Design method for novel multi-observation working mode of high-orbit SAR (Synthetic Aperture Radar)

Abstract

The invention belongs to the technical field of synthetic aperture radars, and discloses a novel multi-observation working mode design method for a high-orbit SAR (Synthetic Aperture Radar). The novel multi-observation working mode design method comprises the following steps of: 1, calculating satellite antenna beam scanning factors in different working time periods of the radar; 2, according to different working time periods of the radar, the satellite antenna beam scanning factors obtained through calculation in the step 1 are adopted, and beam scanning in the first time period to the fourth time period is completed; 3, scanning factors of satellite antenna beams are set according to different working time periods of the radar, and beam scanning in the fifth time period to the ninth time period is completed; and 4, repeating the step 2 and the step 3 in sequence to realize azimuth continuous surveying and mapping. According to the method, a multi-observation working mode cycle design mode is provided, the advantage that the high-orbit SAR can stay for observation for a long time is fully utilized, the antenna beam scanning factors of the high-orbit SAR in different orbit satellites are calculated, beam scanning is completed in different time stages, and azimuth continuous surveying and mapping are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthetic aperture radar, and relates to a design method for a new multi - observation working mode of high - orbit SAR. Background Technique

[0002] The multi - observation mode of space - borne SAR can generally be divided into two types. One is to obtain the multi - view geometric information and scattering information of ground objects in a region through repeated observations of the same region from different azimuth angles, so as to make up for the serious lack of information and poor image interpretability of a single - view SAR system. However, multi - angle observations are generally only for specific target regions or target points, and continuous mapping cannot be achieved in the azimuth direction. The other type can achieve multiple observations of a region and the mapping band in the azimuth direction is continuous.

[0003] The literature "A New Space - borne SAR Moving Target Monitoring Mode Based on Hybrid·TOPS" gives a method for multi - observation of low - orbit SAR. First, the imaging mode of space - borne SAR is quantitatively described by using the mixing factor. On this basis, a new moving target monitoring mode is proposed through the combination of TOPS mode and inverse TOPS mode. This mode can not only achieve multiple observations of the same region, but also has the ability of continuous observation in the azimuth direction. However, this method does not consider the influence of the earth's rotation on the working mode design of high - orbit SAR, and equates the satellite's flight speed to the ground beam speed. If the method in the literature is adopted, multiple observations cannot be achieved, and continuous mapping in the azimuth direction cannot be realized either.

[0004] The literature "Multi - Track Circular - Track SAR 3D Joint Sparse Imaging Method" proposes to use multi - pass information, comprehensively utilize the sparse distribution characteristics of the imaging scene in three dimensions of range, azimuth and height, establish a joint sparse reconstruction model to achieve high - resolution 3D imaging. Further, aiming at the problem that the backscattering characteristics of artificial targets such as buildings change violently with angles, a method of non - coherent superposition of sub - apertures after sparse constraint imaging with molecular apertures is adopted to improve the signal - to - noise ratio and other performance of the final 3D imaging results. When performing joint sparse reconstruction, the use of molecular apertures improves the interpretability of targets. However, this method requires the radar to pass multiple times to collect information and cannot solve the problem of achieving multiple observations in one pass.

[0005] In summary, the current design methods for multi - observation modes are not applicable to high - orbit SAR. Therefore, there is an urgent need to design a method that can achieve multiple observations based on a single pass of high - orbit SAR. Summary of the Invention

[0006] The purpose of the present invention is to provide a design method for a new multi - observation working mode of high - orbit SAR to solve the problem that the current design methods for multi - observation modes are not applicable to high - orbit SAR.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A design method for a new multiple observation working mode of a high-orbit SAR includes the following steps: Step 1: Calculate the satellite antenna beam scanning factors for different time periods of radar operation; Step 2: According to the satellite antenna beam scanning factors obtained in Step 1 for different time periods of radar operation, complete the beam scanning in the 1st to 4th time periods, which specifically includes the following sub-steps: Step 21, when the radar operates in the 1st time period, select the satellite antenna beam scanning factor as 0.075. At this time, the AB area is observed for the 1st time; Step 22, then the radar operates in the 2nd time period, select the satellite antenna beam scanning factor as 0.0376. At this time, the AB area is observed for the 2nd time, and the BC area is observed for the 1st time; Step 23, then the radar operates in the 3rd time period, select the satellite antenna beam scanning factor as -0.075. At this time, the BC area is observed for the 2nd time; Step 24, then the radar operates in the 4th time period, select the satellite antenna beam scanning factor as 0.0376. At this time, the BC area is observed for the 3rd time, and the CD area is observed for the 1st time; Step 3: According to the satellite antenna beam scanning factors set for different time periods of radar operation, complete the beam scanning in the 5th to 9th time periods, which specifically includes the following sub-steps: Step 31, then the radar operates in the 5th time period, select the satellite antenna beam scanning factor as 0.075. At this time, the CD area is observed for the 2nd time; Step 32, then the radar operates in the 6th time period, select the satellite antenna beam scanning factor as 0.0376. At this time, the CD area is observed for the 3rd time, and the DE area is observed for the 1st time; Step 33, then the radar operates in the 7th time period, select the satellite antenna beam scanning factor as -0.075. At this time, the CD area is observed for the 4th time, and the DE area is observed for the 2nd time; Step 34, then the radar operates in the 8th time period, select the satellite antenna beam scanning factor as 0.0376. At this time, the DE area is observed for the 3rd time, and the EF area is observed for the 1st time; Step 35, then the radar operates in the 9th time period, select the satellite antenna beam scanning factor as 0.075. At this time, the EF area is observed for the 2nd time; Step 4: Repeat Step 2 and Step 3 in sequence to achieve continuous mapping in the azimuth direction.

[0008] Further, the satellite antenna beam scanning factor , where is the flight speed of the satellite, is the scanning speed of the beam on the ground.

[0009] The advantages of the present invention compared with the prior art are as follows: The multiple observation mode adapted to high-orbit SAR proposed by the present invention takes into account the influence of the earth's rotation on the design of the working mode; at the same time, a cyclic design method for the multiple observation working mode is proposed, making full use of the advantage that high-orbit SAR can stay for a long time for observation. By calculating the antenna beam scanning factor of high-orbit SAR on satellites with different orbits, the beam scanning is completed in different time stages, realizing continuous mapping in the azimuth direction, and thus realizing continuous multiple observations of the target area. The present invention can be extended and applied to platforms such as medium-orbit SAR and low-orbit ultra-high-resolution SAR. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a flowchart of the design method for the new multiple observation working mode of high-orbit SAR of the present invention; Figure 2 is a schematic diagram of the STK simulation of the new multiple observation working mode.

[0011] The present invention will be further described in detail below with reference to the drawings and embodiments. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] The design method for the new multiple observation working mode of high-orbit SAR given by the present invention, as Figure 1 shown, includes the following steps: Step 1: Calculate the satellite antenna beam scanning factors for different time periods when the radar is working.

[0013] 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 , and the beam ground scanning speed is , then the beam scanning factor .

[0014] Step 2: Complete the beam scanning in the 1st to 4th time periods according to the satellite antenna beam scanning factors calculated in Step 1 for different time periods when the radar is working.

[0015] In the prior art, Step 2 usually includes the following sub-steps: Step 1, select 6 observation points according to the observation needs along the satellite flight direction: Point A to Point F; Step 2, when the radar is working in the 1st time period, select the satellite antenna beam scanning factor 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; Step 3: The radar then operates in the second time period, and the satellite antenna beam scanning factor is selected as 0.25. At this time, the AB area is observed for the second time, and the BC area is observed for the first time. The BC area is the area between point B and point C. Step 4: The radar then operates in the third time period, and the satellite antenna beam scanning factor is selected as -0.5. At this time, the BC area is observed for the second time. Step 5: The radar then operates in the fourth time period, and the satellite antenna beam scanning factor is selected as 0.25. At this time, the BC area is observed for the third time, and the CD area is observed for the first time. The CD area is the area between point C and point D. The above operation steps of the prior art do not take into account the influence of the Earth's rotation on the design of the working mode. It equates the flight speed of the satellite to the ground beam speed. However, in high-orbit SAR, the Earth's rotation will have an impact on the design of the working mode. Therefore, the above satellite antenna beam scanning factor needs to be further multiplied by the Earth's rotation improvement factor. For the sake of simplifying the design, the Earth's rotation improvement factor is considered as 0.15 here. At this time, the working mode of high-orbit SAR can be described as follows: Step 21: Select 6 observation points according to the observation needs along the satellite flight direction: point A to point F. Step 22: The radar operates in the first time period, and the satellite antenna beam scanning factor is selected as 0.075. At this time, the AB area completes the first observation. Step 22: The radar then operates in the second time period, and the satellite antenna beam scanning factor is selected as 0.0376. At this time, the AB area is observed again, and the BC area completes the first observation. Step 24: The radar then operates in the third time period, and the satellite antenna beam scanning factor is selected as -0.075. At this time, the BC area completes the second observation. Step 25: The radar then operates in the fourth time period, and the satellite antenna beam scanning factor is selected 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.

[0016] Step 3: Set the scanning factor of the satellite antenna beam according to different time periods when the radar operates, and complete the beam scanning in the 5th to 9th time periods.

[0017] In the prior art, Step 3 generally includes the following sub-steps: S1: The radar then operates in the fifth time period, and the satellite antenna beam scanning factor is selected as 0.5. At this time, the CD area is observed for the second time. S2. Next, the radar operates in the 6th time period and selects the satellite antenna beam scanning factor as 0.25. At this time, the CD area is observed for the 3rd time, and the DE area is observed for the 1st time. The DE area is the area between point D and point E. S3. Next, the radar operates in the 7th time period and selects the satellite antenna beam scanning factor as -0.5. At this time, the CD area is observed for the 3rd time, and the DE area is observed for the 2nd time. S4. Next, the radar operates in the 8th time period and selects the satellite antenna beam scanning factor as 0.25. At this time, the DE area is observed for the 3rd time, and the EF area is observed for the 1st time. The EF area is the area between point E and point F. S5. Next, the radar operates in the 9th time period and selects the satellite antenna beam scanning factor as 0.5. At this time, the EF area is observed for the 2nd time.

[0018] Similarly, the above operation steps of the prior art do not consider the influence of the earth's rotation on the design of the working mode, and the flight speed of the satellite is equivalent to the ground beam speed. However, in high-orbit SAR, the earth's rotation will affect the design of the working mode. Therefore, the above beam scanning factor needs to be further multiplied by the earth's rotation improvement factor. For the sake of simplifying the design, the earth's rotation improvement factor is considered as 0.15 here. At this time, the working mode of high-orbit SAR can be described as follows: Step 31. Next, the radar operates in the 5th time period and selects the satellite antenna beam scanning factor as 0.075. At this time, the CD area is observed for the 2nd time. Step 32. Next, the radar operates in the 6th time period and selects the satellite antenna beam scanning factor as 0.0376. At this time, the CD area is observed for the 3rd time, and the DE area is observed for the 1st time. Step 33. Next, the radar operates in the 7th time period and selects the satellite antenna beam scanning factor as -0.075. At this time, the CD area is observed for the 4th time, and the DE area is observed for the 2nd time. Step 34. Next, the radar operates in the 8th time period and selects the satellite antenna beam scanning factor as 0.0376. At this time, the DE area is observed for the 3rd time, and the EF area is observed for the 1st time. Step 35. Next, the radar operates in the 9th time period and selects the satellite antenna beam scanning factor as 0.075. At this time, the EF area is observed for the 2nd time.

[0019] Step Four: Repeat the operation steps of Step Two and Step Three in sequence to achieve continuous azimuth mapping.

[0020] To verify the feasibility and effectiveness of the method of the present invention, the following parameters are selected for simulation verification.

[0021] The satellite has an orbital altitude of 42164 Km, an orbital inclination of 20°, an eccentricity of 0°, an argument of perigee of 88°, a true anomaly of 180°, right-side view observation, a radar antenna downwards angle of 3°, and an antenna beam width of 0.6°. The working mode is designed as follows Figure 2 as shown

[0022] Figure 2 In the figure, when the radar works in the first time period, the satellite antenna beam scanning factor is selected as 0.075. At this time, the AB area completes the first observation; then the radar works in the second time period, and the satellite antenna beam scanning factor is selected as 0.0376. At this time, the AB area is observed for the second time, and the BC area is observed for the first time; then the radar works in the third time period, and the satellite antenna beam scanning factor is selected as -0.075. At this time, the BC area is observed for the second time; then the radar works in the fourth time period, and the satellite antenna beam scanning factor is selected 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. It can be seen that starting from point B, each area is observed 3 times, and the observation conditions are the same. It can be seen that the method of the present invention realizes continuous multiple observations of the target region. In actual engineering implementation, different beam scanning factor combinations can be set according to the width of the mapping strip, the position of the target, and the resolution requirements

[0023] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art

Claims

1. A design method for a new multiple observation working mode of a high-orbit SAR, characterized in that: The steps include: Step 1: Calculate the satellite antenna beam scanning factor at different time periods of radar operation; 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, which specifically includes the following sub-steps: Step 21, the radar works 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, and the satellite antenna beam scanning factor is selected to be 0.0376. At this time, the AB area is observed for the second time, and the BC area is observed for the first time; Step 23, the radar then operates in the third time period, and the satellite antenna beam scanning factor is selected to be -0.075, at which time the BC area is observed for the second time; Step 24, the radar then operates in the fourth time period, and the satellite antenna beam scanning factor is selected to be 0.0376. At this time, the BC area is observed for the third time, and the CD area is observed for the first time; Step 3: Set the scanning factor of the satellite antenna beam according to the different time periods of the radar operation, and complete the beam scanning in the 5th to 9th time periods, which specifically includes the following sub-steps: Step 31, the radar then operates in the fifth time period, and the satellite antenna beam scanning factor is selected to be 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, and the satellite antenna beam scanning factor is selected to be 0.0376. At this time, the CD area is observed for the third time, and the DE area is observed for the first time; Step 33, the radar then operates in the 7th time period, and the satellite antenna beam scanning factor is selected to be -0.

075. At this time, the CD area is observed for the 4th time, and the DE area is observed for the 2nd time; Step 34, the radar then operates in the eighth time period, and the satellite antenna beam scanning factor is selected to be 0.0376. At this time, the DE area is observed for the third time, and the EF area is observed for the first time; Step 35, the radar then operates in the 9th time period, and the satellite antenna beam scanning factor is selected to be 0.

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

2. The design method of a new multiple observation working mode of a high-orbit SAR as claimed in claim 1, characterized in that: Satellite antenna beam scanning factor ,in, is the satellite’s flight speed, is the scanning speed of the beam ground.

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