SAR satellite radiation performance monitoring method and system

Abstract

The invention relates to the technical field of SAR data processing, in particular to an SAR satellite radiation performance monitoring method and system. The method comprises the following steps: controlling a target SAR satellite to generate an internal calibration signal gear by gear based on a preset amplitude attenuation gear; the internal calibration signal is preprocessed, and the actual amplitude, corresponding to each amplitude attenuation gear, of the internal calibration signal is obtained; determining a linear change area of attenuation of the internal calibration signal; selecting an amplitude attenuation gear in the linear change area to obtain a corresponding historical actual amplitude; calculating a first difference value between the current actual amplitude value and a corresponding historical actual amplitude value, traversing and detecting all types of internal calibration signals, and if the situation that the first difference value is greater than a corresponding preset threshold value does not occur, judging that the radiation performance of the target SAR satellite does not change; otherwise, the change occurs. By adopting the method provided by the invention, radiation performance monitoring of all available wave positions can be realized, and timeliness and accuracy of SAR satellite radiation performance monitoring are ensured.

Description

Technical Field

[0001] This application relates to the technical field of SAR data processing, and in particular to a method and system for monitoring the radiation performance of SAR satellites. Background Art

[0002] Synthetic Aperture Radar (SAR) is a remote sensing method that actively emits microwaves to obtain target scattering information. As time goes by after the SAR satellite is launched, there are certain changes in the radiation characteristics of the payload. When the radiation characteristics change to a certain extent, it will lead to a significant decrease in the radiation accuracy of the SAR image. Through field calibration, only some wave positions can be monitored, and all available wave positions cannot be covered. Moreover, the timeliness of field calibration monitoring is insufficient. Summary of the Invention

[0003] The purpose of the embodiment of this application is to provide a method for monitoring the radiation performance of a SAR satellite. The internal calibration data of the SAR satellite is composed of multiple types of internal calibration signals. The method includes: S1. Based on a preset amplitude attenuation gear, control the target SAR satellite to generate internal calibration signals gear by gear, and obtain the internal calibration signals; S2. Preprocess the internal calibration signals to obtain the actual amplitudes of the internal calibration signals corresponding to each amplitude attenuation gear; S3. Calculate the first amplitude difference between two adjacent amplitude attenuation gears and the second amplitude difference between the actual amplitudes corresponding to two adjacent amplitude attenuation gears, and determine whether the difference between the first amplitude difference and the second amplitude difference is lower than the non-linear threshold. If so, classify the corresponding amplitude attenuation gear into the linear change region of the internal calibration signal attenuation; S4. Record the amplitude attenuation gears located within the linear change region; S5. Select an amplitude attenuation gear within the linear change region to obtain the corresponding historical actual amplitude; S6. Calculate the first difference between the current actual amplitude and the corresponding historical actual amplitude, and determine whether there is a situation where the first difference is greater than the preset threshold; if so, determine that the radiation performance of the target SAR satellite has changed;

[0004] S7. Otherwise, repeat steps S1 to S6 to traverse and detect all types of internal calibration signals. If the situation where the first difference is greater than the corresponding preset threshold does not occur, it is determined that the radiation performance of the target SAR satellite has not changed.

[0005] Based on the first aspect, in the embodiment of this application, the multiple types of internal calibration signals include reference calibration signals, full-array emission calibration signals, full-array reception calibration signals, and full-array transceiver calibration signals, and each type of internal calibration signal contains multiple pulses.

[0006] Based on the first aspect, in the embodiments of the present application, the preprocessing of the generated internal calibration signal to obtain the actual amplitude of the internal calibration signal corresponding to each amplitude attenuation level includes: using an ideal linear frequency modulation signal to compress each pulse of the internal calibration signal one by one to obtain the amplitude after compression of all pulse signals; wherein, the amplitude after compression of each pulse signal is represented in decibels; taking the average value of the amplitudes after compression of all pulse signals as the actual amplitude of the internal calibration signal corresponding to the amplitude attenuation level.

[0007] Based on the first aspect, in the embodiments of the present application, the expression of the ideal linear frequency modulation signal is: H(f) = exp(jπf 2 / K); where f represents the frequency in the range direction, K represents the chirp rate of the linear frequency modulation signal, and j represents the complex constant.

[0008] Based on the first aspect, in the embodiments of the present application, the method further includes: A1. Obtaining SAR image data of a specific target; A2. Verifying whether the radiation performance of the target SAR satellite has changed according to the SAR image data, and judging whether the detection results of the radiation performance of the target SAR satellite in steps S1 to S7 are consistent based on the verification result.

[0009] Based on the first aspect, in the embodiments of the present application, the specific target is a stable distributed target or a stable point target.

[0010] Based on the first aspect, in the embodiments of the present application, verifying whether the radiation performance of the target SAR satellite has changed according to the SAR image data includes: calculating the current absolute calibration constant of the target SAR satellite using the SAR image data; obtaining the most recent historical absolute calibration constant of the target SAR satellite, and calculating the difference two between the current absolute calibration constant and the most recent historical absolute calibration constant; if the difference two is greater than the fluctuation threshold of the absolute calibration constant, the radiation performance of the target SAR satellite has changed; otherwise, the radiation performance of the target SAR satellite has not changed.

[0011] Based on the first aspect, in the embodiments of the present application, the method further includes: if the detection results are inconsistent, repeating steps S1 to S7 or changing the specific target and repeating steps A1 to A2 until the verification result is consistent with the detection result or the number of repetitions reaches a predetermined number; if the number of repetitions reaches the predetermined number and the detection results are still inconsistent, it is determined that the SAR radiation performance has changed.

[0012] Second aspect, the present application provides a SAR satellite radiation performance monitoring system. The internal calibration data of the SAR satellite consists of multiple types of internal calibration signals. The system includes: a data acquisition module for acquiring internal calibration signals. The acquisition method includes: controlling the target SAR satellite to generate internal calibration signals step by step based on a preset amplitude attenuation level; a data processing module for preprocessing the internal calibration signals to obtain the actual amplitudes of the internal calibration signals corresponding to each amplitude attenuation level; and for recording the amplitude attenuation levels within the linear change region; and also for selecting an amplitude attenuation level within the linear change region to obtain the corresponding historical actual amplitude; a data analysis module for calculating the amplitude difference one between two adjacent amplitude attenuation levels and the amplitude difference two between the actual amplitudes corresponding to two adjacent amplitude attenuation levels, and determining whether the difference between the amplitude difference one and the amplitude difference two is lower than a non-linear threshold. If so, the corresponding amplitude attenuation level is classified into the linear change region of the internal calibration signal attenuation; and also for calculating the difference one between the current actual amplitude and the corresponding historical actual amplitude, and determining whether there is a situation where the difference one is greater than a preset threshold. If there is, it is determined that the radiation performance of the target SAR satellite has changed; otherwise, all types of internal calibration signals are traversed and detected. If the difference one greater than the corresponding preset threshold does not occur in all of them, it is determined that the radiation performance of the target SAR satellite has not changed.

[0013] Based on the second aspect, in an embodiment of the present application, the system further includes: an absolute calibration constant update module for updating the absolute calibration constant of the target SAR satellite. The update steps of the absolute calibration constant are as follows: calculating the current absolute calibration constant of the target SAR satellite using the SAR image data; obtaining the most recent historical absolute calibration constant of the target SAR satellite, and calculating the difference two between the current absolute calibration constant and the most recent historical absolute calibration constant; if the difference two is not less than the fluctuation threshold of the absolute calibration constant, updating the absolute calibration constant of the target SAR satellite to the current absolute calibration constant; otherwise, taking the average value of the absolute calibration constants obtained in the previous N times as the absolute calibration constant of the target SAR satellite, where N≥1.

[0014] The solution provided by the present application has at least the following beneficial effects:

[0015] 1) The method proposed by the present invention for monitoring the radiation characteristics of SAR satellites using internal calibration data can realize the monitoring of the radiation performance of all available wave positions, which has obvious advantages compared with the external field that can only monitor some wave positions. At the same time, the requirements of the present invention are low and the implementation is relatively simple.

[0016] 2) The present invention is suitable for long-term monitoring of the radiation characteristics of SAR satellites, and the stability of the SAR image quality can be improved through long-term monitoring.

[0017] 3) By using the monitoring of the radiation characteristics of the SAR satellite according to the present invention, it can work in cooperation with the in-field calibration, reducing the workload of the in-field calibration of the SAR satellite. When the change in the radiation characteristics of the SAR satellite is greater than the change threshold, it can be verified in time through in-field calibration.

[0018] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings are used to provide a further understanding of the embodiments of the present application, and constitute a part of the specification. Together with the following specific implementation, they are used to explain the embodiments of the present application, but do not constitute a limitation to the embodiments of the present application. In the drawings:

[0020] Figure 1 Schematically shows the flowchart of the method for monitoring the radiation performance of the SAR satellite in the embodiment;

[0021] Figure 2 Schematically shows the amplitude diagram of each level of the attenuation of the full-array transmitted signal in the Q11 waveband of the full-polarization strip mode of the GF-3 satellite in the embodiment of the present application;

[0022] Figure 3 Schematically shows the change curve of the delay reference calibration data in the Q11 waveband of the full-polarization strip mode of the GF-3 satellite in the embodiment of the present application;

[0023] Figure 4 Schematically shows the change curve of the transmitted calibration reference of the full array in the Q11 waveband of the full-polarization strip mode of the GF-3 satellite in the embodiment of the present application;

[0024] Figure 5 Schematically shows the change curve of the received calibration reference of the full array in the Q11 waveband of the full-polarization strip mode of the GF-3 satellite in the embodiment of the present application;

[0025] Figure 6 Schematically shows the change curve of the transmitted and received calibration reference of the full array in the Q11 waveband of the full-polarization strip mode of the GF-3 satellite in the embodiment of the present application;

[0026] Figure 7 Schematically shows the block diagram of the composition of the system for monitoring the radiation performance of the SAR satellite in the embodiment.

[0027] DESCRIPTION OF THE REFERENCE NUMERALS

[0028] 1 - Data acquisition module; 2 - Data processing module; 3 - Data analysis module; 4 - Absolute calibration constant update module. SPECIFIC IMPLEMENTATION

[0029] To make the objectives, technical solutions and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. It should be understood that the specific implementation manners described herein are only for explaining and illustrating the embodiments of this application, and are not used to limit the embodiments of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0030] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of this application, the descriptions of "first", "second", etc. are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0031] Embodiment 1

[0032] A method for monitoring the radiation performance of a SAR satellite, as Figure 1 shown, the internal calibration data of the SAR satellite consists of multiple types of internal calibration signals, and the method includes:

[0033] S1. Based on a preset amplitude attenuation level, control the target SAR satellite to generate internal calibration signals level by level, and obtain the internal calibration signals;

[0034] Specifically, the multiple types of internal calibration signals include a reference calibration signal, a full-array emission calibration signal, a full-array reception calibration signal, and a full-array transceiver calibration signal, and each type of internal calibration signal contains multiple pulses.

[0035] There are multiple (for example, m) amplitude attenuation levels. Exemplarily, the signal amplitudes corresponding to each amplitude attenuation level are A 1 (dB), A 2 (dB)...A m (dB) in sequence. Starting from the first amplitude attenuation level, it attenuates a 1 (dB), a 2 (dB)...a m-1 (dB) in sequence, that is, A 2 = A 1 - a 1 , A 3 = A 2 - a 2 ...A m= A m-1 -a m-1 , where A 1 is the custom signal amplitude, and the above signal amplitude attenuation amount a 1 ~ a m-1 can be the same or different. As Figure 2 shown, taking the full-array emission calibration signal as an example, the full-array emission calibration signal generated by each amplitude attenuation level contains 16 pulses.

[0036] S2. Preprocess the internal calibration signal to obtain the actual amplitude of the internal calibration signal corresponding to each amplitude attenuation level;

[0037] Use the ideal linear frequency modulation signal to compress each pulse of the internal calibration signal one by one to obtain the amplitude after compression of all pulse signals; among them, the amplitude after compression of each pulse signal is represented in decibels; take the average value of the amplitudes after compression of all pulse signals as the actual amplitude of the internal calibration signal corresponding to the corresponding amplitude attenuation level.

[0038] Specifically, the expression of the ideal linear frequency modulation signal is: H(f) = exp(jπf 2 / K); where f represents the frequency in the range direction, K represents the chirp rate of the linear frequency modulation signal, and j represents the complex constant.

[0039] S3. Calculate the amplitude difference one between two adjacent amplitude attenuation levels (i.e., the above a 1 ~ a m-1 ) and the amplitude difference two between the actual amplitudes corresponding to two adjacent amplitude attenuation levels, and determine whether the difference between the amplitude difference one and the amplitude difference two is lower than the nonlinear threshold (when the difference between the amplitude difference one and the amplitude difference two reaches the nonlinear threshold, it is considered that the actual amplitudes corresponding to two adjacent amplitude attenuation levels change nonlinearly). If so, classify the corresponding amplitude attenuation level into the linear change region of the internal calibration signal attenuation (i.e., the target signal can change linearly in this region);

[0040] Taking the full-polarization strip mode Q11 wave position as an example, Figure 2 is the amplitude schematic diagram of each level of the full-array emission signal attenuation. The GF-3 satellite attenuates 3 dB per level (i.e., the amplitude difference one). The amplitude of the signal in the 1-3 attenuation levels drops less than 3 dB, which is the saturation region. The amplitude of the signal in the 4-15 levels drops less than or approximately equal to 3 dB, which is the linear region (linear change region). Starting from the 16th level, it gradually enters the noise region.

[0041] S4. Record the amplitude attenuation levels within the linear change region;

[0042] S5. Select an amplitude attenuation level within the linear change region to obtain the corresponding historical actual amplitude;

[0043] S6. Calculate the difference one between the current actual amplitude and the corresponding historical actual amplitude, and determine whether there is a situation where the difference one is greater than a preset threshold; if so, it is determined that the radiation performance of the target SAR satellite has changed;

[0044] That is, the linear change region usually includes multiple amplitude attenuation levels. To avoid missed detections, in this embodiment, as described in steps S4 to S6, the attenuation values of the internal calibration signals corresponding to each amplitude attenuation level in the linear change region can be monitored respectively to see if they are consistent with the theoretical attenuation values corresponding to the amplitude attenuation levels. Additionally, a certain amplitude attenuation level corresponding to the internal calibration signal in the linear change region can be selected for spot check. The average value of the amplitudes of multiple pulses of this internal calibration signal is taken as the actual amplitude of the internal calibration signal corresponding to this amplitude attenuation level. Then, it is only necessary to determine whether the difference between this actual amplitude and the corresponding nearest historical actual amplitude is greater than the preset threshold to determine the quality of the radiation performance of the target SAR satellite. Using this method can improve the detection efficiency of the radiation performance of the SA satellite.

[0045] Exemplarily, taking the Gaofen-3 satellite as an example, the amplitude change trend of the signal in the fourth attenuation level of the reference calibration in the full polarization strip 1 mode is shown in Figure 3 As shown, the threshold is 0.7 dB. From January 2017 to September 2024, the reference calibration amplitude change range is less than 0.5 dB, indicating that there is no change in the reference calibration amplitude.

[0046] Compare the amplitude of the reference calibration signal of this level with the previous value of the same level. If it is less than the threshold, it indicates that there is no change in the reference calibration signal (temporarily determine that the radiation performance of the target SAR satellite has not changed, and it is still necessary to combine the detection results of other internal calibration signals for judgment), otherwise it indicates that there is a change in the reference calibration signal (then it is determined that the radiation performance of the target SAR satellite has changed).

[0047] S7. Otherwise, repeat steps S1 to S6 to traverse and detect all types of internal calibration signals. If the situation where the difference one is greater than the corresponding preset threshold does not occur, it is determined that the radiation performance of the target SAR satellite has not changed.

[0048] Exemplarily, in addition to the above reference calibration signal, the internal calibration signals also include the full array emission calibration signal, the full array reception calibration signal, and the full array transceiver calibration signal.

[0049] Taking the Gaofen-3 satellite as an example, the amplitude change trend of the signal in the corresponding attenuation level of the full array calibration in the full polarization strip 1 mode is shown in Figure 4 、 Figure 5 and Figure 6As shown, the threshold is 0.7 dB. From January 2017 to September 2024, the amplitude change range of the full-array emission calibration signal is less than 0.5 dB, indicating that there is no change in the full-array emission calibration amplitude. The amplitude change range of the full-array reception calibration signal is less than 0.2 dB, indicating that there is no change in the full-array reception calibration amplitude. The amplitude change range of the full-array transceiver calibration signal is less than 0.2 dB, indicating that there is no change in the full-array transceiver calibration amplitude.

[0050] That is, for the detection of all the above internal calibration signals, the situation where the difference one is greater than the corresponding preset threshold (different internal calibration signals correspond to different thresholds) does not occur. Therefore, it is determined that the radiation performance of the GF-3 satellite in the example has not changed.

[0051] Embodiment 2

[0052] To ensure the accuracy of the detection results of the radiation performance of the target SAR satellite in Embodiment 1, this embodiment also proposes a verification method, which specifically includes:

[0053] A1. Obtain SAR image data of a specific target;

[0054] A2. Verify whether the radiation performance of the target SAR satellite has changed according to the SAR image data, and judge whether the detection results of the radiation performance of the target SAR satellite in steps S1 to S7 are consistent based on the verification results.

[0055] Specifically, the specific target is a stable distributed target (such as the Amazon rainforest, etc.) or a stable point target (such as a corner reflector arranged in the field, etc.).

[0056] Verifying whether the radiation performance of the target SAR satellite has changed according to the SAR image data includes: calculating the current absolute calibration constant of the target SAR satellite using the SAR image data; obtaining the most recent historical absolute calibration constant of the target SAR satellite, and calculating the difference two between the current absolute calibration constant and the most recent historical absolute calibration constant; if the difference two is greater than the fluctuation threshold of the absolute calibration constant, the radiation performance of the target SAR satellite has changed; otherwise, the radiation performance of the target SAR satellite has not changed.

[0057] The method further includes: if the detection results are inconsistent, repeat steps S1 to S7 or change the specific target and repeat steps A1 to A2 until the verification results are consistent with the detection results or the number of repetitions reaches a predetermined number; if the number of repetitions reaches the predetermined number and the detection results are still inconsistent, it is determined that the SAR radiation performance has changed.

[0058] Exemplarily, in this example, an outfield point target is selected for verification. The point target is found from the standard single-look complex image according to the geometric position, a specified window is selected, and N-fold interpolation is performed. The energy P of the point target is accurately extracted and known. The energies of n point targets in the region are sequentially extracted. According to the radar cross section of the point target, the absolute calibration constant of this mode and wave position is calculated. The obtained absolute calibration constant is compared with the previous value (the nearest historical absolute calibration constant). If the change in the absolute calibration constant of the target wave position is less than the fluctuation threshold and the change in the amplitude of the internal calibration signal is less than the preset threshold, it indicates that the results of the two are consistent and the SAR radiation performance has not changed. If the change in the absolute calibration constant of the target wave position is greater than the fluctuation threshold and the change in the amplitude of the internal calibration signal is greater than the preset threshold, it indicates that the SAR radiation performance has changed. If the SAR image data verification result is inconsistent with the internal calibration result, multiple observations are made again.

[0059] The verification of the full polarization strip mode 1 is shown in Table 1. The set threshold is 1 dB. The change range of the absolute calibration constant of the Q7 wave position is 0.89 dB, the change range of the absolute calibration constant of the Q20 wave position is 0.19 dB, and the change range of the wave position of the Q25 absolute calibration constant is 0.39 dB, all of which are less than the threshold and are consistent with the internal calibration verification result, indicating that the SAR radiation performance has not changed.

[0060] Table 1 Calibration Constant Changes of the Full Polarization Strip Mode of the GF-3 Satellite (2017 - 2020)

[0061]

[0062]

[0063] Example 3

[0064] As Figure 7 shown, this example provides a SAR satellite radiation performance monitoring system. The internal calibration data of the SAR satellite consists of multiple types of internal calibration signals. This system is suitable for long-term observation of the satellite radiation performance and can be automated at the same time, which helps to improve the stability of the SAR image. The system includes:

[0065] A data acquisition module 1 for acquiring internal calibration signals; the acquisition method includes: controlling the target SAR satellite to generate internal calibration signals gear by gear based on the preset amplitude attenuation gears;

[0066] A data processing module 2 for preprocessing the internal calibration signals to obtain the actual amplitudes of the internal calibration signals corresponding to each amplitude attenuation gear; and for recording the amplitude attenuation gears within the linear change region; and also for selecting an amplitude attenuation gear within the linear change region to obtain the corresponding historical actual amplitude;

[0067] The data analysis module 3 is used to calculate the amplitude difference one between two adjacent amplitude attenuation levels and the amplitude difference two between the actual amplitudes corresponding to two adjacent amplitude attenuation levels, and determine whether the difference between the amplitude difference one and the amplitude difference two is lower than the non-linear threshold. If so, the corresponding amplitude attenuation level is classified into the linear change region of the internal calibration signal attenuation. It is also used to calculate the difference one between the current actual amplitude and the corresponding historical actual amplitude, and determine whether there is a situation where the difference one is greater than the preset threshold. If so, it is determined that the radiation performance of the target SAR satellite has changed. Otherwise, all types of internal calibration signals are traversed and detected. If the difference one greater than the corresponding preset threshold does not appear in all cases, it is determined that the radiation performance of the target SAR satellite has not changed.

[0068] Further, the system further includes: an absolute calibration constant update module 4, which is used to update the absolute calibration constant of the target SAR satellite. The update steps of the absolute calibration constant are as follows: calculate the current absolute calibration constant of the target SAR satellite by using the SAR image data; obtain the most recent historical absolute calibration constant of the target SAR satellite, and calculate the difference two between the current absolute calibration constant and the most recent historical absolute calibration constant. If the difference two is not less than the fluctuation threshold of the absolute calibration constant, update the absolute calibration constant of the target SAR satellite to the current absolute calibration constant. Otherwise, use the average value of the absolute calibration constants obtained in the previous N times as the absolute calibration constant of the target SAR satellite, where N≥1.

[0069] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0070] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0071] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction means that implements the function specified in one or more of the processes Figure 1 and / or boxes Figure 1 specified in one or more of the processes and / or boxes

[0072] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the function specified in one or more of the processes Figure 1 and / or boxes Figure 1 specified in one or more of the processes and / or boxes

[0073] In a typical configuration, a computing device includes one or more processors (CPUs), an input / output interface, a network interface, and memory.

[0074] The memory may include non-permanent memory in the form of computer-readable media, random access memory (RAM) and / or non-volatile memory such as read only memory (ROM) or flash memory (flash RAM). Memory is an example of computer-readable media.

[0075] Computer-readable media includes both permanent and non-permanent, removable and non-removable media implemented by any method or technology for storing information. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read only memory (ROM), electrically erasable programmable read only memory (EEPROM), flash memory or other memory technologies, compact disc read only memory (CD-ROM), digital versatile discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transitory media such as modulated data signals and carrier waves.

[0076] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or apparatus comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or apparatus. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising the element.

[0077] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A method for monitoring the radiation performance of a SAR satellite, wherein the internal calibration data of the SAR satellite is composed of multiple types of internal calibration signals, characterized in that: The method comprises: S1. Based on a preset amplitude attenuation gear, the target SAR satellite is controlled to generate an internal calibration signal gear by gear, and the internal calibration signal is obtained; S2, preprocessing the internal calibration signal to obtain the actual amplitude of the internal calibration signal corresponding to each amplitude attenuation gear; S3, calculating the amplitude difference 1 between two adjacent amplitude attenuation gears and the amplitude difference 2 between the actual amplitudes corresponding to the two adjacent amplitude attenuation gears, and determining whether the difference between the amplitude difference 1 and the amplitude difference 2 is lower than the nonlinear threshold value, and if so, classifying the corresponding amplitude attenuation gear into the linear change region of the internal calibration signal attenuation; S4, recording the amplitude attenuation level within the linear change region; S5, select an amplitude attenuation gear in the linear change area to obtain the corresponding historical actual amplitude; S6, calculating a difference value one between the current actual amplitude and the corresponding historical actual amplitude, and determining whether the difference value one is greater than a preset threshold; if so, determining that the radiation performance of the target SAR satellite has changed; S7. Otherwise, repeat steps S1 to S6 to traverse and detect all types of internal calibration signals. If the difference is not greater than the corresponding preset threshold, it is determined that the radiation performance of the target SAR satellite has not changed.

2. The SAR satellite radiation performance monitoring method according to claim 1, characterized in that: The multiple types of internal calibration signals include reference calibration signals, full array transmission calibration signals, full array reception calibration signals and full array transceiver calibration signals, and each type of internal calibration signal includes multiple pulses.

3. The SAR satellite radiation performance monitoring method according to claim 2, characterized in that: The preprocessing of the generated internal calibration signal to obtain the actual amplitude of the internal calibration signal corresponding to each amplitude attenuation gear includes: Using an ideal linear frequency modulation signal to compress each pulse of the internal calibration signal one by one, and obtaining the amplitude of all pulse signals after compression; wherein the amplitude of each pulse signal after compression is expressed in decibel form; The average value of the amplitudes of all pulse signals after compression is taken as the actual amplitude of the internal calibration signal of the corresponding amplitude attenuation level.

4. The SAR satellite radiation performance monitoring method according to claim 3, characterized in that: The expression of the ideal linear frequency modulation signal is: H(f)=exp(jπf 2 / K) Wherein, f represents the frequency in the range direction, K represents the modulation frequency of the linear frequency modulation signal, and j represents a complex constant.

5. The SAR satellite radiation performance monitoring method according to claim 1, characterized in that: The method further comprises: A1. Acquire SAR image data of a specific target; A2. Verify whether the radiation performance of the target SAR satellite has changed according to the SAR image data, and determine whether the detection results of the radiation performance of the target SAR satellite in steps S1 to S7 are consistent based on the verification result.

6. The SAR satellite radiation performance monitoring method according to claim 5, characterized in that: The specific target is a stable distributed target or a stable point target.

7. The SAR satellite radiation performance monitoring method according to claim 5, characterized in that: Verifying whether the radiation performance of the target SAR satellite has changed according to the SAR image data includes: Calculating a current absolute calibration constant of a target SAR satellite using the SAR image data; Obtaining the most recent historical absolute calibration constant of the target SAR satellite, and calculating the difference between the current absolute calibration constant and the most recent historical absolute calibration constant; If the second difference is greater than the fluctuation threshold of the absolute calibration constant, the radiation performance of the target SAR satellite has changed; otherwise, the radiation performance of the target SAR satellite has not changed.

8. The SAR satellite radiation performance monitoring method according to claim 5, characterized in that: The method further comprises: If the detection results are inconsistent, repeat steps S1 to S7 or change the specific target to repeat steps A1 to A2 until the verification result is consistent with the detection result or the number of repetitions reaches a predetermined number of times; if the number of repetitions reaches the predetermined number of times and the detection results are still inconsistent, it is determined that the SAR radiation performance has changed.

9. A SAR satellite radiation performance monitoring system, wherein the internal calibration data of the SAR satellite is composed of multiple types of internal calibration signals, characterized in that: The system comprises: The data acquisition module is used to acquire the internal calibration signal; the acquisition method includes: controlling the target SAR satellite to generate the internal calibration signal step by step based on the preset amplitude attenuation gear; A data processing module, used for preprocessing the internal calibration signal to obtain the actual amplitude of the internal calibration signal corresponding to each amplitude attenuation gear; and for recording the amplitude attenuation gear located within the linear change region; and for selecting an amplitude attenuation gear within the linear change region to obtain the corresponding historical actual amplitude; The data analysis module is used to calculate the amplitude difference one between two adjacent amplitude attenuation gears and the amplitude difference two of the actual amplitudes corresponding to the two adjacent amplitude attenuation gears, and judge whether the difference between the amplitude difference one and the amplitude difference two is lower than the nonlinear threshold. If so, the corresponding amplitude attenuation gear is classified into the linear change area of ​​the internal calibration signal attenuation; it is also used to calculate the difference one between the current actual amplitude and the corresponding historical actual amplitude, and judge whether there is a situation where the difference one is greater than a preset threshold; if so, it is judged that the radiation performance of the target SAR satellite has changed; otherwise, all types of internal calibration signals are traversed and detected. If there is no situation where the difference one is greater than the corresponding preset threshold, it is judged that the radiation performance of the target SAR satellite has not changed.

10. The SAR satellite radiation performance monitoring system according to claim 9, characterized in that: The system further comprises: The absolute calibration constant updating module is used to update the absolute calibration constant of the target SAR satellite; the updating steps of the absolute calibration constant are as follows: Calculating a current absolute calibration constant of a target SAR satellite using the SAR image data; Obtaining the most recent historical absolute calibration constant of the target SAR satellite, and calculating the difference between the current absolute calibration constant and the most recent historical absolute calibration constant; If the second difference is not less than the fluctuation threshold of the absolute calibration constant, the absolute calibration constant of the target SAR satellite is updated to the current absolute calibration constant; otherwise, the average value of the absolute calibration constants obtained N times in history is used as the absolute calibration constant of the target SAR satellite; Among them, N≥1.

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