Meteor trail scanning detection laser radar system and method based on optical early warning guidance

Abstract

This invention discloses a lidar system and method for scanning and detecting meteor trails based on optical early warning guidance. The invention actively detects meteor events and predicts the spatiotemporal evolution path of the trail using a wide-area optical early warning module, guiding the scanning lidar detection module to perform precise scanning along the predicted path. This enables the tracking and detection of meteor trails using lidar, and allows for the acquisition of complete temperature evolution information during the meteor trail's evolution, as well as information on the evolution and transformation of various metallic components ablated within the complete trail. Furthermore, it fundamentally solves the problem of traditional lidar's passive "waiting for the right moment" approach and low probability of capturing transient meteor events. Through multi-station collaboration and monitoring strategies, the invention further improves observation efficiency and data quality, providing an efficient and reliable technical means for the study of upper atmospheric dynamics and extraterrestrial materials.

Description

Technical Field

[0001] This invention belongs to the field of atmospheric physics detection and space environment monitoring technology, specifically relating to a lidar system and method for scanning and detecting meteor trails based on optical early warning guidance. Background Technology

[0002] Meteorites enter Earth's atmosphere at high speeds, violently colliding and rubbing against atmospheric molecules. This causes them to ablate and evaporate, ionizing atmospheric molecules along their path and creating a long, thin, columnar region filled with metal ions and free electrons, known as a meteor trail. These trails are of great value for studying the mass distribution, chemical composition, upper atmospheric dynamics, and space environment of meteorites.

[0003] Meteor trails are important natural tracers for studying the dynamics of the upper atmosphere (80-110 km) and extraterrestrial matter. Conventional observation methods include radio meteor radar, all-sky optical cameras, and high-power large-aperture radar. These methods can obtain physical parameters such as the glow phenomenon of meteor trails, the background wind field of the trails, the echo of the meteor plasma column, the plasma trail, and the echo of inhomogeneous bodies. In addition to these conventional methods, some studies have mentioned that lidar has detected meteor trails, but both the emitting laser and the receiving telescope are in a fixed direction. The trail information can only be obtained when the meteor flies past the telescope's receiving field of view, and even then, it only provides information on the density of a single metallic component.

[0004] In summary, current methods for detecting meteor trails lack the information to detect the temperature evolution during the complete evolution of a meteor trail, as well as the evolution and transformation of various ablated metal components within the trail. This information is crucial for understanding the impact of meteoroids on the space environment. Therefore, there is an urgent need in this field for a technical solution that can achieve high-probability capture, provide complete, quantitative, and detailed observations of meteor trails, and obtain information on the temperature evolution during the complete evolution of a meteor trail, as well as the evolution and transformation of various ablated metal components within the trail. Summary of the Invention

[0005] To address the technical problems mentioned above, this invention provides a lidar system for scanning and detecting meteor trails based on optical early warning guidance, comprising: The wide-area optical early warning module is used to monitor meteor events in a designated area in real time. Based on the monitoring results, it calculates the three-dimensional spatial trajectory and velocity vector of the meteor body, and predicts the spatiotemporal evolution path of the meteor tail in the future based on the atmospheric model, generating a path point sequence. The scanning lidar detection module includes a laser emitting unit, a receiving unit, a high-speed photoelectric detection and data acquisition unit, and a data inversion output unit; The central control and data processing module is connected to the wide-area optical early warning module and the scanning lidar detection module, respectively. It is used to receive path point sequences, generate scanning motion commands based on the path point sequences, control the two-axis servo turntable of the large-aperture receiving telescope and the laser transmitter to perform uniform scanning along the spatiotemporal evolution path, and synchronously control data acquisition.

[0006] Preferably, the wide-area optical early warning module includes a group of three or more wide-angle high-speed cameras with known geographic coordinates and synchronized time, and an optical meteor trajectory discrimination device. Based on meteor events monitored in real time by a wide-angle high-speed camera, the three-dimensional spatial trajectory and velocity vector of the meteor body are calculated by an optical meteor trajectory discrimination device, and the spatiotemporal evolution path of the meteor tail is predicted based on an atmospheric model to generate a path point sequence.

[0007] Preferably, the laser emitting unit is a multi-band laser emitting unit, comprising: a laser, a laser frequency shifting device, a laser frequency stabilization and discrimination device, a beam expander, an optical path deflector, and a two-axis servo laser emitting stage; capable of simultaneously emitting several probe lasers of different frequencies.

[0008] Preferably, the receiving unit includes: a telescope, a receiving optical fiber, an echo signal shaping optical path, an echo signal splitting optical path, a filter, a two-axis servo turntable, and an absolute encoder; The telescope, receiving fiber, echo signal shaping optical path, echo signal splitting optical path, and filter work together to complete signal reception. The central control and data processing module controls the movement of the two-axis servo turntable according to the scanning motion command and records the real-time pointing angle through the absolute encoder.

[0009] Preferably, the two-axis servo turntable is equipped with an azimuth reference calibration module, which is used to establish the mapping relationship between the zero position of the turntable encoder and the true north direction, and to periodically correct the pointing deviation caused by mechanical or environmental changes.

[0010] Preferably, the central control and data processing module determines whether the predicted path passes through the effective scanning area of ​​the pre-set guard position based on the path point sequence; if it does, the scanning task is started, and the path point sequence is converted into a smooth scanning motion command to control the two-axis servo laser transmitter and the two-axis servo turntable to scan at a constant speed along the path.

[0011] Preferably, the high-speed photoelectric detection and data acquisition unit receives the echo signal based on the laser emitted by the laser transmitter and acquires the original echo signal; the central control and data processing module maps the original echo signal to the geospatial coordinate system based on the real-time pointing angle to obtain a three-dimensional spatiotemporal data volume.

[0012] Preferably, the data inversion output unit inverts the temperature evolution information during the complete meteor trail evolution process, as well as the evolution and transformation information of the ablated metal components in the complete trail, based on the three-dimensional spatiotemporal data volume.

[0013] This invention also provides a method for scanning and detecting meteor trails, the method being implemented using the aforementioned system, characterized by the following steps: S1: Utilize an optical early warning network to monitor the sky in real time. After detecting a meteor event, calculate the three-dimensional spatial trajectory and velocity vector of the meteor body based on multi-station stereo vision. Combine this with an atmospheric wind field model to predict the spatiotemporal evolution path of the meteor trail and generate a path point sequence. S2: Using the azimuth reference calibration module equipped on the two-axis servo turntable, the lidar system transmitter and telescope are pre-positioned at a specific guard position. The guard position is set according to the scientific observation target, including a fixed elevation angle and azimuth angle; the central control and data processing module determines whether the path predicted by S1 passes through the effective scanning area of ​​the current guard position. The effective scanning area is defined as the spatial area centered on the guard position, with an elevation angle span of ±15° and an azimuth angle span of ±30°; if the predicted path intersects with this area, the scanning task is started; otherwise, the event is ignored. S3: The central control and data processing module converts the predicted path into a smooth scanning motion command, controlling the two-axis servo turntable to scan at a constant speed along the path; the pulsed laser is started simultaneously to emit laser at a fixed repetition frequency, and the data acquisition module continuously records the echo signal, while also recording the real-time pointing angle of the turntable encoder; S4: After performing distance correction and background subtraction on the acquired raw echo signal, a signal intensity sequence is obtained; using the pointing angle data recorded by the encoder, the signal intensity sequence is mapped to the geospatial coordinate system to obtain the wake signal; S5: The extracted trail signal is analyzed and inverted to obtain the temperature evolution information during the evolution of the complete meteor trail, as well as the evolution and transformation information of the ablated metal components in the complete trail.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention actively detects meteor events and predicts the spatiotemporal evolution path of their contrails using a wide-area optical early warning module. This guides a scanning lidar detection module to precisely scan along the predicted path, enabling the tracking and detection of meteor contrails using lidar. It can acquire complete information on temperature evolution during the meteor contrail's evolution, as well as the evolution and transformation of various metallic components ablated within the contrail. Furthermore, it fundamentally solves the problem of traditional lidar's passive "waiting for the right moment" approach and its low probability of capturing transient meteor events. Through multi-station collaboration and monitoring strategies, it further improves observation efficiency and data quality, providing an efficient and reliable technical means for the study of upper atmospheric dynamics and extraterrestrial materials. Attached Figure Description

[0015] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the system structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the method flow according to an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Example 1 like Figure 1 As shown in this embodiment, a meteor trail scanning detection lidar system based on optical early warning guidance is provided, including: a wide-area optical early warning module, a scanning lidar detection module, and a central control and processing module.

[0020] The wide-area optical early warning module consists of three or more wide-angle high-speed cameras with known geographic coordinates and synchronized time, along with an optical meteor trajectory discrimination device. The camera spacing is selected within a range of several kilometers to tens of kilometers based on positioning accuracy requirements and field-of-view coverage needs. The cameras are used to monitor meteor events in a designated area in real time, and the optical meteor trajectory discrimination device calculates the three-dimensional spatial trajectory and velocity vector of the meteoroid, predicting the spatiotemporal evolution path of the meteor contrail over a future period based on an atmospheric model. The three cameras form a spatial convergence measurement network, with a camera frame rate of no less than 30fps and a time synchronization accuracy better than 1 millisecond.

[0021] The scanning lidar detection module is used to emit lasers of a specific wavelength and receive atmospheric echo signals; it includes: a laser emitting unit, a receiving unit, a high-speed photoelectric detection and data acquisition unit, and a data inversion output unit.

[0022] (1) Laser emitting unit The multi-band laser emitting unit includes several lasers, several laser frequency shifting devices, laser frequency stabilization and discrimination devices, several beam expanders, several optical path deflectors, and several two-axis servo laser emitting stages. The lasers can emit wavelengths including, but not limited to, 341nm, 372nm, and 393nm (f...). - ,f0,f + ), 423nm, 589nm (f - ,f0,f + The laser wavelength can be one or more of 770nm, or other wavelengths that can resonate with the components of meteoroid material to produce fluorescence. A laser frequency shifter is used to generate three different frequencies of the same wavelength. A beam expander shapes the laser beam output from the laser, adjusting the laser divergence angle to match the receiving field of view of the large-aperture receiving telescope in the optical receiving unit. After adjustment, the laser divergence angle is ≤300μrad, and the laser pointing accuracy is ≤50μrad. An optical path conversion mirror is used for optical path conversion of the laser in the above-mentioned devices. A two-axis servo laser transmitter emits the collimated beam output from the beam expander into the sky and has arbitrary pointing adjustment capabilities. It is driven by an AC servo motor, equipped with an absolute encoder with a resolution of no less than 20 bits, a maximum angular velocity ≤3° / s, and a pointing accuracy ≤1mrad.

[0023] (2) Receiving unit The system includes a telescope, a two-axis servo turntable, receiving optical fiber, an echo signal shaping optical path, an echo signal splitting optical path, and filters. The telescope has a large aperture (≥400mm) and an adjustable field of view (0.1mrad-1mrad). The two-axis servo turntable is driven by an AC servo motor and equipped with an absolute encoder with a resolution of at least 20 bits, a maximum angular velocity ≤3° / s, and a pointing accuracy ≤1mrad. The echo signal shaping optical path shapes the received echo light signal into parallel light. The signal light output from the echo signal shaping optical path enters the echo signal splitting device, which separates the received light of different wavelengths for output. The filters can be optical filters, etalons, atomic filters, or other filtering devices.

[0024] (3) High-speed photoelectric detection and data acquisition unit It includes: an optical focusing device, a photon detector, and a data acquisition device. Parallel light output from the filter enters the optical focusing device and is focused. After focusing, the light signal is incident on the photosensitive receiving surface of the photon detector to complete the photoelectric conversion; then the data acquisition device collects and stores the data.

[0025] (4) Data inversion output unit The collected signals are inverted using algorithms to obtain physical parameters.

[0026] The central control and data processing module is connected to the optical early warning subsystem and the scanning lidar detection module, respectively. It is used to receive early warning information, generate scanning commands to control the movement of the two-axis servo turntable, and synchronously control laser emission and data acquisition.

[0027] Example 2 like Figure 2 As shown, this embodiment provides a method for scanning and detecting meteor trails. This method is implemented using the system provided by this invention, and the steps include: S1. Early Warning Detection and Path Prediction – The optical early warning network monitors the sky in real time. Upon detecting a meteor event, it calculates the three-dimensional spatial trajectory and velocity vector of the meteoroid based on multi-station stereo vision. Combined with an atmospheric wind field model, it predicts the spatiotemporal evolution path of the meteor contrail within the next 20-60 seconds, generating a path point sequence. .

[0028] S2. Preset Position Guarding and Event Filtering – The lidar transmitter and telescope are pre-positioned at specific guarding positions. These positions are pre-defined based on the scientific observation target, including fixed elevation angles E10 (30°-90° range) and azimuth angles Az0 (0°-360° adjustable). The central control and data processing module determines whether the path predicted in step S1 crosses the effective scanning area of ​​the current guarding position. The effective scanning area is defined as the spatial region centered on the guarding position (Az0, E10), with an elevation angle span of ±15° and an azimuth angle span of ±30°. If the predicted path intersects with this area, the scanning task is initiated; otherwise, the event is ignored.

[0029] S3, Path Scanning and Data Acquisition – The central control and data processing module converts the predicted path into a smooth scanning motion command, controlling the two-axis servo turntable to scan the path at a constant speed of 0.5° / s to 3° / s. Simultaneously, the pulsed laser is started to emit laser at a fixed repetition frequency, and the data acquisition module continuously records the echo signal, while also recording the real-time pointing angle (Az(t), El(t)) of the turntable encoder.

[0030] S4. Data Fusion and Signal Extraction: After distance correction and background subtraction of the acquired raw echo signal, the signal intensity sequence S(r,t) is obtained; using the pointing angle data recorded by the encoder, S(r,t) is mapped to the geospatial coordinate system to obtain the wake signal S(x,y,z,t).

[0031] S5. Physical parameter inversion—Analyze the extracted wake signal S(x,y,z,t) to obtain the temperature evolution information during the complete meteor wake evolution process, as well as the evolution and transformation information of various metal components ablated in the complete wake.

[0032] Example 3 This embodiment demonstrates the single-station high-elevation angle monitoring mode of the system provided by this invention. A system of this invention is deployed at a certain observation station, with the following specific configuration: (1) Early warning network: Three CMOS cameras are deployed in a triangular layout, each 8km apart; the field of view is 120°, the frame rate is 50fps; GPS-PPS time synchronization is achieved with an accuracy of <0.5ms.

[0033] (2) LiDAR: Deploy an all-solid-state lidar with an emission wavelength of 589nm (f - ,f0,f + 372nm, pulse energy 80mJ, repetition rate 200Hz; telescope aperture 400mm; photon counting acquisition, sampling rate 800ps; two-axis servo laser transmitter and telescope turntable maximum speed 10° / s, pointing accuracy 400μrad, encoder 21-bit. (3) Guarding strategy: First, the pre-set positions of the laser transmitter and telescope are: Az0 = 300°, El0 = 75°, where Az is the azimuth angle, the angle between the projection of the laser radar optical axis onto the horizontal plane and true north, with clockwise as positive. El is the elevation angle, the angle between the laser radar optical axis and the horizontal plane, with upward as positive. The effective scanning area is defined as the spatial region centered on this position, with an azimuth angle span of ±30° and an elevation angle span of ±15°, i.e., Az ∈ [270°, 330°], El ∈ [60°, 90°], where Az is the azimuth scanning range.

[0034] When observation was initiated, the early warning network detected a meteor of magnitude -1. Its trajectory was calculated to enter from the northwest of the zenith, ending at an altitude of 96 km. The predicted wake would appear in the region of El=72°-78° and Az=310°-330° within the next 10 seconds. The central unit determined that the path fell within the effective scanning area and immediately initiated a scan. The turntable moved from its current position to Az=310°, El=72° at a speed of 5° / s, taking approximately 2 seconds. At this position, it stared at the target for 50 pulses, then scanned to the next point on the trajectory, Az=311°, El=73°, and stared at the target for another 50 pulses until the entire trajectory was detected; alternatively, it scanned along the trajectory at a speed of 1.5° / s.

[0035] (4) Inversion results: Based on the calculation method, parameters such as the contrail center height, sodium / iron atom number density, sodium / iron atom number density evolution, and temperature evolution at the meteor contrail were derived. The lidar system comprehensively recorded the entire dissipation process at a specific point in the meteor contrail, thus reflecting the origin of the meteoroid.

[0036] Example 4 This embodiment demonstrates the dual-station collaborative networking mode of the system provided by the present invention. Two identical systems are deployed, 50km apart: Station 1: Preset El=75° (zenith zone) Station 2: Preset El=45° (medium elevation angle zone) The central dispatch unit assigns tasks based on the location of the event: events with a zenith distance of less than 30° are assigned to station 1, and events with a zenith distance of 30°-60° are assigned to station 2.

[0037] During a meteor shower, data parameters can be obtained through collaborative detection using scanning methods.

[0038] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A lidar system for scanning and detecting meteor trails based on optical early warning guidance, characterized in that, include: The wide-area optical early warning module is used to monitor meteor events in a designated area in real time. Based on the monitoring results, it calculates the three-dimensional spatial trajectory and velocity vector of the meteor body, and predicts the spatiotemporal evolution path of the meteor tail in the future based on the atmospheric model, generating a path point sequence. The scanning lidar detection module includes a laser emitting unit, a receiving unit, a high-speed photoelectric detection and data acquisition unit, and a data inversion output unit; The central control and data processing module is connected to the wide-area optical early warning module and the scanning lidar detection module, respectively. It is used to receive path point sequences, generate scanning motion commands based on the path point sequences, control the two-axis servo turntable of the large-aperture receiving telescope and the laser transmitter to perform uniform scanning along the spatiotemporal evolution path, and synchronously control data acquisition.

2. The lidar system for scanning and detecting meteor trails based on optical early warning guidance according to claim 1, characterized in that, The wide-area optical early warning module includes a group of three or more wide-angle high-speed cameras with known geographic coordinates and synchronized time, and an optical meteor trajectory discrimination device. Based on meteor events monitored in real time by a wide-angle high-speed camera, the three-dimensional spatial trajectory and velocity vector of the meteor body are calculated by an optical meteor trajectory discrimination device, and the spatiotemporal evolution path of the meteor tail is predicted based on an atmospheric model to generate a path point sequence.

3. The lidar system for scanning and detecting meteor trails based on optical early warning guidance according to claim 1, characterized in that, The laser emitting unit is a multi-band laser emitting unit, including: a laser, a laser frequency shifting device, a laser frequency stabilization and discrimination device, a beam expander, an optical path deflector, and a two-axis servo laser emitting stage; it can simultaneously emit several probe lasers of different frequencies.

4. The lidar system for scanning and detecting meteor trails based on optical early warning guidance according to claim 1, characterized in that, The receiving unit includes: a telescope, a receiving optical fiber, an echo signal shaping optical path, an echo signal splitting optical path, a filter, a two-axis servo turntable, and an absolute encoder. The telescope, receiving fiber, echo signal shaping optical path, echo signal splitting optical path, and filter work together to complete signal reception. The central control and data processing module controls the movement of the two-axis servo turntable according to the scanning motion command and records the real-time pointing angle through the absolute encoder.

5. The lidar system for scanning and detecting meteor trails based on optical early warning guidance according to claim 4, characterized in that, The two-axis servo turntable is equipped with an azimuth reference calibration module, which is used to establish the mapping relationship between the turntable encoder zero position and the true north direction, and to periodically correct the pointing deviation caused by mechanical or environmental changes.

6. The lidar system for scanning and detecting meteor trails based on optical early warning guidance according to claim 5, characterized in that, The central control and data processing module determines whether the predicted path passes through the effective scanning area of ​​the pre-set guard position based on the path point sequence. If it does, the scanning task is started, and the path point sequence is converted into a smooth scanning motion command to control the two-axis servo laser transmitter and the two-axis servo turntable to scan at a constant speed along the path.

7. The lidar system for scanning and detecting meteor trails based on optical early warning guidance according to claim 1, characterized in that, The high-speed photoelectric detection and data acquisition unit receives the echo signal based on the laser emitted by the laser transmitter and collects the raw echo signal; the central control and data processing module maps the raw echo signal to the geospatial coordinate system based on the real-time pointing angle to obtain a three-dimensional spatiotemporal data volume.

8. The lidar system for scanning and detecting meteor trails based on optical early warning guidance according to claim 1, characterized in that, The data inversion output unit inverts the temperature evolution information during the complete meteor trail evolution process, as well as the evolution and transformation information of the ablated metal composition in the complete trail, based on the three-dimensional spatiotemporal data volume.

9. A method for scanning and detecting meteor trails, said method being implemented using the system described in any one of claims 1-8, characterized in that the steps... include: S1: Utilize an optical early warning network to monitor the sky in real time. After detecting a meteor event, calculate the three-dimensional spatial trajectory and velocity vector of the meteor body based on multi-station stereo vision. Combine this with an atmospheric wind field model to predict the spatiotemporal evolution path of the meteor trail and generate a path point sequence. S2: Using the azimuth reference calibration module equipped on the two-axis servo turntable, the lidar system transmitter and telescope are pre-positioned at the guard position; the guard position is set according to the scientific observation target, including fixed elevation and azimuth angles; the central control and data processing module determines whether the path predicted by S1 passes through the effective scanning area of ​​the current guard position. The effective scanning area is defined as the spatial area centered on the guard position, with an elevation angle span of ±15° and an azimuth angle span of ±30°; if the predicted path intersects with this area, the scanning task is started; otherwise, the event is ignored. S3: The central control and data processing module converts the predicted path into a smooth scanning motion command, controlling the two-axis servo turntable to scan at a constant speed along the path; the pulsed laser is started simultaneously to emit laser at a fixed repetition frequency, and the data acquisition module continuously records the echo signal, while also recording the real-time pointing angle of the turntable encoder; S4: After performing distance correction and background subtraction on the acquired raw echo signal, a signal intensity sequence is obtained; using the pointing angle data recorded by the encoder, the signal intensity sequence is mapped to the geospatial coordinate system to obtain the wake signal; S5: The extracted trail signal is analyzed and inverted to obtain the temperature evolution information during the evolution of the complete meteor trail, as well as the evolution and transformation information of the ablated metal components in the complete trail.

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