CN106054210B - A kind of differential absorption lidar and method for detecting earth surface pressure and height above sea level - Google Patents

Abstract

The invention discloses a differential absorption laser radar and a method for detecting the pressure and altitude of the earth's surface. The laser radar is composed of a laser emitting unit, a receiving unit, a control and numerical control acquisition and processing unit. Wherein, the laser emitting unit selects two specific wavelengths in the groove of the oxygen A band line as the detection wavelength and the reference wavelength, and the two laser wavelengths are similar. The receiving unit obtains the surface pulse echo, and the time interval from the pulse emission to the return of the echo pulse can be used to infer the altitude, and the surface pressure can be retrieved from the ratio of the emission energy of the two wavelength lasers to the echo energy. The invention has the advantage that it can detect the surface pressure and altitude at the same time.

Description

A Differential Absorption LiDAR and Method for Detecting Earth's Surface Pressure and Altitude

technical field

The invention relates to a space laser radar, which can detect the distance from a satellite to a sub-satellite point on the earth's surface, thereby knowing the altitude of the point on the surface; the invention also relates to a long optical path differential absorption laser radar to detect the surface atmospheric pressure, and at the same time obtain Two indicators of surface altitude and atmospheric pressure.

Background technique

Air pressure plays an important role in a series of atmospheric processes related to atmospheric dynamics. For example, the horizontal gradient of air pressure and the deflection force of the earth's rotation act on the air mass as the basic force, which is used to deduce the balanced wind. The weather pattern is usually described by the pressure contour map. Such as low pressure, high pressure, low pressure trough, high pressure ridge, anticyclone, introduced atmospheric mode. Furthermore, storm regimes and fronts are important weather phenomena and generate significant air-sea interactions and fluxes in the Earth's boundary layer (PBL). Improvements in modeling at these scales are essential to better determine wind, pressure, sea surface temperature, and frontal locations. The main limitation on model accuracy is the sparsity of the spatial distribution of the input data.

Sea surface atmospheric pressure data are very sparse over large areas of the ocean and the southern hemisphere. Oceanic tropical depressions have a great impact on our country's climate. Due to the lack of sea surface meteorological stations, for example, the sea surface atmospheric pressure observations in the East China Sea and South China Sea are very scarce. The pressure gradient distribution data is very beneficial to accurately predict the formation of typhoons, the direction of landing, and the trajectory of movement, and reduce the losses caused by excessive or insufficient preparedness in government decision-making.

Mongolia and Russia's Siberia region are not our territory, and we cannot arrange ground observation stations there, and the ground observation points in neighboring countries are also very sparse, and the cold high pressure there is very important to the formation of our country's cold wave.

The Xinjiang desert, Qinghai-Tibet Plateau, and polar regions in my country have vast areas with poor environmental conditions, and it is difficult to guarantee the long-term residence of ground observers. Research on the ground-atmosphere coupling process of the Qinghai-Tibet Plateau, the dynamic effect of the multi-scale topography of the Qinghai-Tibet Plateau, the influence of the large terrain of the Qinghai-Tibet Plateau on the atmospheric circulation, the study of the dynamics and thermodynamics of the Qinghai-Tibet Plateau, and the study of the polar atmospheric environment all require densely distributed Atmospheric pressure base data.

Fixed meteorological stations regularly use sounding balloons to detect atmospheric pressure operationally, which is currently the most accurate and reliable detection method for meteorological business departments. This method is still long-term use, irreplaceable and the most effective detection method. However, the aviation control department has strict restrictions on the time for releasing sounding balloons, which cannot allow continuous detection throughout the day.

my country has already realized atmospheric temperature detection by infrared remote sensors and atmospheric humidity detection by microwave radiometers of Fengyun series satellites. However, so far, for atmospheric pressure, except for the pressure sensor on the sounding balloon, my country has not yet successfully operated remote sensing instruments.

Internationally, there are only instruments such as the TANSO-FTS instrument on the GOSAT satellite, the OCO-2 satellite instrument, and the MERIS instrument on the Envisat satellite that have been launched in orbit recently. The accuracy of surface pressure detection does not meet the needs of weather forecasting, and it cannot work without sunlight at night. At present, it is only used to provide oxygen reference data for remote sensing of the column concentration of atmospheric carbon dioxide gas. The Global Atmospheric Research Program (GAP) requires remote sensing of Earth's surface air pressure with an accuracy of 0.3%.

The laser pulse of the differential absorption laser altimeter uses the reflection signal of the hard target on the ground instead of the atmospheric backscattering. The required laser power is several orders of magnitude smaller than that, and the surface atmospheric pressure is not a pressure profile. This is not a major sacrifice, knowing the value of the surface pressure, we can obtain the vertical profile of the atmospheric pressure from the static equations from the satellite measured temperature profile. If the differential absorption laser altimeter can go around with the satellite, the coverage and density of remote sensing data of atmospheric pressure on the earth's surface will be greatly increased.

Using the working mode of the laser altimeter, the atmospheric absorption rate and pulse flight time of the laser pulse passing through the air column are measured. Not only can the surface pressure be obtained, but also the altitude can be obtained at the same time, and the reflection of the cloud and the ground can be distinguished (the atmospheric pressure on the top of the cloud or the pressure on the earth's surface can be separated), which is also more meaningful for meteorological applications.

The atmospheric medium is a random medium, and it is very difficult to describe and express the changing process of the atmosphere. The differential absorption technology is applied to the laser detection process, that is, two kinds of beams are emitted at the same time, one beam is called the detection beam, and the other beam is called the reference beam. Yes, other difficult-to-calculate atmospheric effects are differentially eliminated, thereby highlighting the difference in spectral absorption caused by changes in atmospheric pressure. These are the origins of the present invention.

Contents of the invention

The object of the present invention is to provide a spatial differential absorption laser radar and a data processing method for simultaneously detecting the earth's surface pressure and altitude. The spatial difference laser radar is composed of a laser emitting unit, a receiving unit, a control and a numerical control acquisition and processing unit. Among them, the output of the emitting laser adopts active frequency stabilization, the receiving unit obtains the surface echoes of the detection wavelength and the reference wavelength respectively through polarization beam splitting, and the control and numerical control acquisition processing unit processes the emission pulse energy monitor, time interval measurer, echo Pulse trigger and echo data collector's signal, and finally get surface height and pressure information.

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

1. Structure

A differential absorption laser radar for detecting the pressure and altitude of the earth's surface is composed of a laser emitting unit 1, a receiving unit 2, and a control and numerical control acquisition and processing unit 3;

The laser emitting unit 1 includes a second reflector 11, a polarization beam combiner 12, a first reflector 13, a wavelength monitor 14, a detection wavelength laser 15, a reference wavelength laser 16, and a resonant cavity length piezoelectric controller 17 , pump laser 18, detection wavelength seed laser 19, reference wavelength seed laser 110;

The pumping laser 18 pumps the detection wavelength laser 15 and the reference wavelength laser 16, and the wavelengths of these two lasers are respectively controlled by the detection wavelength seed laser 19 and the reference wavelength seed laser 110; the detection wavelength laser 15 part of the light enters the wavelength monitor 14, and stabilize the laser wavelength output by the detection wavelength laser 15 through the resonant cavity length piezoelectric controller 17; After being a beam of light, it is vertically irradiated to the surface of the earth through the second reflector 11; part of the light from the reference wavelength laser 16 enters the emission pulse trigger 31 and the emission pulse energy monitor 32, and part of the light from the detection wavelength laser 15 enters the emission pulse energy Monitor 32;

The receiving unit 2 includes a telescope 21 on the star, a lens 22, a narrow-band filter 23, a polarizing beam splitter 24, a third mirror 25, a first photodetector 26, and a second photodetector 27; the receiving unit 2 The telescope 21 on the star receives the pulse energy echo signal reflected by the earth surface, passes through the lens 22 and the narrow-band filter 23, passes through the polarizing beam splitter 24, and one path of light directly enters the first light detector 26, and the other light passes through the third Mirror 25 enters second photodetector 27;

Described control and numerical control acquisition processing unit 3 comprise launch pulse trigger 31, launch pulse energy monitor 32, time interval measurer 33, echo pulse trigger and echo data collector 34, microprocessor 35; Time interval measurement The device 33 obtains the time interval from the triggering of the launch pulse trigger 31 and the echo pulse trigger and the echo data collector 34, the microprocessor 35 receives the launch pulse energy monitor 32, the time interval measurer 33, the echo pulse trigger and the echo data collector 34. The signal of the wave data collector 34 is processed to obtain surface height and pressure information;

When the system is working, the laser emitting unit 1 emits two beams of pulsed lasers in the direction vertical to the surface, and its wavelength is; the echo from the ground is received by the receiving unit 2, and the signals received by the two detectors are sent to the control and numerical control. The acquisition and processing unit 3, the control and numerical control acquisition and processing unit 3 processes the signal to obtain the information data of the earth's surface pressure and altitude.

The wavelength of the detection wavelength laser 15 is 759.89632nm.

The wavelength of the reference wavelength laser 16 is 759.10 nm.

A data processing method of a differential absorption laser radar for detecting the earth's surface pressure and altitude is as follows:

Obtain signal data by receiving unit 2, wherein the first detector 26 signal E _on (R), the second detector 27 signal E _off (R), transmit pulse energy monitor 32 signals E _on (0), E _off (0 ), the time interval measurer 33 signal t, the earth surface pressure p ₀ finds out by formula (1):

Among them, C is a constant, which is determined by calibration; at the same time, the altitude data R is obtained by formula 2:

C is the speed of light.

Based on this, the present invention proposes a differential absorption laser radar for detecting the earth's surface pressure and altitude. The advantage of the present invention is that it can detect the earth's surface pressure and altitude at the same time, and provide more meaningful meteorological data than infrared passive detection.

Description of drawings

Figure 1 is a schematic diagram of the structure of a spatial differential absorption lidar. Among them: 1 laser emitting unit, 2 receiving unit, 3 control and numerical control acquisition and processing unit.

Fig. 2 is a schematic diagram of the specific structure of the spatial differential absorption lidar. Among them, 11 second mirrors, 12 polarization beam combiners, 13 first mirrors, 14 wavelength monitors, 15 detection wavelength lasers, 16 reference wavelength lasers, 17 resonant cavity long piezoelectric controllers, 18 pump lasers, 19 Probing wavelength seed laser, 110 reference wavelength seed laser; 21 on-board telescope, 22 lens, 23 narrow-band filter, 24 polarization beam splitter, 25 third mirror, 26 first photodetector, 27 second photodetector ; 31 launch pulse trigger, 32 launch pulse energy monitor, 33 time interval measurer 33, 34 echo pulse trigger and echo data collector, 35 microprocessor.

Detailed ways

Below in conjunction with accompanying drawing, the present invention will be further described.

A differential absorption laser radar for detecting the pressure and altitude of the earth's surface is composed of a laser emitting unit 1, a receiving unit 2, and a control and numerical control acquisition and processing unit 3;

Wherein, the laser emitting unit 1 is composed of a second reflector 11, a polarization beam combiner 12, a first reflector 13, a wavelength monitor 14, a detection wavelength laser 15, a reference wavelength laser 16, a resonant cavity long piezoelectric controller 17, The pump laser 18, the detection wavelength seed laser 19, and the reference wavelength seed laser 110 are composed of; the pump laser 18 pumps the detection wavelength laser 15 and the reference wavelength laser 16, and the wavelengths of these two lasers are respectively composed of the detection wavelength seed laser 19 and the reference wavelength The seed laser 110 is controlled; part of the light from the detection wavelength laser 15 enters the wavelength monitor 14, and the laser wavelength output by the detection wavelength laser 15 is stabilized by the cavity length piezoelectric controller 17; the light emitted by the reference wavelength laser 16 passes through the first reflector 13 reaches the polarization beam combiner 12 and the light emitted by the detection wavelength laser 15 is combined into a beam of light and then vertically shoots to the earth's surface through the second reflector 11; part of the light from the reference wavelength laser 16 enters the emission pulse trigger 31 and emits pulse energy Monitor 32, the detection wavelength laser 15 has some light to enter the emission pulse energy monitor 32;

Receiving unit 2 is made up of telescope 21 on the star, lens 22, narrow-band filter 23, polarization beam splitter 24, the 3rd mirror 25, the first light detector 26, the second light detector 27; The telescope 21 on the star receives the pulse energy echo signal reflected by the ground, passes through the lens 22 and the narrow-band filter 23, passes through the polarizing beam splitter 24, and then one path of light directly enters the first light detector 26, and the other light passes through the third reflector 25 enters the second photodetector 27, and the output terminals of the first photodetector 26 and the second photodetector 27 are respectively connected to the input terminals of the control and numerical control acquisition processing unit 3;

The control and numerical control acquisition and processing unit 3 is composed of a launch pulse trigger 31, a launch pulse energy monitor 32, a time interval measuring device 33, an echo pulse trigger and echo data collector 34, and a microprocessor 35; the microprocessor 35) Receive the signals from the transmit pulse energy monitor 32, the time interval measurer 33, the echo pulse trigger and the echo data collector 34, and obtain height and pressure information after processing.

Claims (4)

1. A differential absorption laser radar for detecting earth surface pressure and altitude, comprising laser emitting unit (1), receiving unit (2), control and numerical control acquisition and processing unit (3), is characterized in that: The laser emitting unit (1) includes a second reflector (11), a polarization beam combiner (12), a first reflector (13), a wavelength monitor (14), a detection wavelength laser (15), a reference wavelength Laser (16), cavity length piezoelectric controller (17), pump laser (18), detection wavelength seed laser (19), reference wavelength seed laser (110); Described pump laser (18) pumps probing wavelength laser (15) and reference wavelength laser (16), the wavelength of these two lasers is controlled by probing wavelength seed laser (19) and reference wavelength seed laser (110) respectively; Part of the light from the detection wavelength laser (15) enters the wavelength monitor (14), and the laser wavelength output by the detection wavelength laser (15) is stabilized by the resonant cavity length piezoelectric controller (17); the light emitted by the reference wavelength laser (16) After the first reflection mirror (13) reaches the light emitted by the polarization beam combiner (12) and the detection wavelength laser (15), it is combined into a beam of light and then vertically shoots to the earth's surface through the second reflection mirror (11); the reference wavelength laser ( 16) Part of the light enters the emission pulse trigger (31) and the emission pulse energy monitor (32), and the detection wavelength laser (15) has part of the light entering the emission pulse energy monitor (32); The receiving unit (2) comprises a telescope (21) on the star, a lens (22), a narrow-band filter (23), a polarizing beam splitter (24), a third reflector (25), and a first photodetector (26), the second photodetector (27); the pulse energy echo signal that the telescope (21) on the star in the receiving unit (2) receives the reflection of the earth's surface passes through the lens (22) and the narrow-band filter (23) after passing through One path of light behind the polarizing beam splitter (24) directly enters the first photodetector (26), and another beam of light enters the second photodetector (27) through the third reflector (25); Described control and numerical control acquisition processing unit (3) comprise launch pulse trigger (31), launch pulse energy monitor (32), time interval measurer (33), echo pulse trigger and echo data collector (34 ), microprocessor (35); time interval measurer (33) obtains time interval from the triggering of launch pulse trigger (31) and echo pulse trigger and echo data collector (34), microprocessor (35) Receive the signals of the launch pulse energy monitor (32), the time interval measuring device (33), the echo pulse trigger and the echo data collector (34), and obtain the surface height and pressure information after processing; When the system is working, the laser emitting unit (1) emits two beams of pulsed lasers in the direction vertical to the surface, and its wavelength is; the echo from the ground is received by the receiving unit (2), and the signals received by the two detectors are sent to To the control and numerical control acquisition and processing unit (3), the control and numerical control acquisition and processing unit (3) processes the signal to obtain the information data of the earth's surface pressure and altitude. 2. A differential absorption laser radar for detecting the earth's surface pressure and altitude according to claim 1, characterized in that the wavelength of the detection wavelength laser (15) is 759.89632nm. 3. A kind of differential absorption lidar for detecting the earth's surface pressure and altitude according to claim 1, characterized in that, the wavelength of the reference wavelength laser (16) is 759.10nm. 4. a kind of data processing method based on the differential absorption laser radar of a kind of detection earth surface pressure and altitude described in claim 1, it is characterized in that method is as follows: Obtain signal data by receiving unit (2), wherein the first photodetector (26) signal E _on (R), the second photodetector (27) signal E _off (R), transmit pulse energy monitor (32) signal E _on (0), E _off (0), time interval measurer (33) signal t, earth's surface pressure p ₀ data is obtained by formula (1): The constant C is determined by calibration; meanwhile, the altitude data R is obtained by formula (2): c is the speed of light.