Method and system for eliminating ground clutters of on-orbit satellite-borne rain-measuring radar in consideration of signal adhesion

Abstract

The invention provides an in-orbit spaceborne rain radar ground clutter elimination method and system considering signal adhesion, and the method comprises the steps: calculating the distance between a satellite and a ground sampling point, and determining the number of a surface layer distance angle library; preprocessing the original radar receiving power signal; smoothing the preprocessed original radar receiving power signal, and calculating the power change rate in the distance direction; searching one by one to-ground sampling points of one by one scanning period from the position of the surface layer from bottom to top, and determining the corresponding position of the maximum power change rate in the distance direction; searching from bottom to top from the corresponding position of the maximum power change rate in the distance direction, and determining the change inflection point and the corresponding position with the change rate being zero; and determining the highest range of the influence of the ground clutters, and completing the elimination of the ground clutters. According to the invention, in a scene in which ground clutter signals and rainfall signals are adhered near the earth surface, the accuracy of detecting target characteristics by the rain detection radar is greatly improved, and the data processing flow of the on-satellite rain detection radar is perfected.

Description

Technical Field

[0001] This invention relates to the field of on-orbit processing of satellite-borne rain measurement radar detection signals, and more specifically, to an on-orbit satellite-borne rain measurement radar ground clutter removal method and system that takes into account signal adhesion. Background Technology

[0002] The echoes received by spaceborne precipitation radar contain clutter, weather signals, and noise signals. Clutter and noise signals, i.e., non-precipitation echoes, are considered invalid radar echo signals; weather signals, i.e., precipitation echoes, are considered valid radar echo signals and can be used to retrieve characteristic parameters of precipitation systems. The detection mode of spaceborne precipitation radar results in severe ground clutter distribution. This clutter is intense and has a wide impact range, significantly interfering with precipitation echo distribution and leading to a decrease in the accuracy of precipitation forecasts. Therefore, effectively removing ground clutter signals is crucial for accurately processing precipitation echo signals and comprehensively improving the ability of meteorological radar to detect cloud precipitation.

[0003] Currently, ground clutter removal mainly employs methods such as thresholding, comparison with ground-based radar detection results, and overall removal after determining the ground clutter distribution boundary. These methods require extensive auxiliary data and are labor-intensive. Furthermore, if ground clutter and effective echoes are intertwined near the surface, these methods can lead to excessive removal of effective echoes and loss of precipitation characteristics near the surface.

[0004] Considering that on-board data processing must be performed under limited computing resources while ensuring the accuracy of ground clutter removal, this paper proposes a ground clutter removal method and system for on-orbit satellite-borne rainfall radar that considers signal adhesion, based on the distribution characteristics of the original echoes received by the rainfall radar in three-dimensional space. This method simplifies the processing flow while ensuring the effectiveness of ground clutter removal, significantly improving the accuracy of target feature detection by the rainfall radar and shortening the remote sensing data processing link. Therefore, it is necessary to propose such a method and system to improve the on-board rainfall radar data processing workflow by considering signal adhesion.

[0005] Patent CN106405513A discloses a ground clutter suppression method for airborne weather radar based on multi-layer scanning comparison, mainly addressing the problems existing in current ground clutter suppression technologies. This patent utilizes the characteristic that ground clutter positions shift with angle changes while weather echo positions remain relatively constant, employing data comparison and confidence level accumulation to identify clutter. However, in practical engineering applications, it has shortcomings in scenarios requiring high real-time performance, especially in dealing with signal congestion.

[0006] In summary, given the problems of the existing technologies, researching a ground clutter removal method and system for on-orbit satellite-borne rain measurement radar that takes into account signal adhesion has become a critical task that urgently needs to be addressed. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for eliminating ground clutter from on-orbit satellite-borne rain measurement radar that takes into account signal adhesion.

[0008] A method for eliminating ground clutter from an on-orbit satellite-borne rainfall radar, considering signal adhesion, according to the present invention, includes the following steps: Step S1: Calculate the distance between the satellite and the ground sampling point to determine the surface distance angle library number; Step S2: Preprocess the original radar received power signal according to the surface layer distance angle database number; Step S3: Smooth the preprocessed original radar received power signal and calculate the power change rate in the range direction; Step S4: Based on the distance corner number of the surface layer and the power change rate in the distance direction, for each sampling point of the ground in each scanning cycle, search from bottom to top from the surface layer position to determine the corresponding position of the maximum power change rate in the distance direction. Step S5: Search from bottom to top from the position corresponding to the maximum power change rate in the distance direction to determine the inflection point of change and the position corresponding to the zero change rate; Step S6: Based on the corresponding positions of the inflection point and the rate of change being zero, determine the maximum range of ground clutter influence and complete the removal of ground clutter.

[0009] Preferably, the step of calculating the distance between the satellite and the ground sampling point and determining the surface distance angle database number includes: calculating the distance between the satellite and the ground sampling point for each ground sampling point in each scanning cycle; and performing layered numbering in the distance direction according to the original sampling interval, wherein the surface distance angle database number is the number corresponding to the number of the first layer of the ground.

[0010] Preferably, the step of preprocessing the original radar received power signal according to the surface range angle database number includes: extracting the received power signal in the range direction from each ground sampling point in each scanning cycle; and marking all data points with range angle database numbers less than or equal to the surface range angle database number as invalid signals and removing them to obtain the preprocessed original radar received power signal.

[0011] Preferably, the smoothing process of the preprocessed original radar received power signal and the calculation of the power change rate in the range direction include: based on the preprocessed radar received power, smoothing the radar received power signal of each ground sampling point in each scan cycle using the MATLAB built-in function LOESS, with the calculation formula as follows:

[0012] in, Represents a smoothing function. This indicates the range angle library corresponding to the original radar received power signal. No. The scan cycle, the first The raw radar received power signal in the distance direction of each ground detection point. Indicates the first The scan cycle, the first Smoothed radar received power signal in the distance direction of each ground detection point; The rate of change of power in the distance direction is obtained as follows:

[0013] in, Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The rate of change of power at each distance angle, Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The smoothed radar received power signal of each range angle. Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The smoothed radar received power signal of each range angle. Indicates the distance direction of the first The distance between the corner of the library and the ground. Indicates the distance direction of the first The distance between the corner of the library and the ground.

[0014] Preferably, the step of determining the maximum range of ground clutter influence based on the corresponding positions of the inflection point and the rate of change being zero, and completing the ground clutter removal, includes: comparing the sizes of two range angle library numbers based on the corresponding positions of the inflection point and the rate of change being zero, and taking the larger value as the maximum range of ground clutter influence; for each ground sampling point in each scanning cycle, mapping the smoothed original radar received power signal distribution to the radar effective detection echo signal distribution to complete the ground clutter removal, the mapping relationship being:

[0015] in, Represents a mapping function. This represents the maximum value of the original radar received power signal distribution range in the range direction. This indicates the maximum effective detection range of the radar in the range direction. Indicates the first The scan cycle, the first The smoothed radar received power signal in the distance direction of each ground detection point Indicates the first The scan cycle, the first Radar echo signals within the effective detection range of each ground detection point in the distance direction.

[0016] This invention also provides an on-orbit spaceborne weathering radar ground clutter removal system considering signal adhesion. This system can be implemented by executing the steps of the on-orbit spaceborne weathering radar ground clutter removal method considering signal adhesion. That is, those skilled in the art can understand the on-orbit spaceborne weathering radar ground clutter removal method considering signal adhesion as a preferred embodiment of the on-orbit spaceborne weathering radar ground clutter removal system considering signal adhesion. The system includes: Module M1 calculates the distance between the satellite and the ground sampling point to determine the Earth's surface distance angle library number; Module M2 preprocesses the original radar received power signal according to the surface layer distance angle database number; Module M3 smooths the pre-processed raw radar received power signal and calculates the power change rate in the range direction. Module M4, based on the distance corner library number of the ground layer and the power change rate in the distance direction, searches from bottom to top of the ground layer position for each sampling point in each scanning cycle to determine the corresponding position of the maximum power change rate in the distance direction; Module M5 searches from bottom to top from the position corresponding to the maximum power change rate in the distance direction to determine the inflection point of change and the position corresponding to the zero change rate; Module M6 determines the maximum range of ground clutter influence based on the corresponding position of the inflection point and the rate of change being zero, and completes the removal of ground clutter.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention deeply analyzes the distribution characteristics of raw echoes received by rain-measuring radar in three-dimensional space. By summarizing the location and signal characteristics of effective echoes and ground clutter, and based on the raw echo distribution of each wave position, it ensures effective removal of ground clutter and simplifies the processing flow. Existing technologies such as thresholding, comparison with ground-based radar detection results, and overall removal after determining the distribution boundary of ground clutter require high levels of auxiliary data and are labor-intensive. Furthermore, if ground clutter and effective echoes are intertwined near the ground surface, these methods can lead to excessive removal of effective echoes and loss of precipitation characteristics near the ground surface. This invention fills the gap in existing technologies, especially in scenarios where ground clutter signals and precipitation signals are intertwined near the ground surface. This invention significantly improves the accuracy of rain-measuring radar in detecting target characteristics, shortens the remote sensing data processing link, and improves the data processing flow of onboard rain-measuring radar. Attached Figure Description

[0018] 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 The flowchart illustrates a method for eliminating ground clutter from an on-orbit satellite-borne rain measurement radar that takes into account signal adhesion, as provided in an embodiment of the present invention. Detailed Implementation

[0019] 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 scope of protection of the present invention.

[0020] Figure 1 A flowchart of an on-orbit satellite-borne rain measurement radar ground clutter removal method considering signal adhesion, provided as an embodiment of the present invention, is shown below. Figure 1 As shown, it includes: Step 1: Calculate the distance between the satellite and the ground sampling point to determine the distance angle library number of the ground surface layer.

[0021] Specifically, the distance between the satellite and the ground sampling point refers to the slant range between the satellite and the ground sampling point, calculated using a spatial geometric model based on the satellite's instantaneous orbital parameters, attitude data, and radar beam pointing angle for each scanning cycle and each ground sampling point. The radar uses a layered numbering system with an original sampling interval of 50m in the range direction, and divides the calculated slant range value by the radar system's range resolution, rounding the result. The ground surface layer range angle is numbered according to the corresponding layer number.

[0022] Step 2: Preprocess the raw radar received power signal according to the surface distance angle database number.

[0023] Specifically, using the surface range angle database number, for each scanning cycle and each ground sampling point, the received power signal distribution in the range direction is analyzed. Signals below the surface are considered invalid and are removed. That is, according to the surface range angle database number determined in step 1, all numbers less than or equal to the surface range angle database number are determined to be invalid, thus completing the preprocessing of the original radar received power signal.

[0024] Step 3: Smooth the original radar received power and calculate the power change rate in the range direction.

[0025] Specifically, using the pre-processed radar received power, the radar received power signal for each scan cycle and each ground sampling point is smoothed using the MATLAB built-in function LOESS to obtain the power change rate in the range direction. The calculation formula is as follows:

[0026] In the formula, Represents a smoothing function. This indicates the range angle library corresponding to the original radar received power signal. No. The scan cycle, the first The raw radar received power signal in the distance direction of each ground detection point. Indicates the first The scan cycle, the first Smoothed radar received power signal in the distance direction of each ground detection point.

[0027]

[0028] In the formula, Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The rate of change of power at each distance angle, Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The smoothed radar received power signal of each range angle. Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The smoothed radar received power signal of each range angle. Indicates the distance direction of the first The distance between the corner of the library and the ground. Indicates the distance direction of the first The distance between the corner of the library and the ground.

[0029] Step 4: Search from bottom to top to the position corresponding to the maximum power change rate.

[0030] Specifically, using the surface distance angle database number and the power change rate in the distance direction, for each scanning cycle and each sampling point on the ground, the distance angle database number corresponding to the maximum power change rate in the distance direction is searched from bottom to top starting from the surface; this is the corresponding location. This step identifies the boundary where the echo intensity transitions most dramatically from the surface-dominant region to the atmospheric-dominant region.

[0031] Step 5: Search upwards from the position of the maximum power change rate to find the inflection point and the position where the change rate is zero.

[0032] Specifically, using the location corresponding to the maximum power change rate, for each scan cycle and each ground sampling point, the search proceeds upwards from this corresponding location to determine the inflection point of change and the two corresponding range angle library numbers where the change rate is zero, i.e., the corresponding locations. This step determines the upper bound of the transition interval for the potential impact of ground clutter.

[0033] Step 6: Determine the maximum range of ground clutter influence, and then complete the removal of ground clutter.

[0034] Specifically, based on the inflection point of change and the position where the rate of change is zero, the sizes of two range angle database numbers are compared, and the larger value is taken as the maximum range of ground clutter influence. For each scan cycle and each ground sampling point, the original radar received power signal distribution is mapped to the radar effective detection echo signal distribution, thereby completing the ground clutter removal. The mapping relationship is shown in the following formula:

[0035] In the formula Represents a mapping function. This represents the maximum value of the original radar received power signal distribution range in the range direction. This indicates the maximum effective detection range of the radar in the range direction. Indicates the first The scan cycle, the first Smoothed radar received power signal in the distance direction of each ground detection point Indicates the first The scan cycle, the first Radar echo signals within the effective detection range of each ground detection point in the distance direction.

[0036] This invention also provides an on-orbit spaceborne weathering radar ground clutter removal system considering signal adhesion. This system can be implemented by executing the steps of the on-orbit spaceborne weathering radar ground clutter removal method considering signal adhesion. That is, those skilled in the art can understand the on-orbit spaceborne weathering radar ground clutter removal method considering signal adhesion as a preferred embodiment of the on-orbit spaceborne weathering radar ground clutter removal system considering signal adhesion. The system includes: Module M1 calculates the distance between the satellite and the ground sampling point to determine the Earth's surface distance angle library number; Module M2 preprocesses the raw radar received power signal based on the surface distance angle database number. Module M3 smooths the pre-processed raw radar received power signal and calculates the power change rate in the range direction. Module M4, based on the distance from the surface layer to the corner library number and the power change rate in the distance direction, searches from bottom to top at each ground sampling point in each scanning cycle to determine the corresponding location of the maximum power change rate in the distance direction. Module M5 searches from bottom to top, starting from the position corresponding to the maximum power change rate in the distance direction, to determine the inflection point of change and the position corresponding to the zero change rate. Module M6 determines the maximum range of ground clutter influence based on the corresponding positions of the inflection point and the rate of change being zero, thus completing the removal of ground clutter.

[0037] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0038] 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 spaceborne weather radar ground clutter rejection method on orbit considering signal sticking, characterized in that, include: Step S1: Calculate the distance between the satellite and the ground sampling point to determine the surface distance angle library number; Step S2: Preprocess the original radar received power signal according to the surface layer distance angle database number; Step S3: Smooth the preprocessed original radar received power signal and calculate the power change rate in the range direction; Step S4: Based on the distance corner number of the surface layer and the power change rate in the distance direction, for each sampling point of the ground in each scanning cycle, search from bottom to top of the surface layer position to determine the corresponding position of the maximum power change rate in the distance direction. Step S5: Search from bottom to top from the position corresponding to the maximum power change rate in the distance direction to determine the inflection point of change and the position corresponding to the zero change rate; Step S6: Based on the corresponding positions of the inflection point and the rate of change being zero, determine the maximum range of ground clutter influence and complete the removal of ground clutter.

2. The method according to claim 1, wherein, The calculation of the distance between the satellite and the Earth sampling point, and the determination of the surface distance angle database number, includes: For each ground sampling point in each scanning cycle, calculate the distance between the satellite and the ground sampling point; The distance direction is used to perform layer numbering based on the original sampling interval, and the surface distance angle database number is the number corresponding to the first layer of the surface.

3. A method for ground clutter rejection of space-borne weather radar on orbit considering signal sticking according to claim 1, characterized in that, The preprocessing of the original radar received power signal based on the surface distance angle database number includes: The received power signal in the distance direction is extracted from each ground sampling point in each scanning cycle; Based on the surface distance angle database number, all data points with a distance angle database number less than or equal to the surface distance angle database number are marked as invalid signals and discarded to obtain the preprocessed original radar received power signal.

4. The method of claim 1, wherein the method is characterized by, The smoothing process of the preprocessed raw radar received power signal and the calculation of the power change rate in the range direction include: Based on the preprocessed radar received power, the radar received power signal of each ground sampling point in each scanning cycle is smoothed using the MATLAB built-in function LOESS. The calculation formula is as follows: wherein, denotes a smoothing function, denotes a range-angle bin corresponding index of the original radar received power signal, the original radar received power signal in the range direction of the thscanning period, the thground-probing point, denotes the smoothed radar received power signal in the range direction of the thscanning period, the thground-probing point; The rate of change of power in the distance direction is obtained as follows: in, Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The rate of change of power at each distance angle, Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The smoothed radar received power signal of each range angle. Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The smoothed radar received power signal of each range angle. Indicates the distance direction of the first The distance between the corner of the library and the ground. Indicates the distance direction of the first The distance between the corner of the library and the ground.

5. A method for eliminating ground clutter from an on-orbit satellite-borne rain-measuring radar considering signal adhesion, as described in claim 1, is characterized in that... The step of determining the maximum range of ground clutter influence based on the corresponding positions of the inflection point and the rate of change being zero, and completing the removal of ground clutter, includes: Based on the corresponding positions of the inflection point and the rate of change being zero, compare the sizes of the two distance angle library numbers and take the larger value as the maximum range of ground clutter influence; For each ground sampling point in each scanning cycle, the smoothed original radar received power signal distribution is mapped to the radar effective detection echo signal distribution to complete ground clutter removal. The mapping relationship is as follows: in, Represents a mapping function. This represents the maximum value of the original radar received power signal distribution range in the range direction. This indicates the maximum effective detection range of the radar in the range direction. Indicates the first The scan cycle, the first The smoothed radar received power signal in the distance direction of each ground detection point Indicates the first The scan cycle, the first Radar echo signals within the effective detection range of each ground detection point in the distance direction.

6. An on-orbit satellite-borne rain measurement radar ground clutter removal system considering signal adhesion, characterized in that, include: Module M1 calculates the distance between the satellite and the ground sampling point to determine the Earth's surface distance angle library number; Module M2 preprocesses the original radar received power signal according to the surface layer distance angle database number; Module M3 smooths the pre-processed raw radar received power signal and calculates the power change rate in the range direction. Module M4, based on the distance corner number of the ground layer and the power change rate in the distance direction, searches from bottom to top at each ground sampling point in each scanning cycle to determine the corresponding position of the maximum power change rate in the distance direction; Module M5 searches from bottom to top from the position corresponding to the maximum power change rate in the distance direction to determine the inflection point of change and the position corresponding to the zero change rate; Module M6 determines the maximum range of ground clutter influence based on the corresponding position of the inflection point and the rate of change being zero, and completes the removal of ground clutter.

7. A ground clutter removal system for an on-orbit satellite-borne rain-measuring radar considering signal adhesion, as described in claim 6, is characterized in that... The calculation of the distance between the satellite and the Earth sampling point, and the determination of the surface distance angle database number, includes: For each ground sampling point in each scanning cycle, calculate the distance between the satellite and the ground sampling point; The distance direction is used to perform layer numbering based on the original sampling interval, and the surface distance angle database number is the number corresponding to the first layer of the surface.

8. A ground clutter removal system for an on-orbit satellite-borne rain-measuring radar considering signal adhesion, as described in claim 6, is characterized in that... The preprocessing of the original radar received power signal based on the surface distance angle database number includes: The received power signal in the distance direction is extracted from each ground sampling point in each scanning cycle; Based on the surface distance angle database number, all data points with a distance angle database number less than or equal to the surface distance angle database number are marked as invalid signals and discarded to obtain the preprocessed original radar received power signal.

9. A ground clutter removal system for an on-orbit satellite-borne rain-measuring radar considering signal adhesion, as described in claim 6, is characterized in that... The smoothing process of the preprocessed raw radar received power signal and the calculation of the power change rate in the range direction include: Based on the preprocessed radar received power, the radar received power signal of each ground sampling point in each scanning cycle is smoothed using the MATLAB built-in function LOESS. The calculation formula is as follows: in, Represents a smoothing function. This indicates the range angle library corresponding to the original radar received power signal. No. The scan cycle, the first The raw radar received power signal in the distance direction of each ground detection point. Indicates the first The scan cycle, the first Smoothed radar received power signal in the distance direction of each ground detection point; The rate of change of power in the distance direction is obtained as follows: in, Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The rate of change of power at each distance angle, Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The smoothed radar received power signal of each range angle. Indicates the first The scan cycle, the first The first Earth detection point, in the distance direction. The smoothed radar received power signal of each range angle. Indicates the distance direction of the first The distance between the corner of the library and the ground. Indicates the distance direction of the first The distance between the corner of the library and the ground.

10. A ground clutter removal system for an on-orbit satellite-borne rain-measuring radar considering signal adhesion, as described in claim 6, is characterized in that... The step of determining the maximum range of ground clutter influence based on the corresponding positions of the inflection point and the rate of change being zero, and completing the removal of ground clutter, includes: Based on the corresponding positions of the inflection point and the rate of change being zero, compare the sizes of the two distance angle library numbers and take the larger value as the maximum range of ground clutter influence; For each ground sampling point in each scanning cycle, the smoothed original radar received power signal distribution is mapped to the radar effective detection echo signal distribution to complete ground clutter removal. The mapping relationship is as follows: in, Represents a mapping function. This represents the maximum value of the original radar received power signal distribution range in the range direction. This indicates the maximum effective detection range of the radar in the range direction. Indicates the first The scan cycle, the first The smoothed radar received power signal in the distance direction of each ground detection point Indicates the first The scan cycle, the first Radar echo signals within the effective detection range of each ground detection point in the distance direction.

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