Method for Detecting Near-Space Wind Field, Temperature and Density Based on Resonance Fluorescence of Iron Atoms and Spaceborne Iron Lidar

Abstract

The present invention relates to a method for detecting the wind field, temperature, and density in near-space based on iron atom resonance fluorescence, comprising the following steps: emitting a 372nm laser into near-space and receiving an iron atom resonance fluorescence echo signal generated by the ULT region and a Rayleigh backscattered echo signal generated by the region below the ULT; defining an atmospheric temperature response function and a wind speed response function based on the iron atom resonance fluorescence echo signal, and calculating the atmospheric temperature and wind speed in the ULT region based on the atmospheric temperature response function and the wind speed response function; inverting the atmospheric molecular density in the region below the ULT using a normalized algorithm based on the Rayleigh backscattered echo signal of the predetermined wavelength laser, and then inverting the atmospheric temperature in the region below the ULT based on the atmospheric molecular density. The present invention can detect the atmospheric temperature and wind speed in the ULT region, as well as the atmospheric molecular density and atmospheric temperature in the region below the ULT, and can obtain wind field, temperature, and density profile information with high precision around the clock.

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 between 20 and 100 km above Earth's surface. Its significant development and application value has attracted widespread international attention. The region between the upper mesosphere and the lower thermosphere (UMLT), approximately 75 to 115 km, is known as the atmospheric metallic layer. This region, due to the production of metallic elements such as Na, K, Ca, Fe, Mg, and K by meteor ablation, creates a complex thermodynamic structure and dynamics, crucial for atmospheric energy and momentum cycles. This region is home to numerous unique natural phenomena, including high-altitude noctilucent clouds, mesopause inversions, and polar stratospheric clouds. Furthermore, gravity wave fragmentation exacerbates atmospheric disturbances in the upper mesosphere, leading to wind shear. Furthermore, atmospheric photochemical reactions in this region contribute to distinct diurnal variations in atmospheric composition. Atmospheric temperature and wind are crucial components of the atmospheric environment. Observing the atmospheric environment in the UMLT region will help advance aerospace activities and deepen our understanding of global climate change, possessing significant scientific and applied significance.

[0003] Currently, satellites and payloads capable of measuring temperature and winds in the UMLT region include the US's Aura / MLS, TIMED / SABER, and ICON / MIGHTI. However, these detection technologies are primarily based on passive remote sensing, relying on sunlight and exhibiting low vertical resolution. LiDAR, as an active remote sensing method, offers the advantages of high-precision, all-weather detection capabilities around the clock and can be used as a payload to monitor the global atmospheric environment. Internationally, spaceborne lidars have been successfully launched to measure atmospheric winds, clouds, aerosols, and carbon dioxide, but no spaceborne lidar specifically designed for measuring atmospheric temperature and winds in the UMLT region has yet to be successfully launched. Ground-based lidar is relatively mature. In 1969, Bowman et al. used the world's first resonant fluorescence lidar to detect sodium atoms in the atmosphere. Subsequently, sodium fluorescence resonance Doppler lidar at a wavelength of 589 nm was used to measure atmospheric temperature and winds, achieving high-precision results. In 1995, the Leibniz Institute for Atmospheric Physics in Germany developed a 770 nm narrowband potassium Doppler lidar, enabling simultaneous and effective observation of potassium 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 resonance fluorescence lidar is the most mature technology among these, and there are reports internationally of its launch as a space payload. For example, NASA has proposed a spaceborne sodium lidar for the International Space Station. Using a 589nm high-energy laser and a highly sensitive photon-counting detector, it uses sodium atoms as tracers to monitor atmospheric temperature and wind speed at ranges of 75-115 km. While the effective backscattering cross-section of iron atoms is approximately 15 times smaller than that of sodium, the iron number density is 2-4 times that of sodium, making the detection difficulty comparable. Furthermore, iron resonance fluorescence, with its wavelength in the near-ultraviolet, significantly enhances the Rayleigh signal relative to the sodium D2 line and potassium D1 line, making it suitable for use as a Rayleigh lidar below the ultraviolet wavelength range (UMLT), enabling the detection of atmospheric wind, density, and temperature. Furthermore, iron atoms lack a hyperfine structure, allowing for the use of higher laser power densities, allowing for enhanced daytime detection performance. However, there are currently no reports on the preparatory work for a spaceborne 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 spaceborne iron lidar that emits 372 nm laser light into near-space and receives the iron atomic resonance fluorescence echo signal generated by the UMLT region and the Rayleigh backscattered echo signal generated by the region below the UMLT.

[0009] S2. Based on 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 respectively 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 backscattered echo signal of the predetermined wavelength laser, 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 spaceborne radar; N represents the number of backscattered echo photons received by the lidar; P L is the laser emission power; Δt represents the integration time; h is Planck's constant; c is the speed of light; Δz represents the vertical resolution of the lidar 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 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, 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 spaceborne iron lidar during the day, ψ represents the proportion time, and SNR0 represents the signal-to-noise ratio of the lidar.

[0030] As a further improvement of the above solution of the present invention, 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 in the UMLT area detected by the spaceborne iron lidar at night, ΔV R-day It represents the random error of wind speed in the UMLT area detected by spaceborne iron lidar during the day.

[0033] As a further improvement of the above solution of the present invention, in step S1, the Rayleigh backscattered echo signal of the laser light of 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 number density of atmospheric molecules.

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

[0037] The altitude of 30 km above the ground is selected as the normalized altitude z0, and the atmospheric density n at the normalized altitude z0 is obtained 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 for 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 normalized temperature at altitude z0, obtained from satellite data or model data; g is the acceleration of gravity.

[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 light quantum 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, the step S3 further includes calculating the relative error σ of the atmospheric temperature in the area below the UMLT detected by the satellite-borne iron laser radar. T / T(z):

[0048]

[0049] The present invention also provides a spaceborne iron laser radar, which adopts the method of 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 for emitting 372nm laser light into near space;

[0051] an optical receiving and detecting system for receiving 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 based on the iron atom resonance fluorescence echo signal, and calculate the atmospheric temperature and wind speed of the UMLT area based on 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 based on the Rayleigh backscattered echo signal of the predetermined wavelength laser, and then invert the atmospheric temperature of the area below the UMLT based on the atmospheric molecular density.

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

[0054] The present invention uses 372nm wavelength laser light to stimulate the resonant fluorescence scattering echo signal of iron atoms. Based on the resonant fluorescence of iron atoms, the present invention can detect the atmospheric temperature and wind speed in the UMLT region, as well as the atmospheric molecular density and atmospheric temperature in the region below the UMLT. It can obtain wind field, temperature, and density profile information with high precision around the clock and in all weather conditions. The present invention has reference value for the development of spaceborne resonant fluorescence Doppler lidar to detect near-space atmospheric parameters, provides theoretical support for the development of spaceborne iron radars, and accelerates the development of payloads. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a conceptual diagram of a space-borne iron laser radar in an embodiment of the present invention;

[0056] Figure 2 This is a graph showing the random error of atmospheric temperature detected by the spaceborne iron laser radar in the UMLT region according to an embodiment of the present invention;

[0057] Figure 3 This is a graph showing the random error of wind speed detected by the satellite-borne iron laser radar in the UMLT area according to 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 space-borne iron lidar in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] To facilitate 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 provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[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 space-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 and thermal management system. 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 program. The power 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 spaceborne iron lidar

[0064]

[0065] Based on the above-mentioned spaceborne iron lidar, this embodiment further proposes a method for detecting near-space wind field, temperature, and density based on iron atomic 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 region and the Rayleigh backscattering echo signal generated by the region below the UMLT.

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

[0068] f + =f0+δf,f - =f0+δf (5)

[0069] Wherein, δf represents the frequency adjustment amount.

[0070] The iron atomic resonance fluorescence echo signal received by the spaceborne 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 srepresents the orbital altitude of the spaceborne radar; N represents the number of backscattered echo photons received by the lidar; P L is the laser emission power; Δt represents the integration time; h is Planck's constant; c is the speed of light; Δz represents the vertical resolution of the lidar 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 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 toward the lower part of the UMLT region, Rayleigh scattering occurs with atmospheric molecules. According to Rayleigh scattering theory and the lidar equation, the satellite-borne iron lidar can be used as a Rayleigh lidar. The Rayleigh backscattered echo signal received by the lidar can be used to determine the number density and temperature of atmospheric molecules. 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 number density of atmospheric molecules.

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

[0080] The spaceborne 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 in is only affected by the effective scattering cross section of the iron atom, which is a function of frequency, temperature, and wind speed. Therefore, when the outgoing laser frequency is known, a two-dimensional lookup table within a certain temperature and wind speed range can be calculated according to the above equations (8) and (9). In actual lidar detection experiments, 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 space-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, in numerical simulations, the lidar equation is used to quantitatively establish the relationship between measurement error and system parameters, thereby guiding the design of the spaceborne lidar system and reducing the impact of random errors. Therefore, performance simulation can be performed based on the error propagation method to calculate the random error of the spaceborne lidar. The expressions for the temperature and wind speed in the UMLT region are expressed using Equations (10) and (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 error of atmospheric temperature and wind speed comes directly from R T 、R VThe random error of the spaceborne iron resonance fluorescence Doppler lidar detection during the day and at night can be expressed by the following formula.

[0088]

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

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

[0091] Normalized algorithms are generally used to invert atmospheric density. Since there is basically no aerosol at 30 km, 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 for the area below the UMLT:

[0094]

[0095] The temperature profile can be inverted from the relative density profile. This method was first proposed by Haunchecome 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 normalized temperature at altitude z0, obtained from satellite data or model data; g is the acceleration of gravity.

[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 photons are independent of each other and the photon number statistics satisfy the Possion distribution: The relative error of atmospheric density measurement can be expressed as:

[0099]

[0100] Among them, σ N is the light quantum 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 atmospheric temperature obtained from 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 spaceborne iron lidar designed in this embodiment in detecting the atmospheric density and temperature in the area below UMLT are as follows: Figure 4 shown.

[0104] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for detecting wind field, temperature and density in near space based on iron atomic resonance fluorescence, characterized in that: It includes the following steps: S1. Emitting 372 nm laser light into near space and receiving the iron atom resonance fluorescence echo signal generated by the UMLT region and the Rayleigh backscattered echo signal generated by the region below the UMLT; S2. Based on 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 respectively according to the atmospheric temperature response function and the wind speed response function; S3 according to the Rayleigh backscatter echo signal, using the normalization algorithm to invert the atmospheric molecular density of the region below UMLT, and then invert the atmospheric temperature of the region below UMLT based on the atmospheric molecular density; 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 spaceborne radar; N represents the number of backscattered echo photons received by the lidar; P L is the laser emission power; Δt represents the integration time; h is Planck's constant; c is the speed of light; Δz represents the vertical resolution of the lidar 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 atmospheric molecule transmittance; The effective scattering cross section is expressed as: Where e is the charge, f 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; The 372nm laser has three different frequencies, which are defined as f0, f + and f-, where: 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:

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: The step S2 further 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 spaceborne iron lidar during the day, ψ represents the proportion time, and SNR0 represents the signal-to-noise ratio of the lidar.

3. 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 further 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 in the UMLT area detected by the spaceborne iron lidar at night, ΔV R-day represents the random error of the wind speed in the UMLT area detected by the spaceborne iron lidar during the day; ψ represents the proportion time, and SNR0 represents the signal-to-noise ratio of the lidar.

4. 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 backscattered echo signal of the laser light of 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 number density of atmospheric molecules.

5. The method for detecting near-space wind field, temperature and density based on iron atom resonance fluorescence according to claim 4, characterized in that: The specific steps of step S3 are: The altitude of 30 km above the ground is selected as the normalized altitude z0, and the atmospheric density n at the normalized altitude z0 is obtained 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 for 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 normalized temperature at altitude z0, obtained from satellite data or model data; g is the acceleration of gravity.

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 S3 also includes calculating the relative error σ of the atmospheric density below the UMLT detected by the satellite-borne iron laser radar n / n(z): Among them, σ N is the light quantum 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 in the area below the UMLT detected by the satellite-borne iron laser radar T / T(z):

7. 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 according to any one of claims 1 to 6 is adopted, which comprises: A laser emission system for emitting 372nm laser light into near space; an optical receiving and detecting system for receiving 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 based on the iron atom resonance fluorescence echo signal, and calculate the atmospheric temperature and wind speed of the UMLT area based on 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 based on the Rayleigh backscattered echo signal of the predetermined wavelength laser, and then invert the atmospheric temperature of the area below the UMLT based on the atmospheric molecular density.

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