CN116520323A - Earth observation method and device for lunar-based synthetic aperture radar - Google Patents
Earth observation method and device for lunar-based synthetic aperture radar Download PDFInfo
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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
Technical Field
The invention relates to the technical field of radars, in particular to a method and a device for earth observation of a moon-based synthetic aperture radar.
Background
Moon-based synthetic aperture radar (Moon-based Synthetic Aperture Radar, moon-based SAR, MB-SAR) is a synthetic aperture radar deployed on the near earth side of the Moon. The month-based SAR may make observations of ground objects (Earth Ground Object, EGO).
Fig. 1 is a schematic diagram of a prior art moon-based SAR earth observation scenario. As shown in fig. 1, the conventional SAR earth observation generally adopts a Back Projection (BP) algorithm, and each pixel point in an Imaging area (Imaging area) is projected to an echo domain, and then coherent superposition is performed. The echo data is typically analyzed imaging in the frequency domain, and less in the time domain. Compared with the frequency domain solving mode, the time domain solving mode can simplify the calculation steps and the complexity of the frequency domain solving mode, but for the time domain solving mode, the large time and space complexity still can influence the calculation cost and the time consumption.
When the traditional BP algorithm is used for earth observation of the lunar SAR, compared with a low-rail platform, the wide-width and long-distance of the MB-SAR can increase the time and space complexity of imaging, and the coherent superposition can generate huge calculation cost and a great amount of time loss.
In conclusion, the existing lunar-based SAR earth observation has the defects of high calculation cost, long time, low efficiency and the like.
Disclosure of Invention
The invention provides a method and a device for observing a lunar-based synthetic aperture radar to the earth, which are used for solving the defect of low efficiency of lunar-based SAR to the earth in the prior art and improving the efficiency of lunar-based SAR to the earth.
The invention provides a earth observation method of a moon-based synthetic aperture radar, which 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 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.
According to the earth observation method of the lunar-based synthetic aperture radar provided by the 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 perform area coherent superposition on the time domain echo data to obtain an observation result of the imaging area, and the earth observation method comprises the following steps:
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.
According to the earth observation method of the lunar-based synthetic aperture radar provided by the invention, the 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 the earth observation method comprises the following steps:
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.
According to the earth observation method of the moon-based synthetic aperture radar provided by the invention, the determining of the corresponding target sampling point of each pixel point in the sub-imaging area on the central line of the sub-imaging area comprises the following steps:
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.
According to the earth observation method of the moon-based synthetic aperture radar provided by the invention, the central line is the diagonal line of the sub-imaging area.
According to the earth observation method of the moon-based synthetic aperture radar provided by the invention, the synthetic aperture is divided into a plurality of mutually non-overlapping sub-apertures based on the length of the synthetic aperture, and the earth observation method comprises the following steps:
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.
According to the earth observation method of the moon-based synthetic aperture radar provided by the invention, the imaging area is divided into a plurality of sub imaging areas which are not overlapped with each other based on the length of the imaging area in the azimuth direction and the length of the imaging area in the distance direction, and the earth observation method comprises the following steps:
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.
The invention also provides a earth observation device of the moon-based synthetic aperture radar, which comprises:
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.
The invention also provides an electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the earth observation method of the month-based synthetic aperture radar as described above when executing the program.
The present invention also provides 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 as described in any of the above.
The invention also provides a computer program product comprising a computer program which when executed by a processor implements a method of earth observation of a month-based synthetic aperture radar as described in any of the above.
According to the earth observation method and device for the moon-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 cost and time can be reduced, the earth observation efficiency of the moon-based SAR can be improved, the possibility of applying the time domain solving algorithm in a long-distance and large-width MB-SAR scene can be increased, and the application prospect is better.
Drawings
In order to more clearly illustrate the invention or the technical solutions of the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a prior art moon-based SAR earth observation scenario;
FIG. 2 is a schematic flow chart of a method for earth observation of a moon-based synthetic aperture radar provided by the invention;
FIG. 3 is a schematic diagram showing a specific flow of step 201 in FIG. 2;
FIG. 4 is a schematic diagram showing a specific flow of step 202 in FIG. 2;
FIG. 5 is a schematic diagram of a sub-aperture and sub-imaging region of a earth observation method of a moon-based synthetic aperture radar provided by the present invention;
FIG. 6 is a schematic diagram of an imaging analysis of a single sub-imaging region through a single sub-aperture in a ground observation method of a moon-based synthetic aperture radar provided by the present invention;
FIG. 7 is one of the schematic diagrams of the observations of the earth-looking method of the moon-based synthetic aperture radar provided by the present invention;
FIG. 8 is a second schematic diagram of the observation result of the earth observation method of the moon-based synthetic aperture radar provided by the present invention;
FIG. 9 is a 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 a 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 schematic diagram of the structure of a ground observation device of the moon-based synthetic aperture radar provided by the invention;
Fig. 12 is a schematic structural diagram of an electronic device provided by the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of embodiments of the present invention, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance and not order.
The earth observation method and device of the moon-based synthetic aperture radar provided by the invention are described below with reference to fig. 2 to 9.
Fig. 2 is a schematic flow chart of a method for earth observation of the moon-based synthetic aperture radar provided by the invention. As shown in fig. 2, the implementation main body of the earth observation method of the lunar-based synthetic aperture radar provided by the embodiment of the present invention may be an earth observation device of the lunar-based synthetic aperture radar, where the method includes: step 201 and step 202.
Step 201, acquiring time domain echo data of a moon-based synthetic aperture radar for observing an imaging area on the earth.
Specifically, the generation of the time domain echo data can be performed based on MB-SAR parameters and spatial motion relations based on any echo data generation method for SAR.
Fig. 3 is a schematic diagram showing a specific flow of step 201 in fig. 2. As shown in fig. 3, real-time motion information such as the spatial position and the speed of the objects such as EGO and MB-SAR can be calculated based on the ephemeris data and the time epoch of the moon; based on the spatial positions of the objects such as EGO, MB-SAR and the like, the distance history can be calculated; based on MB-SAR parameters and distance histories, corresponding echoes can be generated, so that time domain echo data for observing an imaging area on the earth by the moon-based synthetic aperture radar are obtained.
The ephemeris data can adopt high-precision ephemeris data such as JPL ephemeris and the like; EGO is located in the imaging region; MB-SAR parameters may include, but are not limited to, frequency, bandwidth, antenna aperture, pulse width, pulse repetition frequency, and the like.
Step 202, 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, and obtaining an observation result of the imaging area.
Specifically, the distance compression processing may be performed on the time-domain echo data to obtain distance-compressed time-domain echo data.
The synthetic aperture of MB-SAR may be divided into a plurality of mutually non-overlapping sub-apertures. So that there is no identical portion between any two sub-apertures except for the end points of the sub-apertures.
The imaging region may be divided into a plurality of sub-imaging regions that do not overlap each other. So that there is no identical portion between any two sub-imaging areas except the boundaries of the sub-imaging areas. It is understood that the imaging region may be generally considered as rectangular. There are several imaged pixels in each sub-imaging region.
It should be noted that, the MB-SAR parameter, the number of sub-apertures, and the number of sub-imaging regions may be preset by the user according to the requirements of the observation task. The embodiment of the invention does not limit specific values of MB-SAR parameters, the number of sub-apertures and the number of sub-imaging areas.
The BP algorithm can be executed for each sub-aperture and each sub-imaging area respectively, and an imaging result of the sub-imaging area under the sub-aperture is obtained; and then carrying out coherent superposition on imaging results of all sub-imaging areas under all sub-apertures, so that the actual influence of the whole imaging area can be obtained and used as an observation result of the imaging area.
The time domain echo data may be distance-wise matched filtered, and the matched filtered echo may be represented by:
（1）
wherein,,representing signal amplitude +.>Indicating azimuth slow time, < >>Indicate wavelength, & lt + & gt>Indicating distance to fast time, < >>Indicating the speed of light +.>Indicating the distance history.
In the BP algorithm, each pixel point is projected to an echo domain to form a migration track of a ground target, and finally an image is obtained through coherent superposition. The complex domain data for each pixel point can be expressed as
（2）
Wherein,,the method comprises the steps of carrying out a first treatment on the surface of the Representing the two-way delay of the echo.
It should be noted that, if the conventional BP algorithm is used to perform imaging analysis on the whole imaging region under the full synthetic aperture, the coherent superposition may generate huge calculation overhead and a great amount of time. The method is different from a frequency domain solving mode, and is an innovation of the time domain solving mode. For the MB-SAR scene with obvious characteristics of the echo path, the embodiment of the invention can reduce the time and space complexity of the MB-SAR in time domain imaging on the basis of reducing the distance direction coupling, azimuth direction coupling and other steps in imaging analysis by dividing the sub-aperture and the sub-imaging region, improves the operation efficiency of the imaging result, and can provide convenience for real-time data processing on the MB-SAR line in the future, further result generation and the like.
According to the embodiment of the invention, the imaging analysis is carried out on the time domain echo data after the distance compression according to each sub-aperture and each sub-imaging area, and then the coherent superposition is carried out, so that the observation result is obtained, the defects of large time cost and the like of the traditional time domain solving algorithm can be overcome on the basis of avoiding complicated calculation steps of the frequency domain solving mode, the calculation cost and time can be reduced, the efficiency of earth observation of the lunar SAR can be improved, the possibility of applying the time domain solving algorithm in a long-distance and large-width MB-SAR scene can be increased, and the application prospect is better.
Based on the foregoing in any of the foregoing embodiments, performing region-coherent superposition on time-domain echo data based on each sub-aperture of a synthetic aperture of a lunar-based synthetic aperture radar and each sub-imaging region of an imaging region, to obtain an observation result of the imaging region, including: the synthetic aperture is divided into a plurality of mutually non-overlapping sub-apertures based on the length of the synthetic aperture, and the imaging region is divided 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.
Specifically, fig. 4 is a schematic diagram illustrating a specific flow of step 202 in fig. 2. As shown in fig. 4, step 2021, distance compression may be performed first. And performing distance compression processing on the time domain echo data to obtain time domain echo data after distance compression.
After step 2021 is performed, steps 2022 and 2023 may be performed. The sequence of executing step 2022 and executing step 2023 is not particularly limited in the embodiments of the present invention, that is, step 2022 may be executed first and then step 2023 may be executed, step 2023 may be executed first and then step 2022 may be executed, or step 2022 and step 2023 may be executed in parallel (simultaneously).
Step 2022, sub-imaging region division.
Fig. 5 is a schematic diagram of a sub-aperture and a sub-imaging region in a ground observation method of the moon-based synthetic aperture radar provided by the invention. As shown in fig. 5, the length of the imaging region in the azimuth direction and the length of the imaging region in the distance direction are M and N, respectively, and the length of the imaging region in the azimuth direction and the length of the imaging region in the distance direction can be equally divided into alpha 2 And alpha 3 The presentation area can be divided into (alpha) 2 ×α 3 ) A sub-imaging region. The length in the azimuth direction and the length in the distance direction of each sub-imaging region are m and n, respectively. Wherein,,，/>. The area encircled by the dotted line in fig. 5 is an example of one sub-imaging area.
Step 2023, sub-aperture division.
As shown in FIG. 5, the synthetic aperture has a length L s Can be used forSynthetic pore size aliquoting into alpha 1 A plurality of complementary overlapping sub-apertures, each sub-aperture having a length of 。
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 the images of each region to obtain an observation result.
Specifically, after sub-imaging region division and sub-aperture division, step 2025, coherent addition may be performed. The BP algorithm can be executed based on each sub-aperture and each sub-imaging region, imaging analysis is carried out on the time domain echo data after distance compression, and an imaging result of the sub-imaging region under the sub-aperture, namely a region image, is obtained; and performing coherent superposition on all the obtained regional images to obtain an observation result, wherein the images can be imaged.
If along L s The presence of N on the path s The calculated amount of the direct back projection (i.e. without sub-aperture and sub-imaging area division) algorithm is N s When three values are relatively large, the calculation amount is relatively large. In the embodiment of the invention, after the sub-aperture and the sub-imaging area are divided, the calculated amount can be obviously reduced.
According to the embodiment of the invention, the sub-aperture and the sub-imaging area are divided, the time domain echo data after the distance compression is subjected to imaging analysis for each sub-aperture and each sub-imaging area, and then coherent superposition is carried out to obtain the observation result, so that the defects of large time expenditure and the like of the traditional time domain solving algorithm can be overcome on the basis of avoiding complicated calculation steps of the frequency domain solving mode, the calculation expenditure and time can be reduced, the efficiency of earth observation of the moon-based SAR can be improved, the possibility of applying the time domain solving algorithm in a long-distance and large-width MB-SAR scene can be increased, and the method has a better application prospect.
Based on the foregoing in any of the foregoing embodiments, performing imaging analysis on the time-domain echo data after distance compression based on each sub-aperture and each sub-imaging region, respectively, to obtain a region image, including: for each sub-aperture and each sub-imaging region, the following processing is performed:
and respectively determining a target sampling point corresponding to each pixel point in the sub-imaging area on the central line of the sub-imaging area.
Specifically, step 2024, distance interpolation may also be performed prior to step 2025.
Performing distance interpolation may include 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 replacing the pixel point with the corresponding target sampling point to reduce computational overhead of back projection.
The center line of the sub-imaging region is a straight line in the sub-imaging region. The central line is provided with a plurality of sampling points, and the distance between two adjacent sampling points is a preset value.
Alternatively, for each sub-imaging region, the center line of the sub-imaging region may be an edge, a diagonal line, or a line connecting two opposite edges of the sub-imaging region.
Optionally, for each pixel point, the pixel point may be projected to the center line according to the distance, and projected on a certain sampling point on the center line, where the sampling point is a target sampling point corresponding to the pixel point.
And executing a back projection algorithm based on each target sampling point and the time domain echo data after distance compression to acquire a region image.
Specifically, after the pixel point is replaced by the target sampling point corresponding to the pixel point, a BP algorithm can be executed based on the target sampling point, so that imaging analysis is performed on the time domain echo data after distance compression, and an imaging result, namely an area image, of the sub-imaging area under the sub-aperture is obtained.
The embodiment of the invention is improved on the basis of the traditional back projection algorithm, and the imaging complexity and the time complexity of MB-SAR are reduced by a new fast back projection (Fast Back Projection, FBP) algorithm. The conventional BP algorithm that projects each pixel point in the imaging region to the echo domain has not been suitable for MB-SAR scenes, and in order to overcome at least some extent the drawbacks of the MB-SAR time domain solution, the FBP algorithm has been developed.
According to the embodiment of the invention, by adopting the FBP algorithm, the defects of large time cost and the like of the traditional time domain solving mode can be overcome on the basis of avoiding complicated calculating steps of the frequency domain solving mode, the possibility of applying the time domain solving algorithm in a long-distance and large-width MB-SAR scene can be increased, and the method has a better application prospect.
Based on the foregoing in any of the foregoing embodiments, determining a target sampling point corresponding to each pixel point in the sub-imaging region on a center line of the sub-imaging region includes: based on the distance between the sub-aperture and each pixel point, projecting each pixel point onto a central line, and determining a projection point; and determining the sampling point closest to the projection point on the central line as a target sampling point.
Specifically, fig. 6 is a schematic diagram of an imaging analysis of 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 invention. As shown in FIG. 6, B s Is the center position of the sub-aperture, A s To be combined with B in the sub-aperture s Distance u s Other locations of (c) are provided. In B way s For the end points, a center line (such as the line connecting the solid black dots in fig. 6) that can approximately replace the sub-imaging region is determined, and then each pixel in the sub-imaging region is replaced by an approximate point projected onto the center line, so that the computational overhead of back projection is reduced. In FIG. 6, at A respectively s And B s As a center of a circle, arcs with different radiuses can be drawn in the sub-imaging areas. B (B) s C s And B s E s Is of the same length and forms a curve L 1 ；A s C s And A s D s Is of the same length and forms a curve L 2 . Wherein D is s C is the real pixel point to be projected in the sub-imaging area s E is the corresponding projection point on the central line s Is A s D s And radian L 1 Is a cross point of (c). C projected by equal-radius arc s The position of which may not be exactly at the centre lineAny sampling point in the above can be used for replacing C with the nearest sampling point (namely the target sampling point) s Inevitably introducesIs a function of the error of (a). Therefore, when selecting the center line representing the sub-imaging area, the center line may not be too long, thereby generating a large amount of redundant data, or may not be too short, thereby failing to project all the pixels of the sub-imaging area. The diagonal of the sub-imaging area is taken as a central line, so that projection of all pixel points is realized.
In FIG. 6, the true distance between the sub-aperture and the pixel point is A s D s The substitute distance between the sub-aperture and the target projection point is B s C s The distance error between the two is described as follows.
（3）
Wherein,,is oriented in the direction of B s E s An included angle between the two; />Is the center line and B s E s An included angle between the two; r is the true slant distance (e.g. A s C s ）；/>Is A s C s And B is connected with s C s And a skew error between.
Due to distance errorsFar smaller than the MB-SAR to EGO distance, at this point +.>The following formula may be substituted.
（4）
At this time, the skew distance R may be rewritten as follows.
（5）
Further, the formula (5) may be rewritten as the formula (6).
（6）
Wherein r represents radian L 1 Is set, and the radius of (a) is set.
Also, in an actual scenario, the display device,is also far less than->Thus consider the extreme case +>The maximum value of (2) can be expressed as follows.
（7）
Wherein D is s For the length of the sub-imaging region in the azimuth direction, equation (7) shows that after the product of the sub-aperture length and the sub-imaging region is determined, the distance errorThere will be an upper limit value. In general, the distance error should produce a phase error less thanAt this time, the distance error maximum value +.>The inequality is satisfied:
（8）
namely there is. If the denominator is used as the control factor +.>Instead, as can be seen from the formulas (7) and (8), the sub-imaging region length +.>Satisfy inequality->At this time->And->There is a negative correlation of the inverse proportion when +.>When it becomes large, the sub-aperture length +.>Will get closer to the length of the single pulse, which gradually loses the sub-aperture division effect. In general, when parameters->Sub-aperture length +.>May be 16, 32, 64 pulse lengths.
Based on any of the above embodiments, the center line is a diagonal line of the sub-imaging region.
Specifically, the projection of all the pixel points can be realized by taking the diagonal line of the sub-imaging area as the center line.
Based on the content of any of the above embodiments, dividing the synthetic aperture into a plurality of mutually non-overlapping sub-apertures based on the length of the synthetic aperture includes: the arithmetic square root of the length of the synthetic aperture is taken.
In particular, the arithmetic square root of the length of the synthetic aperture can be obtained.
The first number is determined based on the arithmetic square root of the length of the synthetic aperture.
Specifically, in the case where the length of the synthetic aperture is a square number, the arithmetic square root of the length of the synthetic aperture may be determined as the first number; in the case where the length of the synthetic aperture is not a square number, an integer nearest to the arithmetic square root of the length of the synthetic aperture, which is divisible by the length of the synthetic aperture, may be determined as the first number.
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 a first number of sub-apertures.
According to the embodiment of the invention, the first quantity is determined based on the arithmetic square root of the length of the synthetic aperture, so that the synthetic aperture is equally divided into the first quantity of sub-apertures, redundant data can be removed to a greater extent, the calculation cost and time can be reduced, and the efficiency of earth observation of the moon-based SAR can be improved.
Based on the content of any of the above embodiments, 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, includes: the arithmetic square root of the length in the azimuth direction and the arithmetic square root of the length in the distance direction are obtained.
Specifically, the arithmetic square root of the length in the azimuth direction of the imaging region can be obtained, and the arithmetic square root of the length in the distance direction of the imaging region can be obtained.
The second number is determined based on the arithmetic square root of the length in the azimuth direction, and the third number is determined based on the arithmetic square root of the length in the distance direction.
Specifically, in the case where the length in the imaging region azimuth direction is a square number, the arithmetic square root of the length in the imaging region azimuth direction may be determined as the second number; in the case where the length in the imaging region azimuth direction is not a square number, an integer which is closest to the arithmetic square root of the length in the imaging region azimuth direction and which can be divided by the length in the imaging region azimuth direction can be determined as the second number.
In the case where the length of the imaging region in the distance direction is a square number, the arithmetic square root of the length of the imaging region in the distance direction may be determined as the third number; in the case where the length in the imaging region distance direction is not a square number, an integer which is closest to the arithmetic square root of the length in the imaging region distance direction and which can be divided by the length in the imaging region distance direction is determined as the third number.
Dividing the imaging area into a second number of parts in the azimuth direction and dividing the imaging area into a third number of parts in the distance direction to obtain each sub imaging area.
Specifically, the imaging region is equally divided into a second number of copies in the azimuth direction, and the imaging region is equally divided into a third number of copies in the distance direction, resulting in (second number×third number) sub-imaging regions.
According to the embodiment of the invention, the second quantity is determined based on the arithmetic square root of the length in the azimuth direction of the imaging region, and the third quantity is determined based on the arithmetic square root of the length in the distance direction of the imaging region, so that the imaging region is divided into a plurality of sub-imaging regions, redundant data can be removed to a greater extent, the calculation cost and time can be reduced, and the efficiency of earth observation of the moon-based SAR can be improved.
In order to facilitate the understanding of the above embodiments of the present invention, the effect of the earth-looking method of the month-based synthetic aperture radar to reduce the computational overhead and time is described below by way of an example.
Fig. 7 is one of 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 a second schematic diagram of the observation result of the earth observation method of the moon-based synthetic aperture radar provided by the present invention; FIG. 9 is a 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 a diagram showing the observation result of the earth observation method of the moon-based synthetic aperture radar provided by the present invention.
The MB-SAR earth observation scene time is respectively a far-place: 2001.01.24,19:01:00; near site: 2001.01.10, 09:01:00; drop intersection point: 2001.01.15,11:01:00; intersection point of rising: 2001.01.02,22:01:00. The corresponding MB-SAR parameters are basic parameters: the carrier frequency was 9GHz, pulse width 100us, distance to bandwidth 3MHz, distance to/azimuth oversampling rate 1.2, distance to/azimuth width angle 0.028 ° and 0.014 °, and lower viewing angle 0.3 °. Simplified imaging result diagrams of nine point targets as shown in fig. 7 to 10 can be obtained, respectively. Fig. 7, 8, 9 and 10 are simplified imaging result diagrams of the far-place, near-place, descending-intersection and ascending-intersection, respectively.
In these four moments, peak side lobe ratios (Peak Side Lobe Ratio, PSLR) of near and far spots on the cross and longitudinal slices are all over-13 dB, showing good image results and being higher than the PSLR at the rising and falling intersection points. In the parameter setting of FBP, azimuth slice is more sensitive than distance, and too long synthetic aperture time can affect the quality of azimuth slice, at this time, the parameter should be adjusted to raise azimuth slice level.
In the above-described time-domain FBP algorithm, the back projection calculation amount of the imaging region is about The amount of phase interpolation calculation is about +.>The calculated amount of the coherent superposition is +.>The calculated amount of the three is about->Less than the traditional BP calculation amount +.>. With the change of the length of the sub-aperture and the range of the sub-imaging area, the larger the difference of the calculated amount is, the calculation cost and time are reducedThe more pronounced the effect.
Therefore, a user can perform various operations related to MB-SAR time domain imaging according to the self-defining requirements of related tasks such as platform parameters, aperture, region division and the like.
The earth observation device of the moon-based synthetic aperture radar provided by the 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 be correspondingly referred to each other.
Fig. 11 is a schematic structural diagram of a ground observation device of the moon-based synthetic aperture radar provided by the invention. Based on the foregoing content of any one of the foregoing embodiments, as shown in fig. 11, the apparatus includes an echo acquisition module 1101 and a coherent addition module 1102, where:
the echo acquisition module 1101 is configured to acquire time domain echo data observed by the moon-based synthetic aperture radar on an imaging area on the earth;
and the coherent superposition module 1102 is configured to coherently superimpose the time echo data based on each sub-aperture of the synthetic aperture of the month-based synthetic aperture radar and each sub-imaging area of the imaging area, and obtain an observation result of the imaging area.
Specifically, the echo acquisition module 1101 and the coherent addition module 1102 may be electrically connected.
The echo acquisition module 1101 may perform generation of time domain echo data based on MB-SAR parameters and spatial motion relationships based on any echo data generation method for SAR.
The coherent addition module 1102 may perform distance compression processing on the time domain echo data to obtain distance compressed time domain echo data; the BP algorithm can be executed for each sub-aperture and each sub-imaging area respectively, and an imaging result of the sub-imaging area under the sub-aperture is obtained; and then carrying out coherent superposition on imaging results of all sub-imaging areas under all sub-apertures, so that the actual influence of the whole imaging area can be obtained and used as an observation result of the imaging area.
Optionally, the coherent adding module 1102 may include:
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;
the imaging analysis sub-module is used for carrying out imaging analysis on the time domain echo data after the distance compression based on each sub-aperture and each sub-imaging area respectively to obtain an area image;
And the coherent superposition sub-module is used for carrying out coherent superposition on the images of each region to obtain an observation result.
Optionally, the imaging analysis sub-module may include:
the projection unit is used for respectively determining a target sampling point corresponding to each pixel point in the sub-imaging area on the central line of the sub-imaging area;
and the imaging unit is used for executing a backward projection algorithm based on each target sampling point and the time domain echo data after the distance compression to acquire an area image.
Optionally, the projection unit may be specifically configured to project each pixel point onto the central line based on the distance between the sub-aperture and each pixel point, to determine a projection point; and determining the sampling point closest to the projection point on the central line as a target sampling point.
Optionally, the center line is a diagonal of the sub-imaging region.
Optionally, the dividing submodule may include:
a sub-aperture dividing unit for obtaining an arithmetic square root of a 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 sub-apertures.
Optionally, the dividing submodule may include:
a sub-imaging area dividing unit for obtaining an arithmetic square root of a length in an azimuth direction and an arithmetic square root of a length in a distance direction; determining a second number based on the arithmetic square root of the length in the azimuth direction and determining a third number based on the arithmetic square root of the length in the distance direction; dividing the imaging area into a second number of parts in the azimuth direction and dividing the imaging area into a third number of parts in the distance direction to obtain each sub imaging area.
The earth observation device of the moon-based synthetic aperture radar provided by the embodiment of the invention is used for executing the earth observation method of the moon-based synthetic aperture radar, the implementation mode of the earth observation device is consistent with that of the earth observation method of the moon-based synthetic aperture radar provided by the invention, and the same beneficial effects can be achieved, and the description is omitted 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 of each of the foregoing embodiments. Therefore, the description and definition in the earth observation method of the moon-based synthetic aperture radar in the foregoing embodiments may be used for understanding the execution modules in the embodiments of the present invention.
According to the embodiment of the invention, the imaging analysis is carried out on the time domain echo data after the distance compression according to each sub-aperture and each sub-imaging area, and then the coherent superposition is carried out, so that the observation result is obtained, the defects of large time cost and the like of the traditional time domain solving algorithm can be overcome on the basis of avoiding complicated calculation steps of the frequency domain solving mode, the calculation cost and time can be reduced, the efficiency of earth observation of the lunar SAR can be improved, the possibility of applying the time domain solving algorithm in a long-distance and large-width MB-SAR scene can be increased, and the application prospect is better.
Fig. 12 is a schematic structural diagram of an electronic device according to the present invention, and as shown in fig. 12, the electronic device may include: processor 1210, communication interface (Communications Interface), 1220, memory 1230 and communication bus 1240, wherein processor 1210, communication interface 1220 and memory 1230 communicate with each other via communication bus 1240. Processor 1210 may invoke logic instructions in memory 1230 to perform a ground observation method for a month-based synthetic aperture radar, the method comprising: 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.
In addition, the logic instructions in the memory 1230 described above may be implemented in the form of software functional units and sold or used as a stand-alone product, stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method of the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The processor 1210 in the electronic device provided in the embodiment of the present application may call the logic instruction in the memory 1230, and its implementation manner is consistent with the implementation manner of the earth observation method of the month-based synthetic aperture radar provided in the present application, and may achieve the same beneficial effects, which are not described herein again.
In another aspect, the present invention also provides a computer program product comprising a computer program stored on a non-transitory computer readable storage medium, the computer program comprising program instructions which, when executed by a computer, are capable of performing the earth-looking method of a lunar-based synthetic aperture radar provided by the methods described above, the method comprising: 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.
When the computer program product provided in the embodiment of the present application is executed, the earth observation method of the lunar-based synthetic aperture radar is implemented, and the specific implementation manner thereof is consistent with the implementation manner described in the embodiment of the foregoing method, and the same beneficial effects can be achieved, which is not described herein again.
In yet another aspect, the present invention also provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, is implemented to perform the above-provided earth-looking method of a month-based synthetic aperture radar, the method comprising: 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.
When the computer program stored on the non-transitory computer readable storage medium provided in the embodiment of the present application is executed, the earth observation method of the lunar-based synthetic aperture radar is implemented, and the specific implementation manner is consistent with the implementation manner described in the embodiment of the foregoing method, and the same beneficial effects can be achieved, which is not repeated here.
The apparatus embodiments described above are merely illustrative, wherein elements illustrated as separate elements may or may not be physically separate, and elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on such understanding, the foregoing technical solutions may be embodied essentially or in part in the form of a software product, which may be stored in a computer-readable storage medium, such as a ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to perform the various embodiments or methods of some parts of the embodiments.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the 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.
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