CN113340281B - A Method of Passively Measuring Earth's Orbit Eccentricity Using Microwave Radiometer - Google Patents

Abstract

The invention discloses a method for measuring the eccentricity of the earth's orbit by passively measuring the relationship between solar radiation and the distance between the sun and the earth by using a microwave radiometer. The measurement of the eccentricity of the earth's orbital orbit can be realized without other test instruments and special test environments. The technology of measuring the eccentricity of the earth's orbit by passively measuring the solar radiation with the microwave radiometer avoids complicated astronomical calculations and instrumental observation, and the eccentricity of the earth's orbit can be directly measured only by automatically tracking and observing the sun through the microwave radiometer.

Description

A Method for Passively Measuring Earth Orbit Eccentricity Using Microwave Radiometer

【Technical field】

The invention belongs to the field of passive microwave remote sensing detection, and in particular relates to a method for passively measuring the eccentricity of an earth orbit by using a microwave radiometer.

【Background technique】

The change of the eccentricity of the earth's orbit has a significant effect on the elliptical orbit of the earth's revolution, resulting in a small periodic change in the distance between the sun and the earth. In recent years, the study of climate has found that the periodic oscillation of the Earth's orbital eccentricity often corresponds to some important events of climate change. In addition, the Earth's orbital eccentricity has a certain influence on the design of satellite orbit parameters and astronomical observations. Therefore, the monitoring of the Earth's orbit eccentricity is an important task. Nowadays, the eccentricity of Earth's orbit is generally obtained through astronomical telescope observation and complex astronomical calculations. This observation and calculation method requires high equipment and technical level, and the calculation is relatively complicated. Moreover, these equipment are difficult for ordinary people to access, which is not conducive to our long-term observation and calculation. Monitor changes in Earth's orbital eccentricity.

[Content of the invention]

In view of the above problems, the present invention provides a method for passively measuring the eccentricity of the earth's orbit by using a microwave radiometer. The method not only avoids complex astronomical calculations and observations, but also has low requirements on the observation environment and is easy to implement, and can realize automatic measurement and long-term monitoring. , the technology not only realizes the monitoring of the eccentricity of the earth's orbit, but also expands the application field of microwave radiometers.

The present invention is achieved through the following technical solutions, and provides a method for passively measuring the eccentricity of the earth's orbit by using a microwave radiometer, comprising the following steps:

S1 calculates the sun azimuth and altitude in real time;

S2 controls the turntable to make the antenna point to the sun, and the turntable is an azimuth and pitch turntable;

S3 fixes the antenna elevation angle, controls the microwave radiometer turntable antenna to point to the center of the sun by stepping, controls the azimuth turntable to rotate the antenna to scan the sun, and observes the brightness temperature in all directions;

S4 moves the antenna azimuth so that the sun is not in the antenna beam, controls the antenna elevation to scan the sky, and uses the elevation sky scan data to calculate the atmospheric attenuation at each elevation angle;

S5 calibrates atmospheric attenuation, and calculates the radiation brightness temperature of the observed solar radiation reaching the antenna when there is no atmospheric attenuation;

S6 calculates the Earth orbit eccentricity according to S4 and S5.

In particular, the S1 calculates the solar azimuth angle _Az and the altitude angle E1 according to the relationship between the sun-earth orbit, and is specifically calculated according to the following formula:

T ₀ =(t _s -12)·15°(1),

E _l =arcsin( _sinθlat sinδ+cosδcosT ₀ )(2),

In formula (1), t _s is the solar hour angle, in formula (2) and formula (3), δ is the declination of the sun, and θ _lat is the latitude where the microwave antenna is located.

In particular, the azimuth turntable in the S3 rotates the antenna to scan the sun within an angle of -10° to 10°.

In particular, the brightness temperature in S3 includes the brightness temperature of solar radiation reaching the antenna through atmospheric attenuation and atmospheric radiation brightness temperature. When the sun is in the antenna beam, the brightness temperature observed by the antenna is calculated according to the following formula:

When the sun is not in the beam, the brightness temperature when observing the sky is calculated according to the following formula:

The brightness temperature of the solar radiation reaching the antenna and being received is obtained by subtracting the formula (4) and the formula (5), and the following formula is obtained after sorting:

为天线方位角，θ为俯仰角，Ω_S为太阳波束立体角，Ω_A为天线波束立体角,T_m为大气平均辐射温度，T_bg＝2.75K为宇宙背景辐射亮温，T_sun为太阳平均辐射亮温，τ(θ)为天线指定角度的大气厚度。In formula (4)-formula (6), the

is the azimuth angle of the antenna, θ is the elevation angle, Ω _S is the solid angle of the solar beam, Ω _A is the solid angle of the antenna beam, T _m is the average radiation temperature of the atmosphere, T _bg = 2.75K is the brightness temperature of the cosmic background radiation, and T _sun is the sun The mean radiant brightness temperature, τ(θ) is the thickness of the atmosphere at the specified angle of the antenna.

In particular, the atmospheric attenuation in the S4 is calculated according to the following formula:

The thickness of the atmosphere at the specified angle of the antenna is calculated according to the following formula:

In particular, the S5 is specifically implemented as follows:

Bringing formula (7) into formula (6) for atmospheric attenuation calibration, after sorting out the following formula, the brightness temperature of solar radiation without atmospheric attenuation reaching the antenna can be obtained by calculation,

In formula (8), x and y are the angular distances between the center of the antenna beam and the center of the sun in the azimuth and elevation directions.

In particular, the S6 is specifically implemented as follows:

After S61 rotates and scans the S3 antenna around the sun, the antenna pattern is obtained. The antenna scan pattern is expressed as a Gaussian antenna model function as follows:

In formula (9), θ is the beam width of the antenna, and A _d is the brightness temperature observed by the radiometer aiming at the center of the sun;

S62 calculates the brightness temperature observed by the radiometer aiming at the sun, first calculate the sun solid angle Ω _s according to the following formula:

Ω _s = 2π(1-cosθ)(10),

In formula (10), due to the long distance between the sun and the earth, the sun angle θ is calculated according to the following formula:

In formula (11), r is the radius of the sun, and d is the distance between the sun and the earth;

In summary, the antenna solid angle is calculated according to the following formula:

After putting Equation (12) into Equation (8), the brightness temperature ΔT _sun observed by the radiometer aiming at the sun is obtained:

和远日点的亮温

S63 calculates the brightness temperature of the sun at perihelion according to the brightness temperature ΔT _sun observed by the radiometer aiming at the sun

and the brightness temperature of the aphelion

In formula (14) and formula (15), c is the focal length of the earth's orbit, a is the long semi-axis of the earth, a-c is the sun-earth distance of the sun at perihelion, and a+c is the sun-earth distance of the sun at aphelion ;

S64 Earth orbit eccentricity calculation:

The ratio M of formula (14) and formula (15) is as follows:

Divide the numerator and denominator on the right side of formula (16) by a to obtain the following formula:

The Earth orbit eccentricity e can be calculated by arranging formula (17):

The invention provides a method for passively measuring the eccentricity of the earth's orbit by using a microwave radiometer, which has the following beneficial effects:

1) Compared with the traditional astronomical observation, the present invention adopts low requirements on the environment, and can realize the measurement of the eccentricity of the earth's orbit without other precise testing instruments, which not only has the same results as the theoretical calculation, but also reduces the complexity of the observation. ;

2) The present invention utilizes the microwave radiometer itself to realize the measurement of the eccentricity of the earth's orbit, and the calculation process is simple and the results are accurate and rapid;

3) The present invention can be used for monitoring changes in solar radiation, and expands the application field of microwave radiometers.

【Description of drawings】

Fig. 1 is the schematic diagram that adopts microwave radiometer to observe the sun;

Fig. 2 is the result of scanning solar radiation brightness temperature using microwave radiometer;

Fig. 3 is the result graph that utilizes Gaussian function model to fit sun scanning data;

Figure 4. The results of the solar radiation brightness temperature observed by the radiometer near the perihelion and aphelion.

【Detailed ways】

In the present invention, the azimuth scanning refers to that the microwave radiometer antenna has a fixed elevation angle, and only the antenna azimuth turntable is rotated for observation. In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments.

In the following, the solar scanning observation experiment was carried out using the MWP967KV ground-based multi-channel microwave radiometer located at the Qinling Atmospheric Science Experiment Base in Xi'an.

1-4, the present invention provides a method for passively measuring the eccentricity of the earth's orbit by using a microwave radiometer, including the following steps:

S1 calculates the sun's azimuth and altitude in real time according to the relationship between the sun and the earth's orbit. Specifically, it is calculated according to the following formula:

Calculate the solar azimuth angle A _Z and the altitude angle El, specifically according to the following formula:

T ₀ =(t _s -12)·15°(1),

E _l =arcsin( _sinθlat sinδ+cosδcosT ₀ )(2),

In formula (1), t _s is the solar hour angle, in formula (2) and formula (3), δ is the declination of the sun, and θ _lat is the latitude where the microwave antenna is located.

S2 controls the turntable, which is the azimuth and pitch turntable, so that the antenna points to the sun.

S3 fixes the antenna elevation angle, controls the microwave radiometer turntable antenna to point to the center of the sun by stepping, controls the azimuth turntable to rotate the antenna at an angle of -10° to 10° to scan the sun, and observes the brightness temperature in all directions, which includes solar radiation The brightness temperature reaching the antenna through atmospheric attenuation and atmospheric radiation brightness temperature, when the sun is in the antenna beam, the brightness temperature observed by the antenna is calculated according to the following formula:

When the sun is not in the beam, the brightness temperature when observing the sky is calculated according to the following formula:

The brightness temperature of the solar radiation reaching the antenna and being received is obtained by subtracting the formula (4) and the formula (5), and the following formula is obtained after sorting:

为天线方位角，θ为俯仰角，Ω_S为太阳波束立体角，Ω_A为天线波束立体角,T_m为大气平均辐射温度，T_bg＝2.75K为宇宙背景辐射亮温，T_sun为太阳平均辐射亮温，τ(θ)为天线指定角度的大气厚度。In formula (4)-formula (6), the

is the azimuth angle of the antenna, θ is the elevation angle, Ω _S is the solid angle of the solar beam, Ω _A is the solid angle of the antenna beam, T _m is the average radiation temperature of the atmosphere, T _bg = 2.75K is the brightness temperature of the cosmic background radiation, and T _sun is the sun The mean radiant brightness temperature, τ(θ) is the thickness of the atmosphere at the specified angle of the antenna.

S4 moves the antenna azimuth (greater than 10°) so that the sun is not in the antenna beam, and controls the antenna elevation to scan the sky. Due to the scanning time, atmospheric changes during the scanning process can be ignored, and the elevation sky scan data is used to calculate the atmospheric attenuation at each elevation angle , the atmospheric attenuation is calculated according to the following formula:

S5 calibrates the atmospheric attenuation and calculates the radiation brightness temperature of the observed solar radiation reaching the antenna when there is no atmospheric attenuation. The calculation is performed as follows:

Bringing formula (7) into formula (6) for atmospheric attenuation calibration, after sorting out the following formula, the brightness temperature of solar radiation without atmospheric attenuation reaching the antenna can be obtained by calculation,

In formula (8), x and y are the angular distances between the center of the antenna beam and the center of the sun in the azimuth and elevation directions.

S6 calculates the Earth's orbital eccentricity as follows:

After S61 rotates and scans the S3 antenna around the sun, the antenna pattern is obtained. The antenna scan pattern is expressed as a Gaussian antenna model function as follows:

In formula (9), θ is the beam width of the antenna, and A _d is the brightness temperature observed by the radiometer aiming at the center of the sun;

S62 calculates the brightness temperature observed by the radiometer aiming at the sun, first calculate the sun solid angle Ω _s according to the following formula:

Ω _s = 2π(1-cosθ)(10),

In formula (10), due to the long distance between the sun and the earth, the sun angle θ is calculated according to the following formula:

In formula (11), r is the radius of the sun, and d is the distance between the sun and the earth;

In summary, the antenna solid angle is calculated according to the following formula:

After putting Equation (12) into Equation (8), the brightness temperature ΔT _sun observed by the radiometer aiming at the sun is obtained:

和远日点的亮温

S63 calculates the brightness temperature of the sun at perihelion according to the brightness temperature ΔT _sun observed by the radiometer aiming at the sun

and the brightness temperature of the aphelion

In formula (14) and formula (15), c is the focal length of the earth's orbit, a is the long semi-axis of the earth, a-c is the sun-earth distance of the sun at perihelion, and a+c is the sun-earth distance of the sun at aphelion ;

S64 Earth orbit eccentricity calculation:

The ratio M of formula (14) and formula (15) is as follows:

Divide the numerator and denominator on the right side of formula (16) by a to obtain the following formula:

The Earth orbit eccentricity e can be calculated by arranging formula (17):

In the present invention, the observation time is at the beginning of January (near the perihelion) and at the beginning of July (near the aphelion) of each year, and the brightness temperature is observed respectively, and the calculation is performed as above according to the observed data.

Changes in radiation due to changes in the distance of the sun during the day are small and negligible. In addition, the observation data processing should try to avoid using the data during the sunspot outburst. Therefore, in order to reduce the observation error, multiple observations can be made in one day to obtain the average value, as shown in Figure 4. The radiometer can observe the change of solar radiation caused by the change of the distance between the sun and the earth. The statistical calculation results are shown in Table 1. The calculated Earth orbit eccentricity of 0.0169 is consistent with the 0.0167 calculated by astronomical theory.

Table 1 Statistical Results of Observation and Calculation

Claims (7)

1. a method utilizing microwave radiometer to passively measure earth orbit eccentricity, is characterized in that, comprises the following steps: S1 calculates the sun azimuth and altitude in real time; S2 controls the turntable to make the antenna point to the sun, and the turntable is an azimuth and pitch turntable; S3 fixes the antenna elevation angle, controls the microwave radiometer turntable antenna to point to the center of the sun by stepping, controls the azimuth turntable to rotate the antenna to scan the sun, and observes the brightness temperature in all directions; S4 moves the antenna azimuth so that the sun is not in the antenna beam, controls the antenna elevation to scan the sky, and uses the elevation sky scan data to calculate the atmospheric attenuation at each elevation angle; S5 calibrates atmospheric attenuation, and calculates the radiation brightness temperature of the observed solar radiation reaching the antenna when there is no atmospheric attenuation; S6 calculates the Earth orbit eccentricity according to S4 and S5. 2. a kind of method utilizing microwave radiometer to passively measure earth orbit eccentricity according to claim 1, is characterized in that, described S1 calculates solar azimuth angle A _Z and altitude angle E _l according to sun-earth orbit relation, concrete Calculate according to the following formula: T ₀ =(t _s -12)·15° (1), E _l =arcsin(sinθ _lat sinδ+cosδcosT ₀ ) (2),

In formula (1), t _s is the solar hour angle, in formula (2) and formula (3), δ is the declination of the sun, and θ _lat is the latitude where the microwave antenna is located. 3 . The method for passively measuring the eccentricity of the earth's orbit using a microwave radiometer according to claim 1 , wherein the azimuth turntable in the S3 rotates the antenna to scan the sun within an angle of -10° to 10°. 4 . 4. a kind of method utilizing microwave radiometer to passively measure earth orbit eccentricity according to claim 2, is characterized in that, in described S3, the brightness temperature comprises the brightness temperature of solar radiation reaching the antenna through atmospheric attenuation, and the atmospheric radiation brightness temperature, When the sun is in the antenna beam, the brightness temperature observed by the antenna is calculated according to the following formula:

When the sun is not in the beam, the brightness temperature when observing the sky is calculated according to the following formula:

The brightness temperature of the solar radiation reaching the antenna and being received is obtained by subtracting the formula (4) and the formula (5), and the following formula is obtained after sorting:

In formula (4)-formula (6), the

is the azimuth angle of the antenna, θ is the elevation angle, Ω _S is the solid angle of the solar beam, Ω _A is the solid angle of the antenna beam, T _m is the average radiation temperature of the atmosphere, T _bg = 2.75K is the brightness temperature of the cosmic background radiation, and T _sun is the sun The mean radiant brightness temperature, τ(θ) is the thickness of the atmosphere at the specified angle of the antenna. 5. a kind of method utilizing microwave radiometer to passively measure earth orbit eccentricity according to claim 4, is characterized in that, in described S4, atmospheric attenuation is calculated by following formula: The thickness of the atmosphere at the specified angle of the antenna is calculated according to the following formula:

6. a kind of method utilizing microwave radiometer to passively measure earth orbit eccentricity according to claim 5, is characterized in that, described S5 is specifically implemented as follows: Bringing formula (7) into formula (6) for atmospheric attenuation calibration, after sorting out the following formula, the brightness temperature of solar radiation without atmospheric attenuation reaching the antenna can be obtained by calculation,

In formula (8), x and y are the angular distances between the center of the antenna beam and the center of the sun in the azimuth and elevation directions. 7. a kind of method utilizing microwave radiometer to passively measure earth orbit eccentricity according to claim 6, is characterized in that, described S6 is specifically implemented as follows: After S61 rotates and scans the S3 antenna around the sun, the antenna pattern is obtained. The antenna scan pattern is expressed as a Gaussian antenna model function as follows:

In formula (9), θ is the beam width of the antenna, and A _d is the brightness temperature observed by the radiometer aiming at the center of the sun; S62 calculates the brightness temperature observed by the radiometer aiming at the sun, first calculate the sun solid angle Ω _s according to the following formula: Ω _s = 2π(1-cosθ) (10), In formula (10), due to the long distance between the sun and the earth, the sun angle θ is calculated according to the following formula:

In formula (11), r is the radius of the sun, and d is the distance between the sun and the earth; In summary, the antenna solid angle is calculated according to the following formula:

After putting Equation (12) into Equation (8), the brightness temperature ΔT _sun observed by the radiometer aiming at the sun is obtained:

S63 calculates the brightness temperature of the sun at perihelion according to the brightness temperature ΔT _sun observed by the radiometer aiming at the sun

and the brightness temperature of the aphelion

In formula (14) and formula (15), c is the focal length of the earth's orbit, a is the long semi-axis of the earth, a-c is the sun-earth distance of the sun at perihelion, and a+c is the sun-earth distance of the sun at aphelion ; S64 Earth orbit eccentricity calculation: The ratio M of formula (14) and formula (15) is as follows:

Divide the numerator and denominator on the right side of formula (16) by a to obtain the following formula:

The Earth orbit eccentricity e can be calculated by arranging formula (17):

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