A design method for multiple observation working mode of high-orbit SAR

Abstract

The present invention belongs to the technical field of synthetic aperture radars and discloses a method for designing a multiple observation working mode for a high-orbit SAR: Step 1: Calculate the satellite antenna beam scanning factor for different time periods of radar operation; Step 2: Use the satellite antenna beam scanning factor calculated in Step 1 according to the different time periods of radar operation to complete beam scanning in the first to fourth time periods; Step 3: Set the satellite antenna beam scanning factor according to the different time periods of radar operation to complete beam scanning in the fifth to ninth time periods; Step 4: Repeat Steps 2 and 3 in sequence to achieve continuous azimuth mapping. The present invention proposes a method for cyclically designing a multiple observation working mode, fully utilizing the advantage of the high-orbit SAR's ability to conduct long-term resident observations. By calculating the antenna beam scanning factors of the high-orbit SAR on satellites in different orbits, beam scanning is completed in time stages to achieve continuous azimuth mapping.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthetic aperture radar and relates to a method for designing a high-orbit SAR multiple observation working mode. Background Art

[0002] Spaceborne SAR multiple observation modes can generally be divided into two types. One is to obtain multi-view geometric and scattering information of the terrain features in the area by repeatedly observing the same area from different azimuth angles, thereby compensating for the serious information loss and poor image interpretation of single-view SAR systems. However, multi-view observations are generally only for specific target areas or target points, and their azimuth cannot achieve continuous mapping. The other type can achieve multiple observations of the area and the mapping swath in the azimuth is continuous.

[0003] The paper "A New Mode for Moving Target Monitoring with Spaceborne SAR Based on Hybrid-TOPS" proposes a method for multiple observations with low-orbit SAR. First, the hybridization factor is used to quantitatively describe the spaceborne SAR imaging mode. Based on this, a new mode for moving target monitoring is proposed by combining the TOPS mode with the inverse TOPS mode. This mode not only enables multiple observations of the same area but also provides continuous azimuth observation capability. However, this method does not account for the impact of Earth rotation on the operating mode design of high-orbit SAR, and instead equates the satellite's flight velocity with the ground beam velocity. Using this method would result in the inability to perform multiple observations and continuous azimuth mapping.

[0004] The paper "Multi-track Circular SAR Three-dimensional Joint Sparse Imaging Method" proposes a joint sparse reconstruction model based on multiple flyby information, integrating the sparse distribution characteristics of the imaging scene in the three dimensions of range, azimuth, and altitude, to achieve high-resolution three-dimensional imaging. Furthermore, to address the issue of the dramatic angular variation of backscattering characteristics of man-made targets such as buildings, a method of molecular aperture sparse constrained imaging followed by sub-aperture incoherent superposition is employed to improve the signal-to-noise ratio and other performance of the final three-dimensional imaging results. The use of molecular aperture processing during joint sparse reconstruction improves the target's interpretability. However, this method requires multiple radar passes to acquire information and does not address the problem of achieving multiple observations with a single pass.

[0005] In summary, the current multiple observation mode design method is not suitable for high-orbit SAR. Therefore, it is urgent to design a method based on a single high-orbit SAR flight that can achieve multiple observations. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for designing a multiple observation working mode of a high-orbit SAR, so as to solve the problem that the current multiple observation mode design method is not applicable to high-orbit SAR.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for designing a high-orbit SAR multiple observation working mode includes the following steps:

[0009] Step 1: Calculate the satellite antenna beam scanning factor at different time periods of radar operation;

[0010] Step 2: Use the satellite antenna beam scanning factor calculated in step 1 according to the different time periods of radar operation to complete the beam scanning in the first to fourth time periods. The specific sub-steps include the following:

[0011] Step 21: The radar operates in the first time period and the satellite antenna beam scanning factor is selected to be 0.075. At this time, the AB area is observed for the first time.

[0012] Step 22: The radar then operates in the second time period, selecting a satellite antenna beam scanning factor of 0.0376. At this time, the AB region is observed for the second time, and the BC region is observed for the first time.

[0013] Step 23: The radar then operates in the third time period, selecting the satellite antenna beam scanning factor as -0.075. At this time, the BC area is observed for the second time.

[0014] Step 24: The radar then operates in the fourth time period, selecting a satellite antenna beam scan factor of 0.0376. At this time, the BC region is observed for the third time, and the CD region is observed for the first time.

[0015] Step 3: Set the scanning factor of the satellite antenna beam according to the different time periods of radar operation to complete the beam scanning in the 5th to 9th time periods. The specific sub-steps include the following:

[0016] Step 31: The radar then operates in the fifth time period, selecting the satellite antenna beam scanning factor as 0.075. At this time, the CD area is observed for the second time.

[0017] Step 32: The radar then operates in the sixth time period, selecting a satellite antenna beam scanning factor of 0.0376. At this time, the CD region is observed for the third time, and the DE region is observed for the first time.

[0018] Step 33: The radar then operates in the seventh time period, selecting a satellite antenna beam scanning factor of -0.075. At this time, the CD region is observed for the fourth time, and the DE region is observed for the second time.

[0019] Step 34: The radar then operates in the eighth time period, selecting a satellite antenna beam scanning factor of 0.0376. At this time, the DE region is observed for the third time, and the EF region is observed for the first time.

[0020] Step 35: The radar then operates in the ninth time period, selecting a satellite antenna beam scanning factor of 0.075. At this time, the EF region is observed for the second time.

[0021] Step 4: Repeat steps 2 and 3 in sequence to achieve continuous azimuth mapping.

[0022] Furthermore, the satellite antenna beam scanning factor ,in, is the satellite's flight speed, is the scanning speed of the beam ground.

[0023] The advantages of the present invention compared with the prior art are:

[0024] The proposed multiple observation mode for high-orbit SAR (SAR) takes into account the impact of Earth's rotation on the operating mode design. It also proposes a cyclical design for the multiple observation mode, leveraging the long-term resident observation capabilities of high-orbit SAR. By calculating the antenna beam scanning factors of high-orbit SAR on satellites in different orbits, the beam scanning is completed in time phases, enabling continuous azimuth mapping and thus continuous multiple observations of the target area. This invention can be applied to platforms such as medium-orbit SAR (MESAR) and low-orbit ultra-high-resolution SAR (ULSAR). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of the method for designing a high-orbit SAR multiple observation working mode of the present invention;

[0026] Figure 2 Schematic diagram of the STK simulation hybrid new multiple observation working mode.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0028] The design method of high-orbit SAR multiple observation working mode provided by the present invention is as follows: Figure 1 As shown, the following steps are included:

[0029] Step 1: Calculate the satellite antenna beam scanning factor at different time periods of radar operation.

[0030] The satellite antenna beam scanning factor is defined as the ratio of the satellite flight speed to the beam ground scanning speed. Assume that the satellite flight speed is , the scanning speed of the beam ground is , then the beam scanning factor .

[0031] Step 2: According to the different time periods of radar operation, the satellite antenna beam scanning factor calculated in step 1 is used to complete the beam scanning in the 1st to 4th time periods.

[0032] In the prior art, step 2 generally includes the following sub-steps:

[0033] Step 1: Select 6 observation points along the satellite flight direction according to observation needs: point A to point F;

[0034] Step 2: The radar operates in the first time period and the satellite antenna beam scanning factor is selected to be 0.5. At this time, the AB area is observed for the first time; the AB area is the area between point A and point B.

[0035] Step 3: The radar then operates in the second time period, selecting a satellite antenna beam scan factor of 0.25. At this time, the AB region is observed for the second time, and the BC region is observed for the first time; the BC region is the area between point B and point C.

[0036] Step 4: The radar then operates in the third time period, selecting the satellite antenna beam scanning factor as -0.5. At this time, the BC area is observed for the second time.

[0037] Step 5: The radar then operates in the fourth time period, selecting a satellite antenna beam scan factor of 0.25. At this time, area BC is observed for the third time, and area CD is observed for the first time; area CD is the area between points C and D.

[0038] The above-mentioned operation steps of the prior art do not take into account the impact of the Earth's rotation on the working mode design. It equates the satellite's flight speed with the ground beam speed. However, in high-orbit SAR, the Earth's rotation will affect the working mode design. Therefore, the above-mentioned satellite antenna beam scanning factor needs to be further multiplied by the Earth's rotation improvement factor. To simplify the design, the present invention considers the Earth's rotation improvement factor as 0.15. At this time, the working mode of the high-orbit SAR can be described as:

[0039] Step 21: Select six observation points along the satellite flight direction according to observation needs: point A to point F;

[0040] Step 22: The radar operates in the first time period and the satellite antenna beam scanning factor is selected to be 0.075. At this time, the first observation of the AB area is completed;

[0041] Step 22: The radar then operates in the second time period, selecting a satellite antenna beam scan factor of 0.0376. At this time, the AB region is observed again, and the BC region completes its first observation.

[0042] Step 24: The radar then operates in the third time period, selecting a satellite antenna beam scanning factor of -0.075. At this time, the second observation of the BC region is completed.

[0043] In step 25, the radar then operates in the fourth time period and selects the satellite antenna beam scanning factor as 0.0376. At this time, the BC area is observed for the third time and the CD area is observed for the first time.

[0044] Step 3: Set the scanning factor of the satellite antenna beam according to the different time periods of radar operation, and complete the beam scanning in the 5th to 9th time periods.

[0045] In the prior art, step three generally includes the following sub-steps:

[0046] S1, the radar then operates in the fifth time period, selecting the satellite antenna beam scanning factor as 0.5. At this time, the CD area is observed for the second time;

[0047] In S2, the radar then operates in the sixth time period, selecting a satellite antenna beam scanning factor of 0.25. At this time, the CD region is observed for the third time, and the DE region is observed for the first time. The DE region is the area between points D and E.

[0048] In S3, the radar then operates in the seventh time period, selecting the satellite antenna beam scanning factor as -0.5. At this time, the CD area is observed for the third time, and the DE area is observed for the second time.

[0049] S4, the radar then operates in the eighth time period, selecting the satellite antenna beam scanning factor as 0.25. At this time, the DE area is observed for the third time, and the EF area is observed for the first time; the EF area is the area between points E and F.

[0050] S5, the radar then operates in the 9th time period, selecting the satellite antenna beam scanning factor as 0.5. At this time, the EF area is observed for the second time.

[0051] Similarly, the above-mentioned prior art operation steps do not take into account the impact of Earth's rotation on the operating mode design, and equate the satellite's flight speed with the ground beam speed. However, in high-orbit SAR, Earth's rotation will affect the operating mode design. Therefore, the above-mentioned beam scanning factor needs to be further multiplied by the Earth's rotation improvement factor. To simplify the design, the present invention considers the Earth's rotation improvement factor to be 0.15. In this case, the operating mode of the high-orbit SAR can be described as:

[0052] Step 31: The radar then operates in the fifth time period, selecting the satellite antenna beam scanning factor as 0.075. At this time, the CD area is observed for the second time.

[0053] Step 32: The radar then operates in the sixth time period, selecting a satellite antenna beam scanning factor of 0.0376. At this time, the CD region is observed for the third time, and the DE region is observed for the first time.

[0054] Step 33: The radar then operates in the seventh time period, selecting a satellite antenna beam scanning factor of -0.075. At this time, the CD region is observed for the fourth time, and the DE region is observed for the second time.

[0055] Step 34: The radar then operates in the eighth time period, selecting a satellite antenna beam scanning factor of 0.0376. At this time, the DE region is observed for the third time, and the EF region is observed for the first time.

[0056] In step 35 , the radar then operates in the ninth time period and selects the satellite antenna beam scanning factor to be 0.075. At this time, the EF area is observed for the second time.

[0057] Step 4: Repeat steps 2 and 3 in sequence to achieve continuous azimuth mapping.

[0058] In order to verify the feasibility and effectiveness of the method of the present invention, the following parameters are selected for simulation verification.

[0059] The satellite orbit altitude is 42164km, the orbit inclination is 20°, the eccentricity is 0°, the argument of perigee is 88°, the true anomaly is 180°, the right side observation, the radar antenna downward viewing angle is 3°, and the antenna beam width is 0.6°. The working mode is designed as follows Figure 2 shown.

[0060] Figure 2 In the example, the radar operates in the first time period, selecting a satellite antenna beam scan factor of 0.075. At this point, the AB region completes its first observation. The radar then operates in the second time period, selecting a satellite antenna beam scan factor of 0.0376. At this point, the AB region is observed for the second time, and the BC region is observed for the first time. The radar then operates in the third time period, selecting a satellite antenna beam scan factor of -0.075. At this point, the BC region is observed for the second time. The radar then operates in the fourth time period, selecting a satellite antenna beam scan factor of 0.0376. At this point, the BC region is observed for the third time, and the CD region is observed for the first time. It can be seen that, starting from point B, each region is observed three times, all under the same observation conditions. This indicates that the method of the present invention achieves multiple, continuous observations of the target region. In actual engineering implementation, different beam scan factor combinations can be set based on the swath width, target location, and resolution requirements.

[0061] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for designing a high-orbit SAR multiple observation working mode, characterized in that: The steps include: Step 1: Calculate the satellite antenna beam scanning factor at different time periods of radar operation; Satellite antenna beam scanning factor ,in, is the satellite's flight speed, is the scanning speed of the beam ground; Step 2: Use the satellite antenna beam scanning factor calculated in step 1 according to the different time periods of radar operation to complete the beam scanning in the first to fourth time periods. The specific sub-steps include the following: Step 21: The radar operates in the first time period and the satellite antenna beam scanning factor is selected to be 0.

075. At this time, the AB area is observed for the first time. Step 22: The radar then operates in the second time period, selecting a satellite antenna beam scanning factor of 0.0376. At this time, the AB region is observed for the second time, and the BC region is observed for the first time. Step 23: The radar then operates in the third time period, selecting the satellite antenna beam scanning factor as -0.

075. At this time, the BC area is observed for the second time. Step 24: The radar then operates in the fourth time period, selecting a satellite antenna beam scan factor of 0.0376. At this time, the BC region is observed for the third time, and the CD region is observed for the first time. Step 3: Set the scanning factor of the satellite antenna beam according to the different time periods of radar operation to complete the beam scanning in the 5th to 9th time periods. The specific sub-steps include the following: Step 31: The radar then operates in the fifth time period, selecting the satellite antenna beam scanning factor as 0.

075. At this time, the CD area is observed for the second time. Step 32: The radar then operates in the sixth time period, selecting a satellite antenna beam scanning factor of 0.0376. At this time, the CD region is observed for the third time, and the DE region is observed for the first time. Step 33: The radar then operates in the seventh time period, selecting a satellite antenna beam scanning factor of -0.

075. At this time, the CD region is observed for the fourth time, and the DE region is observed for the second time. Step 34: The radar then operates in the eighth time period, selecting a satellite antenna beam scanning factor of 0.0376. At this time, the DE region is observed for the third time, and the EF region is observed for the first time. Step 35: The radar then operates in the ninth time period, selecting a satellite antenna beam scanning factor of 0.

075. At this time, the EF region is observed for the second time. Step 4: Repeat steps 2 and 3 in sequence to achieve continuous azimuth mapping.

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