CN117783058A - Method and system for measuring inclined-path atmospheric transmittance - Google Patents
Method and system for measuring inclined-path atmospheric transmittance Download PDFInfo
- Publication number
- CN117783058A CN117783058A CN202311507873.7A CN202311507873A CN117783058A CN 117783058 A CN117783058 A CN 117783058A CN 202311507873 A CN202311507873 A CN 202311507873A CN 117783058 A CN117783058 A CN 117783058A
- Authority
- CN
- China
- Prior art keywords
- echo
- laser
- time
- atmospheric transmittance
- transmittance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000002834 transmittance Methods 0.000 title claims abstract description 113
- 238000000034 method Methods 0.000 title claims abstract description 66
- 238000012545 processing Methods 0.000 claims abstract description 19
- 230000003287 optical effect Effects 0.000 claims description 35
- 238000001514 detection method Methods 0.000 claims description 25
- 230000005540 biological transmission Effects 0.000 claims description 15
- 230000004044 response Effects 0.000 claims description 12
- 230000010365 information processing Effects 0.000 claims description 8
- 230000005693 optoelectronics Effects 0.000 claims description 3
- 230000035699 permeability Effects 0.000 claims description 3
- 230000008901 benefit Effects 0.000 abstract description 6
- 230000035945 sensitivity Effects 0.000 abstract description 5
- 230000005855 radiation Effects 0.000 description 41
- 238000005516 engineering process Methods 0.000 description 28
- 238000005259 measurement Methods 0.000 description 23
- 238000001228 spectrum Methods 0.000 description 16
- 238000004364 calculation method Methods 0.000 description 12
- 230000010355 oscillation Effects 0.000 description 12
- 230000003595 spectral effect Effects 0.000 description 12
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 9
- 238000010521 absorption reaction Methods 0.000 description 9
- 238000000862 absorption spectrum Methods 0.000 description 7
- 230000003321 amplification Effects 0.000 description 7
- 230000008859 change Effects 0.000 description 7
- 238000003199 nucleic acid amplification method Methods 0.000 description 7
- 238000004088 simulation Methods 0.000 description 7
- 230000006870 function Effects 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 108091006146 Channels Proteins 0.000 description 5
- 101000694017 Homo sapiens Sodium channel protein type 5 subunit alpha Proteins 0.000 description 5
- 238000012937 correction Methods 0.000 description 5
- 230000008033 biological extinction Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 239000000443 aerosol Substances 0.000 description 2
- 239000005427 atmospheric aerosol Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 230000036961 partial effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000001360 synchronised effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 241000863480 Vinca Species 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012067 mathematical method Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005316 response function Methods 0.000 description 1
- 230000001932 seasonal effect Effects 0.000 description 1
- 238000011896 sensitive detection Methods 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Landscapes
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The invention discloses a method and a system for measuring the atmospheric transmittance of a slope, comprising the following steps of transmitting laser pulses to an observation target and recording a main wave signal; recording the main wave moment of the pulse according to the time information; receiving an echo signal returned by an observation target; recording echo time; processing main echo pairing, and accurately measuring round trip time t of laser pulses from a ground station to a satellite; identifying and processing echo signals, and counting the number N of echo photons in unit time; and acquiring and recording a T value according to the T function relation between the number N of echo photons and the transmittance T of the inclined path atmosphere. The technical scheme of the invention can acquire and count the photon number in unit time by using the laser ranging system based on the functional relation between the echo photon number of the laser ranging system and the atmospheric transmittance, and obtain the inclined-path atmospheric transmittance through mathematical inversion, thereby not only retaining the advantages of high precision and high sensitivity of the laser ranging system, but also realizing the day and night observation of the atmospheric transmittance.
Description
Technical Field
The invention relates to the technical field of measuring atmospheric transmittance, in particular to a method and a system for measuring the inclined-path atmospheric transmittance.
Background
Atmospheric air is a very complex system that varies greatly from region to region, from environment to environment, from time to time, etc. The absorption decay of the atmosphere is mainly due to H in the atmosphere 2 O，CO 2 And O 3 The strong absorption of the molecules results. As an important parameter reflecting the transmission property of the atmospheric radiation, the atmospheric transmittance has important significance in researches such as the atmospheric radiation, the remote sensing of earth resources, the air quality detection and the like. In the military field, tracking of objects by aircraft, missiles, and the likeThe warning and searching are affected by the atmospheric transmittance, which is often the decisive factor; in astronomical observation, the atmospheric transmittance influences the radiation intensity and transmittance of an accuracy target measured by an astronomical observation target to jointly determine the signal intensity reaching a detection system; in the remote sensing image, the atmospheric transmittance is a main parameter for atmospheric correction.
The atmospheric transmittance real-time measurement can measure the atmospheric transmittance of a specific foundation, a specific time domain and a specific sky, and atmospheric transmission correction is carried out on the photometric data measured by other foundations, so that the reliability of the observed data is ensured. The method for obtaining the atmospheric transmittance mainly comprises three steps of numerical simulation, software calculation and field measurement. Numerical simulation methods are typically calculated using empirical formulas. In the process of calculating the transmittance, the average atmospheric transmittance of the local infrared band can be conveniently and quickly obtained by utilizing numerical simulation. The atmospheric transmittance is calculated with slightly poorer precision by numerical simulation, and the method can be used in the work with low precision requirement. The simulation software comprises Lowtran, modtran, hitran, fascode and Cart series atmospheric transmittance calculation software packages, and a specific mode is selected for simulation calculation according to the meteorological characteristics of the region and the weather factors of the current day. The software packages invert the current atmospheric optical transmission characteristics by using an empirical formula obtained through statistics, and are required to determine meteorological parameters such as the composition, the spectral distribution, the total content, the temperature and humidity of the atmospheric aerosol in real time, so that certain defects exist in the aspect of calculating the real-time performance of the atmospheric optical transmittance. For example, the Hitran2012 database has problems of partial spectral line parameter redundancy and partial spectral line parameter deficiency, so that the uncertainty exists in the results of simulation calculation based on the spectral line parameters and the mode, and the maximum absolute deviation of the calculation results of different versions with the initial heights of 1km is up to 40% in a 2-5 μm wave band. In addition, the operators in China are wide, the terrains are complex, the geographic condition differences of different areas are obvious, the atmospheric conditions are quite different, and accurate quantitative description of the diversified atmospheric phenomena is difficult to carry out only by means of a statistical and average theoretical model or a mathematical method. Therefore, it is important to measure the transmittance of the whole atmosphere layer in real time by using an instrument.
The first prior art is: the detection of the atmospheric transmittance by using the solar photometer technology is a common and effective monitoring means in the existing foundation remote sensing. The solar photometer is not only widely applied to researches of atmosphere detection, environment detection, climate change and the like, but also is an important tool for satellite remote sensing atmosphere correction, calibration and reliability inspection. The lower panel shows a PM-02 solar photometer.
The solar photometer is an optical instrument capable of measuring the direct radiation characteristic of the sun in real time. The method uses the constant sunlight outside the whole atmosphere as a radiation source, measures the solar spectrum after a certain transmission path, and then inverts the atmospheric transmittance according to the characteristic radiation attenuation information in the solar spectrum. The solar photometer has the characteristics of wide angle and wide spectrum, and can acquire solar radiation reaching the ground through the atmosphere in a wide and various geographic area of the ground surface. Taking a Microtops Solar photometer manufactured by Solar corporation as an example, a photodiode of the instrument converts the illuminance of incident sunlight into current, converts the voltage by a high-precision operational amplifier, and adjusts the voltage to a required amplitude by a feedback resistor. The signal acquisition system consists of 5 channels, and when the signal acquisition system is unsaturated, the illuminance value of the detection surface is in direct proportion to the brightness values of other detection directions, so that the voltage value obtained by the system can reflect the intensity of incident light.
The atmospheric transmittance at time T measured by a photometer is T (λ, T):
wherein V (lambda, t) is the output voltage of the direct solar radiation with the wavelength lambda received by the solar photometer at the moment t, which is proportional to the solar radiation received by the detector, V 0 (lambda) is the solar radiation E corresponding to the daily average distance 0 An instrument output value of (λ), (d) 0 /d) 2 Is a sun-earth distance correction factor used to correct the direct solar irradiance at the upper boundary of the atmosphere. According to the Lambert-Bear theorem, the direct solar radiation I (λ) at wavelength λ on the earth's surface is:
since the output voltage of solar radiation is proportional to the solar radiation received by the detector, equation (6) can be rewritten as:
therefore, the atmospheric transmittance T is:
where τ (λ, t) is the total atmospheric optical thickness at wavelength λ and m (θ) is the relative atmospheric mass along the optical path at zenith angle θ.
As can be seen from the above equation, V (λ, t) and m (θ) have a definite relationship as long as the atmosphere is relatively stable (i.e., τ (λ, t)) remains unchanged. In the Langley-plot calibration method, the logarithm of the formula (8) is given by:
lnV(λ，t)＝lnV 0 (λ)-m(θ)τ(λ) (9)
in the above formula, inV (λ, t) has a linear relationship with m (θ), its slope is the atmospheric optical thickness, and its intercept is related to the solar constant and the instrument constant. The relative atmospheric mass is mainly related by zenith angle, and the following approximate relationship is considered when the influence of the earth curvature is considered:
m(θ)＝secθ-0.01867(secθ-1)-0.002875(secθ-1) 2 -0.0008683(secθ-1) 3 (10)
The zenith angle can be measured directly, can be calculated and found from an astronomical calendar according to standard time and local longitude and latitude, or can be calculated by a formula. Under the conditions of stable atmosphere and clear and cloudless atmosphere, measuring solar irradiance V (lambda, t) at different moments m (theta), and extrapolating a fitting straight line to obtain an intercept InV (lambda, t); on the basis, by combining the formula (8), V (lambda, T) is obtained according to a certain moment, and the whole atmosphere transmittance T at the moment can be obtained.
The solar photometer mainly comprises a sun tracking part, a signal receiving part and a computer. The sun tracking part can adjust the direction of the light cylinder according to the change of the sun altitude angle, so that the instrument can be ensured to receive the direct solar radiation. An automatic tracking device is usually implemented by combining a four-quadrant detector with a stepping motor. In addition, as the instrument is in an outdoor state, the environmental change is large, especially the temperature fluctuation is obvious, and the temperature control module can be adopted, so that the working temperature of the instrument is maintained in a relatively stable range.
The following diagram shows the connections and data flow between solar photometer functional modules: the front-end optical system of the solar photometer comprises a tracking light path for automatically searching a sun center, and a spectrum detection light path for collecting radiation and converting the radiation into a digital signal; the realization method of the tracking system adopts a dual-mode tracking technology combining a sun-viewing track method and a four-quadrant detector, and spectrum signals are transmitted to the embedded system after noise reduction and correction; the key of the solar photometer servo driving system is a two-dimensional turntable with supporting and stabilizing functions, and an embedded main control system consisting of ARM-Linux software and hardware platforms controls and coordinates the operation of all measuring modules. At the same time, the human-machine interface written at the server side monitors the real-time spectrum signal and the module state.
Fig. 3 is a schematic diagram of a front-end optical system of a solar photometer. The optical system mainly comprises a lens, an optical filter, a diaphragm and a photoelectric detector. Firstly, the light rays which are parallel to normal incidence are changed into converging light rays through the collecting lens, the converging light rays are focused at the focal point of the lens, and some oblique light rays, namely stray light, are mixed in the light rays entering the light cylinder and need to be filtered. A diaphragm is arranged at the focal position for removing stray light focused on the focal plane. Thus, the lens and diaphragm combination can make the light in a specific solid angle enter the next part of the light path, and the light emitted from the receiving lens can still be regarded as parallel light because the collecting lens and the receiving lens are confocal. And then filtering radiation in a non-detection band by using an optical filter, finally performing energy aggregation by using a converging lens, receiving converging light by using a photoelectric detector, and converting the light signal into an electric signal to finish detection.
The prior art one has the following drawbacks: the solar photometer generally adopts ICCD, and adjusts the voltage gain signal according to the intensity of the collected light signal, thereby amplifying the weak signal. The method can meet the requirement of acquiring weak new light signals at night and complete the task of measuring the transmittance of the whole atmosphere. However, the voltage regulation gain of the ICCD has a non-negligible disadvantage, and the amplification gain corresponds to a value every time a voltage shift is increased or decreased. The value of the ICCD can change along with the service time of the ICCD, and the corresponding value is determined again, so that the ICCD needs to be returned to the manufacturer for recalibration. Meanwhile, in the long-term observation process, the solar photometer is affected by factors such as natural environment and the like to have attenuation, performance degradation of the photosensitive material of the detector can occur, attenuation and optical path drift of optical components and optical filters in the instrument can also occur, and the average annual amplitude is about 1% -10%, so that adverse effects on the measurement of the atmospheric transmittance can be generated.
And the second prior art is as follows: the laser heterodyne technology is a high-sensitivity spectrum detection technology based on the coherent detection principle, and utilizes local oscillation light (such as narrow bandwidth infrared laser) and signal light (sunlight) to carry out coherence on a photosensitive surface of a fast response detector through a beam combiner to generate an optical mixing signal, wherein an alternating current part of the signal responded on a square-rate detector is a heterodyne signal. The heterodyne signal is subjected to radio frequency amplification, band-pass filtering, square-rate detection, demodulation and the like, and then a spectrum signal with high resolution and high sensitivity can be obtained. The laser heterodyne technology greatly reduces the processing difficulty of signals because the infrared band laser with the frequency of 1013-1014 Hz is converted into the radio frequency signal with the frequency of 106-108 Hz. In summary, the laser heterodyne technology not only maintains the advantages of a solar radiometer, but also has the advantages of a semiconductor laser with narrow linewidth, so that the laser heterodyne technology has extremely high spectral resolution and high noise suppression performance.
Assume that the electric field components of the local oscillation light and the signal light are E respectively 1 And E is 2 Then
E 1 ＝A 1 ω 1 t，E s ＝A s ω s t, wherein A 1 、A 2 、W 1 、W 2 The amplitude and the frequency of the local oscillation light and the signal light are respectively. The quantum efficiency of the two beams of light is alpha at the detector lightMixing on the sensitive surface produces photocurrent, and the output signal of the detector can be expressed as
The former term is a direct current signal I dc The latter term is alternating current signal I ac The alternating current part is heterodyne signal.
The heterodyne signal has a local oscillator optical frequency W 1 And the signal light frequency W 2 And (3) a difference. The frequency of the signal which is similar to the frequency of the local oscillation light can be transferred from infrared to the radio frequency range, and the processing of the subsequent signal is facilitated. When the local oscillation light line width is narrow enough, the high-resolution detection of the signal light can be realized. In addition, because the amplitude of the heterodyne signal is in direct proportion to the product of the amplitudes of the local oscillation light and the signal photoelectric field, the power of the heterodyne signal is in direct proportion to the optical power of the local oscillation light and the signal light; therefore, even if the observed signal light is relatively weak, the signal light can be amplified through the local oscillation light to obtain a higher signal-to-noise ratio, so that high-sensitivity detection is realized.
The laser heterodyne technology has the characteristics of high spectral resolution detection and weak signal light amplification, so that the laser heterodyne spectrometer developed based on the technology is very suitable for developing high spectral resolution and high sensitivity detection of the whole atmosphere absorption spectrum. By calibrating the observed original absorption spectrum data, the direct measurement of the whole atmosphere transmittance can be realized after the response characteristic of the spectrometer is obtained. And a measuring system for realizing the whole atmosphere transmittance based on the laser heterodyne technology. The basic composition mainly comprises three modules: the device comprises a solar tracking module, a heterodyne light path module and a signal processing module. The specific composition and function are as follows:
The solar tracking module consists of a solar tracker and a pair of parabolic mirrors. The module is mainly used for tracking the sun in real time and guiding sunlight into the heterodyne light path module, and the size of the angle of view, tracking precision, transmission efficiency and the like of the module have great influence on measurement of an absorption spectrum.
The heterodyne optical path module is a core module of a laser heterodyne spectrometer and consists of a local oscillator laser, a laser controller, a chopper, a beam combiner, a high-speed photoelectric detector and the like. The module is mainly used for converting optical signals into electric signals. And modulating sunlight captured by the solar tracking module through a chopper, combining the sunlight with local oscillation light through a beam combining lens, and inputting the combined light into a fast-response heterodyne detector to generate heterodyne signals. The data quality of the absorption spectrum can be directly affected by the signal transmission loss, the beam combining quality of the signal light and the local oscillator light, the anti-interference capability of the optical path and the like. Therefore, in the heterodyne optical path module, two beams of light need to be subjected to mode matching, and parameters of a lens are optimized to obtain an ideal heterodyne signal.
The signal processing module is a key part for acquiring an absorption spectrum signal and consists of a pre-amplifier, a radio frequency filter, a band-pass filter, a radio frequency power detector, a phase-locked amplifier and the like. The heterodyne signal is generally extracted and processed by a modulation and demodulation mode, and the whole layer of atmospheric solar absorption spectrum signal is reproduced.
During experiments, sunlight is captured by a sun tracking device and used as signal light, narrow-linewidth laser is used as local oscillation light, the sunlight penetrating through the whole atmosphere and the local oscillation laser are subjected to optical mixing in a heterodyne detector, and after pre-amplification, intermediate frequency filtering and square-rate detection, the sunlight and the local oscillation laser are input into a lock-in amplifier for demodulation and amplification, and finally are collected by a computer for further analysis and processing.
The second prior art has the following drawbacks: for a laser heterodyne system, the solar energy is used as a radiation source, so that measurement can be performed only in the daytime, and the atmospheric transmittance cannot be measured around the clock. Meanwhile, the signal to noise ratio of the laser heterodyne detection system is weak. When the collection time of one absorption spectrum is too long, the solar zenith angle can be greatly changed in the period of time, and inaccuracy and complexity of the simulation calculation of the atmospheric transmittance can be increased.
The third prior art is: the Fourier transform spectrometer (FTIR) has the characteristics of fast scanning, large information quantity, high precision and the like. When measuring the transmission of the whole atmosphere by using an FTIR instrument, it is generally necessary to combine a fourier transform spectrometer with a solar tracking device and guide the sunlight captured by the solar tracking device into the fourier transform spectrometer for measurement. And meanwhile, stable atmospheric conditions are selected, the spectrum obtained by measurement is calibrated by using the Langley-plot method or the improved method thereof, the solar irradiation intensity of the atmospheric top layer of the interested wave band can be obtained, and the measured near-ground irradiation intensity is compared with the irradiation intensity of the atmospheric top layer, so that the whole atmospheric transmittance can be obtained. When the FTIR instrument is used for measuring the transmittance of the whole atmosphere, the requirements of high spectral resolution and wide measurement spectrum can be met, and the extinction thickness of the aerosol and the column concentration and even profile concentration of various atmospheric molecules can be measured by selecting a proper detection wave band.
The atmospheric transmittance experiment system mainly comprises an FTIR spectrometer, a receiving telescope, an infrared light source, a collimator and a computer. As shown. Wherein the infrared light source provides a standard radiation source; the receiving telescope introduces the radiation of the atmosphere and the infrared light source to the FTIR spectrometer; the collimator expands and collimates the emergent light; the computer collects the detector signals, and utilizes Fourier transformation to complete the conversion from the time domain interference pattern to the frequency domain spectrum pattern, and finally, the corresponding infrared spectrum radiation curve is obtained.
On the premise of meeting the linear response, the output signal of the spectrometer and the target radiation brightness received by the telescope need to meet the following conditions:
V(σ，T)＝R(σ)[L(σ，T)+L bcg (σ) (12)
wherein V (sigma, T) represents the measured output voltage, R (sigma) represents the response function of the instrument, L (sigma) represents the radiance of the target source, L bcg (sigma) represents the radiance or background signal of stray light inside the spectrometer.
Since the spectrometer sensor measures irradiance, irradiance reaching the spectrometer at different distances satisfies:
wherein: l (L) 0 (sigma) represents the intensity of radiation emitted from the light source and not absorbed by the atmosphere, L dist (sigma) represents L 0 (lambda) the received radiance of the spectrum after passing through a certain transmission path, L 0 (sigma) and L dist (sigma) also includes the responsive background radiation. A is that c Represents the area of the collimator, A s The blackbody aperture area is represented, f represents the focal length of the collimator, and d represents the distance from the spectrometer to the collimator.
In the linear range, the infrared wave propagation satisfies Beer-Bouguer-Lamert law
Where τ (σ) represents the atmospheric transmittance, and according to the above formula, the background radiation under different conditions is subtracted to give a calculation formula of the transmittance:
wherein V is dist (sigma) represents the response output voltage of the detector after a certain length of time to the light source, V disback (sigma) represents the response output voltage of the detector to a certain long-range background, V 0 (sigma) represents the response output voltage of the detector to the short-range light source, V 0back (sigma) represents the detector output voltage in response to a short-range background, where k is called the scaling factor, and A c 、A s F, d.
The third prior art has the following drawbacks: in FTIR atmospheric transmittance measurement systems, the atmospheric transmittance is related to the scaling factor of the system. Determining the scaling factor relationship requires the accurate use of optics specific accuracy parameters. In practical measurements, it is often necessary to calculate the relative transmittance ratio at this wavenumber using a FASCODE, MODTRAN procedure to consider it as an ideal scaling factor, since it is difficult to meet these requirements. Or by an approximate approach, such as a light source as close to the spectrometer as possible or a short distance from the spectrometer, which adversely affects the accuracy of the laser atmospheric transmittance.
In summary, how to design a method for obtaining the slant atmospheric transmittance by using the number of echo photons to replace the irradiance of the sun (fixed star) as a variable is a problem to be solved by those skilled in the art.
Disclosure of Invention
The embodiment of the invention mainly aims at providing a method and a system for measuring the atmospheric transmittance of an inclined process, and aims at designing a method for acquiring the atmospheric transmittance of the inclined process by taking the number of echo photons to replace solar irradiance as a variable.
The technical scheme for solving the technical problems is that the invention provides a method for measuring the atmospheric transmittance of a slope, which comprises the following steps:
transmitting laser pulses to an observation target, and recording a main wave signal;
recording the main wave moment of the pulse according to the time information;
receiving an echo signal returned by an observation target;
recording echo time;
processing main echo pairing, and accurately measuring round trip time t of laser pulses from a ground station to a satellite;
identifying and processing echo signals, and counting the number N of echo photons in unit time;
acquiring and recording a T value according to the T function relation between the number N of echo photons and the transmittance T of the inclined path atmosphere;
wherein, the echo photon number N and the inclined path atmospheric transmittance T function relation are as follows:
Calculating the average number of echo photons N detected per second p ：
Wherein P is D The detection probability is C-SPAD; p (P) FA The probability of the false alarm is C-SPAD; θ j Tracking error for azimuth or pitch;
calculating the number n of received noise photons b ：
Wherein N is λ For background brightness, calculating by using a sky light background star and the like at night; θ r To receive the angle of view; q is the ratio of the transmission band of the interference filter to the response bands of the receiving optical system and the receiving device; τ G Is the width of the distance gate;
calculating the average photon number N s ：
N p -n b ＝N s (3)
Will N s And carrying out formula 4 to obtain the slant-range atmospheric transmittance T:
wherein, E laser monopulse energy; s is the number of photons per joule of energy; a is that s Is the effective area of the reflector on the satellite; a is that r Is the effective area of the receiving mirror; k (K) t Is the efficiency of the transmitting system; k (K) r For receiving the efficiency of the optical system; t is the local atmospheric transmittance; η is the quantum efficiency of the receiving optoelectronic device; beta is the attenuation efficiency; r is the slope distance from the station to the satellite; θ t Divergence angle of laser beam (via divergence mirror); θ s Is the beam divergence angle of the satellite reflector.
Further, the step of transmitting the laser pulse to the observation target and recording the main wave signal further comprises the following steps;
acquiring the forecast ephemeris of the observation target on the same day, and acquiring the information such as azimuth, altitude, distance and the like of the observation target;
The servo control system guides the telescope to track and observe the target, and the laser pulse is emitted after stable tracking.
Further, the step of transmitting the laser pulse to the observation target and recording the main wave signal includes:
the laser transmitting module transmits laser pulses to an observation target according to the instruction, and transmits a main wave signal to the echo receiving module, and the echo receiving module records the main wave signal;
further, the step of recording the main pulse moment according to the time information includes:
and the echo receiving module records the main wave moment of the pulse according to the time information provided by the time frequency module.
Further, the step of receiving the echo signal returned by the observation target includes:
and the echo receiving module receives an echo signal returned by the observation target according to the door opening signal provided by the tracking control module.
Further, the step of recording the echo time includes:
and the echo receiving module records the echo time according to the time information provided by the time frequency module.
In order to solve the above technical problem, the present application further provides a system for measuring the transmittance of the inclined-path atmosphere, including:
the laser emission module is used for completing the emission of laser signals;
the tracking control module is used for laser emission control, distance gate control, event timer control, time-frequency control and servo system control;
The echo receiving module is used for receiving the optical pulse signals reflected by the tested satellite and accurately measuring the round trip time of the laser pulse from the ground station to the satellite;
a time frequency module for providing absolute time coordinates of operation of the system; and
And the information processing module is used for identifying and processing echo signals and calculating the inclined-path atmospheric transmittance.
The technical proposal of the invention has the following beneficial effects
1. Unlike the prior art, the method and the device acquire the inclined-path atmospheric transmittance based on the SLR technology, do not use the sun as a radiation source, break the limitation that the existing measurement technology only can acquire data in daytime, and can realize day and night measurement.
2. Different from the prior art, the method can select a plurality of artificial satellites with different distances and different directions, and provides richer original data for inverting the atmospheric transmittance of the inclined path.
3. Unlike available technology, the artificial satellite may have laser inclined atmosphere transmittance several hundred kilometers or several thousand kilometers from the earth to break through the limitation of available technology only to obtain near stratum level atmosphere transmittance.
4. Different from the prior art, the method adopts a photon counting method (counting echo photon numbers), and obtains the slope atmospheric transmittance by accurately acquiring the inversion of the average echo photon numbers, thereby effectively improving the measurement accuracy.
5. Different from the prior art, the method adopts the high-precision SLR data identification technology to acquire echo data, and compared with the rough image enhancement method adopted in the prior art, the method effectively improves the measurement precision.
6. Unlike available technology, the present application adopts SLR system without needing additional sun tracker to reduce the cost.
7. Different from the prior art, the ground target ranging technology in the SLR system is adopted, the system error can be acquired in real time, the equipment time delay is corrected, the factory does not need to be returned for rescaling, the instability of the prior measuring technology is effectively improved, and the inaccuracy of the prior measuring technology is effectively reduced.
8. Different from the prior art, the method adopts the SLR technology with high repetition frequency, the experiment has repeatability, a large amount of echo data can be obtained, and the measurement accuracy is effectively improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of the steps of a method for measuring the permeability of a slant range atmosphere according to the present invention;
FIG. 2 is a graph showing the measured number of average echo photons of Lageos-1 according to the present invention;
FIG. 3 is a graph of the atmospheric transmittance calculation result and the actual measurement result obtained based on the 532nmSLR technology;
FIG. 4 is a graph of atmospheric transmittance calculation results and actual measurement results obtained based on a 532nm daytime SLR technology;
FIG. 5 is a graph of data for a system for measuring the transmission of a bias atmospheric in accordance with the present invention;
FIG. 6 is a graph of atmospheric transmittance data obtained by the present invention based on a 1.2m near infrared SLR system.
Detailed Description
The following description of the embodiments of the present invention will be made more apparent and fully by reference to the accompanying drawings, in which embodiments of the invention are shown, it being understood that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "several", "a plurality" or "a plurality" is at least two, such as two, three, etc., unless specifically defined otherwise.
In the present invention, unless specifically stated and limited otherwise, the terms "connected," "affixed," and the like are to be construed broadly, and for example, "affixed" may be a fixed connection, a removable connection, or an integral body; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered as not existing, and not falling within the scope of protection claimed by the present invention.
Key term interpretation and technical abbreviations:
1. laser ranging (laser ranging): laser ranging is mainly achieved based on the time-of-flight principle. Depending on the implementation, it can be divided into direct time-of-flight measurements and indirect time-of-flight measurements. Direct time-of-flight ranging is to acquire the distance information of a target by measuring the time of flight of laser pulses to and from the target; indirect time-of-flight ranging can be classified into linear frequency modulation laser ranging, phase laser ranging and amplitude modulation laser ranging according to the difference of the implementation methods. In addition, laser ranging is classified into satellite laser ranging (Satellite laser ranging, SLR), space debris laser ranging (Debris laser ranging, DLR), lunar laser ranging (Lunar laser ranging, LLR), and the like according to the observation target.
2. After the sun light radiation enters the earth atmosphere, the radiation reaching the ground is attenuated under the influence of the absorption and scattering of atmospheric molecules and atmospheric aerosol particles. The attenuation effect of the whole atmosphere on the fixed light radiation signal is characterized by the whole atmosphere transmittance, and the whole atmosphere transmittance maps the extinction condition of the whole atmosphere. The foundation acquires the whole layer of atmosphere transmittance information, which is of great significance to the study of atmosphere optics.
3. The whole layer of atmosphere transmittance: the ratio of the observed value of solar radiation passing through the earth with a certain thickness and the intrinsic radiant energy of the top of the atmosphere. The overall atmospheric transmittance reflects the visual physical quantity of the extinction condition of the atmosphere.
4. Whole layer atmosphere: the transmittance of the atmosphere between the path from the atmosphere layer to the ground observation position is a very important parameter reflecting the optical characteristics of the whole atmosphere. The overall atmospheric transmittance depends on the interaction strength of the atmosphere in the time domain of light transmission in the atmosphere, including absorption and scattering of atmospheric molecules and aerosol particles, which leads to attenuation of the intensity of light radiation. The atmospheric system is complex and changeable, and has huge differences under different longitude and latitude, altitude, seasonal time and other conditions. The transmittance is closely related to the radiation wavelength, spectral bandwidth, transmission angle, detection path, barometric temperature, and path distribution of atmospheric components.
Ccd (charge couple device): a solid imaging sensor. The basic result is that the MOS switches in the form of a number of photodiodes are arranged in a certain order. The MOS gate consists of a technology, oxide of silicon (silicon dioxide), doped semiconductor. The metal layer is used as a grid electrode to provide bias voltage, the oxide layer plays an insulating role, and the semiconductor is a place where photoelectric conversion occurs. The other part of the structure is a read-out shift register, which is responsible for sequentially shifting out the generated electrical signals.
6. Direct solar radiation: the solar radiation reaching the ground has two parts, namely, the scattered solar radiation is transmitted to the ground from the sky and becomes scattered radiation; the sun is directly projected onto the ground in the form of parallel rays, and the sum of the parallel rays is called total radiation.
7. Altitude and azimuth of the sun: the position of the sun is described. Beta represents a height angle, which is an included angle between the sun direction and the horizontal plane; alpha represents azimuth angle, which is the angle of deviation of the horizontal projection of the sun direction from the south direction.
Schematic of solar altitude and azimuth
For an observer on the ground at a latitude phi (representing the position of the observation point) and a longitude phi, the solar zenith angle theta (the residual angle of the solar altitude) and azimuth angle alpha observed at a certain moment can be calculated in the following manner.
Wherein, the declination of the sun (the included angle between the sun-earth center line and the equatorial plane) changes along with the position of the earth on the revolution orbit, namely, the difference of the sun, and represents the change of seasons (date), and the declination of the whole year changes between +/-23 degrees 27'; the time angle is defined as the rotation angle of the earth after the circle of the observation point coincides with the sun (namely, the local noon), the day is changed from 0 to 360, and the time angle at noon is 0, which represents the change of time.
8. Irradiation intensity (irradiance) refers to the radiant power (in W/m 2) per unit area passing through a point in the radiation field.
9. Line-by-line integration method: the transmittance is calculated by evaluating the absorption coefficients of all spectral lines in the wave band one by one, and the method is an accurate method for solving the atmospheric radiation transmission problems such as the non-uniform path of the atmosphere, the overlapping of absorption bands and the like.
10. Band pattern method: the average transmittance of a spectrum interval is calculated through a series of band parameters assuming that the absorption lines and positions of atmospheric molecules are distributed according to a specific rule.
11. Related K distribution method: the transmittance is obtained by the calculation of the gas spectrum transmittance according to the absorption coefficient ruler k, and the method is used for treating the average gas absorption rate in a certain wave number range of a non-uniform path.
12. A sun-viewing movement track method: a method of tracking the sun. The current time is calculated by the perpetual calendar chip, the solar orientation and the height of the current position are calculated by combining the local longitude and latitude, the direct current motor and the angle monitoring potentiometer are combined, the two motors are driven through calculation, comparison and output control of the single-chip microcomputer system, the photovoltaic cell panel can be controlled to conduct biaxial rotation, the optimal azimuth of the received sun is finally determined, and all-weather tracking of the sun is achieved.
13. Photoelectric tracking: another common method of tracking the sun. The photoelectric sensor is used for generating a constant feedback signal to the computer according to the intensity change of the incident light, and the computer runs a program to adjust the angle of the solar panel so as to realize tracking of the sun. Its advantages are high sensitivity, convenient structural design, and high influence from weather, and if the sun is blocked by clouds, it can not track the sun, and even misoperation of executing mechanism
14. Four-quadrant detector (Quadrant Detector, QD): the detector is formed by integrating four Photodiodes (PIN) or Avalanche Photodiodes (APD) with almost identical performances in a four-quadrant distribution mode and is used for monitoring the position on an image sensitive surface of a fine tracking detector.
15. Chopper: a high-precision element capable of performing weak signal conversion. Chopping is the interruption of a current, beam of light or beam of infrared radiation at uniform time intervals. Chopper can convert weak dc voltage or current into ac output for amplification, typically converting a slowly varying signal into a fast varying signal, which is convenient for amplification. There are many kinds of choppers, and mechanical choppers, solid-state choppers, photointerrupters, magnetically modulated choppers, and choppers made using other physical effects are commonly used.
16. Digital lock-in amplifier: an amplifier for phase-sensitive detection of alternating signals uses reference signals as a comparison standard, which can effectively inhibit the noise which does not work and effectively improve the detection signal-to-noise ratio.
17. Fourier Transform Infrared (FTIR) spectrometer: the Michelson interferometer, modulation technique and computer technique are combined by utilizing the principle of split beam interference, and the recovery from an interferogram to a spectrum is realized by a Fourier transform method. FTIR spectrometers have no dispersive element and consist essentially of a light source, an interferometer, a detector and a recorder. The core is a michelson interferometer. The signal from the light source is mainly sent to a computer in the form of interference pattern to carry out the mathematical treatment of Fourier transform, and finally the interference pattern is restored into a spectrogram. In comparison with conventional dispersive spectrometers, a fourier spectrometer can be understood as a spectrometer that encodes spectral information in some mathematical way, which can measure and record signals of all spectral elements simultaneously, and collect short-shot energy from a light source with higher efficiency, so that it has a much higher signal-to-noise ratio and resolution than conventional spectrometers; and the digitized spectrum data of the method is convenient for computer processing and deduction of the data.
The invention provides a method and a system for measuring the atmospheric transmittance of a slope, and aims to design a method for acquiring the atmospheric transmittance of the slope by taking the number of echo photons to replace solar irradiance as a variable.
The method for measuring the transmittance of the inclined process atmosphere according to the present invention will be described in the following embodiments:
in the technical solution of the present embodiment, as shown in fig. 1, a method for measuring the transmittance of the air in the inclined process includes the following steps:
s10: transmitting laser pulses to an observation target, and recording a main wave signal;
s20: recording the main wave moment of the pulse according to the time information;
s30: receiving an echo signal returned by an observation target;
s40: recording echo time;
s50: processing main echo pairing, and accurately measuring round trip time t of laser pulses from a ground station to a satellite;
s60: identifying and processing echo signals, and counting the number N of echo photons in unit time;
s70: acquiring and recording a T value according to the T function relation between the number N of echo photons and the transmittance T of the inclined path atmosphere;
wherein, the echo photon number N and the inclined path atmospheric transmittance T function relation are as follows:
calculating the average number of echo photons N detected per second p ：
Wherein P is D The detection probability is C-SPAD; p (P) FA The probability of the false alarm is C-SPAD; θ j Tracking error for azimuth or pitch;
calculating the number n of received noise photons b ：
Wherein N is λ Is a backJing Liangdu, it can be calculated at night by using the sky background star; θ r To receive the angle of view; q is the ratio of the transmission band of the interference filter to the response bands of the receiving optical system and the receiving device; τ G Is the width of the distance gate;
calculating the average photon number N s ：
N p -n b ＝N s (3)
Will N s And carrying out formula 4 to obtain the slant-range atmospheric transmittance T:
wherein, E laser monopulse energy; s is the number of photons per joule of energy; a is that s Is the effective area of the reflector on the satellite; a is that r Is the effective area of the receiving mirror; k (K) t Is the efficiency of the transmitting system; k (K) r For receiving the efficiency of the optical system; t is the local atmospheric transmittance; η is the quantum efficiency of the receiving optoelectronic device; beta is the attenuation efficiency; r is the slope distance from the station to the satellite; θ t Divergence angle of laser beam (via divergence mirror); θ s Is the beam divergence angle of the satellite reflector.
It can be understood that the method is based on the functional relation (formula 4) between the number of echo photons of the laser ranging system and the atmospheric transmittance, the laser ranging system is utilized to acquire and count the number of photons in unit time, and the inclined-path atmospheric transmittance is obtained through mathematical inversion. Compared with the prior art, the invention uses the echo photon number to replace solar irradiance as a variable to acquire the inclined-path atmospheric transmittance, not only maintains the advantages of high precision and high sensitivity of the laser ranging system, but also realizes the day and night observation of the atmospheric transmittance.
Further, the step of transmitting the laser pulse to the observation target and recording the main wave signal further includes:
acquiring the forecast ephemeris of the observation target on the same day, and acquiring the information such as azimuth, altitude, distance and the like of the observation target;
the servo control system guides the telescope to track and observe the target, and the laser pulse is emitted after stable tracking.
Further, the step of transmitting the laser pulse to the observation target and recording the main wave signal includes:
the laser transmitting module transmits laser pulses to an observation target according to the instruction, and transmits a main wave signal to the echo receiving module, and the echo receiving module records the main wave signal;
further, the step of recording the main pulse moment according to the time information includes:
and the echo receiving module records the main wave moment of the pulse according to the time information provided by the time frequency module.
Further, the step of receiving the echo signal returned by the observation target includes:
and the echo receiving module receives an echo signal returned by the observation target according to the door opening signal provided by the tracking control module.
Further, the step of recording the echo time includes:
and the echo receiving module records the echo time according to the time information provided by the time frequency module.
In a possible implementation, the laser source of the laser emitting module may be 532nm, 1064nm, 1550nm, etc., where the applicable wavelength is not unique.
In one possible implementation, the laser repetition frequency of the laser emitting module may be 1KHz, 2KHz, 100KHz, etc., and the laser repetition frequency is not unique.
In one possible embodiment, the observation target may be selected from an artificial satellite, a space debris, a moon, an aircraft, etc., and the observation target is not unique.
In one possible embodiment, the optical telescope system of the tracking control module may be a separate transceiver or a coaxial transceiver system, and the telescope system is not unique.
In one possible embodiment, the optical telescope of the tracking control module may be 60cm, 120cm, 250cm, and the telescope aperture is not unique.
In one possible implementation, the single photon detector of the tracking control module may be APD, PMT, SNSPD, etc., with the detector being non-unique in choice.
In one possible implementation, the computer device time delay calibration technique of the information processing module may be a super-near target, a far target, etc., and the calibration technique is not unique.
The application also provides a system for measuring the transmittance of the inclined-path atmosphere, which comprises:
The laser emission module is used for completing the emission of laser signals;
the tracking control module is used for laser emission control, distance gate control, event timer control, time-frequency control and servo system control;
the echo receiving module is used for receiving the optical pulse signals reflected by the tested satellite and accurately measuring the round trip time of the laser pulse from the ground station to the satellite;
a time frequency module for providing absolute time coordinates of operation of the system; and
And the information processing module is used for identifying and processing echo signals and calculating the inclined-path atmospheric transmittance.
Example 1:
taking a Changchun station SLR system as an example, the SLR system receives telescope 0.251m2; the laser single pulse energy is about 1mJ; the emission frequency is 1KHz; the laser wavelength is 532nm; the efficiency of the laser emission system is 0.6; the pulse width of the laser energy is 50ps; the divergence angle of the emitted beam is 11 angular seconds; the receiving efficiency is 0.5; the quantum efficiency of the receiving photoelectric device is 0.2; the receiving field angle is 40 angular seconds; the distance gate width is 100ns; the attenuation efficiency is-13 dB; the tracking error is 7 angular seconds (1 sigma); the ratio of the transmission band of the filter to the response band of the receiving optical system is 1/500. An observation target is set as Lageos-1, and the effective area of the observation target is 257cm < 2 >; the background brightness in the daytime is 019 photons/s.m2.steradians.
And downloading the current day Lageos-1 forecast ephemeris to obtain information such as azimuth, altitude, distance and the like of the Lageos-1.
The servo control system guides the telescope to track Lageos-1, and laser pulse is emitted after stable tracking.
And the synchronous signal of the laser pulse generated by the PIN is transmitted to the CFD, the main wave signal is output to enter the same channel of the time timer A, and the main wave moment is recorded by the echo receiving module.
The echo photons are converged to the target surface of the single photon detector through the receiving telescope and generate echo signals, and the echo signals are transmitted to a time timer B channel, the echo time is recorded and transmitted to an echo receiving module; the difference between the main wave moment and the echo moment is the distance between the star and the ground.
The information processing module completes the pairing processing of the main echo, accurately displays, records and counts echo information, and generates standard format data.
The information processing module automatically calculates the atmospheric transmittance based on the functional relation between the echo photon number and the atmospheric transmittance and stores the test data.
Based on the functional relation between SLR echo photon number and atmospheric transmittance, the SLR system is utilized to acquire and count photon number in unit time, and the inclined-path atmospheric transmittance is obtained through mathematical inversion. Taking a 60cm SLR system of a Changchun station as an example, an observation target is Lagueos-1, and a measured result of average echo photon number of Lagueos-1 is shown in FIG. 2. As can be seen from fig. 2, unlike the existing measurement method, the present application can obtain a large amount of original observation data due to the use of the high-repetition frequency laser source, and provides richer original data for inversion calculation of the slope atmospheric transmittance.
Based on equation (4), the vinca station system parameters are combined. FIG. 3 is a graph showing the calculation of atmospheric transmittance based on 532nmSLR technique; from the figure, it can be seen that the atmospheric transmittance measured based on the SLR technique is similar to the experimental data obtained by using the solar photometer. In order to further verify the applicability and accuracy of the method, an Ajisai satellite is selected as an observation target, daytime satellite laser ranging is performed, and an atmospheric transmittance calculation result and an actual measurement result are obtained based on a 532nm daytime SLR technology as shown in fig. 4; as can be seen from the figure, the present application can achieve diurnal observation. The artificial satellite is used for replacing the sun as an observation target, and the limitation that the existing measurement technology can only observe in the daytime is broken through. At the same time, the application can provide richer original data. The method adopts the artificial satellites with different distances and different directions as the observation targets, provides richer observation targets except sun or other stars, and provides a brand new technical means for the actual measurement of the atmospheric transmittance. FIG. 5 shows the near-to-ground target data of a system for measuring the atmospheric transmittance in the inclined path, and the system error can be acquired in real time and the equipment delay can be corrected by using the ground target ranging technology in the SLR system without returning to the manufacturer for rescaling, so that the instability of the prior measuring technology is effectively improved, and the inaccuracy of the prior measuring technology is effectively reduced.
Example 2
The near infrared laser ranging system adopts 1064nm laser as emission wavelength, and has the advantages of high laser energy, high atmospheric transmittance and sky background radiation.
And downloading the current day Lageos-1 forecast ephemeris to obtain information such as azimuth, altitude, distance and the like of the Lageos-1.
The servo control system guides the telescope to track Lageos-1, and laser pulse is emitted after stable tracking.
And the synchronous signal of the laser pulse generated by the PIN is transmitted to the CFD, the main wave signal is output to enter the same channel of the time timer A, and the main wave moment is recorded by the echo receiving module.
The echo photons are converged to the target surface of the single photon detector through the receiving telescope and generate echo signals, and the echo signals are transmitted to a time timer B channel, the echo time is recorded and transmitted to an echo receiving module; the difference between the main wave moment and the echo moment is the distance between the star and the ground.
The information processing module completes the pairing processing of the main echo, accurately displays, records and counts echo information, and generates standard format data.
The information processing module automatically calculates the atmospheric transmittance based on the functional relation between the echo photon number and the atmospheric transmittance and stores the test data.
In order to verify the accuracy of the results of this patent, we choose Modtran data for comparison, fig. 6 is the atmospheric transmittance data obtained based on the 1.2m near infrared SLR system, and it can be seen from the figure that the atmospheric transmittance data obtained based on the 1.2m near infrared SLR system substantially matches with the results obtained by using Modtran software, which indicates that the oblique path atmospheric transmittance can be effectively obtained by using the laser ranging technique.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
Claims (7)
1. A method of measuring the permeability of a slant range atmosphere comprising the steps of:
transmitting laser pulses to an observation target, and recording a main wave signal;
recording the main wave moment of the pulse according to the time information;
receiving an echo signal returned by an observation target;
recording echo time;
processing main echo pairing, and accurately measuring round trip time t of laser pulses from a ground station to a satellite;
identifying and processing echo signals, and counting the number N of echo photons in unit time;
acquiring and recording a T value according to the T function relation between the number N of echo photons and the transmittance T of the inclined path atmosphere;
wherein, the echo photon number N and the inclined path atmospheric transmittance T function relation are as follows:
calculating the average number of echo photons N detected per second p ：
Wherein P is D The detection probability is C-SPAD; p (P) FA The probability of the false alarm is C-SPAD; θ j Tracking error for azimuth or pitch;
calculating the number n of received noise photons b ：
Wherein N is λ For background brightness, calculating by using a sky light background star and the like at night; θ r To receive the angle of view; q is the ratio of the transmission band of the interference filter to the response bands of the receiving optical system and the receiving device; τ G Is the width of the distance gate;
calculating the average photon number N s ：
N p -n b ＝N s (3)
Will N s And carrying out formula 4 to obtain the slant-range atmospheric transmittance T:
wherein, E laser monopulse energy; s is the number of photons per joule of energy; a is that s Is the effective area of the reflector on the satellite; a is that r Is the effective area of the receiving mirror; k (K) t Is the efficiency of the transmitting system; k (K) r For receiving the efficiency of the optical system; t is the local atmospheric transmittance; η is the quantum efficiency of the receiving optoelectronic device; beta is the attenuation efficiency; r is the slope distance from the station to the satellite; θ t Is the divergence angle of the laser beam; θ s Is the beam divergence angle of the satellite reflector.
2. The method of measuring the slope atmospheric transmittance of claim 1, wherein the step of transmitting the laser pulse to the observation target and recording the main wave signal further comprises, prior to:
acquiring the forecast ephemeris of the observation target on the same day, and acquiring the information such as azimuth, altitude, distance and the like of the observation target;
The servo control system guides the telescope to track and observe the target, and the laser pulse is emitted after stable tracking.
3. The method of measuring the slope atmospheric transmittance of claim 1, wherein the step of recording the main wave signal by emitting laser pulses to the observation target comprises:
the laser transmitting module transmits laser pulses to an observation target according to the instruction, and transmits a main wave signal to the echo receiving module, and the echo receiving module records the main wave signal.
4. The method of measuring the atmospheric transmittance of a slope according to claim 1, wherein the step of recording the main pulse time according to time information comprises:
and the echo receiving module records the main wave moment of the pulse according to the time information provided by the time frequency module.
5. The method of measuring the slope atmospheric transmittance of claim 1, wherein the step of receiving the echo signal returned by the observation target comprises:
and the echo receiving module receives an echo signal returned by the observation target according to the door opening signal provided by the tracking control module.
6. The method of measuring the slope atmospheric transmittance according to claim 1, wherein the step of recording the echo time instants comprises:
And the echo receiving module records the echo time according to the time information provided by the time frequency module.
7. A system for measuring the permeability of a slant range atmosphere, comprising:
the laser emission module is used for completing the emission of laser signals;
the tracking control module is used for laser emission control, distance gate control, event timer control, time-frequency control and servo system control;
the echo receiving module is used for receiving the optical pulse signals reflected by the tested satellite and accurately measuring the round trip time of the laser pulse from the ground station to the satellite;
a time frequency module for providing absolute time coordinates of operation of the system; and
And the information processing module is used for identifying and processing echo signals and calculating the inclined-path atmospheric transmittance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311507873.7A CN117783058A (en) | 2023-11-14 | 2023-11-14 | Method and system for measuring inclined-path atmospheric transmittance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311507873.7A CN117783058A (en) | 2023-11-14 | 2023-11-14 | Method and system for measuring inclined-path atmospheric transmittance |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN117783058A true CN117783058A (en) | 2024-03-29 |
Family
ID=90380438
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311507873.7A Pending CN117783058A (en) | 2023-11-14 | 2023-11-14 | Method and system for measuring inclined-path atmospheric transmittance |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN117783058A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN119354503A (en) * | 2024-12-24 | 2025-01-24 | 中国科学院西安光学精密机械研究所 | Space optical system stray light measurement system and method based on time channel screening |
| CN119805416A (en) * | 2024-12-13 | 2025-04-11 | 北京空间机电研究所 | A method for correcting sea surface ranging errors using satellite-borne single-photon lidar |
| CN120429662A (en) * | 2025-07-08 | 2025-08-05 | 中国气象科学研究院 | Photometer detection temperature correction method and system based on machine learning |
-
2023
- 2023-11-14 CN CN202311507873.7A patent/CN117783058A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN119805416A (en) * | 2024-12-13 | 2025-04-11 | 北京空间机电研究所 | A method for correcting sea surface ranging errors using satellite-borne single-photon lidar |
| CN119354503A (en) * | 2024-12-24 | 2025-01-24 | 中国科学院西安光学精密机械研究所 | Space optical system stray light measurement system and method based on time channel screening |
| CN120429662A (en) * | 2025-07-08 | 2025-08-05 | 中国气象科学研究院 | Photometer detection temperature correction method and system based on machine learning |
| CN120429662B (en) * | 2025-07-08 | 2025-09-26 | 中国气象科学研究院 | Photometer detection temperature correction method and system based on machine learning |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Zhou et al. | Design of supercontinuum laser hyperspectral light detection and ranging (LiDAR)(SCLaHS LiDAR) | |
| CN117783058A (en) | Method and system for measuring inclined-path atmospheric transmittance | |
| Abshire et al. | Pulsed airborne lidar measurements of atmospheric CO2 column absorption | |
| Kern et al. | Theoretical description of functionality, applications, and limitations of SO 2 cameras for the remote sensing of volcanic plumes | |
| Dinoev et al. | Raman lidar for meteorological observations, RALMO–Part 1: Instrument description | |
| CN110133626B (en) | Method and system for checking parallelism of receiving and transmitting optical axes of laser ranging system | |
| CN1316262C (en) | Detection method and laser radar of Raman-Mie scattering laser atmospheric signal | |
| Wu et al. | A new Fabry-Perot interferometer for upper atmosphere research | |
| CN105928902A (en) | High-spectrum-resolution total atmospheric spectral transmittance measuring method | |
| CN112683796A (en) | Differential absorption spectrometer optical system based on geosynchronous orbit observation | |
| McDermid et al. | Differential absorption lidar systems for tropospheric and stratospheric ozone measurements | |
| CN116577324B (en) | A hyperspectral remote sensing system for scanning and imaging pollution sources in industrial areas | |
| Yu et al. | Broadband continuous-wave differential absorption lidar for atmospheric remote sensing of water vapor | |
| Gerding et al. | Mesospheric temperature soundings with the new, daylight-capable IAP RMR lidar | |
| Baidar et al. | Development of a digital mobile solar tracker | |
| CN115826088B (en) | Laser heterodyne spectroscopy measurement method and system for vertical wind profiles in the middle and upper atmosphere | |
| Eichinger et al. | The development of a scanning Raman water vapor lidar for boundary layer and tropospheric observations | |
| Marchant et al. | Aglite lidar: a portable elastic lidar system for investigating aerosol and wind motions at or around agricultural production facilities | |
| Chiang et al. | A new mobile and portable scanning lidar for profiling the lower troposphere | |
| O’Brien et al. | High-precision, high-resolution measurements of absorption in the oxygen A-band | |
| CN117664895A (en) | Active gas detection system based on high-temperature infrared radiation source | |
| Ballester et al. | A 1.8 m Class Pathfinder Raman LIDAR for the Northern Site of the Cherenkov Telescope Array Observatory—Technical Design | |
| Kumar | Concept design, analysis, and Integration of the new UPC multispectral lidar system | |
| CN114563082B (en) | Programmable solar forward extinction and small-angle scattering spectrum detection system and detection method | |
| Dinoev et al. | Raman Lidar for Meteorological Observations, RALMO-Part I: Instrument description. |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |