WO2018113016A1 - 一种全自动太赫兹大气特性测量系统及其校准方法 - Google Patents

一种全自动太赫兹大气特性测量系统及其校准方法 Download PDF

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Publication number
WO2018113016A1
WO2018113016A1 PCT/CN2016/113040 CN2016113040W WO2018113016A1 WO 2018113016 A1 WO2018113016 A1 WO 2018113016A1 CN 2016113040 W CN2016113040 W CN 2016113040W WO 2018113016 A1 WO2018113016 A1 WO 2018113016A1
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terahertz
calibration
beam splitter
black body
signal
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PCT/CN2016/113040
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English (en)
French (fr)
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史生才
潘恩斯科特
姚骑均
林镇辉
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中国科学院紫金山天文台
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Publication of WO2018113016A1 publication Critical patent/WO2018113016A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/45—Interferometric spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation
    • G01N21/3586—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation by Terahertz time domain spectroscopy [THz-TDS]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/12—Circuits of general importance; Signal processing
    • G01N2201/127—Calibration; base line adjustment; drift compensation
    • G01N2201/12707—Pre-test of apparatus, e.g. dark test, sensor test

Definitions

  • the invention relates to an atmospheric characteristic measuring device and a calibration method for a terahertz astronomical site, belonging to the research and application field of terahertz technology.
  • the terahertz band (0.1 to 10 THz) is in the microwave and optical bands and is a new band that has yet to be fully developed and studied. Since nearly 50% of the photon energy in the cosmic space and a large amount of molecular line radiation fall in the terahertz band, and this band is most suitable for observing the early cold and dark universe, the terahertz band is a unique band for cosmological and astrophysics research. Terahertz radiation is heavily absorbed by the Earth's atmosphere, especially water vapor, and terrestrial terahertz astronomical observations require high altitude, dry and low temperature environments. The measurement and evaluation of the long-period variation of atmospheric transmittance at the terahertz astronomical site is an important task in the pre-construction of the terahertz observatory.
  • the Fourier Transform Spectrometer is important for detecting weak terahertz radiation sources (terahertz molecular lines or terahertz continuum) because of its wide bandwidth, large amount of light, and multiplexing.
  • the technical means is especially suitable for the measurement of terahertz broadband atmospheric radiation characteristics and has been widely used in the measurement of atmospheric transmittance at the terahertz astronomical site.
  • Internationally, the terahertz astronomical sites such as Mauna Kea in Hawaii, Chajnantor Plateau in Chile, and South Pole in Chile all use Fourier spectroscopy.
  • a device system for terahertz atmospheric transmission measurement typically includes calibration equipment, terahertz Fourier spectrometers, and system control equipment.
  • the calibration equipment mainly provides standard signal sources for calibration of observation signals, and the system control equipment performs system parameter setting, calibration process control, system status monitoring, and observation data acquisition and storage.
  • the terahertz Fourier spectrometer mainly performs spectral scanning on the input terahertz signals (including the calibration signal source and the observation signal source) to form interference fringes, and then forms an electrical signal for the interference fringes to be processed for subsequent processing by the system control device.
  • Fourier spectrometer When using Fourier spectrometer to measure the spectral characteristics of terahertz atmospheric transmittance, it is first necessary to measure the atmospheric radiation spectrum.
  • the atmospheric transmittance spectrum is finally derived based on the thermal radiation transfer equation and the Plank theorem.
  • the calibration process involves two calibration sources with different radiant temperatures. Traditionally, it is a high temperature black body signal source and a low temperature (liquid nitrogen temperature zone) black body signal source in a closed environment.
  • terahertz atmospheric transmittance measurements require high and low temperature calibration sources.
  • the low-temperature calibration source generally uses a black-body signal source in the liquid nitrogen temperature zone.
  • the problem is that since liquid nitrogen is easily dissipated into nitrogen, continuous and effective operation for a long time (such as an anniversary) cannot be achieved; in addition, liquid nitrogen needs to be stored in Insulated and sealed in a liquid nitrogen tank.
  • This kind of black body using liquid nitrogen temperature zone The signal source brings inconvenience to the transportation, storage and use of materials during the evaluation of the terahertz astronomical site at high altitude, remote plateau or mountainous area.
  • the calibration accuracy of the radiant temperature is also a difficulty.
  • the terahertz atmospheric transmittance spectrum analysis bandwidth depends mainly on the operating bandwidth of the terahertz Fourier spectrum detector. Due to the influence of the narrow-band spectral line and continuum of the Earth's atmospheric water vapor and other molecular spectral lines such as N 2 and O 3 , the transmission attenuation of the terahertz signal in the 1 to 5 THz frequency band is very serious. In order to improve the measurement signal-to-noise ratio, current devices usually use a single detector with large luminous flux reception to cover the frequency bands of interest below 5 THz for measurement.
  • the single detector technology solution will limit the measurement of the broadband transmittance of the wider terahertz, especially in the wider frequency range (including the 5 to 15 THz interval), and comprehensively evaluate the characteristics of the water vapor shift spectrum and the unsaturated water vapor radiation spectrum. The situation of influence.
  • the present invention proposes a fully automatic terahertz atmospheric characteristic measuring system which is simpler in calibration equipment, adapts to a low temperature environment, and can be operated unattended.
  • a fully automatic terahertz atmospheric characteristic measuring system comprising a calibration signal source, a calibration device, a terahertz spectrometer based on interference principle and a system control device, characterized in that:
  • the calibration signal source is a dual temperature calibration signal source based on natural environment temperature, including a calibration black body working outdoors and a reference black body working indoors, the indoor environment temperature is higher than the outdoor environment temperature, that is, the calibration black body Used as a low temperature calibration source, the reference black body is used as a high temperature calibration source;
  • the calibration device is connected to the system control device, and includes a signal transmission device, a reciprocating driving device and an outdoor environment temperature collecting device.
  • the signal transmission device is provided with a straight-shaped transmission channel, and the top end of the transmission channel is provided with a sealed first a media window, the bottom end of the transmission channel is provided with a closed second medium window, the upper part of the transmission device is located outdoors, and the lower part extends into the room;
  • the calibration black body is mounted on the actuator of the reciprocating drive device, and driven by the driving device Transferable to or removed from the first media window;
  • the terahertz spectrometer is arranged in a closed indoor environment, connected to the system control device, and the indoor environment temperature collecting device is arranged in the room;
  • the components of the terahertz spectrometer include:
  • the first and second terahertz detectors have overlapping detection range ranges of the two detectors, and the upper limit of the detection range of one of the detectors is greater than the upper limit of the detection range of the other detector;
  • a first beam splitter obliquely disposed at a position below the output end of the signal transmission device for synthesizing an external radiation signal input to the terahertz spectrometer and a radiation signal of the reference black body through the signal transmission device, the reference black body being disposed at the first The left side of the beam splitter;
  • a first absorbing black body disposed below the first beam splitter for absorbing residual signals
  • a second beam splitter disposed on a right side of the first beam splitter and disposed obliquely in a form that is opposite to the first beam splitter;
  • a fixed roof mirror disposed above the second beam splitter for reflecting the reflected signal from the second beam splitter to the second beam splitter again;
  • a movable roof mirror disposed on a right side of the second beam splitter for reflecting the transmitted signal from the second beam splitter to the second beam splitter again;
  • a mirror disposed below the second beam splitter to reflect signals from the second beam splitter to the terahertz detector
  • a third beam splitter disposed between the mirror and the terahertz detector, dividing the reflected signal from the mirror into two signals that are polarized orthogonally, so that they are respectively first and second terahertz Detector received;
  • the second absorbing black body is disposed on one side of the third beam splitter opposite to the terahertz detector that receives the reflected signal from the third beam splitter for absorbing the residual signal.
  • the driving device is a rotating device, the rotating device is provided with a rotating arm and a support for mounting the rotating arm, the calibration black body is mounted at one end of the rotating arm, and the other end of the rotating arm is mounted with a cleaning brush, the cleaning The brush is swept over the first media window by the rotating arm.
  • the cleaning brush preferably employs a bristle material which maintains good softness at very low temperatures.
  • the first and second terahertz detectors use receiving horns of different apertures.
  • the mirror is a parabolic mirror for shaping the beam of its transmitted signal to match the beamwidth of the two terahertz detector receiving horns.
  • the indoor ambient temperature collecting device, the components of the terahertz spectrometer and the reference black body are integrated in an aluminum metal box, and the top surface of the metal box is provided with a third medium window aligned with the second medium window.
  • the first beam splitter is disposed directly below the third media window.
  • the outdoor ambient temperature collecting device includes a plurality of indoor thermometers disposed on a circumference side of the calibration black body. When the calibration black body is located above the first medium window, the distance between the indoor thermometer and the calibration black body is not more than 50 cm.
  • the barrel of the signal transmission device and the first medium window and the second medium window are both HPDE (High Density Polyethylene) materials, wherein the first dielectric window is 2 mm thick and the second dielectric window is 50 mm thick.
  • HPDE High Density Polyethylene
  • the first medium window is inclined, and the inclination angle thereof is preferably set to 15°.
  • the outer side of the calibration black body is provided with a metal cover for shielding sunlight, so as to avoid the problem of uneven local temperature distribution of the black body caused by the sun oblique shot at the outdoor work site.
  • the detection range of the first terahertz detector ranges from 0.75 to 15 THz
  • the detection range of the second terahertz detector ranges from 0.75 to 3.6 THz
  • the detection ranges of the two terahertz detectors overlap in the low frequency band of the first terahertz detector.
  • the first beam splitter, the second beam splitter, and the third beam splitter are grating polarizers.
  • the external radiation signal incident on the first beam splitter and the reference black body radiation signal are respectively formed under the interference structure formed by the second beam splitter and the two roof mirrors, respectively forming interference fringes, and passing through the third beam splitter
  • the splitting is performed so that the two signals after the splitting are respectively received by the first and second terahertz detectors.
  • the calibration method further includes the following steps:
  • the outdoor ambient temperature collected by the outdoor ambient temperature collecting device is used as the radiant temperature of the calibrated black body
  • the indoor ambient temperature collected by the indoor ambient temperature collecting device is used as the radiant temperature of the reference blackbody
  • the reciprocating driving device adopts the rotating device
  • the calibration black body and the cleaning brush are mounted on both ends of the rotating arm, and the rotating arm is continuously rotated in the same direction, so that the calibration black body and the cleaning brush are alternately exchanged from the first medium. Turn over the window to complete the calibration and cleaning work.
  • the fully automatic terahertz atmospheric characteristic measuring system of the present invention designs a dual-band overlapping ultra-wideband MPI (Martin-Puplett Interferometer) type terahertz Fourier spectrometer, which adopts a two-port input and a two-port output form, and inputs a black body calibration signal.
  • MPI Martin-Puplett Interferometer
  • the source or atmospheric radiation signal source and the built-in reference black body signal source form interference fringes under the action of the interferometer, and then output to the detection frequency band to overlap the two detectors in the low frequency region, and the two detectors independently receive and output the interference fringe electrical signals,
  • the signal-to-noise ratio of the calibration data of the overlapping band observations can be improved (the low-band signal is based on Planck blackbody distribution is relatively weak).
  • the two detectors use receiving horns with different apertures to optimize the high and low frequency band signal reception, and further improve the light throughput, measurement signal to noise ratio and accuracy of the low frequency band (overlap frequency band).
  • the system of the invention adopts a dual temperature calibration signal source based on natural environment temperature, which is a low temperature calibration black body working outdoors and a high temperature reference black body working indoors, and the radiation temperature of both is the natural environment temperature of the black body, that is, no
  • the source mode of operation (as opposed to the active mode of manual heating or cooling) effectively simplifies the calibration equipment and improves the system calibration accuracy, ensuring that the system can be continuously and unattended for long periods of time.
  • the system of the invention completes the snow removal and dust removal of the media window of the signal transmission device through the integrated calibration and the medium window cleaning device, and simultaneously performs the calibration of the black body signal source and the atmospheric radiation signal source of the rotating device, and ensures the signal transmission channel.
  • the smoothness and reliability of long-term measurement data is the smoothness and reliability of long-term measurement data.
  • Figure 1 is a schematic structural view of a system of the present invention
  • Figure 2 is a schematic diagram of the principle of the method of the present invention.
  • a fully automatic terahertz atmospheric characteristic measuring system as shown in FIG. 1 includes a calibration signal source, a calibration device 1, a terahertz spectrometer 2, and a system control device 3.
  • the calibration signal source is a dual temperature calibration signal source based on natural ambient temperature, including a calibration black body 12 operating outdoors and a reference black body 23 operating indoors, the ambient temperature of the room being higher than the outdoor ambient temperature.
  • the calibration device 1 is connected to a system control device, and includes components such as a signal transmission device, a reciprocating drive device, and an outdoor ambient temperature acquisition device.
  • the signal transmission device is provided with a vertically arranged cylindrical transmission channel made of a low temperature resistant HPDE material, the upper part of the transmission channel is located in an outdoor cold environment, and the top port is passed through a 2 mm thick HPDE material.
  • the first media window 14 is closed and the first media window 14 is mounted at an oblique angle of about 15°, primarily in view of wind resistance, snow protection, and reduced multiple reflection effects of the signal.
  • the lower portion of the transmission channel extends into the chamber, and the bottom port is closed by a 50 mm thick HPDE material second dielectric window 15, ensuring that the transmission of the signal is not affected by the safe operation of the system.
  • the use of HDPE dielectric material to close the two windows can also avoid the disturbance of the atmospheric convection caused by the indoor and outdoor temperature difference, and effectively maintain a certain temperature difference between indoor and outdoor.
  • the reciprocating driving device adopts a rotating device, and the rotating device is provided with a support and a rotating arm. 11 and an angular displacement sensor, the middle portion of the rotating arm 11 is mounted on a support, a calibration black body 12 is mounted below one end of the rotating arm 11, and a cleaning brush 13 made of pig hair is mounted on the other end, the calibration black body 12 or The cleaning brush 13 can be turned over the first media window 12 of the transport channel by the rotating arm.
  • the rotating arm 11 can sustain 360° rotation under motor drive to achieve alternate switching between the outdoor calibration source and the observation signal source, and to clean the first dielectric window 14 to ensure smooth signal transmission.
  • the angular displacement sensor includes a set of clamp switches 18 having a phase difference of 90° for controlling the start and stop position of the rotary arm 11.
  • the cleaning brush 13 is equivalent in weight to the calibration black body 12 to ensure smooth rotation of the rotating arm 11.
  • the calibration black body 12 uses a absorbing material TK RAM produced by Thomas Keating Lt Co., Ltd., and is used as a low temperature (black body) calibration source.
  • the outer side of the calibration black body 12 is provided with a metal cover for shielding sunlight, so as to avoid the problem of uneven local temperature distribution caused by the sun oblique at the outdoor work site.
  • the outdoor ambient temperature collecting device includes a thermometer 16 and a thermometer 17 symmetrically disposed on both sides of the calibration black body 12 when the calibration black body 12 is turned over the first medium window 14.
  • the ambient temperature data monitored by the two thermometers will be As the radiant temperature of the calibrated black body 12, considering the difference in the distribution of the outdoor temperature, the two thermometers should be as close as possible to the calibrated black body, and the distance between the two thermometers and the calibrated black body 12 located above the first medium window 14 is generally controlled within 50 cm. Simultaneous monitoring with two thermometers is mainly based on improving system operational reliability (mutual backup) and improving monitoring temperature accuracy (two effective data cumulative averaging).
  • the terahertz spectrometer 2 adopts an MPI (Martin Puplett Interferometer) interferometer structure, is connected to the system control device 3, and is disposed in a closed indoor environment.
  • MPI Martin Puplett Interferometer
  • the terahertz spectrometer 2 is an MPI type terahertz Fourier spectrometer, and its components include: A) a first terahertz detector 2B, a second terahertz detector 2C, wherein the first terahertz detector 2B The detection frequency range is 0.75 ⁇ 15THz, and the detection range of the second terahertz detector 2C is 0.75 ⁇ 3.6THz. The detection range of the two terahertz detectors overlaps in the low frequency region, and the two detectors use receiving horns with different apertures.
  • the first beam splitter 22 is disposed obliquely at an angle of 135° below the output of the signal transmission device for synthesizing the external radiation signal input to the terahertz spectrometer 2 via the signal transmission device and the radiation generated by the reference black body 23. a signal; C) a first absorbing black body 24 disposed directly below the first beam splitter 22 for absorbing residual signals;
  • a parabolic mirror 28 disposed below the second beam splitter 25, shaping the signal from the second beam splitter 25 and reflecting it onto the two terahertz detectors to beam-match the two terahertz detections of the reflected signal Receiver beamwidth of the horn;
  • the second absorption black body 2A is disposed above the third beam splitter 29 for absorbing residual signals.
  • the reference black body 23, the first absorbing black body 24, and the second absorbing black body 2A are both absorbing materials ECCOSROB AN72 manufactured by Emerson & Cuming Microwave Co.
  • the first beam splitter 22, the second beam splitter 25, and the third beam splitter 29 are both grating polarizers.
  • the reference black body 23 is disposed on the left side of the first beam splitter 22 and serves as a high temperature (black body) calibration source, and four circumferentially arranged indoor thermometers are disposed on the circumferential side thereof to collect the indoor ambient temperature.
  • the closed indoor environment has a good temperature balance, and the indoor thermometer is generally controlled within a range of 1 meter from the reference black body. In a constant temperature environment, the indoor thermometer can be placed anywhere in the indoor environment.
  • the components of the indoor thermometer, the reference black body 23 and the terahertz spectrometer are integrated in an aluminum metal box, and the top surface of the metal box is provided with a third alignment with the second medium window 15
  • the medium window 21, the first beam splitter 22 is disposed directly below the third medium window 21.
  • the first beam splitter 22, the second beam splitter 25, and the third beam splitter 29 can also select and adjust the polarization direction of the signal to enable the terahertz detector.
  • the received signal is the difference between the interference fringes formed by the reference black body 23 and the externally calibrated black body 12 radiation signal (the interference fringes received by the second terahertz detector 2C of the low frequency band are interference fringes formed by the calibration black body 12 and the reference black body 23 radiation signal.
  • the difference is that the interference fringe received by the first terahertz detector 2B in the high frequency band is opposite to the low frequency band terahertz detector 2C, which is the difference between the interference fringes formed by the reference black body 23 and the calibrated black body 12 radiation signal.
  • the system control device mainly includes a data IO board 31, a data acquisition board 32, a CPU board 33, and application observation software.
  • the user can set the operating parameters of the calibration device 1, the control calibration device 1, the driving of the MPI terahertz Fourier spectrometer 2 motor, the readout detector interference fringe data, and the monitoring temperature data of the indoor and outdoor monitoring thermometers through the system control device 3,
  • the observed interference fringe data will be recorded during the observation process, and the integration and data storage will be performed for a certain period of time.
  • the system control equipment Based on the above-mentioned integrated calibration and window cleaning equipment and calibration signal source based on ambient temperature scale, the system control equipment has built-in continuous application observation software to realize unattended operation, remote operation of equipment, data download and system work. Condition monitoring.
  • the external radiation signal incident on the first beam splitter 25 and the reference black body 23 radiation signal are respectively formed under the interference structure formed by the second beam splitter 25 and the two roof mirrors, respectively forming interference fringes
  • the three beam splitter 29 performs splitting, so that the two signals after the splitting are respectively received by the first and second terahertz detectors, and the two terahertz detectors convert the collected signals into electrical signals and respectively transmit the data to the system control device 3.
  • the acquisition board 32 measurement data of high and low frequency bands are formed.
  • the calibration method includes the following steps:
  • the system control device 3 starts an application program, and controls the rotation device to rotate counterclockwise. Under the action of the first clamp photoelectric switch group 18, the calibration black body 12 is turned to the positive direction of the first medium window 14 of the signal transmission device. When it is above (position A in Fig. 2), it is stopped for a period of time, so that the radiation signal of the calibration black body 12 passes through the signal transmission device to enter the terahertz spectrometer 2, and the calibration data is measured by the terahertz spectrometer 2, in order to improve the signal noise. Comparing, repeating 8 interference scans in succession, checking 8 times of data formed and accumulating averages as final measurement data;
  • the rotating device activating the rotating device to continue counterclockwise rotation to remove the calibration black body 12 from above the first dielectric window 14, and to maintain the position when the rotating arm 11 passes the second embedded photoelectric switch group 18.
  • Fixed position B in Fig. 2
  • the zenith terahertz atmospheric radiation signal passes through the signal transmission device, enters the terahertz spectrometer (2), and the zenith atmospheric radiation signal is measured by the terahertz spectrometer 2, and is continuously repeated.
  • Perform 8 interference scans to collect the interference fringes received by the first and second terahertz detectors (2B, 2C) to form the final measurement data corresponding to the zenith atmospheric radiation signal in the high and low frequency bands, and then the 8 data formed.
  • the core and the accumulated average are used as the final measurement data;
  • step (3) collecting and storing steps (1) the measured calibration data, the atmospheric radiation signal data measured in step (2), and the indoor and outdoor temperature data to form an observation data file of a complete calibration period;
  • the cycle steps (1) to (4) can be repeated to start a new round of calibration and observation process to realize fully automatic long-period continuous atmospheric transmittance measurement.
  • the temperature reading of the outdoor thermometer is used as the radiant temperature of the calibration black body 12
  • the temperature reading of the indoor thermometer is taken as the radiant temperature of the reference black body 23.
  • the measurement system of this embodiment achieves continuous measurement of the terahertz atmospheric transmittance characteristics in the Antarctic hail A (Dome A) for nearly two years, and has obtained the ground station site so far.
  • the invention proposes a fully automatic terahertz atmospheric characteristic measuring device which is more wide-band, simpler to calibrate equipment, adapts to a very low temperature environment (down to minus 80°), and can be unattended, and realizes super-omeric covering the frequency range of 0.75 to 15 THz. Wide-bandwidth atmospheric transmittance is observed continuously over long periods.

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Abstract

一种全自动太赫兹大气特性测量系统及校核方法，系统包括校准信号源、校准设备（1）、太赫兹光谱仪（2）和系统控制设备（3），校准信号源为基于自然环境温度的双温校准信号源，即无源工作方式，有效简化了校准设备（1），并提高系统校准精度，确保系统可长周期连续、无人值守工作；太赫兹光谱仪（2）为双频段交叠超宽带MPI型太赫兹傅立叶光谱仪，采用两端口输入和两端口输出形式，输入黑体校准信号源或大气辐射信号源和内置参考黑体信号源在干涉仪作用下形成干涉条纹，然后输出到两个探测频段范围不同但在低频段交叠的探测器上，两探测器分别独立接收并输出干涉条纹电信号，在频域通过校对和累加平均后处理，提高了交叠频段观测校准数据信噪比。

Description

一种全自动太赫兹大气特性测量系统及其校准方法 技术领域
本发明涉及一种太赫兹天文站址大气特性测量设备与校准方法，属于太赫兹技术研究及应用领域。
背景技术
太赫兹波段(0.1～10THz)介于微波和光学波段，是仍有待全面开发及研究的新波段。由于宇宙空间近50％的光子能量以及大量的分子谱线辐射落在太赫兹波段，而且该波段最适合观测早期冷暗宇宙，因此太赫兹波段是进行宇宙学及天体物理研究的独特波段。太赫兹辐射由于受地球大气，特别是水汽的严重吸收，地面太赫兹天文观测需要具有高海拔、干燥以及低温的环境。开展太赫兹天文站址的大气透过率长周期变化特性的测量及评估，是太赫兹天文台建设前期的一项重要工作。
太赫兹傅立叶光谱仪(Fourier Transform Spectrometer，FTS)，因其具有宽带、通光量大以及多路复用等特点，是开展微弱太赫兹辐射源(太赫兹分子谱线或太赫兹连续谱)探测的重要技术手段，特别适用于太赫兹宽带大气辐射特性测量，并在太赫兹天文站址的大气透过率测量中得到了广泛应用。国际上如夏威夷的Mauna Kea、智利的Chajnantor高原、南极点(South Pole)等太赫兹天文站址评估均采用了傅立叶光谱技术。
用于太赫兹大气透过率测量的一台设备系统通常包括校准设备、太赫兹傅立叶光谱仪、以及系统控制设备等。校准设备主要提供观测信号校准用的标准信号源，系统控制设备则进行系统参数设置、校准过程控制、系统状态监测、以及观测数据采集和存储。太赫兹傅立叶光谱仪主要将输入太赫兹信号(包括校准信号源以及观测信号源)进行分光扫描形成干涉条纹，然后对干涉条纹接收形成电信号，为系统控制设备进行后续处理。采用傅立叶光谱仪进行太赫兹大气透过率频谱特性测量时，首先需要测量大气辐射谱，在此基础上根据热辐射转移方程和Plank定理，最终导出大气透过率频谱。为了实现大气辐射谱的校准，校准过程需涉及两个具有不同辐射温度的校准源。传统采用是的以密闭环境的高温黑体信号源和低温(液氮温区)黑体信号源。
目前用于太赫兹大气特性测量的傅立叶光谱仪系统主要存在如下不足：
首先，在校准设备方面，太赫兹大气透过率测量需要高、低温校准源。低温校准源一般采用液氮温区黑体信号源，这带来的问题是：由于液氮易于耗散成氮气，无法实现长时间(如周年)的连续有效工作；此外，需将液氮存放于隔热密闭液氮罐内。这种采用液氮温区的黑体 信号源，给处于高海拔、偏远高原或山区的太赫兹天文站址评估时的物资运输、存储和使用带来诸多不便。对于需要加热的高温校准源，其辐射温度的定标精度也是一个难点。
其次，在太赫兹傅立叶光谱仪所采用探测器方面，太赫兹大气透过率频谱分析带宽主要取决于太赫兹傅立叶频谱仪探测器的工作带宽。由于地球大气水汽窄带谱线和连续谱、以及其他分子谱线如N2和O3等的影响，导致太赫兹信号在1～5THz频段的传输衰减非常严重。为了提高测量信噪比，当前设备通常采用大光通量接收的单一探测器来覆盖5THz以下所感兴趣的频段进行测量。单一探测器技术方案将限制更宽带太赫兹大气透过率测量，特别在需要更宽频率范围(如包括5～15THz区间)全面评估水汽转动谱和不饱和水汽辐射线谱对大气透过率特性影响的情况。
发明内容
针对上述传统太赫兹傅立叶光谱仪系统存在的问题，本发明提出了一种校准设备更简易、适应低温环境，以及可无人值守工作的全自动太赫兹大气特性测量系统。
本发明公开的技术方案为：
一种全自动太赫兹大气特性测量系统，包括校准信号源，校准设备、基于干涉原理的太赫兹光谱仪和系统控制设备，其特征在于：
所述校准信号源为基于自然环境温度的双温校准信号源，包括工作于室外的校准黑体和工作于室内的参考黑体，所述室内的环境温度要高于室外环境温度，即所述校准黑体用作低温校准源，所述参考黑体用作高温校准源；
所述校准设备与系统控制设备连接，包括信号传输装置、往复式驱动装置和室外环境温度采集装置，所述信号传输装置设有直筒状的传输通道，所述传输通道的顶端设有密闭的第一介质窗口，传输通道底端设有密闭的第二介质窗口，传输装置的上部位于室外，下部延伸到室内；所述校准黑体安装在往复式驱动装置的执行机构上，在驱动装置带动下，可转移到所述第一介质窗口的上方或从第一介质窗口上移开；
所述太赫兹光谱仪设置在密闭的室内环境中，与系统控制设备连接，室内设有室内环境温度采集装置；
所述太赫兹光谱仪的组成部件包括：
第一、第二太赫兹探测器，两探测器的探测频段范围有交叠，且其一且其一探测器探测频段范围上限大于另一探测器的探测频段范围上限；
第一波束分离器，倾斜地设置在信号传输装置输出端的下方位置，用于合成经过信号传输装置输入太赫兹光谱仪的外部辐射信号与所述参考黑体的辐射信号，所述参考黑体设置在第一 波束分离器的左侧；
第一吸收黑体，设置在第一波束分离器的下方，用于吸收残余信号；
第二波束分离器，设置在第一波束分离器的右侧，以与第一波束分离器相对仰倒的形式倾斜设置；
固定屋面镜，设置在第二波束分离器的上方，用于将来自第二波束分离器的反射信号再次反射到第二波束分离器上；
可移动屋面镜，设置在第二波束分离器的右侧，用于将来自第二波束分离器的透射信号再次反射到第二波束分离器上；
反射镜，设置在第二波束分离器的下方，将来自第二波束分离器的信号反射到太赫兹探测器上；
第三波束分离器,设置在所述反射镜与太赫兹探测器之间，将来自所述反射镜的反射信号分成极化正交的两路信号，使其分别被第一、第二太赫兹探测器接收到；
第二吸收黑体，设置在第三波束分离器的一侧，与接收第三波束分离器反射信号的太赫兹探测器相反的一侧，用于吸收残余信号。
在上述方案的基础上，进一步改进或优选的方案还包括：
所述驱动装置为旋转装置，所述旋转装置设有旋转臂和安装旋转臂的支座，所述校准黑体安装在所述旋转臂的一端，旋转臂的另一端安装有清洁刷，所述清洁刷在旋转臂带动下，可从第一介质窗口的上方扫过。
所述清洁刷优选采用猪毛材料，其在极低温度下仍能保持良好的柔软性。
所述第一、第二太赫兹探测器采用不同孔径的接收喇叭。
所述反射镜为抛物面反射镜，用于整形其传输信号的波束以匹配两太赫兹探测器接收喇叭的波束宽度。
所述室内环境温度采集装置、太赫兹光谱仪的组成部件和参考黑体集成于一铝制的金属箱中，所述金属箱的顶面设有对准所述第二介质窗口的第三介质窗口，第一波束分离器设置在第三介质窗口的正下方。
所述室外环境温度采集装置包括设置在校准黑体周侧的多个室内温度计，当校准黑体位于所述第一介质窗口上方时，所述室内温度计与校准黑体的距离均不超过50cm。
所述信号传输装置的筒体以及第一介质窗口、第二介质窗口均为HPDE(高密度聚乙烯)材料，其中第一介质窗口厚2毫米，第二介质窗口厚50毫米。
所述第一介质窗口倾斜设置，其倾角优选设为15°。
所述校准黑体的外侧安装有遮蔽阳光的金属罩，避免室外工作现场太阳斜射引起的黑体局部温度分布不均匀的问题。
所述第一太赫兹探测器的探测频段范围为0.75～15THz，第二太赫兹探测器的探测频段范围为0.75～3.6THz，二者探测范围在第一太赫兹探测器的低频段交叠。
所述第一波束分离器、第二波束分离器、第三波束分离器为光栅极化器。
用于如上所述全自动太赫兹大气特性测量系统的校准方法，其特征在于,包括驱动所述可移动屋面镜，进行干涉扫描的步骤；
在干涉扫描过程中，入射到第一波束分离器的外部辐射信号与参考黑体辐射信号在第二波束分离器和两屋面镜构成的干涉结构作用下，各自形成干涉条纹，通过第三波束分离器进行分光，使分光后的两路信号分别被第一、第二太赫兹探测器接收。
进一步的，所述校准方法，还包括以下步骤：
(一)启动所述往复式驱动装置，将校准黑体(12)转移到信号传输装置第一介质窗口的正上方时停止，并保持一段时间，使校准黑体的辐射信号经过所述信号传输装置进入到太赫兹光谱仪，重复进行多次干涉扫描，并对形成的多次数据进行累加平均后作为最终测量数据；
(二)再次启动所述旋转装置，将校准黑体(12)从所述第一介质窗口的上方移开，使天顶太赫兹大气辐射信号经过所述信号传输装置，进入到太赫兹光谱仪，重复进行多次干涉扫描，并对形成的多次数据进行累加平均后作为最终测量数据。
(三)采集并保存步骤(一)测量的校准数据、步骤(二)测量的大气辐射信号数据、室内外的温度数据，形成一次完整校准周期的观测数据文件。
本发明校准方法中，以室外环境温度采集装置采集的室外环境温度作为校准黑体的辐射温度，以室内环境温度采集装置采集的室内环境温度作为参考黑体的辐射温度。
进一步的，所述往复式驱动装置采用旋转装置时，将所述校准黑体和清洁刷安装在其旋转臂的两端，持续同向转动旋转臂，可使校准黑体与清洁刷交替从第一介质窗口上方转过，完成校准和清扫的工作。
有益效果：
1)本发明全自动太赫兹大气特性测量系统，设计了一种双频段交叠超宽带MPI(Martin-Puplett Interferometer)型太赫兹傅立叶光谱仪，采用两端口输入和两端口输出形式，输入黑体校准信号源或大气辐射信号源和内置参考黑体信号源在干涉仪作用下形成干涉条纹，然后输出到探测频段在低频区交叠两个探测器上，两探测器分别独立接收并输出干涉条纹电信号，在频域通过校对和累加平均后处理，可提高交叠频段观测校准数据信噪比(低频段信号基于 普朗克黑体分布较为微弱)。此外，两探测器采用不同孔径的接收喇叭，优化高、低频段信号接收的同时，进一步提高了低频段(交叠频段)的通光量、测量信噪比及精度。
2)本发明系统采用基于自然环境温度双温校准信号源，分别为工作于室外的低温校准黑体和工作于室内的高温参考黑体，两者的辐射温度均为黑体所处自然环境温度，即无源工作方式(相对于人工加热或制冷的有源工作方式)，有效简化了校准设备，并提高了系统校准精度，确保系统可长周期连续、无人值守工作。
3)本发明系统通过一体化的校准与介质窗口洁净装置，在旋转装置进行校准黑体信号源和大气辐射信号源切换的同时，也完成了对信号传输装置介质窗口的除雪除尘，确保信号传输通道的畅通和长周期测量数据的可靠性。
4)本发明系统及方法设计合理，易于实现，可适应低温环境，适合推广使用。
附图说明
图1为本发明系统的结构示意图；
图2为本发明方法的原理示意图。
具体实施方式
为了进一步阐明本发明的技术方案和工作原理，下面结合附图与具体实施例对本发明做进一步的介绍。
如图1所示的一种全自动太赫兹大气特性测量系统，包括校准信号源、校准设备1、太赫兹光谱仪2和系统控制设备3。
所述校准信号源为基于自然环境温度的双温校准信号源，包括工作于室外的校准黑体12和工作于室内的参考黑体23，所述室内的环境温度要高于室外环境温度。
所述校准设备1与系统控制设备连接，包括信号传输装置、往复式驱动装置和室外环境温度采集装置等组成部分。
所述信号传输装置设有竖直设置的圆筒状传输通道，所述传输通道采用耐低温的HPDE材料制成，传输通道的上部位于室外冷环境中，其顶部端口通过2毫米厚的HPDE材料第一介质窗口14封闭，所述第一介质窗口14按约15°的倾斜角度安装，主要是考虑到抗风、防积雪、并减小信号的多重反射效应。所述传输通道的下部延伸到室内，其底部端口通过50毫米厚的HPDE材料第二介质窗口15封闭，确保系统工作安全情况下不影响信号的透过率。同时，采用HDPE介质材料封闭两窗口还可避免室内外温差引起的大气对流对测量信号的扰动，以及有效维持室内外一定温差。
本实施例中，所述往复式驱动装置采用旋转装置，所述旋转装置设有支座、旋转臂 11以及角度位移传感器，所述旋转臂11的中部安装在支座上，旋转臂11一端的下方安装有校准黑体12，另一端安装有猪毛制成的清洁刷13,所述校准黑体12或清洁刷13在旋转臂带动下，可转到传输通道第一介质窗口12的上方。旋转臂11在电机驱动下可持续进行360°旋转，以实现室外校准源和观测信号源之间的交替切换，以及对第一介质窗口14进行清扫，确保信号传输通畅。所述角度位移传感器包括一组相位差为90°的嵌位开关组18，用于控制旋转臂11的启停位置。
所述清洁刷13与校准黑体12重量相当，以确保旋转臂11的平稳转动。
本实施例中，所述校准黑体12采用了Thomas Keating Lt公司生产的吸波材料TK RAM，用作低温(黑体)校准源。所述校准黑体12的外侧安装有遮蔽阳光的金属罩，避免室外工作现场太阳斜射引起的局部温度分布不均匀的问题。
所述室外环境温度采集装置包括在校准黑体12转到第一介质窗口14上方时，对称设置在校准黑体12两侧的温度计16和温度计17，本实施例中，两温度计监测的环境温度数据将作为校准黑体12的辐射温度，考虑到室外温度的分布差异，两温度计应当尽可能靠近校准黑体，两温度计与位于第一介质窗口14上方的校准黑体12的距离一般控制在50cm以内。采用两个温度计同时监测，主要是基于提高系统工作可靠性(相互备份)和提高监测温度精度(两路有效数据累加平均)。
所述太赫兹光谱仪2采用了MPI(Martin Puplett Interferometer)干涉仪结构，与系统控制设备3连接，设置在密闭的室内环境中。
本实施例中，所述太赫兹光谱仪2为MPI型太赫兹傅立叶光谱仪，其组成部件包括：A)第一太赫兹探测器2B、第二太赫兹探测器2C，其中第一太赫兹探测器2B的探测频段范围为0.75～15THz，第二太赫兹探测器2C的探测频段范围为0.75～3.6THz，二者探测范围在低频区重叠，且两探测器采用不同孔径的接收喇叭。
B)第一波束分离器22，以135°角倾斜地设置在信号传输装置输出端的下方位置，用于合成经过信号传输装置输入太赫兹光谱仪2的外部辐射信号与所述参考黑体23产生的辐射信号；C)第一吸收黑体24，设置在第一波束分离器22的正下方，用于吸收残余信号；
D)第二波束分离器25，设置在第一波束分离器22的右侧，以与第一波束分离器22相对仰倒的形式倾斜设置，其倾角为45°；
E)固定屋面镜26，设置在第二波束分离器25的上方，用于将来自第二波束分离器25的反射信号再次反射到第二波束分离器25上；
F)可移动屋面镜27，设置在第二波束分离器25的右侧，用于将来自第二波束分离器25的 透射信号再次反射到第二波束分离器25上；
G)抛物面反射镜28，设置在第二波束分离器25的下方，将来自第二波束分离器25的信号整形后反射到两太赫兹探测器上,使其反射信号的波束匹配两太赫兹探测器接收喇叭的波束宽度；
H)第三波束分离器29,设置在所述反射镜28与太赫兹探测器之间，按135°的倾角安装，将来自所述反射镜28的反射信号分成极化正交的两路信号，使其分别被第一、第二太赫兹探测器接收到；
I)第二吸收黑体2A，设置在第三波束分离器29的上方，用于吸收残余信号。
本实施例中，所述参考黑体23、第一吸收黑体24和第二吸收黑体2A均采用Emerson&Cuming Microwave Co公司生产的吸波材料ECCOSROB AN72。所述第一波束分离器22、第二波束分离器25、第三波束分离器29均为光栅极化器。所述参考黑体23设置在第一波束分离器22的左侧，用作高温(黑体)校准源，其周侧设有四个均匀布置的室内温度计，采集室内环境温度。密闭的室内环境温度平衡性较好，室内温度计一般控制在距离参考黑体1米以内的范围。恒温环境下，室内温度计则可设置在室内环境的任意地方。
本实施例中，上述室内温度计、参考黑体23和太赫兹光谱仪的组成部件集成于一铝制的金属箱中，所述金属箱的顶面设有对准所述第二介质窗口15的第三介质窗口21，第一波束分离器22设置在第三介质窗口21的正下方。所述第一波束分离器22、第二波束分离器25和第三波束分离器29除了对传输信号进行分光、合成外，还可对信号的极化方向进行选择和调整，使太赫兹探测器接收的信号为参考黑体23与外部校准黑体12辐射信号形成的干涉条纹的差值(低频段的第二太赫兹探测器2C所接收的干涉条纹是校准黑体12与参考黑体23辐射信号形成干涉条纹之差，而高频段的第一太赫兹探测器2B所接收的干涉条纹则与低频段太赫兹探测器2C相反，是参考黑体23与校准黑体12辐射信号形成的干涉条纹之差。)
所述系统控制设备主要包括数据IO板31、数据采集板32、CPU板33以及应用观测软件。用户可通过系统控制设备3设置校准设备1的工作参数、控制校准设备1、MPI太赫兹傅立叶光谱仪2电机的驱动、读出探测器干涉条纹数据、以及室内外监测温度计的监测温度数据，同时在观测过程中将记录的观测干涉条纹数据，进行一定时间的积分和数据存盘。在前述一体化校准及窗口洁净设备、以及采用基于环境温标的校准信号源的基础上，系统控制设备内置连续工作的应用观测软件，实现设备无人值守工作、设备远程操作、数据下载和系统工作状态监测。
用于如上所述全自动太赫兹大气特性测量系统的校准方法，包括驱动所述可移动屋面镜27，进行干涉扫描的步骤。
在上述干涉扫描过程中，入射到第一波束分离器25的外部辐射信号与参考黑体23辐射信号在第二波束分离器25和两屋面镜构成的干涉结构作用下，各自形成干涉条纹，通过第三波束分离器29进行分光，使分光后的两路信号分别被第一、第二太赫兹探测器接收，两太赫兹探测器将采集信号转换为电信号，分别输送至系统控制设备3的数据采集板32中，形成高、低两频段的测量数据。
所述校准方法，具体过程包括以下步骤：
(一)系统控制设备3启动应用程序，控制所述旋转装置逆时针转动，在第一个嵌位光电开关组18的作用下，使校准黑体12转到信号传输装置第一介质窗口14的正上方(图2位置A)时停止，并保持一段时间，使校准黑体12的辐射信号经过所述信号传输装置进入到太赫兹光谱仪2，通过太赫兹光谱仪2对校准数据进行测量，为了提高信噪比，连续重复进行8次干涉扫描，对形成的8次数据进行校核和累加平均后作为最终测量数据；
(二)启动所述旋转装置，使其继续逆时针转动，将校准黑体12从所述第一介质窗口14上方移开，当旋转臂11经过第二个嵌位光电开关组18时，保持位置固定(图2中位置B)，使天顶太赫兹大气辐射信号经过所述信号传输装置，进入到太赫兹光谱仪(2)，通过太赫兹光谱仪2对天顶大气辐射信号进行测量，同样连续重复进行8次干涉扫描，采集第一、第二太赫兹探测器(2B，2C)接收的干涉条纹，形成高低两频段对应天顶大气辐射信号的最终测量数据，之后对形成的8次数据进行校核和累加平均后作为最终测量数据；
(三)采集并保存步骤(一)测量的校准数据、步骤(二)测量的大气辐射信号数据以及室内外的温度数据，形成一次完整校准周期的观测数据文件；
(四)启动所述旋转装置，继续逆时针转动，使清洁刷13转过所述第一介质窗口14上方，对第一介质窗口14的表面进行清扫。
之后，根据用户的使用需求，可重复循环步骤(一)到步骤(四)，开始新一轮的校准和观测过程，实现全自动的长周期连续大气透过率特性测量。上述过程中，室外温度计的温度读数即作为校准黑体12的辐射温度，室内温度计的温度读数即作为参考黑体23的辐射温度。
通过以上策略及方案，结合连续运行的应用观测软件，本实施例测量系统在南极冰穹A(Dome A)实现了近两年的太赫兹大气透过率特性连续测量，取得了地面台址迄今为止太赫兹波段最高的大气透过率测量结果，以及该波段全新的极低温环境水汽吸收谱。
本发明提出了一种更宽带、校准设备更简易、适应极低温环境(低达零下80°)、以及可无人值守工作的全自动太赫兹大气特性测量设备，实现覆盖0.75～15THz频段的超宽带宽大气透过率长周期连续观测。以上显示和描述了本发明的基本原理、主要特征和本发明的优点。本行业的技术人员应该了解，本发明不受上述实施例的限制，上述实施例和说明书中描述的只是说明本发明的原理，在不脱离本发明精神和范围的前提下，本发明还会有各种变化和改进，本发明要求保护范围由所附的权利要求书、说明书及其等效物界定。本申请权利要求书及说明书中使用的“左”“右”“上”“下”等方位名词，为便于本领域技术人员理解的相对参照，随着参照物的改变，其绝对方位会有相应变化。

Claims (16)

  1. 一种全自动太赫兹大气特性测量系统，包括校准信号源、校准设备(1)、基于干涉原理的太赫兹光谱仪(2)和系统控制设备(3)，其特征在于：
    所述校准信号源为基于自然环境温度的双温校准信号源，包括工作于室外的校准黑体(12)和工作于室内的参考黑体(23)，所述室内的环境温度要高于室外环境温度，即所述校准黑体(12)用作低温校准源，所述参考黑体(23)用作高温校准源；
    所述校准设备(1)与系统控制设备连接，包括信号传输装置、往复式驱动装置和室外环境温度采集装置，所述信号传输装置设有直筒状的传输通道，所述传输通道的顶端设有密闭的第一介质窗口(14)，传输通道底端设有密闭的第二介质窗口(15)，传输装置的上部位于室外，下部延伸到室内；所述校准黑体(12)安装在往复式驱动装置的执行机构上，在驱动装置带动下，可转移到传输通道第一介质窗口(12)的上方或从第一介质窗口(12)上移开；所述太赫兹光谱仪(2)设置在密闭的室内环境中，与系统控制设备(3)连接，室内设有室内环境温度采集装置；
    所述太赫兹光谱仪(2)的组成部件包括：
    第一、第二太赫兹探测器(2B，2C)，两探测器的探测频段范围有交叠，且其一探测器探测频段范围上限大于另一探测器的探测频段范围上限；
    第一波束分离器(22)，倾斜地设置在信号传输装置输出端的下方位置，用于合成经过信号传输装置输入太赫兹光谱仪(2)的外部辐射信号与所述参考黑体(23)的辐射信号，所述参考黑体(23)设置在第一波束分离器(22)的左侧；
    第一吸收黑体(24)，设置在第一波束分离器(22)的下方，用于吸收残余信号；
    第二波束分离器(25)，设置在第一波束分离器(22)的右侧，以与第一波束分离器(22)相对仰倒的形式倾斜设置；
    固定屋面镜(26)，设置在第二波束分离器(25)的上方，用于将来自第二波束分离器(25)的反射信号再次反射到第二波束分离器(25)上；
    可移动屋面镜(27)，设置在第二波束分离器(25)的右侧，用于将来自第二波束分离器(25)的透射信号再次反射到第二波束分离器(25)上；
    反射镜(28)，设置在第二波束分离器(25)的下方，将来自第二波束分离器的信号反射到太赫兹探测器上；
    第三波束分离器(29),设置在所述反射镜(28)与太赫兹探测器之间，将来自所述反射镜(28)的反射信号分成极化正交的两路信号，使其分别被第一、第二太赫兹探测器接收到；
    第二吸收黑体(2A)，设置在第三波束分离器(29)的一侧，与接收第三波束分离器(29) 反射信号的太赫兹探测器相反的一侧，用于吸收残余信号。
  2. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述往复式驱动装置为旋转装置，所述旋转装置设有旋转臂(11)和安装旋转臂(11)的支座，所述校准黑体(12)安装在所述旋转臂(11)的一端，旋转臂(11)的另一端安装有清洁刷(13)，所述清洁刷(13)在旋转臂(11)带动下，可从第一介质窗口(12)的上方扫过。
  3. 根据权利要求2所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述清洁刷(13)为猪毛材料。
  4. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述第一、第二太赫兹探测器(2B，2C)采用不同孔径的接收喇叭。
  5. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述反射镜(28)为抛物面反射镜，用于整形传输信号的波束以匹配两太赫兹探测器接收喇叭的波束宽度。
  6. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述室内环境温度采集装置、太赫兹光谱仪的组成部件和参考黑体(23)集成于一铝制的金属箱中，所述金属箱的顶面设有对准所述第二介质窗口(15)的第三介质窗口(21)，第一波束分离器(22)设置在第三介质窗口(21)的正下方。
  7. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于：
    所述室外环境温度采集装置包括设置在校准黑体(12)周侧的多个室外温度计，当校准黑体(12)位于所述第一介质窗口(13)上方时，所述室外温度计与校准黑体(12)的距离均不超过50cm。
  8. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述信号传输装置的筒体以及第一介质窗口(14)、第二介质窗口(15)均为HPDE材料，其中第一介质窗口(14)厚2毫米，第二介质窗口(15)厚50毫米。
  9. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述第一介质窗口(14)倾斜设置，其倾角为15°。
  10. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述校准黑体(12)的外侧安装有遮蔽阳光的金属罩。
  11. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述第一太赫兹探测器(2B)的探测频段范围为0.75～15THz，第二太赫兹探测器(2C)的探测频段范围为0.75～3.6THz。
  12. 根据权利要求1所述的一种全自动太赫兹大气特性测量系统，其特征在于，所述第一波束分离器(22)、第二波束分离器(25)、第三波束分离器(29)为光栅极化器。
  13. 用于如权利要求1-12中任一项所述全自动太赫兹大气特性测量系统的校准方法，其特征在于,包括驱动所述可移动屋面镜(27)，进行干涉扫描的步骤；在干涉扫描过程中，入射到第一波束分离器(25)的外部辐射信号与参考黑体(23)辐射信号在第二波束分离器(25)和两屋面镜构成的干涉结构作用下，各自形成干涉条纹，通过第三波束分离器(29)进行分光，使分光后的两路信号分别被第一、第二太赫兹探测器接收。
  14. 根据权利要求13所述的校准方法，其特征在于，包括以下步骤：
    (一)启动所述往复式驱动装置，将校准黑体(12)转移到信号传输装置第一介质窗口(14)的正上方时停止，并保持一段时间，使校准黑体(12)的辐射信号经过所述信号传输装置进入到太赫兹光谱仪(2)，重复进行多次干涉扫描，并对形成的多次数据进行累加平均后作为最终测量数据；
    (二)再次启动所述驱动装置，将校准黑体(12)从所述第一介质窗口(14)的上方移开，使天顶太赫兹大气辐射信号经过所述信号传输装置，进入到太赫兹光谱仪(2)，重复进行多次干涉扫描，并对形成的多次数据进行累加平均后作为最终测量数据；
    (三)采集并保存步骤(一)测量的校准数据、步骤(二)测量的大气辐射信号数据、室内外的温度数据，形成一次完整校准周期的观测数据文件。
  15. 根据权利要求14所述的校准方法，其特征在于：
    以室外环境温度采集装置采集的室外环境温度作为校准黑体(12)的辐射温度，以室内环境温度采集装置采集的室内环境温度作为参考黑体(23)的辐射温度。
  16. 根据权利要求14所述的校准方法，其特征在于：
    所述往复式驱动装置为旋转装置，将所述校准黑体(12)和清洁刷(13)安装在其旋转臂(11)两端，持续同向转动旋转臂(11)，使校准黑体(12)与清洁刷(13)交替从第一介质窗口(12)上方转过。
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