An airborne glacier detection radar system and imaging processing method

Abstract

The present invention provides an airborne glacier detection radar system and an imaging processing method, belonging to the technical field of radar information acquisition. The airborne glacier detection radar system is composed of a full-polarization 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. By transmitting and receiving electromagnetic wave signals through the antenna, it conducts perspective detection on glaciers, obtains echo signals of the atmosphere and the glacier surface layer, the internal structure of the glacier, the bottom of the glacier and the bedrock, and has the ability of glacier perspective detection. The airborne glacier detection radar is integrated on an aircraft platform to obtain one-dimensional profile information of the glacier through airborne movement. Among them, the vertical resolution of the very high frequency airborne glacier detection radar is better than 2 meters, and the glacier detection depth is better than 100 meters. The present invention provides a new technical means for the application research of airborne glacier detection systems in aspects such as polar glacier reserve estimation, ice thickness measurement, glacier fine structure and subglacial landform detection, etc.

Description

Technical Field

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

[0002] The electromagnetic wave theory is the research basis of glacier microwave detection technology. It is a geophysical detection method that uses a transmitter to emit electromagnetic waves to the ground through an antenna and studies the characteristics of ice and snow media and the three-dimensional structure information of glaciers using the echo signal. The combination of glacier microwave detection technology and aviation observation technology overcomes the limitations of platform factors, as well as climate and geographical factors in the test area, realizes an airborne glacier detection system with wide coverage and high revisit, obtains three-dimensional tomographic imaging data of mountain glaciers and polar ice sheets, and provides 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, which mainly measures the ice sheet thickness and detects the electromagnetic echo intensity profile information inside the ice sheet. By using the echoes with different pulse widths in different receivers to measure the difference in propagation time between the ice surface and the bedrock respectively, the ice layer thickness is calculated. Subsequently, the interdisciplinary "Polar Ice Sheet Detection System (PRISM)" research plan was launched. The PARIS system first realized high-altitude flight measurement of similar systems and used long waves in the 150 MHz frequency band to detect the internal structure of the ice sheet and the subglacial topography. In 2016, the CReSIS VHF / HF detection system was successfully developed, which has a dual-band system of 14 MHz and 30 - 35 MHz, and is carried on the Twin Otter DHC-6 aircraft and the YAK-54 small unmanned aircraft platform. The test results show that by using a multi-channel synthetic cross-track array, clutter can be reduced and sensitivity can be improved.

[0004] The research on airborne glacier detection systems in China started relatively late, with limitations such as limited observation means, single observation area, limited observation data, and insufficient data analysis and interpretation capabilities. At present, there is still no domestically developed airborne system dedicated to polar glacier detection in China, lacking high-resolution active microwave detection technology means for the polar cryosphere, unable to support the research of frontier scientific issues such as rapid glacier change monitoring and prediction, ice basement material classification and discrimination, snow cover and permafrost change, and unable to meet the research needs of key common technologies such as multi-layer perspective detection of the earth. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an airborne glacier detection radar system and an imaging processing method, which realize the antenna design under the coupling effect of the antenna feed and the airframe structure by comprehensively considering the multipath effect introduced by the airframe structure, obtain the echo signals of the atmosphere, the glacier surface layer, the internal structure of the glacier, the bottom layer of the glacier and the bedrock, and have the ability of glacier perspective detection.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An airborne glacier detection radar system includes a full-polarization 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; the full-polarization 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; each module inside the host control unit is interconnected through an integrated circuit board, and at the same time realizes high-speed data transmission with the storage unit, and the host control unit receives the real-time integrated navigation information of the inertial navigation unit; the power supply unit provides a stable DC voltage to the host control unit; the upper computer monitoring unit monitors the state of the radar system and controls the issued instructions; the host control unit is connected to the upper computer monitoring unit; the full-polarization antenna unit vertically points to the glacier surface layer and emits electromagnetic wave signals to the glacier target area. After passing through the atmosphere, a part of the electromagnetic wave signals form strong reflection signals in the glacier surface layer area, a part of the electromagnetic wave signals penetrate the ice surface layer, propagate and attenuate inside the ice layer to form weak reflection signals, and another part of the electromagnetic wave signals penetrate the ice layer to form electromagnetic wave reflection signals on the bedrock under the ice.

[0008] Furthermore, the airborne glacier detection radar system adopts a long-wave broadband design, including high frequency (HF, 3 MHz - 30 MHz), very high frequency (VHF, 30 MHz - 300 MHz), and ultra-high frequency (300 MHz - 3 GHz), to improve the electromagnetic wave glacier perspective detection ability and detection accuracy.

[0009] Furthermore, the full-polarization antenna unit is installed in the belly radome of the aircraft. When designing it, the coupling effect between the radar signal source and the fuselage is considered, and the integrated design of the fuselage-antenna is carried out. 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 will occur, which will change the electromagnetic characteristics of the full-polarization antenna unit for transmitting and receiving; since the operating frequency of the airborne glacier detection radar system is low and the antenna beam is wide, the external radiation of the full-polarization antenna unit is greatly affected by the aircraft fuselage.

[0010] The present invention also provides an imaging processing method for an airborne glacier detection radar system, including the following steps:

[0011] 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 cross-track direction, and obtain the radar data after error compensation.

[0012] Step 2: Perform the focusing technology applicable to multi-layer media in the along-track direction based on the radar data after error compensation, and obtain the radar data after two-dimensional focusing processing in the along-track direction.

[0013] Step 3: Adopt the cross-track clutter suppression algorithm to suppress the clutter of the profile of the radar data after two-dimensional focusing processing in the along-track direction, and obtain a high-resolution radar image.

[0014] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the imaging processing method of the above-mentioned airborne glacier detection radar system are implemented.

[0015] 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 implemented.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The present invention provides a new type of airborne glacier detection radar system. A special radar antenna is designed for the glacier topography and landforms, which improves the distortion of the performance pattern of the traditional radar antenna under the glacier topography and landforms. The echo signals of the atmosphere and the glacier surface layer, the internal structure of the glacier, and the glacier bottom and bedrock are obtained, and the glacier perspective detection ability is possessed. The glacier thickness information is obtained, and the three-dimensional structure of the glacier is established, providing a new technical means for further application research such as obtaining glacier reserves, glacier fine structure, and subglacial topography and landforms. The present invention solves the problem that the prior art lacks high-resolution active microwave detection technical means and cannot support the research of frontier scientific issues such as the rapid change monitoring and prediction of glaciers. Since there is no such technology in China at present, the present invention not only fills the technical gap but also has a broad application prospect and is expected to play an important role in multiple fields such as mountain glaciers, polar glaciers, and plateau permafrost. Description of the Drawings

[0018] Figure 1 It is a block diagram of the composition of the airborne glacier detection radar system of the present invention;

[0019] Figure 2a It is the front view of the first sub-module and the second sub-module;

[0020] Figure 2b It is the side view of the first sub-module and the second sub-module;

[0021] Figure 2c are perspective views of the first dipole module and the second dipole module;

[0022] Figure 3 is a schematic diagram of the arrangement of the full-polarization antenna dipole modules;

[0023] Figure 4 is a schematic diagram of the connection between the full-polarization antenna power divider module and the dipole module;

[0024] Figure 5 is a flowchart of the glacier radar data imaging processing algorithm;

[0025] Figure 6 is a diagram of the imaging geometric relationship of the airborne glacier detection radar system.

[0026] Among them, the reference numerals are: full-polarization antenna unit 1, power amplifier unit 2, host control unit 3, storage unit 4, inertial navigation unit 5, power supply unit 6, upper computer monitoring unit 7, first dipole module 1.1 and second dipole module 1.2, first power divider module 1.3, second power divider module 1.4, box assembly 1.1.1, antenna polarization sheet 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 driving assembly 2.1.2, power component 2.1.3, amplification component 2.2.1 and filtering component 2.2.2, frequency source module 3.1, digital module 3.2, control board component 3.2.1, DAC component 3.2.2, ADC component 3.2.3, bottom plate 8, structural bracket 9, weight reduction groove 10, back cavity outer wall 11, slotted polarization sheet 12, polarization sheet bracket 13, center point 14. Detailed implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to 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 used 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.

[0028] 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 indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings. They are 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 a limitation of 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.

[0029] In the present invention, unless otherwise clearly specified and defined, terms such as "installation", "connection", "linkage", "fixation", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral body; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] As Figure 1 shown, the airborne glacier detection radar system of the embodiment of the present invention includes a full-polarization 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.

[0031] The full-polarization antenna unit 1 and the power amplifier unit 2 are connected through two RF cables to achieve the transmission of high-power signals; the power amplifier unit 2 and the host control unit 3 communicate through RF signals to achieve the transmission and reception of broadband signals; each module inside the host control unit 3 is interconnected through an integrated circuit board, and at the same time, high-speed data transmission with the storage unit 4 is achieved through a fiber optic cable, and real-time integrated navigation information reception with the inertial navigation unit 5 is achieved through a serial port; the power supply unit 6 provides a stable DC voltage to the host control unit 3 through a whole-machine cable. The host computer monitoring software monitors the state of the radar system and issues command control through a serial port or a network port. The host control unit 3 is connected to the host computer monitoring unit 7 through a serial port / network port.

[0032] The full-polarization antenna unit 1 includes the same first dipole module 1.1 and second dipole module 1.2, and the same first power divider module 1.3 and second power divider module 1.4. The following descriptions are all based on the first dipole module 1.1 and the first power divider module 1.3. Each first dipole module 1.1 is composed of a box body component 1.1.1, an antenna polarization sheet component 1.1.2, a plurality of structural brackets 9, cables, etc.

[0033] As Figure 2a , Figure 2b , Figure 2c shown, the box body component 1.1.1 is a back cavity with an opening downward. The bottom plate 8 of the back cavity is square with a side length of 1000 mm. Structural brackets 9 are provided on the outer side of the bottom plate for connecting to 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 with a side length of 1000 mm, the short side is the depth of the back cavity, which is 290 mm, and a weight reduction groove 10 is provided on the outer side of the outer wall.

[0034] The antenna polarization sheet assembly 1.1.2 includes four rectangular slotted polarization sheets 12 and corresponding polarization sheet brackets 13, which are placed diagonally. Each slotted polarization sheet 12 is fixed on the bottom plate 8 in the back cavity of the box assembly 1.1.1 by two parallelly arranged polarization sheet brackets 13, and the material used is aluminum alloy 6061-T6. The slotted polarization sheet is made of flat metal material, and the length of the polarization sheet bracket 13 is 340 mm. The center point 14 of the overall shape of the four slotted polarization sheets is the same as the center point of the bottom plate of the box assembly 1.1.1, and the angle between the sides of the square structure formed by the four slotted polarization sheets and the sides of the bottom plate 8 is 45°. The overall height of the box assembly 1.1.1 is 441 mm, as Figure 2b shown.

[0035] As Figure 3 shown, the first dipole module 1.1 and the second dipole module 1.2 are installed on the belly of the aircraft and arranged front and back along the aircraft fuselage structure, and the center distance between the modules is 1500 mm. The box assembly 1.1.1 and the antenna polarization sheet assembly 1.1.2 are connected by cables to transmit signals.

[0036] The full-polarization antenna unit 1 adopts a low-profile broadband monopole antenna design, which can achieve a relatively wide operating frequency band; while adopting a full-metal structure, it ensures that the antenna realizes directional radiation and avoids the loss caused by the printed board. 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.

[0037] The full-polarization antenna unit 1 is affected by the aircraft structure, and its radiation pattern is seriously affected and distorted, and the distortion of the low-frequency radiation pattern is more serious than that of the high-frequency. For example, the H-polarization radiation pattern of the antenna at 150 MHz cannot be normally applied. Based on the low-profile broadband monopole antenna design method, the present invention adds a metal electric wall around the first dipole module 1.1 and the second dipole module 1.2 to realize a loop cavity antenna. Through simulation and comparison of the radiation patterns of antennas at different frequency points, it can effectively reduce the beam distortion, improve the antenna radiation pattern, and achieve good antenna radiation characteristics.

[0038] The full-polarization antenna unit 1 is installed in the belly radome of the aircraft. When designing, the coupling effect between the radar signal source and the fuselage is considered, and the integrated design of the fuselage-antenna is carried out. 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 will occur, which will change the transceiver electromagnetic characteristics of the full-polarization antenna unit; since the operating frequency of the airborne glacier detection radar system is low and the antenna beam is wide, the outward radiation of the full-polarization antenna unit is greatly affected by the aircraft fuselage.

[0039] The first power divider module 1.3 outputs the signals in different directions received from the power component 2.1.3 to the first antenna element module 1.1 and the second antenna element module 1.2. Among them, the first power divider module 1.3 outputs the horizontal direction channel signals to the first antenna element module 1.1 and the second antenna element module 1.2 respectively, and the second power divider module 1.4 outputs the vertical direction channel signals to the first antenna element module 1.1 and the second antenna element module 1.2 respectively. The specific connection method is as Figure 4 shown.

[0040] The power amplifier unit 2 includes a transmitting module 2.1, identical first receiving modules 2.2 and second receiving modules 2.3. The following description is based on the first receiving module 2.2.

[0041] The transmitting module 2.1 includes a switch coupling component 2.1.1, a pre-driver component 2.1.2, and a power component 2.1.3. The switch coupling component 2.1.1 performs ping-pong switching on the radio frequency signals generated by the DAC component 3.2.2 between the horizontal direction channel and the vertical direction channel, and outputs them to the pre-driver component 2.1.2. The pre-driver component 2.1.2 is used to perform primary power amplification and filtering on the radio frequency signals input by the switch coupling component 2.1.1, and output them to the power component 2.1.3, mainly for providing gain, and the saturated output power is 25 dBm. The power component 2.1.3 is used to perform secondary power amplification on the radio frequency signals input by the pre-driver component 2.1.2, and output them to the full-polarization antenna unit 1, and the saturated output power is 59 dBm.

[0042] The receiving module 2.2 includes an amplification component 2.2.1 and a filtering component 2.2.2. The amplification component 2.2.1 amplifies the power of the radio frequency signals input by the full-polarization antenna unit 1, and outputs them to the filtering component 2.2.2. The filtering component 2.2.2 is used to filter the radio frequency signals input by the amplification component 2.2.1, and output them to the host control unit ADC component 3.2.3.

[0043] The host control unit 3 includes a frequency source module 3.1 and a digital module 3.2.

[0044] The frequency source module 3.1 is mainly composed of a digitally configurable PLL component, a crystal oscillator component, a filter component, etc. The crystal oscillator component generates one 100 MHz clock signal and two 2 GHz clock signals, which are processed by the digitally configurable PLL component and the filter component, and output to the digital module of the host control unit.

[0045] The digital module 3.2 mainly consists of a control board component 3.2.1, a DAC component 3.2.2, an ADC component 3.2.3, etc. 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-way clock signals of a 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 amplification unit; the function of the ADC component 3.2.3 is to collect the radio frequency signals received by the power amplifier unit.

[0046] The storage unit 4 is used to store the original radar echo data and inertial navigation auxiliary data. The storage medium selected for the storage unit 4 is a wide-temperature industrial-grade hard disk, which supports online transcription, supports the NVMe1.2 protocol, has a transmission interface of PCIe3.0x4, a maximum sequential write speed of 1.7GB / s, and a maximum sequential read speed of 3.2GB / s.

[0047] 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 performs timing on the original IMU data based on the GNSS time information, and at the same time, based on the Kalman filtering algorithm, realizes the fusion processing of GNSS data and IMU data to obtain real-time integrated navigation information.

[0048] The power supply unit 6 is used to regulate and rectify the input DC power supply, and output a stable secondary power supply to other units of the airborne glacier detection radar system, and has the capabilities of wide voltage range input and multi-channel output. Wide voltage input range: 16V to 36V. Multi-channel output capabilities: three-way +12V and two-way +24V.

[0049] The upper computer monitoring unit 7 monitors and controls the status and working mode of the airborne glacier detection radar system in real time, and is installed on a computer under the windows 10 operating system.

[0050] To enable the airborne glacier detection radar system of the embodiments of the present invention to process the acquired glacier radar data and generate high-resolution radar images, an embodiment of an imaging processing method for the airborne glacier detection radar system is provided, which mainly includes three technologies or algorithms, such as Figure 5 As shown, the following steps are carried out:

[0051] 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 the cross-track direction;

[0052] Step 2: Perform focusing technology applicable to multi-layer media along the track direction based on the radar data after error compensation to obtain the radar data after two-dimensional focusing processing along the track direction;

[0053] Step 3: Use the cross-track clutter suppression algorithm to perform clutter suppression on the radar data profile after two-dimensional focusing processing along the track direction, and obtain a high-resolution radar image.

[0054] Specifically, the said Step 1 includes the following steps:

[0055] Step 1.1: Based on the glacier radar data along the track direction, perform equally spaced interpolation 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 maintains its original information at the target sampling rate.

[0056] The resampled signal is:

[0057] ;

[0058] where 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, represents time, represents the time of resampling.

[0059] Step 1.2: Perform range-Doppler phase compensation to eliminate the influence of the Doppler effect on the glacier radar data and improve the measurement accuracy and reliability of the radar for moving targets.

[0060] The data signal after Doppler phase compensation is:

[0061] ;

[0062] where represents the initial phase, represents the radar wavelength, represents the velocity, represents the imaginary unit.

[0063] Step 1.3: Correlate the glacier radar data of adjacent tracks, and use methods such as geometric relationships and triangulation to calculate the relative distance of the cross-track target points according to the relative positions of the radars.

[0064] Specifically, the said Step 2 includes the following steps:

[0065] 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 layer, propagates and attenuates inside the ice layer. The development of ice layer 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 ice-bedrock interface, as Figure 6 shown. Among them, h represents the relative height of the aircraft, d represents the ice layer thickness, v represents the flight speed, and θ represents half of the radar field of view angle. The radar receives the signals of the electromagnetic wave passing through multiple media such as air and inside the ice layer. Considering factors such as the influence of different media and the signal propagation time, the equivalent distance between the radar and the point target is calculated as follows:

[0066] ;

[0067] Among them, represents the distance in the air, represents the distance inside the ice layer, represents the coefficient of attenuation during propagation inside the ice layer, represents the range-time, represents the azimuth-time, represents the moment of the range-time, represents the moment of the azimuth-time;

[0068] Step 2.2: Calculate the focusing 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 focusing degree and resolution of the image. The focusing reference function is expressed as:

[0069] ;

[0070] Among them, is the speed of light.

[0071] Step 2.3: Simultaneously perform focusing in the azimuth and range directions according to the focusing reference function, and improve the resolution and clarity of the image in both the azimuth and range directions. The focused signal is expressed as:

[0072] ;

[0073] Specifically, the said Step 3 includes the following steps:

[0074] Step 3.1: Based on the extracted radar altitude, ice surface elevation, ice surface tilt angle, airborne radar motion error, and ground environment data, use the existing digital elevation model to simulate the surface clutter signal and analyze the characteristics of the clutter signal.

[0075] Step 3.2: Combine the simulated clutter signal with the SAR imaging algorithm to generate a simulation diagram, and automatically register between the radar diagram and the simulation diagram.

[0076] Step 3.3: Extract the surface clutter echoes from the radar diagrams of adjacent tracks, perform clutter suppression in the cross-track direction, improve the image quality, and make the target features more obvious.

[0077] In addition, the airborne glacier detection radar system according to 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 storage according to the radar images. The specific method is as follows:

[0078] Based on the three-dimensional imaging geometry of the glacier, change the current line integral based on the cross-section to an area integral calculation based on the three-dimensional imaging geometry to achieve an accurate estimation of the ice storage. The calculation model is as follows:

[0079] For each target point of the glacier, the corresponding ice thickness is:

[0080] ;

[0081] where represents the number of sampling points in the range direction corresponding to the bedrock layer, represents the number of sampling points in the range direction corresponding to the ice layer, represents the time interval of the sampling points in the range direction, represents the propagation speed of electromagnetic waves in ice.

[0082] The average ice thickness of the corresponding area is:

[0083] ;

[0084] where represents the number of sampling points within the region.

[0085] The ice storage is estimated as:

[0086]

[0087] where represents the integral area size corresponding to the ice thickness data within the region range.

[0088] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the imaging processing method of the above-mentioned airborne glacier detection radar system are implemented.

[0089] 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 an airborne glacier detection radar system as described above are performed.

[0090] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can 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 code. The solutions in the embodiments of the present invention can be implemented in various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript.

[0091] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows 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 the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0092] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the specified functions in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0093] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are performed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the specified functions in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0094] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made to these embodiments by those skilled in the art once they learn of the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present invention.

[0095] 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 equivalent technologies, 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 full-polarization 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; the full-polarization antenna unit is connected to the power amplifier unit to achieve the transmission of high-power signals; the power amplifier unit communicates with the host control unit to achieve the transmission and reception of broadband signals; each module inside the host control unit is interconnected through an integrated circuit board, and at the same time, high-speed data transmission is achieved with the storage unit. The host control unit receives the real-time integrated navigation information of the inertial navigation unit; the power supply unit provides a stable DC voltage to the host control unit; the upper computer monitoring unit monitors the state of the radar system and controls the issued instructions; the host control unit is connected to the upper computer monitoring unit; the full-polarization antenna unit vertically points to the glacier surface layer and emits electromagnetic wave signals to the glacier target area. After atmospheric transmission, part of the electromagnetic wave signals form strong reflection signals in the glacier surface layer area, part of the electromagnetic wave signals penetrate the ice surface layer, propagate and attenuate inside the ice layer to form weak reflection signals, and another part of the electromagnetic wave signals penetrate the ice layer to form electromagnetic wave reflection signals on the subglacial bedrock; 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 penetration detection ability and detection accuracy; the frequency range of high frequency is 3 MHz - 30 MHz, the frequency range of very high frequency is 30 MHz - 300 MHz, and the frequency range of ultra-high frequency is 300 MHz - 3 GHz; The full-polarization antenna unit is installed inside the antenna radome on the belly of the aircraft; the full-polarization antenna unit adopts a low-profile broadband monopole with a surrounding metal electric wall cavity; The full-polarization antenna unit includes the same first dipole module and second dipole module, and the same first power divider module and second power divider module; each first dipole module is composed of a box body component, an antenna polarization sheet component, multiple structural brackets, and cables; the box body component is a back cavity with an opening downward; structural brackets are provided on the outer side of the bottom plate for connecting to the belly of the aircraft; the antenna polarization sheet component includes a rectangular slotted polarization sheet and a corresponding polarization sheet bracket, which are placed diagonally. Each slotted polarization sheet is fixed on the bottom plate inside the back cavity of the box body component by two parallel polarization sheet brackets.

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

3. An airborne glacier detection radar system according to claim 1, characterized in that, The vertical resolution of the airborne glacier detection radar system in the very high frequency band is better than 2 meters, and the glacier detection depth is better than 100 meters.

4. An imaging processing method for an airborne glacier detection radar system, characterized in that, Using the airborne glacier detection radar system described in any one of claims 1 - 3, processing the obtained glacier radar data and generating a high-resolution radar image, including the following steps: Step 1, using 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 cross-track direction, and obtaining the radar data after error compensation; Step 2, performing a focusing technology applicable to multi-layer media in the along-track direction based on the radar data after error compensation to obtain the radar data processed by two-dimensional focusing in the along-track direction; Step 3: Apply the cross-track clutter suppression algorithm to suppress clutter in the profile of the radar data processed by two-dimensional focusing along the track, and obtain a high-resolution radar image.

5. The imaging processing method of an airborne glacier detection radar system according to claim 4, characterized in that The said Step 1 includes the following steps: Step 1.1: Based on the glacier radar data along the track, perform equally-spaced interpolation 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 is as follows: ； Among them, 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, represents time, represents the time of resampling; Step 1.2: Perform range-Doppler phase compensation to eliminate the influence of the Doppler effect on the glacier radar data and improve the measurement accuracy and reliability of the radar for moving targets. The data signal after Doppler phase compensation is as follows: ； Among them, represents the initial phase, represents the radar wavelength, represents the velocity, represents the imaginary unit; Step 1.3: Correlate the glacier radar data of adjacent tracks and calculate the relative distance of the cross-track target points according to the relative position of the radar.

6. The imaging processing method of an airborne glacier detection radar system according to claim 5, characterized in that The said 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 layer, propagates and attenuates inside the ice layer. The development of ice layer cracks and the internal structure have a significant impact on the propagation and attenuation characteristics of electromagnetic waves, forming a weak reflection signal. Part of the electromagnetic wave signal penetrates the ice layer and forms an electromagnetic wave reflection signal at the ice-bedrock interface. The radar receives the signal of the electromagnetic wave passing through multiple internal media including air and ice layer. By synthesizing the influence of different media and the signal propagation time, the equivalent distance between the radar and the point target is calculated. As follows: ； Among them, represents the distance in air, represents the distance inside the ice layer, represents the coefficient of propagation attenuation inside the ice layer, represents range time, represents azimuth time, represents the moment of range time, represents the moment of azimuth time; Step 2.2: Calculate the focusing 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 focusing degree and resolution of the image; the focusing reference function is expressed as: ； wherein, c is the speed of light; Step 2.3: Simultaneously perform focusing in the azimuth and range directions according to the focusing reference function, while improving the resolution and clarity of the image in the azimuth and range directions; the focused signal is expressed as: 。 7. The imaging processing method of an airborne glacier detection radar system according to claim 4, characterized in that, The said Step 3 includes the following steps: Step 3.1: Based on the extracted radar altitude, ice surface elevation, ice surface tilt angle, airborne radar motion error, and ground environment data, use the existing digital elevation model to simulate the clutter signal on the surface 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 diagram and automatically register between the radar diagram and the simulation diagram. Step 3.3: Extract the clutter echoes on the surface from the radar diagrams of adjacent tracks, perform cross-track clutter suppression to improve the image quality and make the target features more obvious.

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