A test method for AIS guiding on-board real-time processing of SAR

Abstract

The application discloses a kind of test methods for AIS guided SAR on-board real-time processing, by constructing the test environment consisting of control ground equipment, GPS simulator, AIS signal source, SAR echo simulation equipment, general control equipment and ground data receiving processing equipment, the equivalent simulation of in-orbit satellite state and the full-element detection target and scene is realized, the application of the test device effectively improves the test confidence for AIS guided SAR on-board real-time processing.

Description

Technical Field

[0001] This invention belongs to the field of synthetic aperture radar satellite integrated testing technology, specifically relating to a testing method for real-time on-board processing of AIS-guided SAR satellites. Background Technology

[0002] The Automatic Identification System (AIS) is an autonomous communication system for ship status. It autonomously transmits information such as identity, location, speed, and heading, which is then relayed by satellite for global ship monitoring. AIS-guided real-time SAR imaging enables the instant fusion of AIS data and SAR imaging data, providing an important data foundation for multi-dimensional ship status acquisition and monitoring.

[0003] Testing the onboard real-time processing function of AIS-guided SAR is a system-level test project based on the collaborative operation of multiple satellite subsystems. It requires designing test methods to achieve equivalent verification of the entire process of AIS-guided SAR real-time imaging, based on a constructed test environment, in order to provide test verification conclusions and ensure the normal operation of the onboard function. However, existing test methods for the onboard real-time processing of AIS-guided SAR suffer from low test confidence levels due to the lack of completeness in the constructed test environment, especially for new real-time imaging functions, where effective testing methods are still lacking. Summary of the Invention

[0004] In view of this, the present invention provides a test method for real-time on-board processing of AIS-guided SAR satellites, which realizes the test of the real-time on-board processing of SAR satellites in a test environment including the satellite's status in orbit, the target being detected, and the scene.

[0005] This invention provides a testing method for real-time on-board processing of AIS-guided SAR satellites, specifically including the following steps:

[0006] A simulated flight test environment is constructed by controlling ground equipment. An on-orbit simulated flight state is established in the simulated flight test environment. The GPS simulator provides navigation and positioning data for the satellite during the simulated flight. During the satellite flight, the ground control equipment uploads a guidance imaging command packet containing the ship's maritime movement identification code. After the satellite data management subsystem parses the guidance imaging command packet, it enters the guidance imaging mode. The AIS signal source simulates and generates AIS message data containing the target ship's MMSI. The SAR echo simulation equipment simulates and generates SAR echo signals. After completing the real-time guidance imaging processing on the satellite, the AIS message data and SAR target detection results are transmitted down. Then, the ground data receiving and processing equipment is used to interpret the AIS message data and SAR target detection results to obtain the test conclusion.

[0007] Furthermore, the simulated flight test environment is for controlling ground equipment and includes a sensor data injection module, an actuator data acquisition module, a ground dynamics and kinematics simulation module, a test integrated control module, and a signal interface adapter conditioner;

[0008] The sensor data injection module calculates parameters such as angular velocity, star and sun azimuth based on the celestial attitude and orbital parameters. It then uses the sensor model to obtain the output signals from the gyroscope, star sensor, and sun sensor as sensor signals. These sensor signals are processed by the signal interface adapter conditioner and sent to the satellite control subsystem. The satellite control subsystem acquires the sensor signals and uses an attitude determination algorithm to determine the satellite attitude. Based on the desired attitude and preset control law, it generates actuator control signals. The actuator control signals are acquired by the actuator data acquisition module, which obtains the thruster pulse width signal, momentum wheel speed signal, and magnetic torquer current signal, and transmits these signals to the ground dynamics and kinematics simulation module. The ground dynamics and kinematics simulation module performs simulation calculations on the thruster pulse width signal, momentum wheel speed signal, and magnetic torquer current signal to obtain the celestial attitude and orbital parameters, which are then transmitted to the sensor data injection module.

[0009] Furthermore, the satellite orbital attitude dynamics equations adopted by the ground dynamics and kinematics simulation module are as follows:

[0010]

[0011] Where V is the satellite's velocity vector, F out F is the resultant external force of the gravitational pull of the Earth, Moon, and Sun, atmospheric drag, and solar radiation pressure. Thruster The thrust generated by the thruster, ω is the attitude angular velocity vector, and M is the thrust generated by the thruster. out M is the resultant torque of the gravitational gradient torque, aerodynamic torque, and solar pressure torque. Thruster M is the control torque generated by the thruster. Wheel Let m be the torque generated by the momentum exchange device, m be the total mass of the satellite, and I be the total inertia of the satellite.

[0012] Furthermore, the ground control equipment uploads a guidance imaging instruction package containing the ship's maritime movement identification code, and also specifies the maximum working time for this guidance imaging. If the guidance imaging is not completed within this time, the guidance imaging will be terminated.

[0013] Furthermore, after parsing the guidance imaging command packet, the satellite data management subsystem enters the guidance imaging mode. The AIS signal source simulates and generates AIS message data containing the target ship's MMSI. The process of the SAR echo simulation equipment simulating and generating SAR echo signals also includes: after receiving the guidance imaging command packet, the satellite data management subsystem verifies the packet header and checksum. If correct, it transparently forwards the valid data area content to the AIS subsystem. After obtaining the matching AIS position report based on the ship's MMSI information in the guidance imaging command packet, the AIS subsystem, assuming the time from receiving the imaging command packet to starting imaging is T0, determines whether the target ship is within the SAR beam azimuth within T0 after obtaining the matching AIS position report. If the target ship is predicted to be within the SAR imaging beam range, the SAR imaging command packet is designed and sent to the SAR payload subsystem. The real-time processor startup time is calculated based on the imaging time, and the command is sent to complete the status settings of the real-time processor and data transmission subsystem. If the target ship is predicted to be outside the SAR imaging beam range, the status information is returned, indicating that the guidance does not meet the SAR imaging conditions and SAR imaging cannot be guided.

[0014] Furthermore, the AIS signal source consists of signal source main control software, baseband signal processing board, radio frequency channel module and power supply.

[0015] Furthermore, the SAR echo simulation device generates SAR echo signals by using a real-time convolution method based on the satellite-ground geometry and the characteristics of the target scene and ship target.

[0016] Furthermore, the method for obtaining test conclusions by interpreting AIS message data and SAR target detection results using ground data receiving and processing equipment is as follows: the ground data receiving and processing equipment uses a demodulator to demodulate SAR imaging data and AIS data to generate baseband data. After decoding, formatting removal, and decompression, the baseband data generates payload service data. Then, the SAR imaging data and AIS data are identified through a virtual channel identifier. The position information of the target ship corresponding to the MMSI is found from the AIS data. The position error and imaging results are compared, and the performance indicators of the AIS-guided SAR real-time processing function are interpreted to obtain test conclusions.

[0017] Beneficial effects:

[0018] 1. This invention achieves full-element equivalent simulation of the on-orbit satellite status and the detection target and scene by constructing a test environment consisting of control ground equipment, GPS simulator, AIS signal source, SAR echo simulation equipment, master control equipment and ground data receiving and processing equipment. The application of this test device effectively improves the test confidence of real-time on-board processing of AIS-guided SAR.

[0019] 2. The test method proposed in this invention achieves quantitative evaluation of performance indicators by comparing the target ship position information in AIS data with the target ship positioning information in the real-time processor detection results, effectively improving test accuracy and test coverage.

[0020] 3. The testing method proposed in this invention matches the on-orbit application process, realizing the goal of "how to use it on orbit and how to test it on the ground", achieving the purpose of system-level testing, and laying a good foundation for the verification of the real-time imaging function of AIS-guided SAR satellite. Attached Figure Description

[0021] Figure 1 This invention provides a test environment system composition diagram for a test method of real-time on-board processing of AIS-guided SAR satellites.

[0022] Figure 2 This invention provides a test method for real-time on-board processing of AIS-guided SAR satellites, which includes a diagram of the control ground equipment.

[0023] Figure 3 This invention provides a test scenario channel data structure diagram for a test method of real-time on-board processing of AIS-guided SAR satellites.

[0024] Figure 4 This is a schematic diagram of the AIS detectable area and antenna pattern.

[0025] Figure 5 This is a block diagram illustrating the signal flow and basic principle of a SAR payload echo simulator. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] This invention provides a test method for real-time on-board processing of AIS-guided SAR satellites, the test system of which is composed as follows: Figure 1 As shown, its core idea is as follows: a simulated flight test environment is constructed by controlling ground equipment, and an on-orbit simulated flight state is established in the test environment. The GPS simulator provides navigation and positioning data for the satellite during the simulated flight. During the satellite flight, a guidance imaging command packet containing the Maritime Mobile Identifier (MMSI) of the ship is uploaded through the ground control equipment. After the satellite data management subsystem parses the command packet, it enters the guidance imaging mode. The AIS signal source simulates and generates AIS message data containing the MMSI of the target ship. The SAR echo simulation equipment simulates and generates SAR echo signals. After completing the real-time guidance imaging processing on the satellite, the AIS message data and SAR target detection results are transmitted down. Then, the ground data receiving and processing equipment is used to interpret the AIS message data and SAR target detection results and give the test conclusion.

[0028] This invention provides a testing method for real-time on-board processing of AIS-guided SAR satellites, comprising the following steps:

[0029] Step 1: Construct a simulated flight test environment and establish the SAR satellite's simulated on-orbit flight state based on this test environment. The simulated flight test environment constructed in this invention is a control ground equipment, including a sensor data injection module, an actuator data acquisition module, a ground dynamics and kinematics simulation module, a test integrated control module, and a signal interface adapter conditioner, as shown below. Figure 2 As shown, the simulated flight test environment and the satellite control subsystem form a closed-loop control circuit.

[0030] The sensor data injection module calculates parameters such as angular velocity, star and sun azimuth based on the celestial attitude and orbital parameters. It then uses the sensor model to obtain the output signals from the gyroscope, star sensor, and sun sensor as sensor signals. These sensor signals are processed by the signal interface adapter conditioner and sent to the satellite control subsystem. The satellite control subsystem acquires the sensor signals and uses an attitude determination algorithm to determine the satellite attitude. Based on the desired attitude and preset control law, it generates actuator control signals. The actuator control signals are acquired by the actuator data acquisition module, which obtains the thruster pulse width signal, momentum wheel speed signal, and magnetic torquer current signal, and transmits these signals to the ground dynamics and kinematics simulation module. The ground dynamics and kinematics simulation module performs simulation calculations on the thruster pulse width signal, momentum wheel speed signal, and magnetic torquer current signal to obtain the celestial attitude and orbital parameters, which are then transmitted to the sensor data injection module.

[0031] The satellite orbital attitude dynamics equations used in the ground dynamics and kinematics simulation module of this invention are as follows:

[0032]

[0033] Where V is the satellite's velocity vector, F out F is the resultant external force of the gravitational pull of the Earth, Moon, and Sun, atmospheric drag, and solar radiation pressure. Thruster The thrust generated by the thruster, ω is the attitude angular velocity vector, and M is the thrust generated by the thruster. out M is the resultant torque of the gravitational gradient torque, aerodynamic torque, and solar pressure torque. Thruster M is the control torque generated by the thruster. Wheel Let m be the torque generated by the momentum exchange device, m be the total mass of the satellite, and I be the total inertia of the satellite.

[0034] The ground dynamics and kinematics simulation module uses a GPS simulator to provide navigation and positioning data during simulated flight. Since the SAR needs preparation time from receiving the imaging command packet to starting imaging, the GPS simulator is required to have orbit extrapolation capability. During the simulated flight, commands are sent from the ground control equipment to simulate satellite separation from the launch vehicle, initial deviation correction, coarse orientation, high-precision attitude control, and other processes, and then a normal simulated flight state is established.

[0035] Step 2: Use ground control equipment to inject guidance imaging command packets into the satellite to put the satellite into guidance imaging mode.

[0036] The AIS-guided SAR real-time imaging command package is uploaded by the ground control equipment. The satellite data management subsystem parses the command package and controls the satellite control subsystem to enter the guided imaging mode via the bus. The command package contains the ship's MMSI information and specifies the maximum working time for this guided imaging. If the guided imaging is not completed within this time, the guided imaging will be terminated.

[0037] The AIS-guided SAR imaging command packet definition is shown in Table 1:

[0038] Table 1

[0039]

[0040] After receiving the guidance imaging command packet, the satellite data management subsystem verifies the packet header and checksum. If correct, it transparently forwards the valid data area content to the AIS subsystem. The AIS subsystem obtains the matching AIS position report based on the ship's MMSI information in the guidance imaging command packet. Let T0 be the time from when the SAR receives the imaging command packet to when it starts imaging. It determines whether the target ship is within the SAR beam azimuth within T0 after obtaining the matching AIS position report. If the target ship is predicted to be within the SAR imaging beam range, a SAR imaging command packet is designed (defined in Table 2) and sent to the SAR payload subsystem. The real-time processor startup time is calculated based on the imaging time, and commands are sent to complete the status settings of the real-time processor and data transmission subsystem. If the target ship is predicted not to be within the SAR imaging beam range, a status information is returned, indicating that the guidance does not meet the SAR imaging conditions and SAR imaging cannot be guided.

[0041] Table 2

[0042]

[0043] Step 3: Simulate ship AIS message information using an AIS signal source. Simulate the AIS message sent by the ship according to the ship AIS message format. The ship MMSI information in the AIS message includes the ship information in the uploading command packet. Simulate the ship AIS message in the detectable area based on the AIS antenna coverage range, satellite orbit parameters, and SAR payload beam coverage range.

[0044] Shipboard AIS signal generators can simulate the transmission of a fixed number of terminal signals within the visible range based on satellite orbits. The signal power of each terminal is determined by the antenna pattern and the terminal's location. The AIS signal generator consists of main control software, a baseband signal processing board, a radio frequency channel module, and a power supply.

[0045] The main control software of the signal source selects the target ship terminal within the visible range based on the satellite orbit, the distribution of terminals on the sea surface, and the satellite antenna pattern, and sends the selected terminal information to the baseband signal processing board. The baseband signal processing board completes the calculation of channel parameters such as channel delay, Doppler offset, and power. At the same time, the baseband signal processing board completes the signal time slot allocation. The baseband data is modulated by the radio frequency channel module to generate an AIS signal, which is then fed into the on-board AIS receiver.

[0046] Baseband AIS data contains two frequency points, each including fixed frame data and AIS frame data, and its data structure is as follows: Figure 3 As shown, the frame formats of fixed frames and AIS frames are shown in Tables 3 and 4.

[0047] Table 3

[0048]

[0049] Table 4

[0050]

[0051] AIS detectable area and antenna pattern are as follows: Figure 4 As shown.

[0052] Step 4: Use SAR echo simulation equipment to simulate SAR payload echo signals.

[0053] Based on the geometry between the satellite and the ground, as well as the characteristics of the target scene and the ship target, a simulated echo is generated using a real-time convolution method. After the SAR payload images according to the guidance command, the echo simulation device starts working and feeds the echo signal into the SAR receiving channel. After the SAR completes imaging, the echo data is transmitted to the real-time processor through a splitter, and the real-time processor completes the SAR imaging.

[0054] The SAR payload echo simulator receives the PRF pulse signal from the onboard SAR payload in real time. Using the PRF pulse signal as a time reference, it receives and acquires the SAR payload's radio frequency transmission signal via ADC to obtain the baseband transmission signal at each PRF moment. Simultaneously, the echo simulator receives the second pulse signal generated by the GPS simulator, reads and interpolates the internally stored satellite orbit PVT table to obtain the satellite position data at the current PRF moment, and obtains attitude information through the interface with the control subsystem. Based on the satellite position data and the set ground target scene, it calculates the target scene response at each PRF moment. Finally, it performs convolution modulation, DAC playback, and up-conversion processing on the target scene response and radar baseband transmission signal to obtain the radio frequency echo signal at each PRF moment, which is injected into the SAR payload's receiving channel, completing the echo generation and injection process for each PRF. Its signal flow and basic principle block diagram are shown below. Figure 5 As shown.

[0055] Step 5: Data reception, processing, and interpretation.

[0056] The ground data receiving and processing equipment receives SAR imaging data and AIS data. After demodulation by the demodulator, baseband data is generated. The baseband data is then decoded, deformatted, and decompressed to generate payload service data. The SAR imaging data and AIS data are identified by the virtual channel identifier.

[0057] The on-board real-time processing results are target ship slice information and location information. The location information of the target ship corresponding to the MMSI is found from the AIS data. The location error and imaging results are compared. The performance indicators of the AIS-guided SAR real-time processing function are interpreted and the interpretation conclusion is given.

[0058] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A test method for AIS guided SAR on-board real-time processing, characterized in that, Specifically comprising the following steps: The simulation flight test environment is constructed by controlling the ground equipment, the in-orbit simulation flight state is established in the simulation flight test environment, the GPS simulator provides navigation positioning data of the satellite during the simulation flight, the guiding imaging instruction package containing the marine mobile identification code of the ship is uploaded to the satellite during the flight by the ground general control equipment, the satellite management subsystem enters the guiding imaging mode after analyzing the guiding imaging instruction package, the AIS signal source simulates to generate the AIS message data containing the MMSI of the target ship, the SAR echo simulation equipment simulates to generate the SAR echo signal, the AIS message data and the SAR target detection result are downloaded after the guiding real-time imaging processing is completed on the satellite, and the test conclusion is obtained by using the ground data receiving and processing equipment to interpret the AIS message data and the SAR target detection result. The process that the satellite management subsystem analyzes the guiding imaging instruction package and enters the guiding imaging mode, and the AIS signal source simulates to generate the AIS message data containing the MMSI of the target ship and the SAR echo simulation equipment simulates to generate the SAR echo signal further comprises the following steps: after receiving the guiding imaging instruction package, the satellite management subsystem checks the package header and the check sum, and transparently forwards the content of the effective data area to the AIS subsystem after verification, the AIS subsystem obtains the matched AIS position report according to the ship MMSI information in the guiding imaging instruction package, sets the time from receiving the imaging instruction package to starting imaging as T0, judges whether the target ship is located in the SAR beam direction within T0 after obtaining the matched AIS position report, if the target ship is predicted to be in the SAR imaging beam range, the SAR imaging instruction package is designed and sent to the SAR load subsystem, the starting time of the real-time processor is calculated according to the imaging time, and the state setting of the real-time processor and the data transmission subsystem is completed by sending the instruction; if the target ship is predicted to be not in the SAR imaging beam range, the state information is returned, the guiding does not meet the SAR imaging condition, and the SAR imaging cannot be guided. The method for obtaining the test conclusion by using the ground data receiving and processing equipment to interpret the AIS message data and the SAR target detection result is that: the ground data receiving and processing equipment uses a demodulator to demodulate the SAR imaging data and the AIS data to generate baseband data, the baseband data is decoded, deformatted and decompressed to generate load service data, the SAR imaging data and the AIS data are identified through a virtual channel identifier, the position information of the target ship corresponding to the MMSI is searched from the AIS data, the position error and the imaging result are compared, the test conclusion is obtained by interpreting the AIS guiding SAR real-time processing function performance index.

2. The test method of claim 1, wherein, The simulation flight test environment is for controlling the ground equipment, and comprises a sensor data injection module, an actuator data acquisition module, a ground dynamics and kinematics simulation module, a test comprehensive control module and a signal interface adaptation conditioner. The sensor data injection module calculates angular velocity, star and sun azimuth parameters based on the celestial body attitude and orbit parameter, and then obtains the output signals of the gyro, star sensor and sun sensor as the sensor signals by using a sensor model, and the sensor signals are sent to the satellite control subsystem after being processed by a signal interface adapter conditioner; the satellite control subsystem collects the sensor signals and realizes satellite attitude determination by using an attitude determination algorithm, and forms an actuator control signal according to the expected attitude and a preset control rate; the actuator control signal is collected by an actuator data collection module to obtain a thruster pulse width signal, a momentum wheel rotation speed signal and a magnetic torque device current signal, and the signals are transmitted to the ground dynamics and kinematics simulation module; the ground dynamics and kinematics simulation module simulates and calculates the thruster pulse width signal, the momentum wheel rotation speed signal and the magnetic torque device current signal to obtain the celestial body attitude and orbit parameter, and transmits the celestial body attitude and orbit parameter to the sensor data injection module.

3. The test method of claim 2, wherein, The satellite orbit attitude dynamics equation used by the ground dynamics and kinematics simulation module is: where V is the velocity vector of the satellite, F out is the resultant external force of the earth, moon, sun gravity, atmospheric drag and solar pressure, F Thruster is the thrust generated by the thrusters, ω is the attitude angular velocity vector, M out is the resultant moment of the gravity gradient moment, aerodynamic moment and solar pressure moment, M Thruster is the control moment generated by the thrusters, M Wheel is the moment generated by the momentum exchange device, m is the total mass of the satellite, and I is the total inertia of the satellite.

4. The test method of claim 1, wherein, The ground total control equipment injects a guiding imaging instruction package containing a ship offshore mobile identification code, and also stipulates the longest working time for this time guiding imaging, and if the guiding imaging is not completed within the time, the guiding imaging is exited.

5. The test method of claim 1, wherein, The AIS signal source is composed of a signal source main control software, a baseband signal processing board, a radio frequency channel module and a power supply.

6. The test method of claim 1, wherein, The SAR echo simulation device generates SAR echo signals in the following manner: the SAR echo simulation device generates simulated echoes, i.e., SAR echo signals, by using a real-time convolution method according to the satellite-ground geometry and the target scene and ship target characteristics.

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