A Rayleigh lidar system based on a stratospheric floating platform

Abstract

The present invention discloses a Rayleigh LiDAR system based on a stratospheric floating platform, which is used to achieve all-weather and all-day observation of the middle atmosphere. The system includes a stratospheric floating platform and a Rayleigh LiDAR system. The stratospheric floating platform includes a mounting interface, a power supply module, and a communication data transmission module. The Rayleigh LiDAR system includes a laser emission subsystem, an optical receiving subsystem, a signal detection subsystem, a temperature control subsystem, a power supply subsystem, an automatic control subsystem, and an electrical box mechanical subsystem. Compared with ground-based LiDAR, which requires clear nighttime observation conditions with good visibility, the Rayleigh LiDAR system can avoid the influence of bad weather and achieve all-weather observation of the middle atmosphere; it can avoid background noise caused by strong background scattering at low altitudes and achieve all-day observation of the middle atmosphere; it can shorten the distance to the target area, increase the detection altitude, or adopt a simpler and lower-cost LiDAR system to achieve observation of the middle atmosphere.

Description

Technical Field

[0001] The present invention relates to the technical field of atmospheric laser radar, and in particular to a Rayleigh laser radar system for mid-level atmospheric observation. Background Art

[0002] The middle atmosphere is becoming increasingly valuable in basic science, climate and environmental research, and national defense and military affairs. Currently, the main methods used to detect the middle atmosphere can be divided into four categories: sounding rockets, microwave radar, satellites, and lidar. Lidar offers the advantages of high precision, high temporal and spatial resolution, and continuous detection. Lidar measures environmental parameters of the middle atmosphere by collecting backscattered signals from atmospheric molecules or components.

[0003] Based on their detection principles, lidars can be categorized as Raman scattering, resonant fluorescence, and Rayleigh scattering. Raman lidars can cover ground depths up to 30 km, resonant fluorescence lidars can cover depths of 80 to 110 km, and Rayleigh lidars can detect atmospheric parameters up to 110 km. Rayleigh lidars offer advantages such as a simple principle, strong echo signals, and independence from gas composition. They enable high-precision, long-term, continuous observation of the atmospheric environment at all altitudes in near-space, making them crucial for studying atmospheric dynamics in near-space. Atmospheric density and temperature data retrieved from Rayleigh lidars can be used to further investigate gravity waves, tidal changes, stratospheric warming, planetary waves, mesosphere inversion layers, seasonal variations, and noctilucent clouds.

[0004] Rayleigh lidar is the most commonly used method for detecting the middle atmosphere, and increasing its detection range is a core goal of the Rayleigh lidar platform. Currently, Rayleigh lidar is primarily ground-based. After decades of development, it can obtain echo signals within 110 km, making it a key force in middle atmosphere detection. Because ground-based lidar detects the middle atmosphere at long distances, increasing its detection range is extremely costly. Furthermore, it cannot avoid issues such as inclement weather and strong background noise caused by scattered sunlight during the day. These issues are key factors that hinder lidar's ability to detect the middle atmosphere around the clock. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a Rayleigh lidar system based on a stratospheric floating platform, which solves the problems of existing ground-based lidars that cannot avoid bad weather and strong background scattering noise at low altitudes, and can realize all-weather and all-day observation of the middle atmosphere.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A Rayleigh LiDAR system based on a stratospheric floating platform, used to achieve all-weather and all-day observation of the middle atmosphere, comprises: a stratospheric floating platform and a Rayleigh LiDAR system; the stratospheric floating platform comprises a mounting interface, a power supply module, and a communication data transmission module; the Rayleigh LiDAR system comprises a laser emission subsystem, an optical receiving subsystem, a signal detection subsystem, a temperature control subsystem, a power supply subsystem, an automatic control subsystem, and an electrical box mechanical subsystem;

[0008] The laser emission subsystem includes a laser, a beam expander, a deflection mirror and an optical window arranged in sequence;

[0009] The optical receiving subsystem includes a telescope and an optical fiber receiving unit;

[0010] The signal detection subsystem includes a multimode optical fiber, an optical fiber collimator, a narrowband filter, a spectroscope, a first converging mirror, a first single-photon detector, a reflecting mirror, a second converging mirror, a second single-photon detector and a photon counter;

[0011] The temperature control subsystem includes a passive temperature control unit, an air cooling unit, a liquid cooling unit and a heating unit;

[0012] The automatic control subsystem includes a load control unit, a floating platform communication unit and a ground control unit;

[0013] The electrical box mechanical subsystem includes a pod, a steel wire shock absorber, an electrical box cover and an electrical box body;

[0014] The mounting interface is used to connect the stratospheric floating platform and the pod, and the pod and the Rayleigh LiDAR system are connected via a steel wire shock absorber; the power supply module is used to output a wide-range voltage, which is converted by the power supply subsystem into the voltage required by each component of the Rayleigh LiDAR system; the communication data transmission module provides a transmission channel for control instructions and data between the payload control unit and the ground control unit; the temperature control subsystem provides the temperature conditions required for the Rayleigh LiDAR system to operate normally in the low-temperature environment of the stratosphere; the electrical box mechanical subsystem is used to provide the air pressure conditions required for the Rayleigh LiDAR system to operate normally in the low-pressure environment of the stratosphere;

[0015] The ground control unit issues an operation control instruction, which is transmitted to the payload control unit via the communication data transmission module to control the operation of the laser. The liquid cooling unit dissipates heat for the laser. The laser pulse emitted by the laser passes through the beam expander and then enters the deflection mirror, enters the atmosphere through the optical window, interacts with atmospheric molecules, and generates a back-Rayleigh scattered echo signal. The back-Rayleigh scattered echo signal is collected by the telescope and transmitted through the optical fiber receiving unit and enters the interior of the mechanical subsystem of the electrical box through the optical interface on the upper cover of the electrical box. Subsequently, the back-Rayleigh scattered echo signal is transmitted to the optical fiber collimator via a multimode optical fiber, passes through a narrow-band filter and enters the spectroscope to be converted into two beams of echo signals. One beam of echo signal reflected from the spectroscope passes through a first converging mirror and reaches a first single-photon detector. The other beam of echo signal transmitted from the spectroscope passes through a reflecting mirror and enters a second converging mirror and reaches a second single-photon detector. The number of photons recorded by the first single-photon detector and the second single-photon detector are respectively connected to two different channels of the photon counter to realize the recording and storage of the echo photon number profile. The echo photon number is transmitted to the ground control unit via the communication data transmission module.

[0016] Furthermore, the stratospheric floating platform is a floating platform with dynamic characteristics, including but not limited to stratospheric balloons, tethered balloons and stratospheric airships.

[0017] Furthermore, the mounting interface is located at the front end of the stratospheric floating platform, ensuring that the Rayleigh lidar system is mounted at an oblique upward angle.

[0018] Furthermore, the beam expander is used to compress the divergence angle of the laser pulse, the deflection mirror is used to correct the tilt error in the optical path of the laser emission subsystem, and realize the coaxial calibration of the divergence angle of the laser pulse after beam expansion and the field of view angle of the optical receiving subsystem. The optical window is used to transmit the emitted laser pulse while ensuring the airtightness and constant temperature of the mechanical subsystem of the electrical box.

[0019] Furthermore, the passive temperature control unit is used to realize the passive insulation function of the Rayleigh lidar system; the air cooling unit realizes heat exchange between the inside of the electrical box mechanical subsystem and the external environment, so that the inside of the electrical box mechanical subsystem is in a normal temperature environment; the heating unit realizes temperature control of the telescope, the receiving optical fiber unit and the electrical box mechanical subsystem.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0021] 1. All-Weather Observation Capability: This invention's Rayleigh LiDAR system, based on a stratospheric floating platform, effectively protects ground-based observation systems from the effects of inclement weather, ensuring stable observation of the middle atmosphere. Compared to traditional ground-based LiDAR systems, this significantly improves the stability and continuity of atmospheric detection.

[0022] 2. All-day observation capability: Since the system is placed in the stratosphere, away from the interference of strong background scattering noise at low altitude, it avoids the problem of strong scattering background noise caused by daytime sunlight, realizes all-day uninterrupted monitoring of the middle atmosphere, and significantly improves the time resolution of detection.

[0023] 3. Improved detection accuracy and efficiency: The system shortens the distance to the target area through the floating platform, thereby reducing lidar signal attenuation and enhancing the strength of the return signal. Without significantly increasing system complexity and cost, a simpler lidar configuration can be used to achieve high-precision mid-atmosphere observations.

[0024] 4. Optimization of high-altitude working environment: By using temperature control and air pressure control subsystems, the present invention ensures the normal operation of the Rayleigh lidar system in the low-temperature and low-pressure environment of the stratosphere, providing reliable protection for long-term operation.

[0025] 5. Potential for expanded applications: This system can not only be used for environmental monitoring in the middle atmosphere, but can also provide design and application references for other optical equipment operating in the stratosphere, and has great value in expanding applications.

[0026] In summary, the advantages of the present invention in all-weather and all-day observation and improving detection accuracy and efficiency are mentioned, and its potential expanded application value is also mentioned. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a Rayleigh lidar system provided by the present invention mounted on a stratospheric floating platform;

[0028] Figure 2 A system block diagram of a Rayleigh lidar system provided by the present invention;

[0029] Figure 3 An optical block diagram of a Rayleigh lidar system provided by the present invention;

[0030] Figure 4 A block diagram of an automatic control subsystem in a Rayleigh lidar system provided by the present invention;

[0031] Figure 5 This is a block diagram of a temperature control subsystem in a Rayleigh lidar system provided by the present invention.

[0032] Figure numerals: 1-laser emission subsystem, 2-optical receiving subsystem, 3-signal detection subsystem, 4-temperature control subsystem, 5-power supply subsystem, 6-automatic control subsystem, 7-electrical box mechanical subsystem, 11-laser, 12-beam expander, 13-deflection mirror, 14-optical window, 21-telescope, 22-fiber optic receiving unit, 30-photon counter, 31-multimode optical fiber, 32-fiber optic collimator, 33-narrowband filter, 34-beam splitter, 35-first converging mirror, 36-first single-photon detector, 37-reflector, 38-second converging mirror, 39-second single-photon detector, 41-passive temperature control unit, 42-air cooling unit, 43-liquid cooling unit, 44-heating unit, 61-load control unit, 62-floating platform communication unit, 63-ground control unit, 71-optical interface. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific 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.

[0034] It should be noted that, in this embodiment, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0035] Ground-based lidar for detecting the middle atmosphere faces challenges such as high costs for increasing detection range and the inability to avoid severe weather and strong scattered background noise caused by daytime sunlight. In light of these issues, embodiments of the present invention provide a Rayleigh lidar system for all-weather, all-day observation of the middle atmosphere.

[0036] like Figure 1 As shown, this is a schematic diagram of a Rayleigh LiDAR system provided in this embodiment mounted on a stratospheric floating platform. The Rayleigh LiDAR system is mounted at the front end of the stratospheric floating platform at an upward mounting angle of 45°.

[0037] like Figure 2 , which is a system block diagram of a Rayleigh lidar system embodiment provided by this embodiment, including: a laser emission subsystem 1, an optical receiving subsystem 2, a signal detection subsystem 3, a temperature control subsystem 4, a power supply subsystem 5, an automatic control subsystem 6, and an electrical box mechanical subsystem 7;

[0038] The laser emission subsystem 1 is used to generate 532nm laser pulses and emit the laser pulses into the air, interacting with atmospheric molecules to generate backscattered Rayleigh echo signals; the backscattered Rayleigh echo signals are collected by the optical receiving subsystem 2 and enter the signal detection subsystem 3 to realize the statistics of the collected backscattered Rayleigh echo signals and convert them into echo photon number data; the temperature control subsystem 4 controls the temperature of the Rayleigh lidar system to meet the working temperature requirements, the power supply subsystem 5 provides the required power supply voltage for the Rayleigh lidar system to ensure normal operation, and the automatic control subsystem 6 performs information monitoring and work control on the Rayleigh lidar system; the electrical box mechanical subsystem 7 is used to provide a normal temperature and pressure working environment for the laser emission subsystem 1, signal detection subsystem 2, temperature control subsystem 4, power supply subsystem 5 and automatic control subsystem 6.

[0039] like Figure 3 As shown, an optical block diagram of an embodiment of a Rayleigh lidar system provided by the present invention includes: a laser 11, a beam expander 12, a deflection mirror 13, an optical window 14, a telescope 21, an optical fiber receiving unit 22, a photon counter 30, a multimode optical fiber 31, a fiber collimator 32, a narrow-band filter 33, a spectrometer 34, a first converging mirror 35, a first single-photon detector 36, a reflector 37, a second converging mirror 38, a second single-photon detector 39, and an optical interface 71.

[0040] The laser pulse emitted by the laser 11 passes through the beam expander 12 and enters the deflection mirror 13, then enters the atmosphere through the optical window 14 and interacts with atmospheric molecules to generate a backscattered Rayleigh scattering echo signal. The backscattered Rayleigh scattering echo signal is collected by the telescope 21 and transmitted through the optical fiber receiving unit 22 and enters the electrical box mechanical subsystem 7 through the optical interface 71. Subsequently, the backscattered Rayleigh scattering echo signal is transmitted to the optical fiber collimator 32 through the multimode optical fiber 31, passes through the narrowband filter 33 with a bandwidth of 0.25 nm, enters the beam splitter 34 and is converted into two beams of echo signals. One beam of echo signal reflected from the beam splitter 34 passes through the first converging mirror 35 and reaches the first single-photon detector 36. The other beam of echo signal transmitted from the beam splitter passes through the reflecting mirror 37 and enters the second converging mirror 38 and reaches the second single-photon detector 39. The number of photons recorded by the first single-photon detector and the second single-photon detector are respectively connected to two different channels of the photon counter 30 to realize the echo photon number profile recording.

[0041] In this embodiment of the present invention, the beam expander 12 is used to compress the divergence angle of the laser pulse emitted by the laser 11. The beam expansion magnification is 15x, and the expanded spot diameter is 40 mm. The deflection mirror 13 corrects tilt errors in the transmission optical path and ensures coaxial alignment between the divergence angle of the laser pulse after beam expansion and the optical field of view. This ensures that the Rayleigh lidar system's transmit and receive fields of view match and that all echo signals are collected. The optical window 14 transmits the transmitted laser pulse while ensuring the airtightness and temperature stability of the electrical enclosure's mechanical subsystem. The telescope 21 has a diameter of 350 mm and a focal length of 1200 mm. It also includes a 50 mm diameter notch to provide a transmission channel for the laser pulse passing through the optical window. The first and second single-photon detectors are avalanche diodes and photomultiplier tubes, respectively. The optical interface 71 transmits the echo signal to the electrical enclosure's mechanical subsystem while ensuring the airtightness and temperature stability of the subsystem. The two echo signal intensities transmitted and reflected by the beam splitter are 90% and 10%, respectively. The laser 11 is connected to the photon counter 30. The electrical pulse signal output by the laser is connected to the trigger input channel of the counter to control the acquisition timing of the Rayleigh lidar system, thereby realizing automatic recording and storage of the echo signal data.

[0042] like Figure 4 , which is a block diagram of the automatic control subsystem 6 in this embodiment, includes: a load control unit 61 , a floating platform communication unit 62 and a ground control unit 63 .

[0043] like Figure 5 , which is a block diagram of the temperature control subsystem 4 in this embodiment, includes: a passive temperature control unit 41 , an air cooling unit 42 , a liquid cooling unit 43 and a heating unit 44 .

[0044] The passive temperature control unit 41 realizes the passive insulation function of the electrical box mechanical subsystem 7 and the telescope 21. The air cooling unit 42 realizes the heat exchange between the internal and external environment of the electrical box mechanical subsystem, so that the internal of the electrical box mechanical subsystem is in a normal temperature environment. The liquid cooling unit 43 realizes temperature control to ensure the normal operation of the laser 11. The heating unit 44 realizes temperature control inside the telescope 21, the optical fiber receiving unit 22 and the electrical box mechanical subsystem 7.

[0045] The above are only preferred specific embodiments of the present invention, but the scope of protection of the invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in the present invention should be covered by the scope of protection of the present invention.

[0046] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, those skilled in the art may make various specific modifications based on the teachings of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A Rayleigh LiDAR system based on a stratospheric floating platform for all-weather and all-day observation of the middle atmosphere, characterized by: include: Stratospheric floating platform and Rayleigh LiDAR system; the stratospheric floating platform includes a mounting interface, a power supply module, and a communication data transmission module; the Rayleigh LiDAR system includes a laser emission subsystem, an optical receiving subsystem, a signal detection subsystem, a temperature control subsystem, a power supply subsystem, an automatic control subsystem, and an electrical box mechanical subsystem; The laser emission subsystem includes a laser, a beam expander, a deflection mirror and an optical window arranged in sequence; The optical receiving subsystem includes a telescope and an optical fiber receiving unit; The signal detection subsystem includes a multimode optical fiber, an optical fiber collimator, a narrowband filter, a spectroscope, a first converging mirror, a first single-photon detector, a reflecting mirror, a second converging mirror, a second single-photon detector and a photon counter; The temperature control subsystem includes a passive temperature control unit, an air cooling unit, a liquid cooling unit and a heating unit; The automatic control subsystem includes a load control unit, a floating platform communication unit and a ground control unit; The electrical box mechanical subsystem includes a pod, a steel wire shock absorber, an electrical box cover and an electrical box body; The mounting interface is used to connect the stratospheric floating platform and the pod, and the pod and the Rayleigh LiDAR system are connected via a steel wire shock absorber; the power supply module is used to output a wide-range voltage, which is converted by the power supply subsystem into the voltage required by each component of the Rayleigh LiDAR system; the communication data transmission module provides a transmission channel for control instructions and data between the payload control unit and the ground control unit; the temperature control subsystem provides the temperature conditions required for the Rayleigh LiDAR system to operate normally in the low-temperature environment of the stratosphere; the electrical box mechanical subsystem is used to provide the air pressure conditions required for the Rayleigh LiDAR system to operate normally in the low-pressure environment of the stratosphere; The ground control unit issues an operation control instruction, which is transmitted to the payload control unit via the communication data transmission module to control the operation of the laser. The liquid cooling unit dissipates heat for the laser. The laser pulse emitted by the laser passes through the beam expander and then enters the deflection mirror. It enters the atmosphere through the optical window and interacts with atmospheric molecules to generate a backward Rayleigh scattering echo signal. After being collected by the telescope, the backward Rayleigh scattered echo signal is transmitted through the optical fiber receiving unit and enters the mechanical subsystem of the electrical box through the optical interface on the upper cover of the electrical box; then, the backward Rayleigh scattered echo signal is transmitted to the optical fiber collimator through the multimode optical fiber, enters the spectroscope through the narrow-band filter and becomes two beams of echo signals. One beam of echo signal reflected from the spectroscope passes through the first converging mirror and reaches the first single-photon detector, and the other beam of echo signal transmitted from the spectroscope passes through the reflecting mirror and enters the second converging mirror and reaches the second single-photon detector. The number of photons recorded by the first single-photon detector and the second single-photon detector are respectively connected to two different channels of the photon counter to realize the recording and storage of the echo photon number profile, and the echo photon number is transmitted to the ground control unit through the communication data transmission module.

2. The Rayleigh lidar system based on a stratospheric floating platform according to claim 1, characterized in that: The stratospheric floating platform is a floating platform with dynamic characteristics, including but not limited to stratospheric balloons, tethered balloons and stratospheric airships.

3. The Rayleigh lidar system based on a stratospheric floating platform according to claim 1, characterized in that: The mounting interface is located at the front end of the stratospheric floating platform, ensuring that the Rayleigh lidar system is mounted at an oblique upward angle.

4. The Rayleigh lidar system based on a stratospheric floating platform according to claim 1, characterized in that: The beam expander is used to compress the divergence angle of the laser pulse of the laser, the deflection mirror is used to correct the tilt error in the optical path of the laser emission subsystem, and realize the coaxial calibration of the divergence angle of the laser pulse after beam expansion and the field of view angle of the optical receiving subsystem. The optical window is used to transmit the emitted laser pulse while ensuring the airtightness and constant temperature of the mechanical subsystem of the electrical box.

5. The Rayleigh lidar system based on a stratospheric floating platform according to claim 1, characterized in that: The passive temperature control unit is used to realize the passive insulation function of the Rayleigh lidar system; the air cooling unit realizes heat exchange between the inside of the electrical box mechanical subsystem and the external environment, so that the inside of the electrical box mechanical subsystem is in a normal temperature environment; the heating unit realizes temperature control inside the telescope, receiving optical fiber unit and the electrical box mechanical subsystem.

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