CN102998663A - Calibration method for microwave radiometer - Google Patents

Abstract

The invention discloses a calibration method for a microwave radiometer. The calibration method includes calculating sky brightness temperature that a plurality of zenith angles correspond to according to the brightness temperature transfer function, calculating atmosphere total pad value that the plurality of zenith angles correspond to, conducting linear regression treatment on the secant value of the plurality of zenith angles and the atmosphere total pad value that the plurality fo zenith angles correspond to, utilizing slope of a straight line obtained by the linear regression treatment as the atmosphere total pad value at the time when the zenith angle is 0 degree, calculating the sky brightness temperature when the zenith angle is 0 degree, substitute the sky brightness temperature at the time when the zenith angle is 0 degree into the brightness transfer function to calculate the value of the corresponding calibration coefficient a, updating the value of the calibration coefficient a, repeating the above step to obtain a new a and circulating in this way to enable the restrained a as the calibration value. The calibration method only requires one microwave radiometer and a black body, is low in cost, convenient to operate and high in accuracy, and provides forceful support for detection of atmosphere temperature profile, atmosphere humidity profile and the like.

Description

A kind of calibrating method for microwave radiometer

Technical field

The present invention relates to the microwave radiometer technical field, particularly relate to a kind of calibrating method for microwave radiometer.

Background technology

Microwave radiometer is a kind of passive type ground microwave remote sensing equipment, the calibrating method of microwave radiometer is divided into two kinds substantially: a kind of is the substep scaling method, carry out respectively for the calibration of receiver and the calibration of antenna, need the intermediate parameters of measurement more, therefore the source of error of substep scaling method is many, and calibration precision is low; Another kind is whole scaling method, once finish for the calibration that is scaled to final output from antenna, without intermediate link, thus calibration precision the substep scaling method want high.In whole scaling method, usually need to use two noise sources stable, different temperatures, in the reality often with black matrix as the high temperature noise source, with liquid nitrogen as the low temperature noise source, wherein, although use liquid nitrogen to finish calibration accurately, shortcoming is the liquid nitrogen price, and transport and place all inconveniences, it is higher to cause calibrating cost.

Summary of the invention

In order to solve the high problem of calibration cost of microwave radiometer in the prior art, the invention provides a kind of calibrating method for microwave radiometer.

Calibrating method for microwave radiometer of the present invention comprises: step 1, according to bright temperature transport function, bright temperature and corresponding voltage thereof based on reference blackbody, and the initial value of calibration coefficient a, calculate sky temperature corresponding to a plurality of zenith angles, the initial value of wherein said calibration coefficient a is predefined; Step 2 based on the sky temperature under described a plurality of zenith angles, is calculated each self-corresponding atmosphere overall attenuation value of described a plurality of zenith angle; Step 3 for secant value and each self-corresponding atmosphere overall attenuation value of described a plurality of zenith angle of described a plurality of zenith angles, is carried out linear regression processing, and take the slope of linear regression processing gained straight line as zenith angle the atmosphere overall attenuation value during as 0 °; Step 4, the atmosphere overall attenuation value when being 0 ° based on described zenith angle, the sky temperature when the calculating zenith angle is 0 °; Step 5, the described bright temperature transport function of the sky temperature substitution when described zenith angle is 0 ° solves the value of corresponding calibration coefficient a; Step 6, as the described initial value in the step 1, repeating step one to five obtains the value of new a with the value of the calibration coefficient a of described correspondence; So circulation, constantly upgrading the value of a, with the value of a after the convergence scaled values as a, calibration is finished.

Further, described bright temperature transport function is T _Sky=T _Ref+ G (V _Sky-V _Ref) f _w, wherein, T _RefThe bright temperature of reference blackbody, V _RefThe voltage of corresponding catoptron when pointing to reference blackbody; T _SksSky temperature, V _SkyThe voltage of corresponding catoptron when pointing into the sky, f _wBe the constant relevant with the emissivity of the material that covers the microwave radiometer minute surface, G is the calibration gain,

Wherein, $G=\frac{T_{\mathrm{nd}}}{V_{\mathrm{ref}+\mathrm{nd}}-V_{\mathrm{ref}}},$ Then $a=T_{\mathrm{ref}}-\frac{T_{\mathrm{nd}}\·f_w\·V_{\mathrm{ref}}}{V_{\mathrm{ref}+\mathrm{nd}}-V_{\mathrm{ref}}};$ Wherein, V _Ref+ndThe voltage of microwave radiometer catoptron when pointing to reference blackbody and adding noise diode, T _NdBe noise temperature, noise temperature is with the environmental change change; Calibration is equivalent to T to a _NdCalibration.

Further, described bright temperature transport function is T _Sky=f (a, V, σ), wherein, V represents parameter relevant with voltage in the microwave radiometer, and σ represents other parameter in the microwave radiometer.

Further, in the step 2, according to sky temperature, the bright temperature of average radiation and atmosphere overall attenuation three's funtcional relationship, calculate each self-corresponding atmosphere overall attenuation value of described a plurality of zenith angle.

Further, in the step 4, the atmosphere overall attenuation value when being 0 ° according to described zenith angle, the bright gentle sky temperature three's of the average radiation when zenith angle is 0 ° funtcional relationship, the sky temperature when calculating described zenith angle and being 0 °.

Wherein, any two in described a plurality of zenith angles differ 15 ° at least, and arbitrary zenith angle is no more than 70 °.

Beneficial effect of the present invention is as follows:

The present invention with black matrix as high temperature source, according to bright temperature transport function, the bright temperature of zenith when utilizing the sky temperature of microwave radiometer under different zenith angles to calculate zenith angle to be 0 °, substituted the effect as the liquid nitrogen of cold temperature source, saved input cost, and then obtain the value of calibration coefficient by cycle calculations, be applied to the temperature coefficient timing signal to the microwave radiometer noise diode, the temperature that can be good at calibrating noise diode.The present invention only needs a microwave radiometer and a black matrix, and cost is low, and is easy and simple to handle, and precision is high, but and all weather operations.Bright temperature transport function wherein is out of shape, this calibrating method can be extended to linear between the output voltage of receiver and the input noise temperature or be in the Ground-Based Microwave Radiometer of nonlinear relationship, for the profiles such as atmospheric envelope temperature, humidity in real time, efficient, the low-cost detection provide strong support.The present invention can be applicable to the inverting of atmospheric envelope temperature profile, target detection and affirmation, supervision and drawing etc.

Description of drawings

Fig. 1 is the calibrating method process flow diagram that the present invention is used for microwave radiometer.

Fig. 2 is the result schematic diagram that circulates for the first time in the embodiment of the invention calibration process.

Fig. 3 is the result schematic diagram of convergence after Fig. 2 embodiment repeatedly circulates.

Embodiment

Below in conjunction with accompanying drawing and embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, does not limit the present invention.

Fig. 1 is the calibrating method process flow diagram that the present invention is used for microwave radiometer, and the method may further comprise the steps:

Step 1, according to bright temperature transport function, based on bright temperature and the corresponding voltage thereof of reference blackbody, and the initial value of calibration coefficient a, calculating sky temperature corresponding to a plurality of zenith angles, the initial value of wherein said calibration coefficient a is predefined;

Step 2 based on the sky temperature under described a plurality of zenith angles, is calculated each self-corresponding atmosphere overall attenuation value of described a plurality of zenith angle;

Step 3 for secant value and each self-corresponding atmosphere overall attenuation value of described a plurality of zenith angle of described a plurality of zenith angles, is carried out linear regression processing, and take the slope of linear regression processing gained straight line as zenith angle the atmosphere overall attenuation value during as 0 °;

Step 4, the atmosphere overall attenuation value when being 0 ° based on described zenith angle, the sky temperature when the calculating zenith angle is 0 °;

Step 5, the described bright temperature transport function of the sky temperature substitution when described zenith angle is 0 ° solves the value of corresponding calibration coefficient a;

Step 6, as the described initial value in the step 1, repeating step one to five obtains the value of new a with the value of the calibration coefficient a of described correspondence; So circulation, constantly upgrading the value of a, with the value of a after the convergence scaled values as a, calibration is finished.

The method with black matrix as high temperature source, according to bright temperature transport function, the bright temperature of zenith when utilizing the sky temperature of microwave radiometer under different zenith angles to calculate zenith angle to be 0 °, and then calculate corresponding calibration coefficient obtains the value of final calibration coefficient through cycle calculations repeatedly.

Specifically, 1. above-mentioned calibrating method is applied in the Ground-Based Microwave Radiometer linear between the receiver output voltage and input noise temperature, slightly different from the situation in the Ground-Based Microwave Radiometer that is applied to 2. to be nonlinear relationship, below both of these case is described respectively.

1. for Ground-Based Microwave Radiometer linear between receiver output voltage and the input noise temperature, described bright temperature transport function is:

T _sky＝T _ref+G(V _sky-V _ref)f _w

＝T _ref-Gf _wV _ref+Gf _wV _sky

＝a+bV _sky

In the formula, T _RefThe bright temperature of reference blackbody, V _RefThe catoptron of the microwave radiometer voltage when pointing to reference blackbody; T _SkySky temperature, V _SkyThe voltage of catoptron when pointing into the sky, f _wBe the constant relevant with the emissivity of the material that covers the microwave radiometer minute surface, G is the calibration gain; Further, a=T _Ref-Gf _wV _Ref, b=Gf _w, also be

Under the prerequisite of voltage corresponding to the bright gentleness of known reference black matrix, the relation of a and b: a=T _Ref-bV _Ref, b=(T _Ref-a)/V _Ref, a or b are regarded calibration coefficient, a, b can change mutually, and present embodiment is take a as calibration coefficient.

According to bright temperature transport function, the initial value of a given a, then sky temperature value corresponding to different zenith angle θ:

$T_{\mathrm{sky}}\left(\mathrm{\θ}\right)=a+{\mathrm{bV}}_{\mathrm{sky}}\left(\mathrm{\θ}\right)=a+\frac{(T_{\mathrm{ref}}-a)}{V_{\mathrm{ref}}}{V}_{\mathrm{sky}}\left(\mathrm{\θ}\right)$

During zenith angle θ=0 °, the corresponding bright temperature T of zenith _Sky(0 °)=a+bV _Sky(0 °), T _Ref=a+bV _Ref, can be by the bright temperature T of zenith _Sky(0 °) solves a new a value:

This a value back substitution is circulated in bright temperature transport function next time, constantly upgrade a until its convergence, as calibration coefficient accurately, calibration is finished the value of a that obtains.

Again further, the below describes technical scheme of the present invention so that the temperature of microwave radiometer noise diode is calibrated as example.

Under the prerequisite of the bright gentle corresponding voltage of known reference black matrix, ARM(Atmosphere RadiationMeasure, atmosphere radiation is measured) bright temperature computing formula that microwave radiometer provides, namely bright temperature transport function is:

T _sky＝T _ref+G(V _sky-V _ref)f _w （1）

In the formula

G＝T _nd/(V _ref+nd-V _ref) （2）

In the formula, V _Ref+ndThe voltage of radiometer catoptron when pointing to reference blackbody and adding noise diode, T _NdThe temperature of noise diode, although T _NdRelatively stable, but its meeting is along with environmental evolution produces very little change, so T _NdTo need definite calibration coefficient.Here, relate to the calibration coefficient a of an embodiment, have

To a calibrate namely be equivalent to present embodiment to T _NdCalibrate.

So, adopt calibrating method of the present invention, in known first noise source---the bright temperature T of reference blackbody _Ref---prerequisite under, need calculate again second noise source---the bright temperature T of zenith _Sky(0 °) just can solve accurately calibration coefficient T _Nd, concrete computation process is as follows.

Give the calibration coefficient T _NdAn initial value is set, and substitution (1) formula is obtained the bright temperature under the different zenith angles (can choose several bright temperature and differ larger zenith angle):

$T_{\mathrm{sky}}\left(\mathrm{\θ}\right)=T_{\mathrm{ref}}+\frac{T_{\mathrm{nd}}}{(V_{\mathrm{ref}+\mathrm{nd}}-V_{\mathrm{ref}})}(V_{\mathrm{sky}}\left(\mathrm{\θ}\right)-V_{\mathrm{ref}})f_w---\left(3\right)$

With the bright temperature of bright gentle average radiation under each zenith angle that obtains (the bright temperature of average radiation can obtain by itself and the temperature on ground and the statistical relationship of relative humidity) substitution following formula, can obtain the atmosphere overall attenuation under each zenith angle:

${\mathrm{\τ}}_{(0,\∞)}\left(\mathrm{\θ}\right)=\ln \left[\frac{T_m\left(\mathrm{\θ}\right)-2.73}{T_m\left(\mathrm{\θ}\right)-T_{\mathrm{sky}}\left(\mathrm{\θ}\right)}\right]---\left(4\right)$

Herein, formula (4) is zenith angle θ and atmosphere overall attenuation, the bright temperature three's of the bright gentle average radiation of zenith functional relation, the bright temperature T of average radiation _mCan be by the temperature on ground and the statistical relationship of relative humidity be obtained.

Below briefly introduce the derivation of formula (4): this area, the fundamental formular of atmosphere overall attenuation and sky temperature is:

$T_{\mathrm{sky}}{2.73e}^{-\mathrm{\τ}(0,\∞)}+{\∫}_0^{\∞}{k}_e\left(r\right)T\left(r\right)e^{-\mathrm{\τ}(0,r)}\mathrm{dr}---\left(5\right)$

In the formula, r is the distance apart from ground,

Be the atmosphere overall attenuation (or claiming atmosphere optical thickness, the Np of unit) between 0～r, k _eThe body extinction coefficient, the Npm of unit ^-1

The bright temperature T of the average radiation of atmosphere _mBe defined as

Wherein denominator is variable is changed to:

${\∫}_0^{\∞}{k}_e\left(r\right)e^{-\mathrm{\τ}(0,r)}\mathrm{dr}$

$={\∫}_0^{\mathrm{\τ}(0,\∞)}{e}^{-\mathrm{\τ}(0,r)}\mathrm{d\τ}(0,r)$

$=1-e^{-\mathrm{\τ}(0,\∞)}$

Then the bright temperature of zenith can be expressed as the function of atmosphere overall attenuation and average radiation brightness, for:

$T_{\mathrm{sky}}={2.73e}^{-\mathrm{\τ}(0,\∞)}+T_m{\∫}_0^{\∞}{k}_e\left(r\right)e^{-\mathrm{\τ}(0,r)}\mathrm{dr}$

$={2.73e}^{-\mathrm{\τ}(0,\∞)}+T_m[1-e^{-\mathrm{\τ}(0,\∞)}]$

So the atmosphere overall attenuation can be expressed as the function of the bright temperature of the bright gentle average radiation of zenith, i.e. formula (4):

Bright temperature when being 0 ° in order to obtain zenith angle, carry out following calculating:

According to the relation of zenith angle and atmosphere overall attenuation, vertical height is z, and the atmosphere overall attenuation when zenith angle is 0 ° is

And for the uniform atmosphere of level, vertical height is z, and the wrong path electrical path length is r, and the atmosphere overall attenuation when zenith angle is θ is:

Following formula r gets just infinite, obtains:

τ _(0,∞)(θ)＝τ _(0,∞)(0°)sec(θ) （6）

Can be found out that by formula (6) the secant value sec (θ) of atmosphere overall attenuation τ (θ) and zenith angle is linear relationship, crosses initial point by the straight line that linear regression processing obtains, and the atmosphere overall attenuation τ of the slope of this straight line when equaling zenith angle θ and being 0 ° _{(0, ∞)}(0 °) value.

In the reality, the secant value of atmosphere overall attenuation and zenith angle is carried out linear regression, if related coefficient, thinks that linear regression is effective greater than 0.998, then make the atmosphere overall attenuation τ of zenith direction _{(0, ∞)}(0 °) equals its slope, otherwise the weather condition of explanation this moment is relatively poor or be affected by other factors and be not suitable for self calibration.

Atmosphere overall attenuation τ with zenith direction _{(0, ∞)}In (0 °) and the bright temperature substitution of the zenith direction average radiation formula (5), calculate the bright temperature of zenith:

With the bright temperature T of the zenith that obtains _Sky(0 °) substitution formula (1) solves a new T _NdValue:

Then, with this new T _NdValue is to calibration coefficient T _NdUpgrade, repeat said process, constantly upgrade T _Nd, through repeatedly circulating until it is restrained, the T that obtains at last _NdAs calibration coefficient accurately, calibration is finished.

More than, describe the present invention by embodiment and be applied to 1. situation in the Ground-Based Microwave Radiometer linear between the receiver output voltage and input noise temperature, below be the process that is applied to 2. to be in the Ground-Based Microwave Radiometer of nonlinear relationship.

2. for the Ground-Based Microwave Radiometer that is nonlinear relationship between receiver output voltage and the input noise temperature, described bright temperature transport function is:

T _sky＝f(a，V，σ) （8）

Wherein, V represents parameter relevant with voltage in the microwave radiometer, may be a plurality of, and σ represents other parameter in the microwave radiometer, also may be a plurality of, and then the bright temperature value of different zenith angles is:

T _sky(θ)＝f(a，V(θ)，σ)

At calibrating method according to the present invention, when calculating new calibration coefficient by the bright temperature of zenith, with T _SkyBe independent variable, a is dependent variable, and its inverse function is:

a＝f ^-1(T _sky(θ)，V，σ)

The bright temperature substitution of zenith following formula can be obtained new calibration coefficient a=f ^-1(T _Sky(0 °), V (0 °), σ).Follow-up value with new a renewal calibration coefficient repeats said process, constantly upgrades a, is the calibration coefficient value that needs after the convergence.

In addition, calibrating method of the present invention is applied in the dual-frequency microwave radiometer of certain independent development, this radiometer belongs to real-time calibration microwave radiometer, the output equation of radiometer is written as the form of T=a+bV, that is:

$T={\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HDA00002663565700021.png,HDA00002663565700022.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}-\frac{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HDA00002663565700021.png,HDA00002663565700022.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}-{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA00002663565700021.png,HDA00002663565700022.png"\; state="\{\{state\}\}">T</figure-callout>}}_2^{\&prime;}}{V_1-V_2}{\mathrm{<figure-callout\; id="1"\; label="V"\; filenames="HDA00002663565700021.png,HDA00002663565700022.png"\; state="\{\{state\}\}">V</figure-callout>}}_1+\frac{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HDA00002663565700021.png,HDA00002663565700022.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}-{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA00002663565700021.png,HDA00002663565700022.png"\; state="\{\{state\}\}">T</figure-callout>}}_2^{\&prime;}}{V_1-V_2}V=a+\mathrm{bV}$

In the formula

T and V are respectively the bright gentle corresponding voltage that this antenna for radiometer receives, and it can utilize calibrating method of the present invention that calibration coefficient a or b are calibrated calibration.

The bright temperature data of emulation that below will survey by experiment bright temperature data and sounding contrast, and have verified the validity of this calibrating method.

Certain dual-frequency microwave radiometer is placed tall building roof field all around, the zenith angle that (positive north) is chosen at 0 ° of position angle during calibration is 0 °, 45 °, 60 °, for the compensation apparatus lateral error, two equal zenith angles have been increased at 180 ° of position angles again, 45 °, 60 °; The frequency of present embodiment is 23.8GHz.Aspect the selection of zenith angle, consider that the side lobe effect at the low elevation angle is larger on the impact of bright temperature measurement, should guarantee that any two differ 15 ° at least in the selected zenith angle, maximum zenith angle is no more than 70 °.

Fig. 2 is the result of circulation for the first time in the calibration process, and horizontal ordinate is the secant value of zenith angle, the atmosphere overall attenuation value that the circle representative is calculated by initial five bright temperature of zenith angle, and straight line is the figure line after the linear regression, figure line initial point only among Fig. 1.

Fig. 3 is the afterwards result of convergence that repeatedly circulates, and figure line is near initial point, and calibration finishes.The related coefficient of final regression curve is 0.9983, satisfies the requirement (related coefficient is greater than 0.998) of effective self calibration.

Table 1 is the comparing data of surveying the bright temperature of emulation of bright temperature and Qingdao sounding before and after this dual-frequency microwave radiometer calibration on Dec 10th, 2011.Relatively calibrate the difference of front and back bright temperature that radiometer is surveyed, can find out the validity of calibrating method of the present invention.

The comparison of the table 1 bright temperature of actual measurement and the bright temperature of emulation

In sum, calibrating method provided by the invention only needs a microwave radiometer and a black matrix, be applicable to the calibration of general Ground-Based Microwave Radiometer, cost is low, easy and simple to handle, precision is high, but and all weather operations, can be applicable to the fields such as the inverting of atmospheric envelope temperature profile, target detection and affirmation, supervision, drawing.

Although be the example purpose, the preferred embodiments of the present invention are disclosed, it also is possible those skilled in the art will recognize various improvement, increase and replacement, therefore, scope of the present invention should be not limited to above-described embodiment.

Claims (8)

1. a calibrating method that is used for microwave radiometer is characterized in that, comprising:

Step 1, according to bright temperature transport function, based on bright temperature and the corresponding voltage thereof of reference blackbody, and the initial value of calibration coefficient a, calculating sky temperature corresponding to a plurality of zenith angles, the initial value of wherein said calibration coefficient a is predefined;

Step 2 based on the sky temperature under described a plurality of zenith angles, is calculated each self-corresponding atmosphere overall attenuation value of described a plurality of zenith angle;

Step 3 for secant value and each self-corresponding atmosphere overall attenuation value of described a plurality of zenith angle of described a plurality of zenith angles, is carried out linear regression processing, and take the slope of linear regression processing gained straight line as zenith angle the atmosphere overall attenuation value during as 0 °;

Step 4, the atmosphere overall attenuation value when being 0 ° based on described zenith angle, the sky temperature when the calculating zenith angle is 0 °;

Step 5, the described bright temperature transport function of the sky temperature substitution when described zenith angle is 0 ° solves the value of corresponding calibration coefficient a;

Step 6, as the described initial value in the step 1, repeating step one to five obtains the value of new a with the value of the calibration coefficient a of described correspondence; So circulation, constantly upgrading the value of a, with the value of a after the convergence scaled values as a, calibration is finished.

2. the calibrating method for microwave radiometer as claimed in claim 1 is characterized in that, described bright temperature transport function is T _Sky=T _Ref+ G (V _Sky-V _Ref) f _w, wherein, T _RefThe bright temperature of reference blackbody, V _RefThe catoptron of the microwave radiometer voltage when pointing to reference blackbody; T _SkySky temperature, V _SkyThe voltage of catoptron when pointing into the sky, f _wBe the constant relevant with the emissivity of the material that covers the microwave radiometer minute surface, G is the calibration gain, $G=\frac{T_{\mathrm{ref}}-a}{f_w{V}_{\mathrm{ref}}}.$

3. the calibrating method for microwave radiometer as claimed in claim 2 is characterized in that, wherein, $G=\frac{T_{\mathrm{nd}}}{V_{\mathrm{ref}+\mathrm{nd}}-V_{\mathrm{ref}}},$ Then $a=T_{\mathrm{ref}}-\frac{T_{\mathrm{nd}}\&CenterDot;f_w\&CenterDot;V_{\mathrm{ref}}}{V_{\mathrm{ref}+\mathrm{nd}}-V_{\mathrm{ref}}};$ Wherein, V _Ref+ndThe voltage of microwave radiometer catoptron when pointing to reference blackbody and adding noise diode, T _NdThe temperature of noise diode, the temperature T of noise diode _NdWith the environmental change change, a calibrated be equivalent to T _NdCalibrate.

4. the calibrating method for microwave radiometer as claimed in claim 1 is characterized in that, described bright temperature transport function is T _Sky=f (a, V, σ), wherein, V represents parameter relevant with voltage in the microwave radiometer, and σ represents other parameter in the microwave radiometer.

5. the calibrating method for microwave radiometer as claimed in claim 1, it is characterized in that, in the step 2, according to the funtcional relationship of zenith angle, sky temperature, the bright temperature of average radiation and atmosphere overall attenuation, calculate each self-corresponding atmosphere overall attenuation value of described a plurality of zenith angle.

6. the calibrating method for microwave radiometer as claimed in claim 1, it is characterized in that, in the step 4, the funtcional relationship of the atmosphere overall attenuation value when being 0 ° according to sky temperature and described zenith angle, the bright temperature of average radiation when zenith angle is 0 °, the sky temperature when calculating described zenith angle and being 0 °.

7. the calibrating method for microwave radiometer as claimed in claim 1 is characterized in that, any two in described a plurality of zenith angles differ 15 ° at least.

8. the calibrating method for microwave radiometer as claimed in claim 1 is characterized in that, any is no more than 70 ° in described a plurality of zenith angles.

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