Airborne glacier detection radar system and imaging processing method

Abstract

The invention provides an airborne glacier detection radar system and an imaging processing method, and belongs to the technical field of radar information acquisition. The airborne glacier detection radar system consists of a fully polarized antenna unit, a power amplifier unit, a host control unit, a storage unit, an inertial navigation unit, a power supply unit and an upper computer monitoring unit, and is used for transmitting and receiving electromagnetic wave signals through an antenna to carry out perspective detection on a glacier; echo signals of the atmosphere and the glacier surface layer, the glacier internal structure and the glacier bottom layer and bed rock are obtained, and the glacier perspective detection capability is achieved. An airborne glacier detection radar is integrated on an aircraft platform, and one-dimensional section information of a glacier is obtained through airborne motion. Wherein the vertical resolution of the very high frequency airborne glacier detection radar is superior to 2 meters, and the glacier detection depth is superior to 100 meters. According to the invention, a new technical means is provided for the airborne glacier detection system in the application research aspects of polar glacier reserve estimation, ice layer thickness measurement, glacier fine structure and under-ice landform detection and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar information acquisition and processing, and specifically relates to an airborne glacier detection radar system and an imaging processing method for glacier perspective detection. Background Art

[0002] Electromagnetic wave theory is the research basis of glacier microwave detection technology. The transmitter transmits electromagnetic waves to the ground through an antenna, and uses the echo signal to study the characteristics of ice and snow media and the three-dimensional structure of glaciers. The glacier microwave detection technology is combined with aviation observation technology to overcome the limitations of platform factors and climate and geographical factors in the test area, and realize a wide coverage and high revisit airborne glacier detection system, obtain three-dimensional tomographic imaging data of mountain glaciers and polar ice caps, and provide information support for cryosphere scientific research.

[0003] After entering this century, with the continuous emergence of high-precision positioning systems and new technologies, airborne glacier detection systems of different systems have been widely used in multi-directional detection of ice sheets, ice streams, ice caps and glaciers to meet the needs of different research directions. At the end of 2005, the first multi-channel coherent depth sounder (MCoRDS) was successfully developed. It mainly measures the thickness of the ice sheet and detects the electromagnetic echo intensity profile information of the inner layer of the ice sheet. It uses different pulse width echoes in different receivers to measure the difference between the propagation time of the ice surface and the bedrock, and calculates the thickness of the ice layer. After that, the interdisciplinary "Polar Ice Sheet Detection System (PRISM)" research program was initiated. The PARIS system realized the high-altitude flight measurement of similar systems for the first time, and used the 150MHz frequency band long wave to detect the internal structure of the ice sheet and the subglacial terrain. In 2016, the CReSIS VHF / HF detection system was successfully developed with a dual-band system of 14MHz and 30-35MHz. It is carried on the Twin Otter DHC-6 aircraft and the YAK-54 small UAV platform. The test results show that the use of a multi-channel synthetic cross-track array can reduce clutter and improve sensitivity.

[0004] Domestic research on airborne glacier detection systems started late, and there are limitations such as limited observation methods, single observation areas, limited observation data, and insufficient data analysis and interpretation capabilities. At present, China still has no independently developed airborne system dedicated to polar glacier detection, lacks high-resolution polar cryosphere active microwave detection technology, and cannot support the research of cutting-edge scientific issues such as rapid glacier change monitoring and prediction, ice base material classification and resolution, snow cover and frozen soil changes, and cannot meet the research needs of key common technologies such as perspective detection of the Earth's multiple spheres. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides an airborne glacier detection radar system and imaging processing method, which realizes the antenna design under the coupling of antenna feed source and body structure by integrating the multipath effect introduced by the body structure, obtains echo signals of atmosphere and glacier surface, glacier internal structure, glacier bottom layer and bedrock, and has the ability of glacier perspective detection.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: An airborne glacier detection radar system comprises a fully polarized antenna unit, a power amplifier unit, a host control unit, a storage unit, an inertial navigation unit, a power supply unit, and a host computer monitoring unit; the fully polarized antenna unit is connected to the power amplifier unit to realize the transmission of high-power signals; the power amplifier unit communicates with the host control unit to realize the transmission and reception of broadband signals; the modules inside the host control unit are interconnected through an integrated circuit board, and high-speed data transmission is realized between the host control unit and the storage unit, and the host control unit receives real-time combined navigation information of the inertial navigation unit; the power supply unit provides a stable direct current voltage to the host control unit; the host computer monitoring unit monitors the status of the radar system and controls the issued instructions; the host control unit is connected to the host computer monitoring unit; the fully polarized antenna unit is vertically pointed to the surface of the glacier, and emits electromagnetic wave signals to the target area of ​​the glacier. After being transmitted through the atmosphere, a part of the electromagnetic wave signals forms a strong reflection signal in the surface area of ​​the glacier, a part of the electromagnetic wave signals penetrate the ice surface, propagate and attenuate inside the ice layer, and form a weak reflection signal, and another part of the electromagnetic wave signals penetrate the ice layer and form an electromagnetic wave reflection signal in the bedrock under the ice.

[0007] Furthermore, the airborne glacier detection radar system adopts a long-wave broadband design, high frequency (HF, 3MHz-30MHz), very high frequency (VHF, 30MHz-300MHz), and ultra-high frequency (300MHz-3GHz) to improve the electromagnetic wave glacier perspective detection capability and detection accuracy.

[0008] Furthermore, the fully polarized antenna unit is installed in the belly antenna cover of the aircraft. The coupling effect between the radar signal source and the fuselage is considered in its design, and a comprehensive design of the fuselage-antenna is performed. This design is based on two reasons: since the aircraft skin is made of metal conductors, when the skin is irradiated by electromagnetic waves, induction and secondary radiation are generated, which will change the electromagnetic characteristics of the fully polarized antenna unit; since the operating frequency of the airborne ice detection radar system is low and the antenna beam is wide, the outward radiation of the fully polarized antenna unit is greatly affected by the aircraft fuselage.

[0009] The present invention also provides an imaging processing method of an airborne glacier detection radar system, comprising the following steps: Step 1: Use the motion error compensation technology of the airborne glacier detection system to complete the error compensation of the radar data in the along-track direction and the cross-track direction, and obtain the radar data after error compensation; Step 2: performing a focusing technique along the track direction suitable for multi-layer media according to the error-compensated radar data to obtain radar data processed in a two-dimensional along-track direction; Step 3: Use a cross-track clutter suppression algorithm to suppress clutter on the profile of the radar data processed according to the two-dimensional along-track focusing to obtain a high-resolution radar image.

[0010] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the imaging processing method of the above-mentioned airborne glacier detection radar system are implemented.

[0011] The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the imaging processing method of the above-mentioned airborne glacier detection radar system are performed.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a new type of airborne glacier detection radar system. A special radar antenna is designed for glacial topography, which improves the distortion of the performance pattern of traditional radar antennas under glacial topography. The system obtains echo signals of the atmosphere and glacier surface, the internal structure of the glacier, the bottom layer of the glacier and the bedrock, has the ability to detect glaciers through perspective, obtains information on glacier thickness, and establishes a three-dimensional structure of the glacier, providing new technical means for further obtaining glacier reserves, glacier fine structure, and subglacial topography and other applied research. The present invention solves the problem that the prior art lacks high-resolution active microwave detection technology and cannot support research on cutting-edge scientific issues such as monitoring and prediction of rapid glacier changes. Since there is currently no such technology in China, the present invention not only fills the technical gap, but also has broad application prospects. It is expected to play an important role in many fields such as mountain glaciers, polar glaciers, and plateau permafrost. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a block diagram of the composition of the airborne glacier detection radar system of the present invention; Figure 2a This is the main view of the first and second modules; Figure 2b It is a side view of the first and second array modules; Figure 2c It is a three-dimensional picture of the first-stage module and the second-stage module; Figure 3 This is a schematic diagram of the arrangement of fully polarized antenna array modules; Figure 4 This is a schematic diagram of the connection between the full polarization antenna power divider module and the array module; Figure 5 This is a flowchart of the glacier radar data imaging processing algorithm; Figure 6 This is a diagram of the imaging geometry of the airborne glacier detection radar system.

[0014] Among them, the figure marks are: fully polarized antenna unit 1, power amplifier unit 2, host control unit 3, storage unit 4, inertial navigation unit 5, power supply unit 6, host computer monitoring unit 7, first array module 1.1 and second array module 1.2, first power divider module 1.3, second power divider module 1.4, box assembly 1.1.1, antenna polarization plate assembly 1.1.2, transmitting module 2.1, first receiving module 2.2, second receiving module 2.3, switch coupling assembly 2.1.1, pre-stage drive assembly 2.1.2, power assembly 2.1.3, amplification assembly 2.2.1 and filtering assembly 2.2.2, frequency source module 3.1, digital module 3.2, control board assembly 3.2.1, DAC assembly 3.2.2, ADC assembly 3.2.3, bottom plate 8, structural bracket 9, weight reduction groove 10, back cavity outer wall 11, slotted polarization plate 12, polarization plate bracket 13, center point 14. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0016] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. used in the present invention to indicate the orientation or position relationship is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0017] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] like Figure 1 As shown, the airborne glacier detection radar system of an embodiment of the present invention includes a fully polarized antenna unit 1, a power amplifier unit 2, a host control unit 3, a storage unit 4, an inertial navigation unit 5, a power supply unit 6, and a host computer monitoring unit 7.

[0019] The fully polarized antenna unit 1 and the power amplifier unit 2 are connected by two radio frequency cables to realize the transmission of high-power signals; the power amplifier unit 2 and the host control unit 3 communicate through radio frequency signals to realize the transmission and reception of broadband signals; the modules inside the host control unit 3 are interconnected through an integrated circuit board, and high-speed data transmission with the storage unit 4 is realized through an optical fiber, and real-time combined navigation information reception with the inertial navigation unit 5 is realized through a serial port; the power supply unit 6 provides a stable DC voltage to the host control unit 3 through the whole machine cable. The host computer monitoring software monitors the status of the radar system and controls the issuance of instructions through the serial port or network port. The host control unit 3 is connected to the host computer monitoring unit 7 through the serial port / network port.

[0020] The fully polarized antenna unit 1 includes the same first array module 1.1 and second array module 1.2, the same first power divider module 1.3 and second power divider module 1.4. The following description is based on the first array module 1.1 and the first power divider module 1.3. Each first array module 1.1 is composed of a box assembly 1.1.1, an antenna polarization plate assembly 1.1.2, a plurality of structural brackets 9 and cables.

[0021] like Figure 2a , Figure 2b , Figure 2c As shown, the box assembly 1.1.1 is a back cavity with an opening facing downward. The bottom plate 8 of the back cavity is square with a side length of 1000 mm. A structural bracket 9 is provided on the outside of the bottom plate for connection with the belly of the aircraft. The outer wall 11 of the back cavity is rectangular, the long side of the rectangle is connected to the bottom plate 8, the side length is 1000 mm, and the short side is the depth of the back cavity, which is 290 mm. A weight reduction groove 10 is provided on the outer side of the outer wall.

[0022] The antenna polarization plate assembly 1.1.2 includes four rectangular slotted polarization plates 12 and corresponding polarization plate brackets 13, which are placed diagonally. Each slotted polarization plate 12 is fixed on the bottom plate 8 in the back cavity of the box assembly 1.1.1 by two polarization plate brackets 13 arranged in parallel, and is made of aluminum alloy 6061-T6 material. The slotted polarization plate is 12 flat metal material, and the length of the polarization plate bracket 13 is 340mm. The center point 14 of the overall shape of the four slotted polarization plates is the same as the center point of the bottom plate of the box assembly 1.1.1, and the angle between the side of the square structure formed by the four slotted polarization plates and the side of the bottom plate 8 is 45°. The overall height of the box assembly 1.1.1 is 441mm, as shown in FIG. Figure 2b shown.

[0023] like Figure 3 As shown, the first array module 1.1 and the second array module 1.2 are installed on the belly of the aircraft and arranged front and back along the aircraft fuselage structure, with a center spacing of 1500mm. The box assembly 1.1.1 and the antenna polarizer assembly 1.1.2 are connected by cables to transmit signals.

[0024] The fully polarized antenna unit 1 adopts a low-profile broadband monopole antenna design, which can achieve a wider operating frequency band; the all-metal structure ensures that the antenna achieves directional radiation, avoiding the loss caused by the printed plate. The antenna height is about 1 / 4 of the wavelength, so the low-profile broadband monopole antenna can meet the size requirements within the required operating frequency band.

[0025] The fully polarized antenna unit 1 is affected by the aircraft structure, and its radiation pattern is seriously affected and distorted, and the low-frequency radiation pattern distortion is more serious than the high-frequency radiation pattern. For example, the H-polarization radiation pattern of the 150MHz antenna cannot be used normally. Based on the design of a low-profile broadband monopole antenna, the present invention adds a metal electric wall around the first array module 1.1 and the second array module 1.2 to realize a ring cavity antenna. Through simulation and comparison of antenna radiation patterns at different frequencies, it can effectively reduce beam distortion and improve antenna radiation patterns to achieve good antenna radiation characteristics.

[0026] The fully polarized antenna unit 1 is installed in the belly antenna cover of the aircraft. The coupling effect between the radar signal source and the fuselage is considered in its design, and a comprehensive design of the fuselage-antenna is performed. This design is based on two reasons: since the aircraft skin is made of metal conductors, when the aircraft skin is irradiated by electromagnetic waves, induction and secondary radiation are generated, which will change the electromagnetic characteristics of the fully polarized antenna unit for transmission and reception; since the operating frequency of the airborne ice detection radar system is low and the antenna beam is wide, the outward radiation of the fully polarized antenna unit is greatly affected by the aircraft fuselage.

[0027] The first power divider module 1.3 outputs the different direction signals received from the power component 2.1.3 to the first array module 1.1 and the second array module 1.2. The first power divider module 1.3 outputs the horizontal channel signals to the first array module 1.1 and the second array module 1.2 respectively, and the second power divider module 1.4 outputs the vertical channel signals to the first array module 1.1 and the second array module 1.2 respectively. The specific connection method is as follows: Figure 4 shown.

[0028] The power amplifier unit 2 comprises a transmitting module 2.1, a first receiving module 2.2 and a second receiving module 2.3. The first receiving module 2.2 is described below.

[0029] The transmitting module 2.1 includes a switch coupling component 2.1.1, a pre-stage driving component 2.1.2 and a power component 2.1.3. The switch coupling component 2.1.1 performs ping-pong switching between the horizontal channel and the vertical channel of the RF signal generated by the DAC component 3.2.2, and outputs it to the pre-stage driving component 2.1.2. The pre-stage driving component 2.1.2 has the function of performing a first-stage power amplification and filtering process on the RF signal input by the switch coupling component 2.1.1, and outputs it to the power component 2.1.3, which is mainly used to provide gain, and the saturated output power is 25dBm. The power component 2.1.3 has the function of performing a second-stage power amplification on the RF signal input by the pre-stage driving component 2.1.2, and outputs it to the fully polarized antenna unit 1, and the saturated output power is 59dBm.

[0030] The receiving module 2.2 includes an amplifier component 2.2.1 and a filter component 2.2.2. The amplifier component 2.2.1 amplifies the power of the RF signal input by the fully polarized antenna unit 1 and outputs it to the filter component 2.2.2. The filter component 2.2.2 has the function of filtering the RF signal input by the amplifier component 2.2.1 and outputting it to the host control unit ADC component 3.2.3.

[0031] The host control unit 3 includes a frequency source module 3.1 and a digital module 3.2.

[0032] The frequency source module 3.1 is mainly composed of a digital configurable PLL component, a crystal oscillator component, a filter component, etc. The crystal oscillator component generates one 100MHz and two 2GHz clock signals, which are processed by the digital configurable PLL component and the filter component and output to the host control unit digital module.

[0033] The digital module 3.2 is mainly composed of a control board component 3.2.1, a DAC component 3.2.2 and an ADC component 3.2.3. The main functions of the control board component 3.2.1 include: controlling the working modes of the DAC component 3.2.2 and the ADC component 3.2.3, and inputting three clock signals of the frequency source. The function of the DAC component 3.2.2 is to generate a digital broadband intermediate frequency signal and output it to the switch coupling module of the power amplifier unit; the function of the ADC component 3.2.3 is to collect the RF signal received by the power amplifier unit.

[0034] The storage unit 4 is used to store radar raw echo data and inertial navigation auxiliary data. The storage unit 4 selects a wide temperature industrial hard disk, supports online transcription, supports NVMe1.2 protocol, transmission interface PCIe3.0x4, maximum sequential write speed 1.7GB / s, maximum sequential read speed 3.2GB / s.

[0035] The inertial navigation unit 5 includes a GNSS receiver module, an IMU measurement module, and a POS processing module. The GNSS receiver processes the received satellite signals in real time to obtain accurate time information and position information. The IMU measurement module measures the three-axis acceleration and angular velocity information of the carrier in the inertial space. The integrated navigation processing module completes the timing of the IMU raw data based on the GNSS time information, and realizes the fusion processing of the GNSS data and the IMU data based on the Kalman filter algorithm to obtain real-time integrated navigation information.

[0036] The power supply unit 6 is used to stabilize and rectify the input DC power supply, output stable secondary power supply to other units of the airborne ice detection radar system, and has wide voltage range input and multi-channel output capabilities. Wide voltage input range: 16V~36V. Multi-channel output capability: three channels +12V and two channels +24V.

[0037] The host computer monitoring unit 7 monitors and controls the status and working mode of the airborne glacier detection radar system in real time, and the installation environment is a computer under the Windows 10 operating system.

[0038] In order to enable the airborne glacier detection radar system of the embodiment of the present invention to process the acquired glacier radar data and generate a high-resolution radar image, an embodiment of an imaging processing method of the airborne glacier detection radar system is provided, which mainly includes three technologies or algorithms, such as Figure 5 As shown, perform the following steps: Step 1: Use the motion error compensation technology of the airborne glacier detection system to complete the error compensation of radar data in the along-track direction and across-track direction; Step 2: performing a focusing technique suitable for multi-layer media along the track according to the error-compensated radar data to obtain radar data processed in a two-dimensional along-track direction; Step 3: Use a cross-track clutter suppression algorithm to suppress clutter on the radar data profile processed according to the two-dimensional along-track focusing process, and use a cross-track clutter suppression algorithm to obtain a high-resolution radar image.

[0039] Specifically, the step 1 includes the following steps: Step 1.1: Based on the glacier radar data along the track, perform equal-interval interpolation based on the original sampling points to increase the sampling rate of the signal; after increasing the sampling rate, resample and adjust the sampling rate of the signal back to the required target sampling rate to ensure that the signal retains its original information at the target sampling rate.

[0040] The resampled signal for: ; in, is the original echo signal, is the impulse response of the resampling filter, is the time interval at the target sampling rate, is the integer index of the sampling point, Indicates time, Indicates the time of resampling.

[0041] Step 1.2: Perform range Doppler phase compensation to eliminate the influence of the Doppler effect on glacier radar data and improve the radar's measurement accuracy and reliability for moving targets.

[0042] Data signal after Doppler phase compensation for: ; in, represents the initial phase, represents the radar wavelength, Indicates speed, Represents an imaginary unit.

[0043] Step 1.3: Correlate the glacier radar data of adjacent tracks and use geometric relationships, triangulation and other methods to calculate the relative distance of cross-track target points based on the relative positions of the radars.

[0044] Specifically, the step 2 includes the following steps: Step 2.1: The electromagnetic wave signal is transmitted through the atmosphere, forming a strong electromagnetic wave reflection signal in the surface area of ​​the glacier. The electromagnetic wave signal penetrates the ice surface, propagates and attenuates inside the ice layer. The development of ice cracks and internal structure have a significant impact on the propagation and attenuation characteristics of the electromagnetic wave, forming a weak reflection signal. Part of the electromagnetic wave signal penetrates the ice layer and forms an electromagnetic wave reflection signal at the bedrock interface under the ice, such as Figure 6 As shown. Among them, h represents the relative height of the aircraft, d represents the thickness of the ice layer, v represents the flight speed, and θ represents half of the radar's field of view. The radar receives the signal of electromagnetic waves passing through the air, the middle and multi-layer media inside the ice layer, and calculates the equivalent distance between the radar and the point target by combining factors such as the influence of different media and the signal propagation time. as follows: ; in, Represents the distance in air, represents the distance inside the ice layer, represents the coefficient of propagation attenuation inside the ice layer, represents distance to time, Indicates the direction and time, Represents the moment of distance to time, Indicates the moment of time in azimuth; Step 2.2: Calculate the focus reference function for each target depth, compensate for the motion of the radar platform and the geometric position of the target, ensure that every point in the image can be correctly focused, and improve the image focus and resolution. Focus reference function It is expressed as: ; in, The speed of light.

[0045] Step 2.3: Focus in azimuth and range simultaneously according to the focus reference function, and improve the resolution and clarity of the image in azimuth and range. It is expressed as: ; Specifically, step 3 includes the following steps: Step 3.1: Based on the extracted radar height, ice surface elevation, ice surface tilt angle, airborne radar motion error, and ground environment data, the existing digital elevation model is used to simulate the surface clutter signal and analyze the characteristics of the clutter signal.

[0046] Step 3.2: Combine the simulated clutter signal with the SAR imaging algorithm to generate a simulation image, so that the radar image and the simulation image are automatically aligned.

[0047] Step 3.3: Extract surface clutter echoes from the radar images of adjacent tracks, perform cross-track clutter suppression, improve image quality, and make target features more obvious.

[0048] In addition, the airborne glacier detection radar system of the embodiment of the present invention can process the acquired glacier radar data and generate high-resolution radar images, and further calculate or invert glacier elements such as glacier thickness, three-dimensional structure and ice reserves based on the radar images. The specific method is as follows: Based on the 3D imaging geometry of glaciers, the current line integral based on cross sections is transformed into a surface integral calculation based on 3D imaging geometry to achieve accurate estimation of ice reserves. The calculation model is as follows: For each target point on the glacier, the corresponding ice thickness for: ; in, Indicates the number of sampling points in the bedrock layer corresponding to the distance. Indicates the number of sampling points corresponding to the distance of the ice surface layer, Represents the time interval from the sampling point to the distance, Represents the speed at which electromagnetic waves propagate in ice.

[0049] Average ice thickness for the corresponding area for: ; in, Indicates the number of sampling points in the area.

[0050] Ice reserves The estimate is:

[0051] in, Indicates the size of the integrated area corresponding to the ice thickness data within the regional range.

[0052] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the imaging processing method of the above-mentioned airborne glacier detection radar system are implemented.

[0053] The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the imaging processing method of the above-mentioned airborne glacier detection radar system are performed.

[0054] It should be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The solutions in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and interpreted scripting language JavaScript, etc.

[0055] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0056] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0057] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0058] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0059] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An airborne glacier detection radar system, characterized in that: It includes a fully polarized antenna unit, a power amplifier unit, a host control unit, a storage unit, an inertial navigation unit, a power supply unit, and a host computer monitoring unit; the fully polarized antenna unit is connected to the power amplifier unit to realize the transmission of high-power signals; the power amplifier unit communicates with the host control unit to realize the transmission and reception of broadband signals; the modules inside the host control unit are interconnected through an integrated circuit board, and high-speed data transmission is realized with the storage unit, and the host control unit receives real-time combined navigation information of the inertial navigation unit; the power supply unit provides a stable DC voltage to the host control unit; the host computer monitoring unit monitors the status of the radar system and controls the issued instructions; the host control unit is connected to the host computer monitoring unit; the fully polarized antenna unit points vertically to the surface of the glacier and transmits electromagnetic wave signals to the target area of ​​the glacier. After being transmitted through the atmosphere, a part of the electromagnetic wave signals forms a strong reflection signal in the surface area of ​​the glacier, a part of the electromagnetic wave signals penetrate the ice surface, propagate and attenuate inside the ice layer, forming a weak reflection signal, and another part of the electromagnetic wave signals penetrate the ice layer to form an electromagnetic wave reflection signal in the bedrock under the ice.

2. The airborne glacier detection radar system according to claim 1, characterized in that: The airborne glacier detection radar system adopts a long-wave broadband design, including high frequency, very high frequency, and ultra-high frequency, to improve the electromagnetic wave glacier perspective detection capability and detection accuracy; the frequency range of high frequency is 3MHz-30MHz, the frequency range of very high frequency is 30MHz-300MHz, and the frequency range of ultra-high frequency is 300MHz-3GHz.

3. The airborne glacier detection radar system according to claim 1, characterized in that: The fully polarized antenna unit is installed under the belly of the aircraft, and a radome is installed on the outside of the fully polarized antenna unit. The electromagnetic wave beam emitted by the antenna irradiates the fuselage structure of the aircraft to generate induction and secondary radiation.

4. The airborne glacier detection radar system according to claim 1, characterized in that: The power amplifier unit, host control unit, storage unit, inertial navigation unit, power supply unit and host computer monitoring unit are installed in the cabin, fixed on the structural mounting plate, and connected and powered by cables.

5. The airborne glacier detection radar system according to claim 1, characterized in that: The vertical resolution of the airborne glacier detection radar system in the VHF band is better than 2 meters, and the glacier detection depth is better than 100 meters.

6. An imaging processing method for an airborne glacier detection radar system, characterized in that: The steps include: Step 1: Use the motion error compensation technology of the airborne glacier detection system to complete the error compensation of the radar data in the along-track direction and the cross-track direction, and obtain the radar data after error compensation; Step 2: performing a focusing technique along the track direction suitable for multi-layer media according to the error-compensated radar data to obtain radar data processed in a two-dimensional along-track direction; Step 3: Use a cross-track clutter suppression algorithm to suppress clutter on the profile of the radar data processed according to the two-dimensional along-track focusing to obtain a high-resolution radar image.

7. The imaging processing method of an airborne glacier detection radar system according to claim 6, characterized in that: The step 1 comprises the following steps: Step 1.1: Based on the glacier radar data along the track, perform equal-interval interpolation based on the original sampling points to increase the sampling rate of the signal; after increasing the sampling rate, perform resampling to adjust the sampling rate of the signal back to the required target sampling rate to ensure that the signal retains its original information at the target sampling rate; The resampled signal for: ； in, is the original echo signal, is the impulse response of the resampling filter, is the time interval at the target sampling rate, is the integer index of the sampling point, Indicates time, Indicates the time of resampling; Step 1.2: Perform range Doppler phase compensation to eliminate the influence of Doppler effect on glacier radar data and improve the radar's measurement accuracy and reliability for moving targets; Data signal after Doppler phase compensation for: ； in, represents the initial phase, represents the radar wavelength, Indicates speed, represents an imaginary unit; Step 1.3: Correlate the glacier radar data of adjacent tracks and calculate the relative distance of the cross-track target points based on the relative positions of the radars.

8. The imaging processing method of an airborne glacier detection radar system according to claim 6, characterized in that: The step 2 comprises the following steps: Step 2.1: The electromagnetic wave signal is transmitted through the atmosphere, forming a strong electromagnetic wave reflection signal in the surface area of ​​the glacier. The electromagnetic wave signal penetrates the ice surface, propagates and attenuates inside the ice layer. The development of ice cracks and the internal structure have a significant impact on the propagation and attenuation characteristics of the electromagnetic wave, forming a weak reflection signal. Part of the electromagnetic wave signal penetrates the ice layer and forms an electromagnetic wave reflection signal at the bedrock interface under the ice; the radar receives the signal of the electromagnetic wave passing through the internal medium and multi-layer media including air and ice, and calculates the equivalent distance between the radar and the point target by combining the influence of different media and the signal propagation time. as follows: ； in, Represents the distance in air, represents the distance inside the ice layer, represents the coefficient of propagation attenuation inside the ice layer, represents distance to time, Indicates the direction and time, Represents the moment of distance to time, Indicates the moment of time in azimuth; Step 2.2: Calculate the focus reference function for each target depth, compensate for the movement of the radar platform and the geometric position of the target, ensure that each point in the image can be correctly focused, and improve the focus and resolution of the image; Focus reference function It is expressed as: ； in, is the speed of light; Step 2.3: Focus in azimuth and range simultaneously according to the focusing reference function, and improve the resolution and clarity of the image in azimuth and range at the same time; the signal after focusing It is expressed as: 。 9. The imaging processing method of an airborne glacier detection radar system according to claim 6, characterized in that: The step 3 comprises the following steps: Step 3.1: Based on the extracted radar height, ice surface elevation, ice surface tilt angle, airborne radar motion error and ground environment data, the existing digital elevation model is used to simulate the surface clutter signal and analyze the characteristics of the clutter signal; Step 3.2: Combine the simulated clutter signal with the SAR imaging algorithm to generate a simulation image, so that the radar image and the simulation image are automatically registered; Step 3.3: Extract surface clutter echoes from the radar images of adjacent tracks, perform cross-track clutter suppression, improve image quality, and make target features more obvious.

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