CN116520323A - Earth Observation Method and Device of Moon-based Synthetic Aperture Radar - Google Patents

Abstract

The invention provides a ground observation method and device of a lunar-based synthetic aperture radar, and belongs to the technical field of radars. Wherein the method comprises the following steps: acquiring time domain echo data of a moon-based synthetic aperture radar for observing an imaging area on the earth; and carrying out coherent superposition on the time domain echo data after distance compression based on each sub-aperture of the synthetic aperture of the lunar-based synthetic aperture radar and each sub-imaging area of the imaging area, and obtaining an observation result of the imaging area. According to the earth observation method and device for the lunar-based synthetic aperture radar, provided by the invention, the time domain echo data after distance compression is subjected to imaging analysis for each sub-aperture and each sub-imaging area respectively, and then coherent superposition is carried out to obtain an observation result, so that the defects of large time expenditure and the like of a traditional time domain solving algorithm can be overcome on the basis of avoiding complicated calculation steps of a frequency domain solving mode, the calculation expenditure and time can be reduced, and the earth observation efficiency of the lunar-based SAR can be improved.

Description

Earth Observation Method and Device of Moon-based Synthetic Aperture Radar

technical field

The invention relates to the field of radar technology, in particular to an earth observation method and device for a moon-based synthetic aperture radar.

Background technique

Moon-based Synthetic Aperture Radar (Moon-based SAR, MB-SAR) is a synthetic aperture radar deployed on the near side of the moon. Moon-based SAR can observe Earth Ground Object (EGO).

Fig. 1 is a schematic diagram of a moon-based SAR earth observation scene in the prior art. As shown in Figure 1, the existing SAR for earth observation usually adopts the Back Projection (BP) algorithm to project each pixel in the imaging area (Imaging area) to the echo domain, and then perform coherent superposition. Generally, imaging analysis is performed on echo data in the frequency domain, and imaging analysis is rarely performed in the time domain. Compared with the frequency domain solution method, the time domain solution method can simplify the calculation steps and cumbersomeness of the frequency domain solution method, but for the time domain solution method, the large time and space complexity will still affect the calculation overhead and time consumption.

The traditional BP algorithm is used for moon-based SAR earth observation. Compared with low-orbit platforms, the large width and long distance of MB-SAR will increase the time and space complexity of imaging, and coherent stacking will generate huge calculations. Overhead and a lot of time wasted.

To sum up, the existing moon-based SAR earth observation has the disadvantages of high computational cost, long time and low efficiency.

Contents of the invention

The invention provides an earth observation method and device of a moon-based synthetic aperture radar, which is used to solve the defect of low efficiency of moon-based SAR earth observation in the prior art, and realize improving the efficiency of moon-based SAR earth observation.

The invention provides a method for earth observation of a moon-based synthetic aperture radar, comprising:

Obtain time-domain echo data from lunar-based synthetic aperture radar observations of imaging regions on Earth;

Based on each sub-aperture of the synthetic aperture of the moon-based synthetic aperture radar and each sub-imaging area of the imaging area, coherently add the time-domain echo data after the distance compression to obtain the imaging area Observations.

According to the earth observation method of a lunar-based synthetic aperture radar provided by the present invention, each sub-aperture of the synthetic aperture based on the lunar-based synthetic aperture radar and each sub-imaging area of the imaging area are used for the The time-domain echo data are coherently stacked to obtain the observation results of the imaging area, including:

Based on the length of the synthetic aperture, the synthetic aperture is divided into a plurality of non-overlapping sub-apertures, and based on the length of the imaging area in the azimuth direction and the length in the distance direction, the imaging area is divided into a plurality of non-overlapping sub-imaging regions;

Based on each of the sub-apertures and each of the sub-imaging regions, perform imaging analysis on the distance-compressed time-domain echo data to obtain regional images;

performing coherent superposition on each of the regional images to obtain the observation result.

According to the earth observation method of a moon-based synthetic aperture radar provided by the present invention, the time-domain echo data after the distance compression are respectively based on each of the sub-apertures and each of the sub-imaging regions. Imaging analysis, to obtain images of the area, including:

For each sub-aperture and each sub-imaging area, perform the following processing:

Respectively determining target sampling points corresponding to each pixel in the sub-imaging area on the center line of the sub-imaging area;

Based on each of the target sampling points and the distance-compressed time-domain echo data, a back-projection algorithm is executed to acquire the region image.

According to a method for earth observation of a lunar-based synthetic aperture radar provided by the present invention, the determination of the target sampling point corresponding to each pixel in the sub-imaging area on the centerline of the sub-imaging area includes:

Based on the distance between the sub-aperture and each pixel point, project each pixel point onto the center line to determine a projection point;

Determining the sampling point closest to the projection point on the central line as the target sampling point.

According to an earth observation method of a lunar-based synthetic aperture radar provided by the present invention, the center line is a diagonal line of the sub-imaging area.

According to the earth observation method of a lunar-based synthetic aperture radar provided by the present invention, the synthetic aperture is divided into a plurality of non-overlapping sub-apertures based on the length of the synthetic aperture, including:

obtaining the arithmetic square root of the length of the synthetic aperture;

determining a first quantity based on the arithmetic square root of the length of the synthetic aperture;

The synthetic aperture is equally divided into a first number of the sub-apertures.

According to the earth observation method of a moon-based synthetic aperture radar provided by the present invention, the imaging area is divided into a plurality of non-overlapping ones based on the length of the imaging area in the azimuth direction and the length in the distance direction. The sub-imaging area, including:

obtaining the arithmetic square root of the upward length in the azimuth and the arithmetic square root of the upward length in the distance;

determining a second quantity based on the arithmetic square root of the upward length of the azimuth, and determining a third quantity based on the arithmetic square root of the upward length of the distance;

Dividing the imaging area into the second number of parts equally in azimuth, and dividing the imaging area into the third number of parts in distance, to obtain the sub-imaging areas.

The present invention also provides an earth observation device for a moon-based synthetic aperture radar, comprising:

The echo acquisition module is used to acquire the time-domain echo data observed by the moon-based synthetic aperture radar on the imaging area on the earth;

A coherent superposition module, configured to coherently superpose the time-domain echo data based on each sub-aperture of the synthetic aperture of the moon-based synthetic aperture radar and each sub-imaging region of the imaging region, to obtain the imaging Observations for the region.

The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and operable on the processor, when the processor executes the program, it realizes the base synthesis as described above. Aperture Radar Earth Observation Method.

The present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the earth observation method of the lunar-based synthetic aperture radar described in any one of the above-mentioned methods is realized.

The present invention also provides a computer program product, including a computer program. When the computer program is executed by a processor, the method for earth observation of the moon-based synthetic aperture radar described in any one of the above is realized.

The method and device for earth observation of the moon-based synthetic aperture radar provided by the present invention, respectively aim at each sub-aperture and each sub-imaging area, perform imaging analysis on the time-domain echo data after distance compression, and then perform coherent superposition , to obtain the observation results, on the basis of avoiding the cumbersome calculation steps of the frequency domain solution method, it can make up for the shortcomings of the traditional time domain solution algorithm such as the large time cost, which can reduce the calculation cost and time, and can improve the performance of lunar-based SAR for earth observation. Efficiency can increase the possibility of the time-domain solution algorithm being used in long-distance and large-width MB-SAR scenarios, and has better application prospects.

Description of drawings

In order to more clearly illustrate the present invention or the technical solutions in the prior art, the accompanying drawings that need to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings in the following description are the For some embodiments of the present invention, those of ordinary skill in the art can also obtain other drawings based on these drawings on the premise of not paying creative efforts.

FIG. 1 is a schematic diagram of a moon-based SAR earth observation scene in the prior art;

Fig. 2 is a schematic flow chart of the earth observation method of the moon-based synthetic aperture radar provided by the present invention;

FIG. 3 is a schematic flow chart of step 201 in FIG. 2;

FIG. 4 is a schematic flowchart of step 202 in FIG. 2;

Fig. 5 is a schematic diagram of the sub-aperture and sub-imaging regions of the earth observation method of the moon-based synthetic aperture radar provided by the present invention;

6 is a schematic diagram of performing imaging analysis on a single sub-imaging region through a single sub-aperture in the earth observation method of the moon-based synthetic aperture radar provided by the present invention;

Fig. 7 is one of the schematic diagrams of the observation results of the earth observation method of the moon-based synthetic aperture radar provided by the present invention;

Fig. 8 is the second schematic diagram of the observation results of the earth observation method of the moon-based synthetic aperture radar provided by the present invention;

Fig. 9 is the third schematic diagram of the observation results of the earth observation method of the moon-based synthetic aperture radar provided by the present invention;

Fig. 10 is the fourth schematic diagram of the observation results of the earth observation method of the moon-based synthetic aperture radar provided by the present invention;

Fig. 11 is a structural schematic diagram of the earth observation device of the moon-based synthetic aperture radar provided by the present invention;

Fig. 12 is a schematic structural diagram of an electronic device provided by the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention , but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

In the description of the embodiments of the present invention, the terms "first", "second", and "third" are used for description purposes only, and cannot be understood as indicating or implying relative importance, and do not involve order.

The method and device for earth observation of the moon-based synthetic aperture radar provided by the present invention will be described below with reference to FIGS. 2 to 9 .

Fig. 2 is a schematic flow chart of the earth observation method of the moon-based synthetic aperture radar provided by the present invention. As shown in FIG. 2 , the earth observation method for a lunar-based synthetic aperture radar provided by an embodiment of the present invention may be executed by an earth observation device for a lunar-based synthetic aperture radar, and the method includes: step 201 and step 202 .

Step 201 , acquiring time-domain echo data obtained by the Moon-based Synthetic Aperture Radar to observe the imaging area on the earth.

Specifically, time-domain echo data can be generated based on any echo data generation method for SAR, based on MB-SAR parameters and spatial motion relationships.

FIG. 3 is a schematic flowchart of step 201 in FIG. 2 . As shown in Figure 3, real-time motion information such as the spatial position and velocity of objects such as EGO and MB-SAR can be calculated based on the ephemeris data and time epoch of the moon; based on the spatial position of objects such as EGO and MB-SAR, etc., the Calculate the distance history; based on the MB-SAR parameters and the distance history, the corresponding echo can be generated, so as to obtain the time-domain echo data of the moon-based synthetic aperture radar observing the imaging area on the earth.

Among them, the ephemeris data can use high-precision ephemeris data such as JPL ephemeris; EGO is located in the imaging area; MB-SAR parameters can include but not limited to frequency, bandwidth, antenna aperture, pulse width, and pulse repetition frequency.

Step 202 , based on each sub-aperture of the synthetic aperture of the moon-based synthetic aperture radar and each sub-imaging area of the imaging area, perform coherent superposition on the range-compressed time-domain echo data to obtain observation results of the imaging area.

Specifically, range compression processing may be performed on the aforementioned time-domain echo data to obtain range-compressed time-domain echo data.

The synthetic aperture of MB-SAR can be divided into multiple non-overlapping sub-apertures. Thus, apart from the endpoints of the sub-apertures, there is no identical portion between any two sub-apertures.

The imaging area can be divided into multiple non-overlapping sub-imaging areas. Thus, except for the boundaries of the sub-imaging areas, there is no identical portion between any two sub-imaging areas. It can be understood that the imaging area can generally be regarded as a rectangle. There are several imaging pixels in each sub-imaging area.

It should be noted that the MB-SAR parameters, the number of sub-apertures and the number of sub-imaging regions can all be preset by the user according to the requirements of the observation task. The embodiments of the present invention do not limit specific values of the MB-SAR parameters, the number of sub-apertures, and the number of sub-imaging regions.

For each sub-aperture and each sub-imaging area, the BP algorithm can be executed to obtain the imaging result of the sub-imaging area under the sub-aperture; The actual impact of the entire imaged area is obtained as an observation for that imaged area.

Range matching filtering can be performed on time domain echo data, and the echo after matching filtering can be expressed by the following formula:

(1)

in, Indicates the signal amplitude, /> Indicates azimuth slow time, /> Indicates the wavelength, /> Indicates the distance fast time, /> represents the speed of light, /> Indicates the distance course.

In the BP algorithm, each pixel will be projected to the echo domain to form the migration trajectory of the ground target, and finally the image will be obtained through coherent superposition. The complex domain data of each pixel can be expressed as

(2)

in, ; Indicates the round-trip delay of the echo.

It should be noted that if the traditional BP algorithm is used to perform imaging analysis on the entire imaging area under the full synthetic aperture, coherent superposition will generate huge computational overhead and consume a lot of time. Different from the solution in the frequency domain, it is an innovation made in the solution in the time domain in the embodiment of the present invention. For MB-SAR scenes with obvious echo paths, the embodiments of the present invention can reduce the time-to-time delay of MB-SAR on the basis of reducing the range and azimuth coupling in imaging analysis by dividing sub-apertures and sub-imaging regions. The complexity of time and space in domain imaging can be improved, and the calculation efficiency of imaging results can be improved, which can provide convenience for future MB-SAR online real-time data processing and result generation.

In the embodiment of the present invention, for each sub-aperture and each sub-imaging area, the time-domain echo data after distance compression is imaged and analyzed, and then coherently superimposed to obtain the observation results, which can avoid the cumbersome solution in the frequency domain On the basis of the calculation steps of the traditional time-domain solution algorithm, it can make up for the shortcomings of the traditional time-domain solution algorithm such as large time overhead, which can reduce the calculation cost and time, improve the efficiency of moon-based SAR earth observation, and increase the time-domain solution algorithm in long-distance, The possibility of using it in the large-width MB-SAR scene has better application prospects.

Based on the content of any of the above-mentioned embodiments, based on each sub-aperture of the synthetic aperture of the moon-based synthetic aperture radar and each sub-imaging area of the imaging area, regional coherent superposition is performed on the time-domain echo data to obtain the observation results of the imaging area , including: dividing the synthetic aperture into multiple non-overlapping sub-apertures based on the length of the synthetic aperture, and dividing the imaging area into multiple non-overlapping sub-apertures based on the length of the imaging area in the azimuth direction and the length in the distance direction imaging area.

Specifically, FIG. 4 is a schematic flowchart of step 202 in FIG. 2 . As shown in FIG. 4, step 2021, distance compression, may be performed first. That is, performing range compression processing on the aforementioned time-domain echo data to obtain range-compressed time-domain echo data.

After step 2021 is executed, step 2022 and step 2023 may be executed. The embodiment of the present invention does not specifically limit the sequence of executing step 2022 and executing step 2023, that is, executing step 2022 first and then executing step 2023, or executing step 2023 first and then executing step 2022, or executing steps 2022 and 2022 in parallel (simultaneously). Step 2023.

Step 2022, sub-imaging area division.

Fig. 5 is a schematic diagram of the sub-aperture and the sub-imaging area in the earth observation method of the lunar-based synthetic aperture radar provided by the present invention. As shown in Figure 5, the length of the imaging area in the azimuth direction and the length in the distance direction are respectively M and N, and the length of the imaging area in the direction direction and the distance direction can be divided into α ₂ and α ₃ parts respectively, then it can be divided into The rendering area is divided into (α ₂ ×α ₃ ) sub-imaging areas. The azimuth-up length and the distance-up length of each sub-imaging area are m and n, respectively. in, , /> . The area surrounded by a dotted line in FIG. 5 is an example of a sub-imaging area.

Step 2023, sub-aperture division.

As shown in Figure 5, the length of the synthetic aperture is L _s , and the synthetic aperture can be equally divided into α ₁ complementary overlapping sub-apertures, then the length of each sub-aperture is .

Based on each sub-aperture and each sub-imaging area, image analysis is performed on the time-domain echo data after distance compression to obtain regional images; coherent superposition is performed on the images of each area to obtain observation results.

Specifically, after performing sub-imaging region division and sub-aperture division, step 2025, coherent superposition, may be performed. First, based on each sub-aperture and each sub-imaging area, execute the BP algorithm to perform imaging analysis on the time-domain echo data after distance compression, and obtain the imaging result of the sub-imaging area under the sub-aperture, that is, the area image; Coherently superimpose all the obtained regional images to form images and obtain observation results.

It should be noted that if there are N _s sampling points along the L _s path, the calculation amount of the direct back projection (that is, without sub-aperture and sub-imaging area division) algorithm is N _s ×M×N, when three When the value is relatively large, the amount of calculation will be quite large. However, in the embodiment of the present invention, after the sub-apertures and sub-imaging regions are divided, the calculation amount can be significantly reduced.

In the embodiment of the present invention, by dividing the sub-aperture and the sub-imaging area, respectively, for each sub-aperture and each sub-imaging area, the time-domain echo data after the distance compression is imaged and analyzed, and then coherently superimposed to obtain the observation result , on the basis of avoiding the cumbersome calculation steps of the frequency domain solution method, it can make up for the shortcomings of the traditional time domain solution algorithm such as large time overhead, can reduce the calculation cost and time, can improve the efficiency of moon-based SAR earth observation, and can increase the The possibility of using the large time-domain solution algorithm in the long-distance and large-width MB-SAR scene has a better application prospect.

Based on the content of any of the above-mentioned embodiments, based on each sub-aperture and each sub-imaging area, the time-domain echo data after distance compression is imaged and analyzed to obtain an image of the area, including: for each sub-aperture and each sub-imaging area Sub-imaging area, perform the following processing:

A target sampling point corresponding to each pixel point in the sub-imaging area on the center line of the sub-imaging area is respectively determined.

Specifically, before step 2025, step 2024, distance interpolation, may also be performed.

Performing distance interpolation may include determining the target sampling point corresponding to each pixel point in the sub-imaging area on the center line of the sub-imaging area, and replacing the pixel point with the corresponding target sampling point to reduce the calculation of back projection overhead.

The centerline of a sub-imaging area is a straight line in the sub-imaging area. There are multiple sampling points on the center line, and the distance between two adjacent sampling points is a preset value.

Optionally, for each sub-imaging area, the centerline of the sub-imaging area may be a side, a diagonal line or a line between two opposite sides of the sub-imaging area.

Optionally, for each pixel point, the pixel point may be projected to the center line according to the distance, and projected on a sampling point on the center line, and the sampling point is a target sampling point corresponding to the pixel point.

Based on each target sampling point and the compressed time-domain echo data, a back-projection algorithm is performed to obtain an area image.

Specifically, after the pixel point is replaced by the target sampling point corresponding to the pixel point, the BP algorithm can be executed based on the target sampling point, so as to realize the imaging analysis of the time-domain echo data after distance compression, and obtain the The imaging result of the sub-imaging area, that is, the area image.

The embodiment of the present invention improves the traditional back projection algorithm, and reduces the imaging complexity and time complexity of MB-SAR through a new fast back projection (Fast Back Projection, FBP) algorithm. The traditional BP algorithm, which projects each pixel in the imaging area to the echo domain, is no longer suitable for MB-SAR scenarios. In order to overcome the disadvantages of MB-SAR time-domain solution at least to a certain extent, the FBP algorithm came into being .

By adopting the FBP algorithm in the embodiment of the present invention, on the basis of avoiding the tedious calculation steps of the frequency domain solution method, it can make up for the shortcomings of the traditional time domain solution method such as large time overhead, and can increase the time domain solution algorithm in long distances and large widths. It is possible to use it in the large-scale MB-SAR scene and has a better application prospect.

Based on the content of any of the above-mentioned embodiments, determining the target sampling point corresponding to each pixel point in the sub-imaging area on the center line of the sub-imaging area includes: based on the distance between the sub-aperture and each pixel point, each A pixel point is projected onto the center line to determine the projection point; the sampling point closest to the projection point on the center line is determined as the target sampling point.

Specifically, FIG. 6 is a schematic diagram of performing imaging analysis on a single sub-imaging region through a single sub-aperture in the earth observation method of the lunar-based synthetic aperture radar provided by the present invention. As shown in Figure 6, B _s is the center position of the sub-aperture, and A _s is the other position in the sub-aperture with a distance of u _s from B _s . With B _s as the endpoint, determine the centerline that can approximately replace the sub-imaging area (as shown in Figure 6, the connection line of solid black dots), and then project each pixel in the sub-imaging area onto the centerline Approximate point substitution to reduce the computational overhead of backprojection. In Fig. 6, arcs with different radii can be drawn in the sub-imaging regions with A _s and B _s as the centers respectively. B _s C _s and B _s E _s have the same length, forming an arc L ₁ ; A _s C _s and A _s D _s have the same length, forming an arc L ₂ . Wherein, D _s is the real pixel point to be projected in the sub-imaging area, C _s is the corresponding projection point on the center line, and E _s is the intersection point of A _s D _s and the arc L ₁ . The position of C _s obtained by projection with an equal-length radius arc may not be strictly located at any sampling point on the center line, and C _s can be replaced by the nearest adjacent sampling point (ie, the target sampling point). It is inevitable introduced error. Therefore, when selecting the centerline representing the sub-imaging area, the centerline should not be too long to generate a large amount of redundant data, nor should it be too short to project all the pixels of the sub-imaging area. Here, the diagonal line of the sub-imaging area is used as the center line to realize the projection of all pixels.

In Figure 6, the real distance between the sub-aperture and the pixel point is A _s D _s , the alternative distance between the sub-aperture and the target projection point is B _s C _s , and the distance error between the two is described as the following formula.

(3)

in, is the angle between the azimuth and B _s E _s ;/> is the angle between the center line and B _s E _s ; R is the real slope distance (such as A _s C _s );/> is the slope distance error between A _s C _s and B _s C _s .

due to distance error Much smaller than the distance from MB-SAR to EGO, at this time /> Can be replaced by the following formula.

(4)

At this time, the slope distance R can be rewritten as the following formula.

(5)

Further, formula (5) can be rewritten as formula (6).

(6)

where r represents the radius in radians _L1 .

Similarly, in actual scenarios, is also much smaller than /> , so consider the extreme case, /> The maximum value of can be expressed as follows.

(7)

Among them, D _s is the length of the sub-imaging area in the azimuth direction. Equation (7) shows that when the product of the sub-aperture length and the sub-imaging area is determined, the distance error There will be an upper limit. Generally speaking, the phase error caused by the distance error should be less than , at this time the maximum distance error /> satisfy the inequality:

(8)

that is . If the denominator is controlled by the factor /> Instead, it can be seen from equations (7) and (8) that the length of the sub-imaging region /> satisfy the inequality /> , at this time /> with /> There is an inverse proportional negative correlation relationship, when /> becomes very large, the subaperture length /> will be closer and closer to the length of a single pulse, which gradually loses the role of sub-aperture division. In general, when the parameter /> When suitable for the scene, the sub-aperture length /> Can be 16, 32, 64 pulse lengths.

Based on the content of any of the above embodiments, the center line is a diagonal line of the sub-imaging area.

Specifically, the diagonal line of the sub-imaging area can be used as the center line to realize the projection of all pixel points.

Based on the content of any of the above embodiments, dividing the synthetic aperture into multiple non-overlapping sub-apertures based on the length of the synthetic aperture includes: obtaining the arithmetic square root of the length of the synthetic aperture.

Specifically, the arithmetic square root of the length of the synthetic aperture may be obtained.

The first quantity is determined based on the arithmetic square root of the length of the synthetic aperture.

Specifically, when the length of the synthetic aperture is a square number, the arithmetic square root of the length of the synthetic aperture can be determined as the first quantity; when the length of the synthetic aperture is not a square number, the length of the synthetic aperture can be The integer that is closest to the arithmetic square root of and can be divisible by the length of the synthetic aperture is determined as the first quantity.

The synthetic aperture is equally divided into a first number of sub-apertures.

Specifically, based on the first number, the synthetic aperture is equally divided to obtain the first number of sub-apertures.

In the embodiment of the present invention, the first number is determined based on the arithmetic square root of the length of the synthetic aperture, thereby dividing the synthetic aperture into the first number of sub-apertures, which can remove redundant data to a greater extent, and reduce calculation overhead and time. It can improve the efficiency of moon-based SAR for earth observation.

Based on the content of any of the above embodiments, based on the length of the imaging area in the azimuth direction and the length in the distance direction, the imaging area is divided into multiple non-overlapping sub-imaging areas, including: obtaining the arithmetic square root of the length in the direction direction and the distance Arithmetic square root of the length up.

Specifically, the arithmetic square root of the upward length of the imaging area in azimuth may be acquired, and the arithmetic square root of the upward length of the imaging area in distance may be acquired.

The second quantity is determined based on the arithmetic square root of the length upward in the azimuth, and the third quantity is determined based on the square root of the length upward in the distance.

Specifically, in the case where the length in the azimuth direction of the imaging area is a square number, the arithmetic square root of the length in the azimuth direction of the imaging area can be determined as the second quantity; The integer that is closest to the arithmetic square root of the length in the azimuth direction of the imaging region and can be divisible by the length in the direction direction of the imaging region is determined as the second quantity.

In the case where the length of the imaging region upwards is a square number, the arithmetic square root of the length upwards of the imaging region distance can be determined as the third quantity; The integer that is closest to the arithmetic square root of the length of the region from upward and can be divisible by the length of the imaging region from upward is determined as the third quantity.

The imaging area is equally divided into the second number of parts in the azimuth direction, and the imaging area is divided into the third number of parts in the distance direction, so as to obtain sub-imaging areas.

Specifically, the imaging area is equally divided into the second number of parts in the azimuth direction, and the imaging area is equally divided into the third number of parts in the distance direction, to obtain (second number×third number) sub-imaging areas.

In the embodiment of the present invention, the second number is determined based on the arithmetic square root of the upward length of the imaging area, and the third number is determined based on the arithmetic square root of the upward length of the imaging area, so that the imaging area is divided into multiple sub-imaging areas, which can be more Removing redundant data to a large extent can reduce computing overhead and time, and can improve the efficiency of lunar-based SAR earth observation.

In order to facilitate the understanding of the above-mentioned embodiments of the present invention, an example will be used below to illustrate the effect of reducing the calculation cost and time of the earth observation method of the moon-based synthetic aperture radar.

Fig. 7 is one of the schematic diagrams of the observation results of the earth observation method of the moon-based synthetic aperture radar provided by the present invention. Fig. 8 is the second schematic diagram of the observation result of the earth observation method of the lunar-based synthetic aperture radar provided by the present invention; Fig. 9 is the third schematic diagram of the observation result of the earth observation method of the lunar-based synthetic aperture radar provided by the present invention; Fig. 10 is the fourth schematic diagram of the observation results of the earth observation method of the lunar-based synthetic aperture radar provided by the present invention.

The MB-SAR earth observation scene times are apogee: 2001.01.24, 19:01:00; perigee: 2001.01.10, 09:01:00; descending node: 2001.01.15, 11:01:00; ascending node: 2001.01.02, 22:01:00. The corresponding MB-SAR parameters are basic parameters: carrier frequency is 9GHz, pulse width is 100us, range bandwidth is 3MHz, range/azimuth oversampling rate is 1.2, range/azimuth width angle is 0.028° and 0.014°, The viewing angle is 0.3°. The simplified imaging result diagrams of nine point targets as shown in Fig. 7 to Fig. 10 can be respectively obtained. Among them, Fig. 7, Fig. 8, Fig. 9 and Fig. 10 are schematic diagrams of simplified imaging results of apogee, perigee, descending node and ascending node respectively.

In these four moments, the peak side lobe ratio (Peak Side Lobe Ratio, PSLR) of perigee and apogee on the horizontal slice and vertical slice all exceeded -13dB, showing good image results, and higher than the ascending node and descending node PSLR. In the parameter setting of FBP, the azimuth slice is more sensitive than the distance slice, and too long synthetic aperture time will affect the quality of the azimuth slice. At this time, the parameters should be adjusted to improve the level of the azimuth slice.

In the above time-domain FBP algorithm, the calculation amount of the back projection of the imaging area is about , the amount of phase interpolation calculation is about /> , the calculation amount of coherent superposition is /> , the calculation amount of the three is about /> , less than the traditional BP calculation/> . As the length of the sub-aperture and the scope of the sub-imaging area change, the difference in calculation amount is greater, and the effect of reducing calculation overhead and time is more obvious.

Therefore, users can perform diverse operations related to MB-SAR time-domain imaging according to the custom requirements of related tasks such as platform parameters, aperture and area division.

The earth observation device of the moon-based synthetic aperture radar provided by the present invention is described below, and the earth observation device of the moon-based synthetic aperture radar described below and the earth observation method of the moon-based synthetic aperture radar described above can refer to each other .

Fig. 11 is a structural schematic diagram of the earth observation device of the moon-based synthetic aperture radar provided by the present invention. Based on the content of any of the above embodiments, as shown in Figure 11, the device includes an echo acquisition module 1101 and a coherent superposition module 1102, wherein:

The echo acquisition module 1101 is used to acquire the time-domain echo data of the moon-based synthetic aperture radar observing the imaging area on the earth;

The coherent superposition module 1102 is configured to perform coherent superposition on the time-domain echo data based on each sub-aperture of the synthetic aperture of the moon-based synthetic aperture radar and each sub-imaging region of the imaging region to obtain observation results of the imaging region.

Specifically, the echo acquisition module 1101 and the coherent superposition module 1102 may be electrically connected.

The echo acquisition module 1101 can generate time-domain echo data based on any echo data generation method for SAR, based on MB-SAR parameters and spatial motion relationships.

The coherent superposition module 1102 can first perform range compression processing on the aforementioned time domain echo data to obtain the range compressed time domain echo data; it can execute the BP algorithm for each sub-aperture and each sub-imaging area to obtain the sub-aperture The imaging result of the sub-imaging area under the aperture; then the imaging results of each sub-imaging area under each sub-aperture are coherently superimposed, so that the actual influence of the entire imaging area can be obtained as the observation result of the imaging area.

Optionally, the coherent adding module 1102 may include:

The division sub-module is used to divide the synthetic aperture into multiple non-overlapping sub-apertures based on the length of the synthetic aperture, and to divide the imaging area into multiple non-overlapping sub-apertures based on the length of the imaging area in the azimuth direction and the length in the distance direction. overlapping sub-imaging regions;

The imaging analysis sub-module is used to perform imaging analysis on the distance-compressed time-domain echo data based on each sub-aperture and each sub-imaging area respectively, and obtain an area image;

The coherent superposition sub-module is used for coherent superposition of images in each region to obtain observation results.

Optionally, the imaging analysis submodule may include:

The projection unit is used to respectively determine the target sampling point corresponding to each pixel point in the sub-imaging area on the center line of the sub-imaging area;

The imaging unit is configured to execute a back-projection algorithm based on each target sampling point and compressed time-domain echo data to obtain an image of the area.

Optionally, the projection unit can be specifically configured to project each pixel onto the center line based on the distance between the sub-aperture and each pixel, and determine the projection point; determined as the target sampling point.

Optionally, the central line is a diagonal line of the sub-imaging area.

Optionally, sub-modules can be divided into:

The sub-aperture division unit is configured to obtain the arithmetic square root of the length of the synthetic aperture; determine the first quantity based on the arithmetic square root of the length of the synthetic aperture; and divide the synthetic aperture into the first quantity of sub-apertures.

Optionally, sub-modules can be divided into:

The sub-imaging area division unit is used to obtain the arithmetic square root of the length upward in azimuth and the arithmetic square root of the length upward in azimuth; determine the second quantity based on the arithmetic square root of the length upward in azimuth, and determine the second quantity based on the arithmetic square root of the length upward in distance The third number: divide the imaging area into the second number of parts in the azimuth direction, and divide the imaging area into the third number of parts in the distance direction, so as to obtain the sub-imaging areas.

The earth observation device of the moon-based synthetic aperture radar provided by the embodiment of the present invention is used to implement the earth observation method of the above-mentioned moon-based synthetic aperture radar of the present invention, and its implementation mode is the same as that of the moon-based synthetic aperture radar provided by the present invention The implementation of the observation method is the same, and can achieve the same beneficial effect, and will not be repeated here.

The earth observation device of the moon-based synthetic aperture radar is used for the earth observation method of the moon-based synthetic aperture radar in the foregoing embodiments. Therefore, the descriptions and definitions in the earth observation method of the moon-based synthetic aperture radar in the foregoing embodiments can be used to understand the execution modules in the embodiments of the present invention.

In the embodiment of the present invention, for each sub-aperture and each sub-imaging area, the time-domain echo data after distance compression is imaged and analyzed, and then coherently superimposed to obtain the observation results, which can avoid the cumbersome solution in the frequency domain On the basis of the calculation steps of the traditional time-domain solution algorithm, it can make up for the shortcomings of the traditional time-domain solution algorithm such as large time overhead, which can reduce the calculation cost and time, improve the efficiency of moon-based SAR earth observation, and increase the time-domain solution algorithm in long-distance, The possibility of using it in the large-width MB-SAR scene has better application prospects.

Fig. 12 is a schematic structural diagram of an electronic device provided by the present invention. As shown in Fig. 12 , the electronic device may include: a processor (processor) 1210, a communication interface (Communications Interface) 1220, a memory (memory) 1230 and a communication bus 1240, Wherein, the processor 1210 , the communication interface 1220 , and the memory 1230 communicate with each other through the communication bus 1240 . The processor 1210 can call the logic instructions in the memory 1230 to execute the method for observing the earth by the lunar-based synthetic aperture radar, and the method includes: acquiring the time-domain echo data obtained by the lunar-based synthetic aperture radar for observing the imaging area on the earth; Based on each sub-aperture of the synthetic aperture of the lunar-based synthetic aperture radar and each sub-imaging area of the imaging area, the time-domain echo data after range compression is coherently added to obtain the observation results of the imaging area.

In addition, the above-mentioned logic instructions in the memory 1230 may be implemented in the form of software functional units and when sold or used as an independent product, may be stored in a computer-readable storage medium. Based on this understanding, the essence of the technical solution of the present invention or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including Several instructions are used to make a computer device (which may be a personal computer, server, or network device, etc.) execute all or part of the steps of the methods in various embodiments of the present invention. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk, and other media that can store program codes. .

The processor 1210 in the electronic device provided in the embodiment of the present application can call the logic instructions in the memory 1230, and its implementation is consistent with the implementation of the moon-based synthetic aperture radar earth observation method provided in the application, and can achieve the same Beneficial effects are not repeated here.

On the other hand, the present invention also provides a computer program product. The computer program product includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by the computer, the computer can execute The earth observation method of the moon-based synthetic aperture radar provided by the above-mentioned methods, the method includes: obtaining the time-domain echo data obtained by the moon-based synthetic aperture radar to observe the imaging area on the earth; Each sub-aperture of the aperture and each sub-imaging area of the imaging area perform coherent superposition on the distance-compressed time-domain echo data to obtain observation results of the imaging area.

When the computer program product provided in the embodiment of the present application is executed, the above-mentioned earth observation method of lunar-based synthetic aperture radar is realized. effects, which will not be repeated here.

In yet another aspect, the present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it is implemented to perform the earth observation of the above-mentioned moon-based synthetic aperture radar. The method comprises: obtaining the time-domain echo data of the moon-based synthetic aperture radar observing the imaging area on the earth; based on each sub-aperture of the synthetic aperture of the moon-based synthetic aperture radar and each sub-imaging area of the imaging area , coherently superimpose the range-compressed time-domain echo data to obtain the observation results of the imaging region.

When the computer program stored on the non-transitory computer-readable storage medium provided by the embodiment of the present application is executed, the above-mentioned earth observation method of the moon-based synthetic aperture radar is realized, and its specific implementation mode is the same as that described in the embodiment of the aforementioned method The implementation methods are the same, and can achieve the same beneficial effect, and will not be repeated here.

The device embodiments described above are only illustrative, and the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place , or can also be distributed to multiple network elements. Part or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. It can be understood and implemented by those skilled in the art without any creative efforts.

Through the above description of the implementations, those skilled in the art can clearly understand that each implementation can be implemented by means of software plus a necessary general-purpose hardware platform, and of course also by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the prior art can be embodied in the form of software products, and the computer software products can be stored in computer-readable storage media, such as ROM/RAM, magnetic discs, optical discs, etc., including several instructions to make a computer device (which may be a personal computer, server, or network device, etc.) execute the methods of various embodiments or some parts of the embodiments.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (10)

1. A method of earth observation for a moon-based synthetic aperture radar, comprising:

acquiring time domain echo data of a moon-based synthetic aperture radar for observing an imaging area on the earth;

and performing coherent superposition on the time domain echo data after distance compression based on each sub-aperture of the synthetic aperture of the lunar-based synthetic aperture radar and each sub-imaging area of the imaging area to obtain an observation result of the imaging area.

2. The earth observation method of a month-based synthetic aperture radar according to claim 1, wherein the performing regional coherent superposition on the time-domain echo data based on each sub-aperture of the synthetic aperture of the month-based synthetic aperture radar and each sub-imaging region of the imaging region to obtain an observation result of the imaging region comprises:

dividing the synthetic aperture into a plurality of mutually non-overlapping sub-apertures based on the length of the synthetic aperture, and dividing the imaging region into a plurality of mutually non-overlapping sub-imaging regions based on the length of the imaging region in the azimuth direction and the length of the imaging region in the distance direction;

imaging analysis is carried out on the time domain echo data after distance compression based on each sub-aperture and each sub-imaging area respectively, and an area image is obtained;

And performing coherent superposition on each regional image to obtain the observation result.

3. The earth observation method of a month-based synthetic aperture radar according to claim 2, wherein the imaging analysis of the time-domain echo data after distance compression based on each of the sub-apertures and each of the sub-imaging areas, respectively, acquires an area image, comprises:

for each of the sub-apertures and each of the sub-imaging regions, performing the following:

respectively determining a target sampling point corresponding to each pixel point in the sub-imaging region on a central line of the sub-imaging region;

and executing a backward projection algorithm based on each target sampling point and the time domain echo data after distance compression, and acquiring the region image.

4. A method of earth observation of a month-based synthetic aperture radar according to claim 3, wherein said determining a corresponding target sampling point for each pixel point in the sub-imaging region on a centerline of the sub-imaging region comprises:

based on the distance between the sub-aperture and each pixel point, projecting each pixel point onto the central line, and determining a projection point;

And determining a sampling point closest to the projection point on the central line as the target sampling point.

5. A method of earth observation of a month-based synthetic aperture radar according to claim 3 or 4 wherein the centre line is a diagonal of the sub-imaging region.

6. The earth observation method of a month-based synthetic aperture radar according to claim 2, wherein the dividing the synthetic aperture into a plurality of the sub-apertures that do not overlap each other based on a length of the synthetic aperture includes:

obtaining the arithmetic square root of the length of the synthetic aperture;

determining a first number based on an arithmetic square root of a length of the synthetic aperture;

the synthetic aperture is equally divided into a first number of the sub-apertures.

7. The earth observation method of a month-based synthetic aperture radar according to claim 2, wherein the dividing the imaging region into a plurality of the sub imaging regions that do not overlap each other based on a length of the imaging region in an azimuth direction and a length of the imaging region in a distance direction includes:

acquiring the arithmetic square root of the length in the azimuth direction and the arithmetic square root of the length in the distance direction;

determining a second number based on the arithmetic square root of the length in the azimuth direction and a third number based on the arithmetic square root of the length in the distance direction;

And equally dividing the imaging area into the second number of parts in the azimuth direction and equally dividing the imaging area into the third number of parts in the distance direction to obtain each sub-imaging area.

8. A ground observation device of a lunar-based synthetic aperture radar, comprising:

the echo acquisition module is used for acquiring time domain echo data of the moon-based synthetic aperture radar for observing an imaging area on the earth;

and the coherent superposition module is used for carrying out coherent superposition on the time domain echo data based on each sub-aperture of the synthetic aperture of the lunar-based synthetic aperture radar and each sub-imaging area of the imaging area to obtain an observation result of the imaging area.

9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the earth-looking method of the month-based synthetic aperture radar of any of claims 1 to 7 when the program is executed.

10. A non-transitory computer readable storage medium having stored thereon a computer program, which when executed by a processor implements a method of earth observation of a month-based synthetic aperture radar according to any of claims 1 to 7.