A Spaceborne SAR Wide Swath Mode Design Method and System Based on Payload and Attitude Coordination

Abstract

This invention provides a design method and system for a wide-swath SAR mode based on payload and attitude coordination. The implementation steps are as follows: calculate the satellite side-swing angle; maneuver the satellite around the Xb axis of the system to the side-swing angle; calculate the payload electronic scanning compensation angle and the satellite attitude elevation angle; maneuver the satellite around the Yb axis to the elevation angle to maintain forward-looking imaging; the payload rapidly switches the SAR antenna range direction radio beam to achieve forward-looking ScanSAR imaging; repeat the above steps to sequentially complete forward-looking and backward-looking ScanSAR imaging. This invention utilizes the payload's large-angle electronic scanning capability and the satellite platform's rapid attitude maneuvering capability in an integrated imaging design to achieve wide-swath SAR imaging. Simultaneously, designing the antenna as a one-dimensional electronic scanner greatly simplifies the antenna structure, reduces the overall satellite weight and cost, and meets users' needs for lightweight, low-cost SAR satellites.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of space systems, in particular, to a spaceborne SAR large swath mode design method and system based on load and attitude cooperation. BACKGROUND

[0002] Spaceborne synthetic aperture radar is an all-weather and all-day active ground observation method, which plays an important application in high-resolution observation, natural resource monitoring, and ocean monitoring. With the development of spaceborne SAR application demand, low-cost and lightweight SAR satellites have become a hot spot in the development of spaceborne SAR systems. In terms of spaceborne SAR satellite demand, large swath imaging mode of the load is of great significance to meet the requirements of large-area and wide-coverage precise observation. Although the parabolic antenna system SAR satellite realizes lightweight and low-cost, it cannot realize large swath imaging of the load due to its limited beam scanning capability. The two-dimensional planar phased array antenna system SAR satellite can realize large swath imaging of the load through the distance beam ScanSAR scanning mode, but ScanSAR scanning mode often reduces the azimuth resolution as a trade-off for wide observation bandwidth. At the same time, the two-dimensional planar phased array antenna system SAR satellite needs a large number of T / R components in the two-dimensional direction of the antenna, which greatly increases the weight, power consumption, cost, and engineering development difficulty of the whole satellite.

[0003] After searching, there are many invention patents and papers on the method of spaceborne SAR large swath mode, but there are essential differences in the method design compared with the present application, as follows:

[0004] Xian University of Electronic Science and Technology Sun Guangcai et al. invented a spaceborne SAR beam scanning method based on parabolic antenna, patent application number 201910533091.8, which uses parabolic antenna to save the manufacturing cost of spaceborne SAR antenna, but due to the limitation of the parabolic antenna's own electric scanning capability, the distance imaging swath is small.

[0005] Xian Institute of Space Radio Technology Feng Fan et al. invented an on-orbit implementation design method of parabolic spaceborne SAR mosaic mode, patent application number 202010752732.1, which proposed a mosaic mode design method for parabolic antenna system SAR satellite. Although this method uses multi-subblock splicing, due to the limitation of the parabolic antenna's own electric scanning capability, it cannot realize large swath imaging of the load and instantaneous switching of any wave position.

[0006] The TerraSAR-X satellite scanning mode abroad adopts a traditional ScanSAR mode (article name: TerraSAR-X Image Product Guide) to realize, wherein the resolution is designed as 16 m, and the range width is designed as 100 km. If the design method of the application is adopted, the resolution remains unchanged, and the range width can reach 300 km. The narrow scanning mode and the wide scanning mode of the Gaofen-3 satellite at home both adopt the traditional ScanSAR mode (article name: Gaofen-3 satellite overall design and key technology, Gaofen-3 satellite SAR working mode and load design), wherein the resolution of the narrow scanning mode is designed as 50 m, and the range width is designed as 300 km. If the design method of the application is adopted, the resolution remains unchanged, and the range width can reach 900 km.

[0007] Therefore, it is necessary to propose a new technical solution to improve the above technical problems. SUMMARY

[0008] In view of the defects in the prior art, the purpose of the application is to provide a load and attitude cooperating satellite-borne SAR large-width mode design method and system.

[0009] According to the load and attitude cooperating satellite-borne SAR large-width mode design method provided by the application, the method comprises the following steps:

[0010] Step S1: calculating a satellite side swing angle; the satellite is maneuvered to a platform side swing angle around the Xb axis of the body frame under a two-dimensional guiding attitude;

[0011] Step S2: calculating an electric scanning compensation angle and an attitude pitch angle according to the satellite side swing angle, a downward-looking angle and an azimuth oblique angle; the satellite platform drives the SAR antenna electric wave beam to complete the azimuth forward oblique angle scanning through the attitude maneuver around the Yb axis of the body frame, so that the satellite remains in the forward oblique imaging state;

[0012] Step S3: within the imaging time range, the load completes the forward oblique ScanSAR imaging through the rapid switching of the SAR antenna distance electric wave beam;

[0013] Step S4: repeating the above steps S1-S3, the load sequentially completes the forward oblique, rear oblique ScanSAR imaging within the imaging time range.

[0014] Preferably, in the step S1, the selection of the satellite side swing angle is related to the satellite task. When the satellite is mainly used for multi-target observation, the side swing angle is set to 0°, the satellite keeps the flat flight mode, and the distance direction beam of the SAR antenna is switched; when the satellite is mainly used for high-resolution imaging, the platform side swing angle can be calculated according to the look-down angle, the satellite is maneuvered around the Xb axis of the body frame to a fixed angle, and the beam scanning is completed by cooperating with the SAR antenna beam; when the side swing angle is set to a positive value, the satellite keeps the left side view working mode; when the side swing angle is set to a negative value, the satellite keeps the right side view working mode; and when the side swing angle is set to zero, the satellite keeps the flat flight working mode.

[0015] Preferably, in the step S2, the SAR imaging is completed by cooperating the satellite attitude and the load. Before each imaging, a distance direction beam scanning compensation angle θbL1 is provided for the load, and an attitude pitch angle θb1 is provided for the satellite platform; θbL1 and θb1 are calculated according to the satellite side swing angle φcs1, the look-down angle θL1 and the azimuth oblique angle θ1 through the coordinate conversion relationship of and θ bL = arsin[sin(θ L - φ cs )·cosθ].

[0016] Preferably, in the step S3, a one-dimensional planar phased array system SAR antenna is used for distance direction large angle beam scanning.

[0017] Preferably, the step S4 includes the following steps:

[0018] Step S4.1: the satellite is maneuvered around the Xb axis of the body frame to a second platform side swing angle φcs2 under the two-dimensional guidance attitude;

[0019] Step S4.2: the beam scanning compensation angle θbL2 and the attitude pitch angle θb2 are calculated according to the satellite side swing angle φcs2, the look-down angle θL2 and the azimuth oblique angle θ2, the load completes the look-down angle scanning through the distance direction beam of the SAR antenna, and the satellite platform completes the scanning of the azimuth oblique angle from the front oblique view to the positive side view by maneuvering the attitude around the Yb axis of the body frame to drive the SAR antenna beam;

[0020] Step S4.3: within the second imaging time range, the load completes the positive side view ScanSAR strip scanning imaging through the distance direction beam fast switching;

[0021] Step S4.4: the satellite is maneuvered again around the Xb axis of the body frame to a third platform side swing angle φcs3 under the two-dimensional guidance attitude;

[0022] Step S4.5: according to the satellite side swing angle φcs3, the downward-looking angle θL3 and the azimuth oblique angle θ3, the electrical scanning compensation angle θbL3 and the attitude pitch angle θb3 are calculated, the load completes the downward-looking angle scanning through the SAR antenna range electrical beam, and the satellite platform completes the azimuth oblique angle scanning from the normal side view to the rear oblique view through the attitude maneuver around the Yb axis of the body.

[0023] Step S4.6: in the third imaging time range, the load completes the rear oblique view ScanSAR strip scanning imaging through the range electrical beam switching.

[0024] The application further provides a satellite-borne SAR wide swath mode design system based on load and attitude cooperation, which comprises the following modules.

[0025] Module M1: calculating the satellite side swing angle; the satellite is maneuvered around the Xb axis of the body to the platform side swing angle under the two-dimensional guided attitude.

[0026] Module M2: calculating the electrical scanning compensation angle and the attitude pitch angle according to the satellite side swing angle, the downward-looking angle and the azimuth oblique angle; the satellite platform completes the azimuth forward oblique angle scanning through the attitude maneuver around the Yb axis of the body, so that the satellite remains in the forward oblique imaging state.

[0027] Module M3: in the imaging time range, the load completes the forward oblique view ScanSAR imaging through the SAR antenna range electrical beam switching.

[0028] Module M4: repeatedly triggering the above-mentioned modules M1-M3 to perform work, and the load sequentially completes the normal side view, the rear oblique view ScanSAR imaging in the imaging time range.

[0029] Preferably, in the module M1, the selection of the satellite side swing angle is related to the satellite task, when the satellite takes the multi-target observation as the main task, the side swing angle is set to 0°, the satellite remains in the flat flying mode, and the range electrical beam switching is completed through the SAR antenna; if the satellite takes the high-resolution imaging as the main task, the platform side swing angle can be calculated according to the downward-looking angle, the satellite is maneuvered to a fixed angle around the Xb axis of the body, and the beam scanning is completed through the cooperation of the SAR antenna electrical beam; when the side swing angle is set to a positive value, the satellite remains in the left side view working mode; when the side swing angle is set to a negative value, the satellite remains in the right side view working mode; and when the side swing angle is set to zero, the satellite remains in the flat flying working mode.

[0030] Preferably, in the module M2, the satellite attitude and the load are adopted to complete the SAR imaging, before each imaging, a range electrical beam scanning compensation angle θbL1 is provided for the load, and an attitude pitch angle θb1 is provided for the satellite platform; θbL1 and θb1 are calculated according to the satellite side swing angle φcs1, the downward-looking angle θL1 and the azimuth oblique angle θ1 parameters through the following formula: and θ bL = arsin[sin(θ L - φ cs )cos θ] coordinate conversion relationship is calculated.

[0031] Preferably, in the module M3, a one-dimensional planar phased array system SAR antenna is used to scan a large angle of the electric wave beam in the range direction.

[0032] Preferably, the module M4 comprises the following modules:

[0033] Module M4.1: the satellite is maneuvered to a second platform side swing angle φcs2 around the Xb axis of the body system under the two-dimensional guided attitude.

[0034] Module M4.2: the electric scanning compensation angle θbL2 and the attitude pitch angle θb2 are calculated according to the satellite side swing angle φcs2, the downward-looking angle θL2 and the azimuth oblique angle θ2, the downward-looking angle scanning is completed by the SAR antenna range electric wave beam, and the satellite platform completes the scanning of the azimuth oblique angle from the forward oblique view to the normal side view by driving the SAR antenna electric wave beam through the attitude maneuver around the Yb axis of the body system.

[0035] Module M4.3: in the second imaging time range, the normal side view ScanSAR strip scanning imaging is completed by the range electric wave beam.

[0036] Module M4.4: the satellite is maneuvered to a third platform side swing angle φcs3 around the Xb axis of the body system under the two-dimensional guided attitude.

[0037] Module M4.5: the electric scanning compensation angle θbL3 and the attitude pitch angle θb3 are calculated according to the satellite side swing angle φcs3, the downward-looking angle θL3 and the azimuth oblique angle θ3, the downward-looking angle scanning is completed by the SAR antenna range electric wave beam, and the satellite platform completes the scanning of the azimuth oblique angle from the normal side view to the rear oblique view by driving the SAR antenna electric wave beam through the attitude maneuver around the Yb axis of the body system.

[0038] Module M4.6: in the third imaging time range, the rear oblique view ScanSAR strip scanning imaging is completed by the range electric wave beam.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] 1. Compared with the traditional ScanSAR mode, the method proposed in the present application adopts the forward oblique view ScanSAR, the normal side view ScanSAR and the rear oblique view ScanSAR scanning and splicing imaging in the range direction, and the range width can be increased by 3 times.

[0041] 2. Compared with the fixed platform-side viewing angle of SAR satellites based on two-dimensional planar phased array antennas, the method proposed in this invention uses satellite platform maneuvering to multiple side swing angles to cooperate with the SAR antenna radio wave scanning design. By reducing the attenuation of antenna scanning gain, it improves SAR imaging performance indicators such as high-view-angle beamwidth system sensitivity and range ambiguity.

[0042] 3. Compared with the current SAR satellites with reflector antennas, the planar phased array antenna proposed in this invention has a fast, flexible, and efficient radio beam switching function, which can improve the target observation efficiency.

[0043] 4. This invention employs multi-angle scanning modes such as forward squint, side view, and backward squint for satellite imaging, enabling observation of multiple targets at different angles during a single flight, acquiring target scattering characteristics at different azimuth angles, improving target observation efficiency, and enriching target observation information.

[0044] 5. The method proposed in this invention can greatly simplify the antenna structure, reduce the weight, volume and cost of the entire satellite, and meet the user's demand for lightweight and small SAR satellites. Attached Figure Description

[0045] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0046] Figure 1 This is a schematic flowchart of the method of the present invention;

[0047] Figure 2 This is a schematic diagram of the working mode of the method of the present invention;

[0048] Figure 3 This is a schematic diagram illustrating the geometric relationship between satellite attitude maneuvering and payload electronic scanning angle in the method of this invention. Detailed Implementation

[0049] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0050] Example 1

[0051] The present invention provides a spaceborne SAR wide-swath mode design method based on payload and attitude coordination, the method comprising the following steps:

[0052] Step S1: Calculate the satellite side-swing angle; the satellite maneuvers around the Xb axis of its system to the platform side-swing angle under two-dimensional guidance attitude; the selection of the satellite side-swing angle is related to the satellite mission. When the satellite's main mission is multi-target observation, the side-swing angle is set to 0°, and the satellite maintains level flight mode, switching from SAR antenna distance to radio wave beam; if the satellite's main mission is high-resolution imaging, the platform side-swing angle can be calculated based on the downward angle of view, and the satellite maneuvers around the Xb axis of its system to a fixed angle, cooperating with the SAR antenna radio wave beam to complete beam scanning; when the side-swing angle is set to a positive value, the satellite maintains left-side look-ahead working mode; when the side-swing angle is set to a negative value, the satellite maintains right-side look-ahead working mode; when the side-swing angle is set to zero, the satellite maintains level flight working mode.

[0053] Step S2: Calculate the electronic scan compensation angle and attitude elevation angle based on the satellite side tilt angle, down-view angle, and azimuth homing angle; the satellite platform performs attitude maneuvers around its Yb axis to drive the SAR antenna radio beam to complete the forward azimuth angle scan, maintaining the satellite in a forward-looking imaging state; SAR imaging is completed using satellite attitude and payload coordination. Before each imaging, a range-direction radio beam scan compensation angle θbL1 is provided to the payload, and an attitude elevation angle θb1 is provided to the satellite platform; θbL1 and θb1 are calculated based on the satellite side tilt angle φcs1, down-view angle θL1, and azimuth homing angle θ1 parameters, through... and θ bL =arsin[sin(θ) L -φ cs The coordinate transformation relationship is calculated using the equation )·cosθ].

[0054] Step S3: Within the imaging time range, the payload completes forward-looking ScanSAR imaging by rapidly switching the range-direction radio beam of the SAR antenna; a one-dimensional planar phased array SAR antenna is used for range-direction large-angle radio beam scanning.

[0055] Step S4: Repeat steps S1-S3 above, and within the imaging time range, the payload sequentially completes frontal side-looking and back-slanting ScanSAR imaging;

[0056] Step S4.1: The satellite maneuvers around the Xb axis of its own system to the second platform side swing angle φcs2 under two-dimensional guidance attitude;

[0057] Step S4.2: Calculate the electronic scanning compensation angle θbL2 and attitude pitch angle θb2 based on the satellite side tilt angle φcs2, the downward angle θL2 and the azimuth synchroth angle θ2. The payload completes the downward angle scanning through the range radio beam of the SAR antenna. The satellite platform completes the azimuth synchroth angle scanning from the forward synchroth view to the normal side view by attitude maneuvering around the Yb axis of the system.

[0058] Step S4.3: Within the second imaging time range, the payload completes the front-side-looking ScanSAR strip scanning imaging by rapidly switching the range-direction radio wave beam;

[0059] Step S4.4: Under two-dimensional guidance attitude, the satellite maneuvers around the Xb axis of its own system to the third platform side swing angle φcs3;

[0060] Step S4.5: Calculate the electronic scanning compensation angle θbL3 and attitude pitch angle θb3 based on the satellite side tilt angle φcs3, the downward angle θL3 and the azimuth synchroth angle θ3. The payload completes the downward angle scanning through the range radio beam of the SAR antenna. The satellite platform completes the azimuth synchroth angle scanning from the front side view to the rear synchroth view by attitude maneuvering around the Yb axis of the system.

[0061] Step S4.6: Within the third imaging time range, the payload completes the slant-view ScanSAR strip scanning imaging after switching to the range-direction radio wave beam.

[0062] Example 2

[0063] Example 2 is a preferred example of Example 1, and is used to illustrate the present invention in more detail.

[0064] This invention also provides a spaceborne SAR wide-swath mode design system based on payload and attitude coordination, the system comprising the following modules:

[0065] Module M1: Calculates the satellite side-swing angle; the satellite maneuvers around the Xb axis of its own system to the platform side-swing angle under two-dimensional guidance attitude; the selection of the satellite side-swing angle is related to the satellite mission. When the satellite's main mission is multi-target observation, the side-swing angle is set to 0°, and the satellite maintains level flight mode, switching from SAR antenna distance to radio wave beam; if the satellite's main mission is high-resolution imaging, the platform side-swing angle can be calculated based on the downward angle of view, and the satellite maneuvers around the Xb axis of its own system to a fixed angle, cooperating with the SAR antenna radio wave beam to complete beam scanning; when the side-swing angle is set to a positive value, the satellite maintains left-side look-ahead working mode; when the side-swing angle is set to a negative value, the satellite maintains right-side look-ahead working mode; when the side-swing angle is set to zero, the satellite maintains level flight working mode.

[0066] Module M2: Calculates the electronic scan compensation angle and attitude elevation angle based on the satellite's side tilt angle, down-view angle, and azimuth homing angle. The satellite platform performs attitude maneuvers around its Yb axis to drive the SAR antenna radio beam to complete the forward azimuth angle scan, maintaining the satellite in a forward-looking imaging state. SAR imaging is completed using a combination of satellite attitude and payload. Before each imaging operation, a range-direction radio beam scan compensation angle θbL1 is provided to the payload, and an attitude elevation angle θb1 is provided to the satellite platform. θbL1 and θb1 are calculated based on the satellite side tilt angle φcs1, down-view angle θL1, and azimuth homing angle θ1 parameters, through... and θ bL =arsin[sin(θ) L -φ cs The coordinate transformation relationship is calculated using the equation )·cosθ].

[0067] Module M3: Within the imaging time range, the payload completes forward-looking ScanSAR imaging by rapidly switching the range-direction radio beam of the SAR antenna; a one-dimensional planar phased array SAR antenna is used for range-direction large-angle radio beam scanning.

[0068] Module M4: Repeatedly triggers the above modules M1-M3 to perform their work, and within the imaging time range, the payload sequentially completes frontal side-looking and back-slanting ScanSAR imaging;

[0069] Module M4.1: The satellite maneuvers around the Xb axis of its own system to the second platform side swing angle φcs2 under two-dimensional guidance attitude;

[0070] Module M4.2: Calculates the electronic scanning compensation angle θbL2 and attitude pitch angle θb2 based on the satellite side tilt angle φcs2, the downward angle θL2 and the azimuth synchroth angle θ2. The payload completes the downward angle scanning through the range radio beam of the SAR antenna. The satellite platform completes the azimuth synchroth angle scanning from forward synchroth to normal side view by attitude maneuvering around the Yb axis of the system.

[0071] Module M4.3: During the second imaging time range, the payload completes front-side-looking ScanSAR strip scanning imaging by rapidly switching the range-direction radio wave beam;

[0072] Module M4.4: The satellite maneuvers around the Xb axis of its own system to the third platform side swing angle φcs3 under two-dimensional guidance attitude;

[0073] Module M4.5: Calculates the electronic scanning compensation angle θbL3 and attitude pitch angle θb3 based on the satellite side tilt angle φcs3, the downward angle θL3 and the azimuth synchroth angle θ3. The payload completes the downward angle scanning through the range radio beam of the SAR antenna. The satellite platform completes the azimuth synchroth angle scanning from the front side view to the back synchroth view by maneuvering around the Yb axis of the system.

[0074] Module M4.6: During the third imaging time range, the payload performs slant-look ScanSAR strip scanning imaging after switching the range-to-radio wave beam.

[0075] Example 3

[0076] Example 3 is a preferred example of Example 1, and is used to illustrate the present invention in more detail.

[0077] To address the aforementioned problems in existing technologies, this invention employs a spaceborne SAR wide-swath mode design method based on payload and attitude coordination. This method primarily achieves forward-looking, side-looking, and backward-looking ScanSAR multi-scan stitching imaging through a combination of range-direction electronic scanning of the SAR antenna and azimuth-direction satellite attitude maneuvering. Compared to traditional ScanSAR modes, this invention's mode can increase the range-direction swath width by three times. Simultaneously, the rapid, flexible, and efficient beam-to-target switching capability of the planar active phased array antenna ensures target observation performance. Furthermore, designing the planar phased array antenna for one-dimensional large-angle range scanning significantly reduces the overall satellite weight, volume, and cost.

[0078] This embodiment provides a spaceborne SAR wide-swath mode design method based on payload and attitude coordination, including the following steps:

[0079] Step 1: Calculate the satellite's side yaw angle; the satellite maneuvers around the Xb axis of the system to the platform's side yaw angle under two-dimensional guidance attitude;

[0080] Step 2: Calculate the electronic scanning compensation angle and attitude pitch angle based on the satellite's side tilt angle, downward viewing angle, and azimuth scooting viewing angle; the satellite platform drives the SAR antenna radio beam to complete the azimuth forward scooting viewing angle scan by attitude maneuvering around the Yb axis of the system, so that the satellite maintains the forward scooting imaging state.

[0081] Step 3: Within the imaging time range, the payload rapidly switches the SAR antenna range direction radio beam to complete forward-looking ScanSAR imaging;

[0082] Step 4: Repeat steps 1-3 above, and within the imaging time range, the payload will sequentially complete the frontal side-view and back-slant ScanSAR imaging.

[0083] Furthermore, in step 1, the selection of the satellite side-swing angle is related to the satellite mission. When the satellite's primary mission is multi-target observation, the side-swing angle is set to 0°, and the satellite maintains level flight mode, rapidly and flexibly switching between SAR antenna range and radio wave beam to improve target observation efficiency. If the satellite's primary mission is high-resolution imaging, the platform side-swing angle can be calculated based on the downward angle of view. The satellite maneuvers around the Xb axis of its own system to a fixed angle and completes beam scanning in conjunction with the SAR antenna radio wave beam, thus improving payload imaging performance. When the side-swing angle is set to a positive value, the satellite maintains a left-side-view operating mode; when the side-swing angle is set to a negative value, the satellite maintains a right-side-view operating mode; when the side-swing angle is set to zero, the satellite maintains level flight mode. The satellite of this invention uses multiple single-frame control moment gyroscopes to achieve rapid maneuvering of the satellite side-swing angle, and the satellite operating mode can be flexibly switched according to user needs.

[0084] Furthermore, in step 2, this invention employs satellite attitude and payload coordination to complete SAR imaging. Before each imaging operation, to ensure that the satellite attitude maneuver drives the SAR antenna radio beam to point towards the scene center, it is necessary to provide the payload with a range radio beam scanning compensation angle θbL1 and the satellite platform with an attitude pitch angle θb1. θbL1 and θb1 are determined based on parameters such as the satellite side sway angle φcs1, the downward viewing angle θL1, and the azimuth and synchroscopic viewing angle θ1, through... and θ bL =arsin[sin(θ) L -φ cs The coordinate transformation relationship is calculated using the equation )·cosθ].

[0085] Furthermore, in step 3, a one-dimensional planar phased array SAR antenna is used to achieve large-angle radio beam scanning in the range direction, ensuring wide-swath imaging in the range direction. Simultaneously, designing the antenna for one-dimensional scanning significantly reduces the overall weight and cost of the satellite.

[0086] Step 4.1: 1) The satellite maneuvers around the Xb axis of the system under two-dimensional guidance attitude to the second platform side swing angle φcs2; 2) Calculate the electronic scan compensation angle θbL2 and attitude elevation angle θb2 based on the satellite side swing angle φcs2, the down-view angle θL2 and the azimuth synchroth angle θ2. The payload completes the down-view scanning through the range radio beam of the SAR antenna. The satellite platform drives the SAR antenna radio beam to complete the azimuth synchroth angle scanning from forward synchroth to frontal side view by attitude maneuvering around the Yb axis of the system; 3) Within the second imaging time range, the payload completes the frontal side view ScanSAR strip scanning imaging by rapidly switching the range radio beam;

[0087] Step 4.2: 1) The satellite maneuvers around the Xb axis of its own system to the third platform side angle φcs3 under two-dimensional guidance attitude; 2) Calculate the electronic scan compensation angle θbL3 and attitude elevation angle θb3 based on the satellite side angle φcs3, the downward angle θL3 and the azimuth synchroth angle θ3. The payload completes the downward angle scan through the range radio beam of the SAR antenna. The satellite platform drives the SAR antenna radio beam to complete the azimuth synchroth angle scan from the front side view to the rear synchroth view by attitude maneuvering around the Yb axis of its own system; 3) Within the third imaging time range, the payload completes the synchroth ScanSAR strip scan imaging by quickly switching the range radio beam.

[0088] Furthermore, in step 4, within a given imaging time range, the payload achieves rapid switching between multiple adjacent beam positions through SAR antenna range beam scanning, and coordinates with satellite platform attitude maneuvers to sequentially complete front-side looking and back-slanting ScanSAR strip scanning imaging. The start time Ts2 and end time Te2 of the second imaging should satisfy the relationships Ts2 = Te1 + Td and Te2 = Ts2 + S / Vg, respectively. The start time Ts3 and end time Te3 of the third imaging should satisfy the relationships Ts3 = Te2 + Td and Te3 = Ts3 + S / Vg, where Td represents the satellite attitude maneuver time between the two imaging operations.

[0089] In addition, to ensure that the satellite completes attitude maneuvers before the next imaging, the maneuver time Td should meet the following requirements.

[0090] The relationship is as follows (where Re is the Earth's radius, R is the satellite's frontal side-looking slant range, θ is the azimuth slant angle, S is the azimuth imaging length, Vg is the satellite's ground velocity, and Ls is the synthetic aperture length). In this invention, the satellite platform uses multiple single-frame control moment gyroscopes to achieve rapid satellite attitude maneuvers while meeting the normal imaging requirements of the payload.

[0091] Appendix Figure 1 The specific implementation steps of this invention are given below:

[0092] (1) Satellite forward-looking ScanSAR strip imaging:

[0093] Calculate the satellite side-swing angle; the satellite maneuvers around the Xb axis of the system under two-dimensional guidance attitude to the first platform side-swing angle; calculate the electronic scan compensation angle and attitude pitch angle based on the satellite side-swing angle, down-view angle and azimuth scoot angle; the satellite platform drives the SAR antenna radio beam to complete the azimuth forward scoot angle scan by attitude maneuvering around the Yb axis of the system; the payload completes the forward scoot angle ScanSAR strip scan imaging by rapidly switching the range radio beam of the SAR antenna.

[0094] (2) Satellite front-side-looking ScanSAR strip scan imaging:

[0095] Calculate the satellite side-swing angle; the satellite maneuvers around the Xb axis of the system under two-dimensional guidance attitude to the second platform side-swing angle; calculate the electronic scan compensation angle and attitude pitch angle based on the satellite side-swing angle, down-view angle and azimuth synchroth angle; the satellite platform drives the SAR antenna radio beam to complete the azimuth synchroth angle scan from forward synchroth to frontal side-view by attitude maneuvering around the Yb axis of the system; the payload completes the frontal side-view ScanSAR strip scan imaging by rapidly switching the range radio beam of the SAR antenna.

[0096] (3) Satellite back-slant ScanSAR strip imaging:

[0097] Calculate the satellite side-swing angle; the satellite maneuvers around the Xb axis of the system under two-dimensional guidance attitude to the third platform side-swing angle; calculate the electronic scan compensation angle and attitude elevation angle based on the satellite side-swing angle, down-view angle, and azimuth scoliosis angle; the satellite platform drives the SAR antenna radio beam to complete the azimuth scoliosis angle scan from front side view to back scoliosis view by attitude maneuvering around the Yb axis of the system; the payload completes the scoliosis ScanSAR strip scan imaging by rapidly switching the range radio beam of the SAR antenna.

[0098] Please refer to the above steps. Figure 2 , Figure 2 This is a schematic diagram of the working mode of the spaceborne SAR wide-swath mode design method based on payload and attitude coordination, which is provided for the implementation case of this invention.

[0099] In an embodiment of the present invention, Figure 3 This is a schematic diagram of the geometric relationship between satellite attitude maneuvering and payload electronic scanning angle provided for an embodiment of the present invention. In the figure, the right-side flight state is shown, O-XbYbZb is the satellite body system, θL is the satellite downward angle, θ is the azimuth synchro angle, θb is the attitude pitch angle, φcs is the satellite platform side yaw angle, and θbL is the electronic scanning compensation angle.

[0100] The effects of the present invention will be further explained below with reference to simulation data.

[0101] Here, a spaceborne SAR orbital altitude of approximately 500km is selected, in the X-band, with a center angle of 12.92-24.97°. The antenna is designed as a one-dimensional large-angle scanning planar active phased array, with an azimuth angle of ±30°, a resolution of 8m, and an azimuth observation band length of 120km. The range band is designed as ScanSAR 3-hop, with a range swath width of 17km per burst, an overlap of 1-2km between adjacent sigma positions, an imaging bandwidth of 45km for three adjacent sigma positions, and a total range observation band bandwidth of 135km.

[0102] Based on the above-mentioned input system requirements parameters, this section designs and outputs a set of wave position simulation parameters according to the method proposed in this invention, as shown in the table below:

[0103] Table 1 Output parameters in the embodiment

[0104]

[0105]

[0106] The satellite performs its first forward-looking ScanSAR imaging: First, input the wavefront parameters, including the downward angle, side angle, and azimuth synchro angle; calculate the relevant parameters according to the method proposed in this invention; under two-dimensional guidance attitude, the satellite maneuvers around the Xb axis of its own system to the left side of the view 10°, and then maneuvers around the Yb axis of its own system at an elevation angle of 30.03° to maintain the forward-looking imaging state; within a given imaging time, the payload scans the SAR antenna range beam sequentially at -2.53°, -3.92°, and -5.29° to complete the forward-looking ScanSAR strip scan imaging.

[0107] The satellite performs a second frontal side-looking ScanSAR imaging: First, input the wavefront parameters, including the downward angle, side sway angle, and azimuth synchro angle; calculate the relevant parameters according to the method proposed in this invention; under two-dimensional guidance attitude, the satellite maneuvers around the Xb axis of its own system to the left side-looking 20°, and then around the Yb axis of its own system to the elevation angle 0° to maintain the frontal side-looking imaging state; within the given imaging time, the payload scans the SAR antenna range-direction radio wave beam sequentially at 2.33°, 0.81°, and -0.69° to complete the frontal side-looking ScanSAR strip scan imaging.

[0108] The satellite performs its third backward-looking ScanSAR imaging: First, input the wavefront parameters, including the downward angle, side tilt angle, and azimuth synchro angle; calculate the relevant parameters according to the method proposed in this invention; under two-dimensional guidance attitude, the satellite maneuvers around the Xb axis of its own system to the left side 20°, and then maneuvers around the Yb axis of its own system to an elevation angle of -30.02° to maintain the backward-looking imaging state; within a given imaging time, the payload scans the SAR antenna range beam sequentially at -1.86°, -3.10°, and -4.30° to complete the backward-looking ScanSAR strip scan imaging.

[0109] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1 and Embodiment 2.

[0110] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0111] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for designing a space-borne SAR wide-swath mode based on load and attitude cooperation, characterized in that, The method comprises the following steps: Step S1: calculating a satellite side swing angle; the satellite is maneuvered around the Xb axis of the body frame to a platform side swing angle in a two-dimensional guiding attitude; Step S2: calculating an electric scanning compensation angle and an attitude pitch angle according to the satellite side swing angle, a downward-looking angle and an azimuth oblique-looking angle; the satellite platform drives the S AR antenna electric beam to complete the azimuth oblique-looking angle scanning through attitude maneuvering around the Yb axis of the body frame, so that the satellite keeps a forward oblique-looking imaging state; Step S3: within an imaging time range, the load completes forward oblique-looking ScanSAR imaging through distance direction electric beam switching of the S AR antenna; Step S4: within the imaging time range, the load sequentially completes forward-looking, backward oblique-looking ScanSAR imaging; The step S4 comprises the following steps: Step S4.1: the satellite is maneuvered around the Xb axis of the body frame to a second platform side swing angle φcs2 in a two-dimensional guiding attitude; Step S4.2: calculating an electric scanning compensation angle θbL2 and an attitude pitch angle θb2 according to the satellite side swing angle φcs2, a downward-looking angle θL2 and an azimuth oblique-looking angle θ2, the load completes the downward-looking angle scanning through the distance direction electric beam of the S AR antenna, and the satellite platform drives the S AR antenna electric beam to complete the azimuth oblique-looking angle scanning from forward oblique-looking to forward-looking through attitude maneuvering around the Yb axis of the body frame; Step S4.3: within a second imaging time range, the load completes forward-looking ScanSAR strip scanning imaging through distance direction electric beam switching; Step S4.4: the satellite is maneuvered around the Xb axis of the body frame to a third platform side swing angle φcs3 in a two-dimensional guiding attitude; Step S4.5: calculating an electric scanning compensation angle θbL3 and an attitude pitch angle θb3 according to the satellite side swing angle φcs3, a downward-looking angle θL3 and an azimuth oblique-looking angle θ3, the load completes the downward-looking angle scanning through the distance direction electric beam of the S AR antenna, and the satellite platform drives the S AR antenna electric beam to complete the azimuth oblique-looking angle scanning from forward-looking to backward oblique-looking through attitude maneuvering around the Yb axis of the body frame; Step S4.6: within a third imaging time range, the load completes backward oblique-looking ScanSAR strip scanning imaging through distance direction electric beam switching.

2. The load and attitude cooperation based spaceborne SAR large swath mode design method according to claim 1, characterized in that, In the step S1, the selection of the satellite side swing angle is related to the satellite task; when the satellite takes multi-target observation as the main task, the side swing angle is set to 0º, the satellite keeps a flat flying mode, and the distance direction electric beam of the S AR antenna is switched; if the satellite takes high-resolution imaging as the main task, the platform side swing angle can be calculated according to the size of the downward-looking angle, the satellite is maneuvered around the Xb axis of the body frame to a fixed angle, and the beam scanning is completed through cooperation of the S AR antenna electric beam; when the side swing angle is set to a positive value, the satellite keeps a left-looking working mode; when the side swing angle is set to a negative value, the satellite keeps a right-looking working mode; and when the side swing angle is set to zero, the satellite keeps a flat flying working mode.

3. The load and attitude cooperation based spaceborne SAR large swath mode design method according to claim 1, characterized in that, In the step S2, the satellite attitude and the load cooperation are adopted to complete the SAR imaging. Before each imaging, a distance beam scanning compensation angle θbL1 is provided for the load, and an attitude pitch angle θb1 is provided for the satellite platform. θbL1 and θb1 are calculated according to the satellite roll angle φcs1, the downward-looking angle θL1, and the azimuth slant angle θ1 parameters through and coordinate conversion relationship calculation.

4. The load and attitude cooperation based spaceborne SAR large swath mode design method according to claim 1, characterized in that, In the step S3, a one-dimensional planar phased array system S AR antenna is adopted to perform distance direction large-angle electric beam scanning.

5. A load and attitude cooperation based spaceborne SAR large swath mode design system, characterized in that, The system comprises the following modules: Module M1: calculating a satellite side swing angle; the satellite is maneuvered around the Xb axis of the body frame to a platform side swing angle in a two-dimensional guiding attitude; Module M2: calculate the electrical scanning compensation angle and the attitude pitch angle according to the satellite side-slip angle, the downward-looking angle and the azimuth oblique angle; the satellite platform drives the SAR antenna electrical beam to complete the azimuth oblique angle scanning by the attitude maneuver around the Yb axis of the body system, so that the satellite keeps the forward oblique imaging state; Module M3: the load completes the forward oblique ScanSAR imaging by the distance direction electrical beam quick switching of the SAR antenna within the imaging time range; Module M4: the load completes the forward oblique, the backward oblique ScanSAR imaging in turn within the imaging time range; The module M4 comprises the following modules: Module M4.1: the satellite is maneuvered to the second platform side-slip angle φcs2 around the Xb axis of the body system under the two-dimensional guided attitude; Module M4.2: calculate the electrical scanning compensation angle θbL2 and the attitude pitch angle θb2 according to the satellite side-slip angle φcs2, the downward-looking angle θL2 and the azimuth oblique angle θ2, the load completes the downward-looking angle scanning by the distance direction electrical beam of the SAR antenna, and the satellite platform drives the SAR antenna electrical beam to complete the scanning of the azimuth oblique angle from the forward oblique to the forward-looking by the attitude maneuver around the Yb axis of the body system; Module M4.3: the load completes the forward-looking ScanSAR strip scanning imaging by the distance direction electrical beam quick switching within the second imaging time range; Module M4.4: the satellite is maneuvered to the third platform side-slip angle φcs3 around the Xb axis of the body system under the two-dimensional guided attitude again; Module M4.5: calculate the electrical scanning compensation angle θbL3 and the attitude pitch angle θb3 according to the satellite side-slip angle φcs3, the downward-looking angle θL3 and the azimuth oblique angle θ3, the load completes the downward-looking angle scanning by the distance direction electrical beam of the SAR antenna, and the satellite platform drives the SAR antenna electrical beam to complete the scanning of the azimuth oblique angle from the forward-looking to the backward oblique by the attitude maneuver around the Yb axis of the body system; Module M4.6: the load completes the backward oblique ScanSAR strip scanning imaging by the distance direction electrical beam switching within the third imaging time range.

6. The load and attitude cooperation based spaceborne SAR large swath mode design system according to claim 5, characterized in that, In the module M1, the selection of the satellite side-slip angle is related to the satellite task, when the satellite takes the multi-target observation as the main task, the side-slip angle is set to 0º, the satellite keeps the flat flying mode, and the distance direction electrical beam switching of the SAR antenna is completed; if the satellite takes the high-resolution imaging as the main task, the platform side-slip angle can be calculated according to the downward-looking angle, the satellite is maneuvered to a fixed angle around the Xb axis of the body system, and the beam scanning is completed by cooperating with the SAR antenna electrical beam; when the side-slip angle is set to a positive value, the satellite keeps the left-looking working mode; when the side-slip angle is set to a negative value, the satellite keeps the right-looking working mode; when the side-slip angle is set to zero, the satellite keeps the flat flying working mode.

7. The load and attitude cooperation based spaceborne SAR large swath mode design system according to claim 5, characterized in that, In the module M2, the satellite attitude and the load cooperate to complete the SAR imaging. Before each imaging, a distance beam scanning compensation angle θbL1 is provided for the load, and an attitude pitch angle θb1 is provided for the satellite platform. θbL1 and θb1 are calculated according to the satellite roll angle φcs1, the downward-looking angle θL1, and the azimuth slant angle θ1 parameters through and coordinate conversion relationship.

8. The load and attitude cooperation based spaceborne SAR large swath mode design system according to claim 5, characterized in that, In the module M3, the distance direction large-angle electrical beam scanning is completed by using the one-dimensional planar phased array system SAR antenna.

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