satellite load instruction package;

[0034] Module M2: instructing the satellite to start imaging according to a satellite payload instruction package, and acquiring SAR echo data of the target area;

[0035] Module M3: generating a SAR image according to the SAR echo data;

[0036] Module M4: calculating a power statistical value according to the SAR image, and then obtaining a system sensitivity test result of the satellite.

[0037] Preferably, in the module M1, the target area can be covered by a test wave position of the satellite, and the target area includes a tropical rainforest containing a water body.

[0038] Preferably, in the module M2, the imaging includes strip imaging and spotlight imaging.

[0039] In the module M4, the power statistical value includes a first average power value along a distance direction and a second average power value along the distance direction.

[0040] Preferably, in the module M4, the first average power value along the distance direction has a mathematical expression as follows:

[0041]

[0042] wherein P1(i) is an average power value of an i-th column along a distance direction of a panoramic image, i.e., the first average power value along the distance direction, N is a number of image azimuth points of the panoramic image, and f1(i, k) is a power sampling value of an i-th column along the distance direction and a k-th row along an azimuth direction of the panoramic image.

[0043] The second average power value along the distance direction has a mathematical expression as follows:

[0044]

[0045] wherein P2(j) is an average power value of a j-th column along a distance direction of a water body image, i.e., the second average power value along the distance direction, M is a number of image azimuth points of the water body image, f2(j, l) is a power sampling value of a j-th column along the distance direction and a l-th row along an azimuth direction of the water body image, and I represents a number of rows.

[0046] The mathematical expression of the system sensitivity is as follows:

[0047]

[0048] wherein NEσ 0 represents the system sensitivity, and the unit is dB. L is the average power of the water body, unit: dB, L is the number of points along the distance of the water body; min(P1(i)) is the average minimum power value of the panoramic image along the distance, unit: dB; P3 is the average backscattering coefficient of the test area, the P3 value of the tropical rainforest area is-7dB to-6.5dB.

[0049] According to the present application, a computer readable storage medium storing a computer program is provided, and the computer program is executed by a processor to implement the steps of the SAR satellite system sensitivity on-orbit test method.

[0050] According to the present application, an electronic device is provided, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the computer program is executed by the processor to implement the steps of the SAR satellite system sensitivity on-orbit test method.

[0051] Compared with the prior art, the present application has the following beneficial effects:

[0052] 1. The present application only needs single start test, and can quickly and efficiently complete the SAR satellite system sensitivity test task;

[0053] 2. The present application can simultaneously obtain echo and approximate noise data, and can avoid the influence of temperature, attitude and other factors.

[0054] 3. The present application can be used for on-orbit test of SAR satellite system sensitivity indicators, and is used for the traditional test method of twice starting and recording echo and noise data. BRIEF DESCRIPTION OF DRAWINGS

[0055] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0056] Figure 1 The flowchart provided by the present application is shown in the figure;

[0057] Figure 2 The SAR satellite strip mode provided by the present application is shown in the figure;

[0058] Figure 3 The SAR satellite spotlight mode provided by the present application is shown in the figure;

[0059] Figure 4 The selected tropical rainforest area strip mode provided by the present application is shown in the figure; the mode is one start and four imaging;

[0060] Figure 5 The SAR satellite data imaging processing result provided by the present application is shown in the figure;

[0061] Figure 6A SAR satellite panoramic image distance and azimuth schematic diagram provided by the present application;

[0062] Figure 7 A SAR satellite water body image schematic diagram provided by the present application;

[0063] Figure 8 A SAR satellite system sensitivity test result schematic diagram provided by the present application. DETAILED DESCRIPTION

[0064] The present application will be described in detail below with specific embodiments. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of changes and improvements can be made. These are within the scope of the present application.

[0065] In order to improve the SAR satellite strip / burst mode full-wave position system sensitivity test efficiency, the present application provides a SAR satellite system sensitivity on-orbit test method. The SAR satellite is used for water body imaging, and the result is approximately equal to the noise level. The present application uses the average power of the water body area in the image to replace the noise power in the traditional test method to achieve the technical approach.

[0066] According to the SAR satellite system sensitivity on-orbit test method provided by the present application, it comprises:

[0067] Step one: select the tropical rainforest target area covered by the test wave position;

[0068] Specifically, according to the SAR satellite predicted orbit information, the strip / burst test wave position can cover the tropical rainforest target area; the rainforest contains water body.

[0069] Step two: compile satellite load instruction package, and upload to satellite through satellite-ground measurement and control system;

[0070] Step three: the satellite starts imaging on-orbit according to the instruction package parameters, and obtains the SAR echo data of the tropical rainforest target area; the imaging includes strip imaging and burst imaging.

[0071] Step four: the satellite transmits the SAR echo data recorded to the ground;

[0072] In other words, the satellite transmits the SAR echo data obtained to the ground data receiving station.

[0073] Step five: the ground system processes the echo data to obtain SAR image;

[0074] Step six: the SAR image obtained using the method of taking the average along the azimuth direction, the average power value along the distance direction is counted;

[0075] In other words, the SAR image obtained using the method of taking the average along the azimuth direction, the average power value along the distance direction is counted, that is, the first average power value along the distance direction;

[0076] As shown in formula (1), the distance direction and the azimuth direction of the SAR satellite panoramic image are as shown in formula (2). Figure 6

[0077] The mathematical expression of the first average power value along the distance direction is:

[0078]

[0079] Wherein, P1(i) is the average power value of the i-th column of the panoramic image along the distance direction, N is the number of points in the azimuth direction of the panoramic image, f1(i, k) is the power sampling value of the i-th column along the distance direction and the k-th row along the azimuth direction of the panoramic image.

[0080] Step seven: extracting the water area complex image from the SAR image and counting the average power value along the distance direction, that is, the second average power value along the distance direction;

[0081] As shown in formula (2), the SAR satellite water body image is as shown in formula (3). Figure 7

[0082] The mathematical expression of the second average power value along the distance direction is:

[0083]

[0084] Wherein, P2(j) is the average power value of the j-th column along the distance direction of the water body image, that is, the second average power value along the distance direction, M is the number of points in the azimuth direction of the water body image, f2(j, l) is the power sampling value of the j-th column along the distance direction and the l-th row along the azimuth direction of the water body image; I represents the number of rows;

[0085] Step eight: calculating the SAR system sensitivity according to formula.

[0086] According to formula, the SAR system sensitivity is calculated, the system sensitivity (dB) = the average power of water body (dB) - the average minimum power of panoramic image (dB) + the average backscattering coefficient of tropical rainforest (dB), the mathematical expression is shown in formula (3).

[0087]

[0088] Wherein, NEσ0 is the system sensitivity, unit: dB, the average power of water body is ​​The unit is dB, the average minimum power of the panoramic image is min(P1(i)), the unit is dB, the average backscattering coefficient of the tropical rainforest is P3, the unit is dB, and the value can be taken as -7dB to -6.5dB according to the public literature, L is the number of points of the water body along the distance, and a test result diagram is shown in FIG. 1. Figure 8

[0089] Specifically, in step one, according to the SAR satellite predicted orbit information, the tropical rainforest covered by the test wave position is selected, and a water body target area is contained. In order to ensure the rapid acquisition of the tropical rainforest data, a one-time start and multiple imaging mode is recommended. Different wave positions and strip modes are selected between multiple imaging, and the imaging time is 20 seconds each time, so that 5 images can be acquired in a single imaging, which is convenient for ground processing image screening, and ensures the effectiveness of the test sample and the efficiency of the on-orbit test.

[0090] Specifically, in step two, according to the satellite orbit prediction and the SAR wave position selection result, the SAR imaging start and end time and imaging parameters, the synchronous data transmission start and end time and the like are calculated, the load instruction package is compiled, and the satellite is uploaded through the satellite-ground measurement and control system.

[0091] Specifically, in step three, the satellite starts and strips / aggregates according to the parameters in the instruction package on the satellite, and acquires the SAR echo data of the tropical rainforest target area.

[0092] Specifically, in step four, the satellite transmits the acquired SAR echo data to the ground data receiving station.

[0093] Specifically, in step five, the ground system processes the echo data to obtain SAR images.

[0094] Specifically, in step six, the SAR images obtained are processed by using the method of taking the average along the azimuth direction, and the average power value along the distance direction is calculated, that is, the first average power value along the distance direction, as shown in formula (1).

[0095]

[0096] Wherein, P1(i) is the average power value of the i-th column of the panoramic image along the distance direction, that is, the first average power value along the distance direction, N is the number of points of the panoramic image along the azimuth direction, and f1(i, k) is the power sampling value of the i-th column and the k-th row of the panoramic image along the distance direction and the azimuth direction.

[0097] Specifically, in step seven, the water body area complex image is extracted from the SAR image, and the average power value along the distance direction is calculated, that is, the second average power value along the distance direction, as shown in formula (2).

[0098] ​

[0099] Wherein, P2(j) is the average power value of the water body image along the distance direction, i.e., the second average power value along the distance direction, M is the number of points of the water body image along the azimuth direction, f2(j, l) is the power sampling value of the water body image along the distance direction and along the azimuth direction, and I represents the number of rows.

[0100] Specifically, in step eight, the SAR system sensitivity is calculated according to the formula: system sensitivity (dB) = water body average power (dB) - panoramic image average minimum power (dB) + tropical rainforest average backscattering coefficient (dB), and the mathematical expression is shown in formula (3).

[0101]

[0102] Wherein, NEσ 0 The system sensitivity (dB) is water body average power (dB) - panoramic image average minimum power (dB) + tropical rainforest average backscattering coefficient (dB). The panoramic image average minimum power (dB) is max (P1(i)), the target average backscattering coefficient, i.e., the tropical rainforest average backscattering coefficient (dB) is P3, the P3 value of the tropical rainforest area is -7dB to -6.5dB according to the public literature, and L is the number of points of the water body along the distance direction.

[0103] (6) The SAR image obtained is subjected to the azimuth direction average method, and the average power value along the distance direction is counted, as shown in formula (1).

[0104] (7) The water body area complex image is extracted from the SAR image, and the average power value along the distance direction is counted, as shown in formula (2).

[0105] (8) The SAR system sensitivity is calculated according to the formula

[0106] The SAR system sensitivity is calculated according to the formula: system sensitivity (dB) = water body average power (dB) - panoramic image average minimum power (dB) + tropical rainforest average backscattering coefficient (dB), and the mathematical expression is shown in formula (3).

[0107] The application also provides a SAR satellite system sensitivity on-orbit test system, which can be realized by executing the process steps of the SAR satellite system sensitivity on-orbit test method, i.e., the SAR satellite system sensitivity on-orbit test method can be understood as the preferred embodiment of the SAR satellite system sensitivity on-orbit test system by those skilled in the art.

[0108] According to the application, a SAR satellite system sensitivity on-orbit test system is provided, which comprises:

[0109] Module M1: selecting a target area, compiling a satellite payload instruction package;

[0110] Module M2: instructing the satellite to start imaging according to the satellite payload instruction package, and obtaining SAR echo data of the target area;

[0111] Module M3: generating a SAR image according to the SAR echo data;

[0112] Module M4: calculating a power statistical value according to the SAR image, and obtaining a system sensitivity test result of the satellite.

[0113] Those skilled in the art know that, in addition to implementing the system provided by the present application and each device, module and unit thereof in the form of pure computer readable program code, the system provided by the present application and each device, module and unit thereof can also be implemented in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers and embedded microcontrollers, etc. to achieve the same functions by logically programming the method steps. Therefore, the system provided by the present application and each device, module and unit thereof can be considered as a hardware component, and the devices, modules and units included therein for achieving various functions can also be considered as structures within the hardware component; the devices, modules and units for achieving various functions can also be considered as both software modules for implementing methods and structures within hardware components.

[0114] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, which do not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily without conflict.

Claims

1. A method for on-orbit testing of the sensitivity of a SAR satellite system, characterized in that, include: Step S1: Select the target area and compile the satellite payload command package; Step S2: Instruct the satellite to power on and image according to the satellite payload command packet to acquire SAR echo data of the target area; Step S3: Generate SAR imagery based on the SAR echo data; Step S4: Calculate the power statistics based on the SAR imagery, and then obtain the system sensitivity test results of the satellite.

2. The on-orbit testing method for SAR satellite system sensitivity according to claim 1, characterized in that, In step S1, the target area is covered by the test wavelength of the satellite, and the target area includes tropical rainforests containing water bodies.

3. The on-orbit testing method for SAR satellite system sensitivity according to claim 1, characterized in that, In step S2, the imaging includes strip imaging and beamforming; In step S4, the power statistics include: a first average power value along the distance direction and a second average power value along the distance direction.

4. The on-orbit testing method for SAR satellite system sensitivity according to claim 3, characterized in that, In step S4, the mathematical expression for the first average power value along the distance direction is: Where P1(i) is the average power value of the i-th column in the range direction of the panoramic image, that is, the average power value along the first range direction, N is the number of points in the azimuth direction of the panoramic image, and f1(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 panoramic image. The mathematical expression for the second average power value along the range direction is: Where P2(j) is the average power value of the water body image along the j-th column in the range direction, i.e., the second average power value along the range direction; M is the number of points in the azimuth direction of the water body image; f2(j,l) is the power sample value of the water body image in the j-th column in the range direction and the l-th row in the azimuth direction; I represents the row number. The mathematical expression for the system sensitivity is: Among them, NEσ 0 This indicates the system sensitivity, expressed in dB. The average power of the water body is expressed in dB, and L is the number of points along the distance of the water body; min(P1(i)) represents the average minimum power value of the panoramic image along the distance, expressed in dB; P3 represents the average backscattering coefficient of the test area, and the P3 value for the tropical rainforest area is -7dB to -6.5dB.

5. An on-orbit sensitivity testing system for SAR satellite systems, characterized in that, include: Module M1: Select the target area and compile the satellite payload command package; Module M2: Instructs the satellite to power on and image according to the satellite payload command packet, and acquire SAR echo data of the target area; Module M3: Generates SAR images based on the SAR echo data; Module M4: Calculates power statistics based on SAR images, and then obtains the system sensitivity test results of the satellite.

6. The SAR satellite system sensitivity on-orbit testing system according to claim 5, characterized in that, In module M1, the target area can be covered by the test wavelength of the satellite, and the target area includes tropical rainforests containing water bodies.

7. The SAR satellite system sensitivity on-orbit testing system according to claim 5, characterized in that, In module M2, the imaging includes strip imaging and beamforming; In module M4, the power statistics include: a first average power value along the distance direction and a second average power value along the distance direction.

8. The SAR satellite system sensitivity on-orbit testing system according to claim 7, characterized in that, In module M4, the mathematical expression for the first average power value along the distance direction is: Where P1(i) is the average power value of the i-th column in the range direction of the panoramic image, that is, the average power value along the first range direction, N is the number of points in the azimuth direction of the panoramic image, and f1(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 panoramic image. The mathematical expression for the second average power value along the range direction is: Where P2(j) is the average power value of the water body image along the j-th column in the range direction, i.e., the second average power value along the range direction; M is the number of points in the azimuth direction of the water body image; f2(j,l) is the power sample value of the water body image in the j-th column in the range direction and the l-th row in the azimuth direction; I represents the row number. The mathematical expression for the system sensitivity is: Among them, NEσ 0 This indicates the system sensitivity, expressed in dB. The average power of the water body is expressed in dB, and L is the number of points along the distance of the water body; min(P1(i)) represents the average minimum power value of the panoramic image along the distance, expressed in dB; P3 represents the average backscattering coefficient of the test area, and the P3 value for the tropical rainforest area is -7dB to -6.5dB.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the on-orbit testing method for the sensitivity of a SAR satellite system as described in any one of claims 1 to 4.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is executed by the processor, it implements the steps of the on-orbit testing method for the sensitivity of a SAR satellite system as described in any one of claims 1 to 4.

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