RU2018104C1 - Method of determination of profile of attenuation factor in specified section of atmosphere - Google Patents

Abstract

FIELD: optical detection and ranging. SUBSTANCE: sending of light pulses of different duration is accomplished from not less than three points confined between boundary points of specified section of atmosphere along this section. Echoes are received from same volumes of atmosphere and are differentiated by duration of pulses. EFFECT: enhanced accuracy of determination of attenuation factor. 1 dwg

Description

 The invention relates to optical location and can be used to determine the profile of the coefficient of attenuation of the atmosphere.

 Known methods for determining the profile of the attenuation coefficient in a given section of the atmosphere [1 and 2].

 According to the method [1], sounding is performed by sending a light pulse of short duration to the atmosphere, converting the light scattered in the opposite direction into electrical signals and accumulating these signals for a certain time, depending on the total length of the investigated section with an increase in the gain of the received signals in proportion to the square of the current time, counted from the moment of sending a pulse to the atmosphere.

 The method makes it possible to determine the profile of the attenuation coefficient with insufficient accuracy, since it involves the constancy of the ratio of the backscattering coefficient to the attenuation coefficient on the sensing path, which is not performed in a real atmosphere. In addition, the lack of accuracy of the method is due to the fact that using real equipment it is possible to send probing pulses of finite duration.

 According to the method [2], the profile of the attenuation coefficient in a given section of the atmosphere is determined by sending light pulses of different duration to the atmosphere and receiving radiation scattered in the opposite direction from the measured powers of the received echo signals for each duration of the probe pulse.

 The method makes it possible to determine the profile of the attenuation coefficient with insufficient accuracy, since it assumes the equality of the backscattering coefficients averaged over the spatial extent of pulses of different durations, which is not performed in a real atmosphere.

 The purpose of the invention is to increase the accuracy of determining the profile of the attenuation coefficient in a given section of the atmosphere.

ln

-

ln

, где S(r_iR) =

τ - длительность зондирующего импульса;
r_i - точки посылки импульсов;
Р(r_i, R) - измеренные мощности от объема атмосферы с координатой R;
А - лидарная постоянная;
f - геометрический фактор;
с - скорость света.To this end, in the method for determining the profile of the attenuation coefficient in a given section of the atmosphere, including sending into the atmosphere light pulses of various durations and receiving for each duration of radiation scattered in the opposite direction, probe pulses are sent from three or more points located between the boundary points of a given section of the atmosphere, in the direction along this section, measuring the power of the echo signals from the same atmospheric volumes, differentiate the measured power values by the impulse duration of ice, and the attenuation coefficient σ at the point r of a given section is determined by the formula
σ (r) =

ln

-

ln

where S (r _i R) =

τ is the duration of the probe pulse;
r _i - point sending pulses;
P (r _i , R) - measured power from the volume of the atmosphere with the coordinate R;
A is the lidar constant;
f is the geometric factor;
c is the speed of light.

The drawing shows a diagram that implements a method for three points of sending probe pulses located at these points by lidars, which is possible for given sections [r ^l , r ^ll ], for which the linear approximation σ (r) = a + br is valid, for approximations more high order is required to send probing pulses from a larger number of points.

f(r-r_i)β(r)exp

-2

(l)dl

dr,
(1) где β - коэффициент обратного рассеяния;
l - переменная интегрирования.The measured powers are related to the optical characteristics of the atmosphere by the optical-location equation
P (r _i , R, τ) =

f (rr _i ) β (r) exp

-2

(l) dl

dr
(1) where β is the backscattering coefficient;
l is the integration variable.

=

f(R-r_i)β(R)exp

-2

(r)dr

.Differentiation of the measured power with respect to the pulse duration (it should be noted that the lidar constant is proportional to the pulse duration) leads to a simpler ratio in which the coefficient β appears at only one point R;

=

f (Rr _i ) β (R) exp

-2

(r) dr

.

r $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ -r

b =

ln

(3)
(r₃-r₁)a +

r $\genfrac{}{}{0ex}{}{\text{2}}{\text{3}}$ -r

b =

ln

(4)
Следует отметить, что величина σ зависит от переменной r и не зависит от переменной R, поэтому значение R может быть любым в пределах дальности зондирования (рационально также выбрать его вне ближней зоны лидара, где известна функция f(R - r_i) = (R - r_i ^-2).(2)
This circumstance allows us to exclude this unknown quantity by dividing equation (2) on top of each other for two points of sending probe pulses. And taking into account when integrating the coefficient σ the linearity of the approximation, considered as an example, makes it possible to obtain a system of equations for determining the unknown coefficients a, b, writing them for two pairs of sending points
(r ₂ -r ₁ ) a +

r $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ -r

b =

ln

(3)
(r ₃ -r ₁ ) a +

r $\genfrac{}{}{0ex}{}{\text{2}}{\text{3}}$ -r

b =

ln

(4)
It should be noted that the value of σ depends on the variable r and does not depend on the variable R, therefore, the value of R can be any within the sensing range (it is also rational to choose it outside the near zone of the lidar, where the function f (R - r _i ) = (R - r _i ^-2 ).

ln

-

ln

.The solution of the system of equations (3) and (4) makes it possible to obtain the formula for determining the attenuation coefficient
σ (r) =

ln

-

ln

.

 (5)

Claims (1)

THE METHOD FOR DETERMINING THE PROBLEM OF THE ATTENUATION RATIO AT A SPECIFIED AREA OF THE ATMOSPHERE, which consists in sending light pulses of different duration to the atmosphere, receiving for each duration of radiation scattered in the opposite direction, and measuring the power of the received echo signals when determining the profile of the attenuation coefficient, characterized in that sounding pulses from three or more points located between the boundary points of a given section of the atmosphere, in the direction along this section, the power received echo the cores are measured from the same atmospheric volumes, the measured power values are differentiated by the pulse duration, and the attenuation coefficient σ at the point r of a given atmospheric section is determined by the formula
σ (r) =

ln

-

ln

,,
Where
S (r _i R) =

^; ;
τ is the duration of the probe pulse;
r _i - point sending pulses;
P (r _i , R) - measured power from the volume of the atmosphere with the coordinate R;
A is the lidar constant;
f is the geometric factor;
c is the speed of light.

Images