Method for detecting near space wind field, temperature and density based on iron atom resonance fluorescence and satellite-borne iron laser radar

Abstract

The invention relates to a method for detecting a near space wind field, temperature and density based on iron atom resonance fluorescence. The method comprises the following steps: emitting 372 nm laser to a near space, and receiving an iron atom resonance fluorescence echo signal generated by a UMLT region and a Rayleigh back scattering echo signal generated by a region below the UMLT; according to the iron atom resonance fluorescence echo signal, an atmospheric temperature response function and a wind speed response function are defined, and the atmospheric temperature and the wind speed of a UMLT area are calculated according to the atmospheric temperature response function and the wind speed response function; and according to the Rayleigh backscattering echo signal of the predetermined wavelength laser, using a normalization algorithm to invert the atmospheric molecular density of the area below the UMLT, and then according to the atmospheric molecular density, inverting the atmospheric temperature of the area below the UMLT. According to the invention, the atmospheric temperature and wind speed of the UMLT region and the atmospheric molecular density and atmospheric temperature of the region below the UMLT region can be detected, and the wind field, temperature and density profile information can be obtained all day long and all day long with high precision.

Description

Technical Field

[0001] The present invention relates to the technical field of near-space atmosphere detection, and in particular to a method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence and a satellite-borne iron laser radar. Background Art

[0002] Near-space generally refers to the atmospheric region within the range of 20-100km from the earth's surface. It has attracted wide attention internationally due to its important development and application value. Among them, the region from the top of the mesosphere to the bottom of the thermosphere (UMLT, Upper mesosphere and lowerthermosphere) is about 75-115km, which is called the atmospheric metal layer. This is because the ablation of meteors produces metal elements such as Na, K, Ca, Fe, Mg, and K. The thermodynamic structure and dynamic characteristics of the atmosphere in this region are relatively complex, which plays a very critical role in the energy and momentum circulation of the atmosphere. There are many special natural phenomena such as high-altitude noctilucent clouds, mesotope inversions, and polar stratospheric clouds. In addition, the crushing of gravity waves makes the atmospheric disturbance in the top area of ​​the mesosphere more intense, and wind shear occurs. In addition, the atmospheric photochemical reaction in this region makes the atmospheric composition have obvious day-night variation characteristics. Among them, atmospheric temperature and wind are important components of the atmospheric environment. The detection of the atmospheric environment in the UMLT region helps to promote the development of aerospace activities and deepen the understanding of global climate change, which has important scientific research and application significance.

[0003] At present, the satellites and payloads that can obtain the temperature and wind in the UMLT region include Aura / MLS, TIMED / SABER and ICON / MIGHTI of the United States, etc. However, these detection technologies are mainly based on passive remote sensing methods, and have disadvantages such as dependence on sunlight and low vertical resolution. As an active remote sensing method, lidar has the advantages of high-precision detection all day and all weather, and can be used as a payload to detect the global atmospheric environment. At present, the international community has successfully launched satellite-borne lidars that can detect atmospheric wind fields, clouds, aerosols and carbon dioxide, but has not yet successfully launched satellite-borne lidars for atmospheric temperature and wind detection in the UMLT region. Ground-based lidars are relatively mature. In 1969, Bowman et al. used the world's first resonant fluorescence lidar to detect sodium atoms in the high altitude. Subsequently, the sodium fluorescence resonance Doppler lidar with a wavelength of 589nm was used to detect atmospheric temperature and wind, and achieved high-precision detection results. In 1995, the Leibniz Institute for Atmospheric Physics in Germany developed a 770nm narrow-band potassium Doppler lidar, which achieved simultaneous and effective observation of potassium layer density and temperature. After entering the 21st century, scientific research institutions such as IAP, CU-Boulder and DLR used various laser technologies to produce iron fluorescence resonance lidar with wavelengths of 386nm and 372nm, and simultaneously detected the iron atom number density, temperature and wind in the UMLT region.

[0004] Sodium resonant fluorescence lidar is the most mature technology among them. At present, there are also reports internationally that it has been launched into space as a payload. For example, NASA proposed a satellite-borne sodium lidar on the International Space Station, which uses a 589nm high-energy laser and a highly sensitive photon counting detector to detect the atmospheric temperature and wind speed at 75-115km with sodium atoms as tracers. Compared with sodium atoms, the effective backscattering cross section of iron atoms is about 15 times smaller, but the number density of iron atoms is 2-4 times that of sodium atoms, so there is not much difference in the difficulty of detection between the two; secondly, the wavelength of iron resonance fluorescence is in the near ultraviolet, and the Rayleigh signal is greatly enhanced compared to the sodium atom D2 line and the potassium atom D1 line. It can be used as a Rayleigh lidar below the UMLT region, so it can detect atmospheric wind field, density and temperature; in addition, iron atoms do not have a hyperfine structure, and a laser with higher power density can be used under the permission of the saturation effect to enhance the daytime detection performance. However, there is no report on the preparatory work of the satellite-borne iron resonance fluorescence Doppler lidar payload. Summary of the invention

[0005] Based on this, the purpose of the present invention is to provide a method for detecting the wind field, temperature and density in near space based on iron atomic resonance fluorescence and a satellite-borne iron lidar, which can simultaneously obtain the wind field, temperature and density in near space.

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

[0007] The present invention provides a method for detecting wind field, temperature and density in near space based on iron atom resonance fluorescence, which comprises the following steps:

[0008] S1. Design a satellite-borne iron laser radar, use the satellite-borne iron laser radar to emit 372nm laser into the near space and receive the iron atom resonance fluorescence echo signal generated by the UMLT area and the Rayleigh backscattering echo signal generated by the area below the UMLT;

[0009] S2. According to the iron atom resonance fluorescence echo signal, define the atmospheric temperature response function and the wind speed response function, and calculate the atmospheric temperature and wind speed of the UMLT region according to the atmospheric temperature response function and the wind speed response function;

[0010] S3. Invert the atmospheric molecular density of the area below the UMLT using a normalization algorithm based on the Rayleigh backscattering echo signal of the laser of the predetermined wavelength, and then invert the atmospheric temperature of the area below the UMLT based on the atmospheric molecular density.

[0011] As a further improvement of the above solution of the present invention, in step S1, the iron atom resonance fluorescence echo signal generated in the UMLT region is expressed as:

[0012]

[0013] Among them, λ Fe represents the predetermined wavelength of the laser; z represents the distance from the detection target to the ground; z s represents the orbital altitude of the satellite-borne radar; N represents the number of backscattered echo photons received by the lidar; P L is the emission power of the laser; Δt is the integration time; h is Planck's constant; c is the speed of light; Δz is the vertical resolution of the laser radar system; σ Fe represents the effective scattering cross section of iron resonance fluorescence; N Fe is the number density of iron atoms; A is the area of ​​the receiving telescope; η represents the total efficiency of the system, including the quantum efficiency of the detector and the optical efficiency of the system; N B is the background noise, including sunlight background noise counts and detector dark counts; T Fe is the transmittance of the iron layer to the light signal; T R Indicates the transmittance of atmospheric molecules.

[0014] As a further improvement of the above solution of the present invention, the effective scattering cross section is expressed as:

[0015]

[0016] Where e is the charge, f is ik is the oscillator strength; ε0 is the vacuum dielectric constant; m e is the mass of the electron; f Fe is the center frequency of the iron resonance absorption line; k B is the Boltzmann constant; T is the atmospheric temperature; M Fe is the mass of an iron atom; σ L is the line width of the emitted laser; A n is the relative abundance of stable isotopes.

[0017] As a further improvement of the above solution of the present invention, the 372nm laser has three different frequencies, which are defined as f0, f + and f - ,in:

[0018] f + =f0+δf,f - =f0+δf (5)

[0019] Among them, δf represents the frequency adjustment amount;

[0020] In step S2, the calculation of the atmospheric temperature and wind speed in the UMLT area includes:

[0021] The atmospheric temperature response function R T , wind speed response function R V Respectively expressed as:

[0022]

[0023] According to formula (1), formula (6) and formula (7) are simplified as follows:

[0024]

[0025] According to the atmospheric temperature response function R T , wind speed response function R V , the atmospheric temperature T and wind speed V in the UMLT area R Respectively expressed as:

[0026]

[0027] As a further improvement of the above solution of the present invention, the step S2 further includes calculating the random error of the atmospheric temperature detected by the satellite-borne iron laser radar in the UMLT area:

[0028]

[0029] Where, ΔT night represents the random error of the atmospheric temperature in the UMLT region detected by the spaceborne iron lidar at night, ΔTday represents the random error of the atmospheric temperature in the UMLT area detected by the satellite-borne iron lidar during the day, ψ represents the proportion time, and SNR0 represents the signal ratio of the lidar.

[0030] As a further improvement of the above solution of the present invention, the step S2 further includes calculating the random error of wind speed detected by the satellite-borne iron laser radar in the UMLT area:

[0031]

[0032] Where, ΔV R-night represents the random error of the wind speed detected by the satellite-borne iron lidar in the UMLT area at night, ΔV R-day It represents the random error of wind speed detected by satellite-borne iron lidar in the UMLT area during the day.

[0033] As a further improvement of the above solution of the present invention, in step S1, the Rayleigh backscattering echo signal of the laser of the predetermined wavelength generated in the area below the UMLT is expressed as:

[0034]

[0035] Among them, σ R is the Rayleigh backscattering cross section, n R is the molecular density of the atmosphere.

[0036] As a further improvement of the above solution of the present invention, the specific steps of step S3 are:

[0037] Select the height of 30km from the ground as the normalized height z0, and obtain the atmospheric density n at the normalized height z0 through satellite data or model data. R (z0), and the number of echo photons at the normalized height z0 is obtained:

[0038]

[0039] Dividing equation (16) by equation (17) yields the relative atmospheric density profile of the area below the UMLT:

[0040]

[0041] The temperature profile of the area below the UMLT is obtained by inverting the relative atmospheric density profile of the area below the UMLT:

[0042]

[0043] T(z) is the atmospheric temperature at altitude z obtained from the Rayleigh scattering signal; M and R are the atmospheric molar mass and thermodynamic constant, respectively; T(z0) is the temperature at the normalized altitude z0, obtained through satellite data or model data; g is the gravitational acceleration.

[0044] As a further improvement of the above solution of the present invention, the step S3 further includes calculating the relative error σ of the atmospheric density of the area below the UMLT detected by the satellite-borne iron laser radar n / n(z):

[0045]

[0046] Among them, σ N is the photon noise count, N is the number of echo photons and satisfies the Poisson distribution.

[0047] As a further improvement of the above solution of the present invention, step S3 further includes calculating the relative error σ of the atmospheric temperature of the area below UMLT detected by the satellite-borne iron laser radar T / T(z):

[0048]

[0049] The present invention also provides a satellite-borne iron laser radar, which adopts the method for detecting the wind field, temperature and density in near space based on the resonance fluorescence of iron atoms as described above, and comprises:

[0050] A laser emission system, which is used to emit 372nm laser in near space;

[0051] An optical receiving and detecting system, which is used to receive the iron atom resonance fluorescence echo signal generated by the UMLT region and the Rayleigh backscattering echo signal generated by the region below the UMLT;

[0052] A data acquisition and control system is used to define an atmospheric temperature response function and a wind speed response function according to the iron atom resonance fluorescence echo signal, and to calculate the atmospheric temperature and wind speed of the UMLT area according to the atmospheric temperature response function and the wind speed response function respectively; it is also used to invert the atmospheric molecular density of the area below the UMLT using a normalized algorithm according to the Rayleigh backscattering echo signal of the predetermined wavelength laser, and then invert the atmospheric temperature of the area below the UMLT according to the atmospheric molecular density.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The present invention emits 372nm wavelength laser to excite the iron atom resonance fluorescence scattering echo signal, and detects the wind field, temperature and density in near space based on the iron atom resonance fluorescence. It can detect the atmospheric temperature and wind speed in the UMLT area and the atmospheric molecular density and atmospheric temperature in the area below the UMLT, and can obtain wind field, temperature and density profile information with high precision all day and all weather. The method of the present invention has reference value for the development of space-borne resonance fluorescence Doppler laser radar to detect near space atmospheric parameters, and provides a reference for the research and development of space-borne iron radar.

[0055] The system provides theoretical support and accelerates the development of payloads. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A conceptual diagram of a satellite-borne iron laser radar in an embodiment of the present invention; Figure 2 It is a graph showing the random error of atmospheric temperature in the UMLT region detected by the satellite-borne iron laser radar in an embodiment of the present invention;

[0057] Figure 3 It is a curve diagram of the random error of wind speed in the UMLT area detected by the satellite-borne iron laser radar in an embodiment of the present invention;

[0058] Figure 4 This is a graph showing relative errors of atmospheric density and temperature in the area below the UMLT detected by a satellite-borne iron laser radar in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0061] Reference Figure 1, this embodiment first provides a satellite-borne iron laser radar, which includes a laser emission system, an optical receiving and detection system, a data acquisition and control system, and a power supply and thermal management subsystem. The laser emission system is used to emit 372nm laser in near space to excite the iron atom resonance fluorescence scattering echo signal. The optical receiving and detection system is used to receive the iron atom resonance fluorescence echo signal generated by the UMLT area and the Rayleigh backscattering echo signal generated by the area below the UMLT. The data acquisition and control system is used to quantify and temporarily store the electrical signal output by the optical receiving and detection system, and control the laser radar to work according to the preset timing according to the instructions and preset programs. The power supply and thermal management system is used to distribute power supply to various parts of the laser radar, as well as the corresponding thermal management to ensure that the core components of the laser radar operate within a suitable temperature range.

[0062] In this embodiment, the design parameters of the satellite-borne iron laser radar are shown in Table 1.

[0063] Table 1 Design parameters of satellite-borne iron lidar

[0064]

[0065] Based on the above-mentioned satellite-borne iron laser radar, this embodiment further proposes a method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence, which includes the following steps:

[0066] S1. Use the laser emission system to emit 372nm laser into the near space; the data acquisition and control system receives the iron atom resonance fluorescence echo signal generated by the UMLT area and the Rayleigh backscattering echo signal generated by the area below the UMLT.

[0067] The three different frequencies of 372nm laser are f0, f + and f-, where:

[0068] f + =f0+δf,f - =f0+δf (5)

[0069] Among them, δf represents the frequency adjustment amount.

[0070] The iron atom resonance fluorescence echo signal received by the satellite-borne iron lidar in the UMLT region can be expressed by formula (1):

[0071]

[0072] Among them, λ Fe represents the predetermined wavelength of the laser; z represents the distance from the detection target to the ground; z s represents the orbital altitude of the satellite-borne radar; N represents the number of backscattered echo photons received by the lidar; PL is the emission power of the laser; Δt is the integration time; h is Planck's constant; c is the speed of light; Δz is the vertical resolution of the laser radar system; σ Fe represents the iron resonance fluorescence backscattering differential cross section; N Fe is the number density of iron atoms; A is the area of ​​the receiving telescope; η represents the total efficiency of the system, including the quantum efficiency of the detector and the optical efficiency of the system; N B is the background noise, including sunlight background noise counts and detector dark counts; T Fe is the transmittance of the iron layer to the light signal; T R Indicates the transmittance of atmospheric molecules.

[0073] The effective scattering cross section is expressed by formula (2). Since the effective scattering cross section contains the basic information of Doppler broadening and Doppler frequency shift, formula (2) is the most important theoretical model for inverting temperature and wind speed.

[0074]

[0075] Where e is the charge, f is ik is the oscillator strength; ε0 is the vacuum dielectric constant; m e is the mass of the electron; f Fe is the center frequency of the iron resonance absorption line; k B is the Boltzmann constant; T is the atmospheric temperature; M Fe is the mass of an iron atom; σ L is the line width of the emitted laser; A n is the relative abundance of stable isotopes.

[0076] When the 372nm wavelength laser continues to transmit to the lower part of the UMLT area, Rayleigh scattering occurs with atmospheric molecules. According to the Rayleigh scattering theory and the lidar equation, the satellite-borne iron lidar can be used as a Rayleigh lidar. The number density and temperature information of atmospheric molecules can be determined by using the Rayleigh backscattered echo signal received by the lidar. The Rayleigh backscattered echo signal received by the lidar is expressed as:

[0077]

[0078] Among them, σ R is the Rayleigh backscattering cross section, n R is the molecular density of the atmosphere.

[0079] S2. The data acquisition and control system defines an atmospheric temperature response function and a wind speed response function according to the iron atom resonance fluorescence echo signal, and calculates the atmospheric temperature and wind speed of the UMLT area according to the atmospheric temperature response function and the wind speed response function.

[0080] The satellite-borne iron lidar also uses the classic three-frequency ratio method to invert the atmospheric temperature and wind speed, defining the atmospheric temperature response function R T , wind speed response function R V for:

[0081]

[0082] After removing the background noise by combining formula (1), R T , R V Simplify further.

[0083]

[0084] From the above formula, we can find that the response function R T , R V The change of is only affected by the effective scattering cross section of iron atoms, and the effective scattering cross section is only a function of frequency, temperature and wind speed. Therefore, when the outgoing laser frequency is known, the two-dimensional lookup table within a certain temperature and wind speed range can be calculated according to the above formulas (8) and (9). In the actual laser radar detection experiment, the measured response function is substituted into the two-dimensional lookup table to find the corresponding atmospheric temperature and wind speed.

[0085] Random errors affect the accuracy of temperature and wind speed measurements by satellite-borne lidar. For lidar, random errors, mainly photon noise, are the biggest influencing factor and are closely related to the lidar system parameters. If the number of received echo photons is N and satisfies the Poisson distribution, then the photon noise count is approximately Therefore, the lidar equation is used in numerical simulation to quantitatively establish the relationship between the measurement error and the system parameters, thereby guiding the design of the satellite-borne lidar system and reducing the influence of random errors. Therefore, performance simulation can be performed based on the error transfer method to calculate the random error of the satellite-borne lidar. The expressions of temperature and wind speed in the UMLT area are expressed by formula (10) and formula (11).

[0086]

[0087] Among them, R T , R V It can be directly calculated using the laser radar echo signal. According to the error transmission theory, the measurement errors of atmospheric temperature and wind speed are directly derived from R T , R V The error of the satellite-borne iron resonance fluorescence Doppler lidar detection during the day and at night can be expressed by the following formula.

[0088]

[0089] Where, ΔT nightrepresents the random error of the atmospheric temperature in the UMLT region detected by the spaceborne iron lidar at night, ΔT day represents the random error of the atmospheric temperature detected by the satellite-borne iron lidar in the UMLT region during the day, ΔV R-night represents the random error of the wind speed detected by the satellite-borne iron lidar in the UMLT area at night, ΔV R-day represents the random error of the wind speed detected by the satellite-borne iron laser radar in the UMLT area during the day, ψ represents the proportion time, and SNR0 represents the signal ratio of the laser radar. The random errors of the atmospheric temperature and wind speed detected by the satellite-borne iron laser radar in the UMLT area designed in this embodiment are as follows: Figure 2 , Figure 3 shown.

[0090] S3. The data acquisition and control system uses a normalized algorithm to invert the atmospheric molecular density of the area below the UMLT based on the Rayleigh backscatter echo signals of three different frequencies, and then inverts the atmospheric temperature of the area below the UMLT based on the atmospheric molecular density.

[0091] Normalized algorithm is generally used to invert atmospheric density. Since there is basically no aerosol at 30km, the main method is Rayleigh scattering of atmospheric molecules. This height is selected as the normalized height z0. The atmospheric density at this height z0 is generally obtained through satellite data or model data, and the number of echo photons at the normalized height z0 is obtained at the same time:

[0092]

[0093] Dividing equation (16) by equation (17) yields the relative atmospheric density profile of the area below the UMLT:

[0094]

[0095] The temperature profile can be inverted from the relative density profile. This method was first proposed by Haunchecorne and Chanin based on the ideal gas theory and the hydrostatic equilibrium equation:

[0096]

[0097] T(z) is the atmospheric temperature at altitude z obtained from the Rayleigh scattering signal; M and R are the atmospheric molar mass and thermodynamic constant, respectively; T(z0) is the temperature at the normalized altitude z0, obtained through satellite data or model data; g is the gravitational acceleration.

[0098] Since the atmospheric density at height z is positively correlated with the number of echo photons at that height, the density inversion error is mainly caused by the random statistical error of the number of echo photons. Under the assumption that the photons are independent of each other and the photon number statistics satisfy the Possion distribution: The relative error of the measurement of atmospheric density can be expressed as:

[0099]

[0100] Among them, σ N is the photon noise count, N is the number of echo photons and satisfies the Poisson distribution.

[0101] Similarly, the inversion error of atmospheric temperature also depends on the statistical error of the echo photon number. The relative error σ of the atmospheric temperature obtained from the Rayleigh signal is T / T(z) is also approximately inversely proportional to the square root of the number of echo photons.

[0102]

[0103] The random errors of the atmospheric density and temperature in the area below UMLT detected by the satellite-borne iron laser radar designed in this embodiment are as follows: Figure 4 shown.

[0104] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence, characterized in that: It includes the following steps: S1. emit 372nm laser into the near space and receive the iron atom resonance fluorescence echo signal generated by the UMLT region and the Rayleigh backscattering echo signal generated by the region below the UMLT; S2. According to the iron atom resonance fluorescence echo signal, define the atmospheric temperature response function and the wind speed response function, and calculate the atmospheric temperature and wind speed of the UMLT region according to the atmospheric temperature response function and the wind speed response function; S3. Invert the atmospheric molecular density of the area below the UMLT using a normalization algorithm based on the Rayleigh backscattering echo signal of the laser of the predetermined wavelength, and then invert the atmospheric temperature of the area below the UMLT based on the atmospheric molecular density.

2. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 1, characterized in that: In step S1, the iron atom resonance fluorescence echo signal generated in the UMLT region is expressed as: Among them, λ Fe represents the predetermined wavelength of the laser; z represents the distance from the detection target to the ground; z s represents the orbital altitude of the satellite-borne radar; N represents the number of backscattered echo photons received by the lidar; P L is the emission power of the laser; Δt is the integration time; h is Planck's constant; c is the speed of light; Δz is the vertical resolution of the laser radar system; σ Fe represents the effective scattering cross section of iron resonance fluorescence; N Fe is the number density of iron atoms; A is the area of ​​the receiving telescope; η represents the total efficiency of the system, including the quantum efficiency of the detector and the optical efficiency of the system; N B is the background noise, including sunlight background noise counts and detector dark counts; T Fe is the transmittance of the iron layer to the light signal; T R Indicates the transmittance of atmospheric molecules.

3. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 2, characterized in that: The effective scattering cross section is expressed as: Where e is the charge, f is ik is the oscillator strength; ε0 is the vacuum dielectric constant; m e is the mass of the electron; f Fe is the center frequency of the iron resonance absorption line; k B is the Boltzmann constant; T is the atmospheric temperature; M Fe is the mass of an iron atom; σ L is the line width of the emitted laser; A n is the relative abundance of stable isotopes.

4. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 3 is characterized in that: The 372nm laser has three different frequencies, which are defined as f0, f + and f - ,in: f + =f0+δf,f - =f0+δf (5) Among them, δf represents the frequency adjustment amount; In step S2, the calculation of the atmospheric temperature and wind speed in the UMLT area includes: The atmospheric temperature response function R T , wind speed response function R V Respectively expressed as: According to formula (1), formula (6) and formula (7) are simplified as follows: According to the atmospheric temperature response function R T , wind speed response function R V , the atmospheric temperature T and wind speed V in the UMLT area R Respectively expressed as:

5. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 1, characterized in that: The step S2 also includes calculating the random error of the atmospheric temperature in the UMLT region detected by the satellite-borne iron laser radar: Where, ΔT night represents the random error of the atmospheric temperature in the UMLT region detected by the spaceborne iron lidar at night, ΔT day represents the random error of the atmospheric temperature in the UMLT area detected by the satellite-borne iron lidar during the day, ψ represents the proportion time, and SNR0 represents the signal ratio of the lidar.

6. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 1, characterized in that: The step S2 also includes calculating the random error of wind speed detected by the satellite-borne iron laser radar in the UMLT area: Where, ΔV R-night represents the random error of the wind speed detected by the satellite-borne iron lidar in the UMLT area at night, ΔV R-day It represents the random error of wind speed detected by satellite-borne iron lidar in the UMLT area during the day.

7. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 1, characterized in that: In step S1, the Rayleigh backscattering echo signal of the laser with a predetermined wavelength generated in the area below the UMLT is expressed as: Among them, σ R is the Rayleigh backscattering cross section, n R is the molecular density of the atmosphere.

8. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 7, characterized in that: The specific steps of step S3 are: Select the height of 30km from the ground as the normalized height z0, and obtain the atmospheric density n at the normalized height z0 through satellite data or model data. R (z0), and the number of echo photons at the normalized height z0 is obtained: Dividing equation (16) by equation (17) yields the relative atmospheric density profile of the area below the UMLT: The temperature profile of the area below the UMLT is obtained by inverting the relative atmospheric density profile of the area below the UMLT: T(z) is the atmospheric temperature at altitude z obtained from the Rayleigh scattering signal; M and R are the atmospheric molar mass and thermodynamic constant, respectively; T(z0) is the temperature at the normalized altitude z0, obtained through satellite data or model data; g is the gravitational acceleration.

9. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 1, characterized in that: The step S3 also includes calculating the relative error σ of the atmospheric density of the area below the UMLT detected by the satellite-borne iron laser radar n / n(z): Among them, σ N is the photon noise count, N is the number of echo photons and satisfies the Poisson distribution; And / or, the step S3 further comprises calculating the relative error σ of the atmospheric temperature of the area below the UMLT detected by the satellite-borne iron laser radar T / T(z):

10. A satellite-borne iron laser radar, characterized in that: The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence as claimed in any one of claims 1 to 9 comprises: A laser emission system, which is used to emit 372nm laser in near space; An optical receiving and detecting system, which is used to receive the iron atom resonance fluorescence echo signal generated by the UMLT region and the Rayleigh backscattering echo signal generated by the region below the UMLT; A data acquisition and control system is used to define an atmospheric temperature response function and a wind speed response function according to the iron atom resonance fluorescence echo signal, and to calculate the atmospheric temperature and wind speed of the UMLT area according to the atmospheric temperature response function and the wind speed response function respectively; it is also used to invert the atmospheric molecular density of the area below the UMLT using a normalized algorithm according to the Rayleigh backscattering echo signal of the predetermined wavelength laser, and then invert the atmospheric temperature of the area below the UMLT according to the atmospheric molecular density.

Images