RU2789346C1 - Method for determining laser radiation intensity on a spherical space object - Google Patents

Abstract

FIELD: measuring technology.

SUBSTANCE: invention relates to the field of measuring technology and relates to a method for determining the intensity of laser radiation on a spherical space object. The method includes laser radiation probing of a diffusely reflecting space object with a phase function that is minimally different from the phase function of a diffusely reflecting ball, the linear dimensions of which do not exceed the diameter of the laser radiation profile on the space object. In this case, the space object is illuminated by the Sun so that between the direction from the space object to the Sun and the direction from the space object to the laser source, a minimum phase angle is provided that does not exceed 10°. In this case, the intensity of the laser and solar radiation reflected from the space object is recorded. According to the results obtained, the intensity of the laser radiation of the source on the space object is calculated.

EFFECT: ensuring the possibility of determining the intensity of laser radiation on space objects located outside the atmosphere, without placing recording equipment and reflectors on them.

3 cl, 3 dwg

Description

This invention relates to photonics, in particular, to a method for measuring the parameters of laser radiation, and can be used to determine the intensity of probing laser radiation on a space object (hereinafter referred to as SC) not equipped with special reflectors.

An important characteristic of a laser location station (hereinafter referred to as LLS) is the intensity of the laser radiation generated by it (hereinafter LI) at the CO. Knowing only the light intensity (power and divergence) of the probing laser radiation is not enough to determine the intensity at the SO, since errors in pointing the LI at the SO are possible, when passing through the Earth's atmosphere, random changes in the power density over the beam cross section, its effective diameter and a shift in its center of gravity occur. relative to the optical axis (wavefront distortion).

The task to be solved by the claimed invention is to create a method for determining the intensity of laser radiation on a spherical space object not equipped with special reflectors.

From the existing level of technology, similar developments aimed at solving this problem have not been identified.

As a result of a patent information search, a method was revealed for measuring the power of laser radiation propagating in the surface atmosphere at a distance of -1 km [1], which consists in propagating along the path the radiation of a pulsed laser with an angular divergence of the order of 10 ^-6 rad, at the opposite end a triple prism is placed in the laser beam, which acts as a corner reflector and returns radiation back, and the radiation reflected from the prism is recorded by a receiver combined with the radiation source, while the transmission coefficient of laser radiation by the atmosphere is calculated by calculation based on the model of phase screens.

This method is intended only for ground-based experiments, when the triple-prism is located on the Earth's surface and is stationary.

The technical result of the claimed invention consists in making it possible to determine the intensity of laser radiation on space objects located outside the atmosphere, without placing recording equipment and reflectors on them.

лазерного излучения источника на космическом объекте по формуле:The specified technical result in the method for determining the intensity of laser radiation on a space object is achieved by the fact that it includes probing a space object with laser radiation with a divergence known in order of magnitude and a generated laser source operating in a continuous or repetitively pulsed mode, while choosing a space object with a phase a function that is minimally different from the phase function of a diffusely reflecting ball, while all structural elements of the space object reflect radiation only diffusely, and its linear dimensions do not exceed the diameter of the laser radiation profile on the space object, while the space object is illuminated by the Sun so that between the direction from the space object on the Sun and the direction from the space object to the laser source provides a minimum phase angle Ψ not exceeding 10°, after which the intensity of the laser and solar radiation reflected from the space object is recorded, d For this purpose, on the surface of the Earth at a distance L from the laser source, a receiving system is installed that registers the reflected laser radiation and the reflected solar radiation, and the intensity is determined by calculation

laser radiation source on a space object according to the formula:

- величина спектральной интенсивности солнечного излучения на КО на длине волны ЛИ; Δλ₁ - эквивалентная ширина рабочего спектрального диапазона фотоприемника, регистрирующего отраженного ЛИ; Ф - фаза солнечной подсветки КО;

- интенсивность отраженного ЛИ на Земле,

- интенсивность отраженного солнечного излучения на Земле в спектральном диапазоне работы фотоприемника, регистрирующего отраженное ЛИ.Where

- the magnitude of the spectral intensity of solar radiation on the CR at the wavelength of the LI; Δλ ₁ - equivalent width of the working spectral range of the photodetector, registering the reflected LI; Ф - phase of solar illumination of KO;

is the intensity of the reflected LI on the Earth,

- the intensity of the reflected solar radiation on the Earth in the spectral range of the photodetector, which registers the reflected LR.

In addition, when the laser source is operating in continuous mode, the distance L can be selected from the condition 100 m ≤ L ≤ 10 km, and the registration of reflected solar radiation can be performed in the spectral range centered on the wavelength λ ₂ determined based on the condition

When the laser source operates in the repetitively pulsed mode, the distance L can be selected from the condition 0 m≤L≤10 km, and the registration of the reflected solar radiation can be performed in the spectral range centered on the wavelength λ ₁ , and for the selection of the repetitively repetitive laser signal from a mixture with a continuous signal of reflected solar radiation, temporal filtering is used.

The influence of the features of the method on the above technical result.

Probing a spherical CO with radiation generated by a laser source operating in a continuous or repetitively pulsed mode makes it possible to deliver radiation to the CO and then determine its intensity at the CO.

Illumination of the SO by the Sun makes it possible to estimate the equivalent scattering surface (hereinafter ESR) of the SO from the reflected solar radiation.

Knowing the LR divergence in order of magnitude makes it possible to choose CRs with linear dimensions that certainly do not exceed the LR profile diameter on the CR, to bring the uniformity of laser illumination of the CR surface closer to the uniformity of solar illumination. An increase in the uniformity of the laser illumination when choosing a SO that reflects radiation only diffusely makes it possible to calculate the LR intensity on the SO based on the EPR estimation of the SO made in solar radiation. Sounding of SO with a phase function that is minimally different from the phase function of a diffusely reflecting ball, at solar illumination phase angles Ψ<10°, makes it possible to estimate the error in determining the LR intensity on the SO associated with the actual difference in the solar illumination phase of the selected SO from the solar illumination phase of the diffuse ball.

On the Earth's surface, the displacement of the receiving system from the laser source by a distance L, determined from the conditions 0 m≤L≤10 km (with repetitively repetitive LR) and 100 m≤L≤10 km (with continuous LR) makes it possible to eliminate the effect of LR backscatter interference in the Earth's atmosphere on the process of registration of the reflected LR.

Determining the intensity of laser radiation at the CO by calculation allows one to indirectly determine the intensity at the CO without the use of measuring equipment at the CO.

при работе лазерного источника в непрерывном режиме, позволяет минимизировать связанную с неизвестным цветом ошибку пересчета ЭПР КО.The choice of the center of the spectral range of the background photodetector centered on the wavelength λ ₂ determined based on the condition

when the laser source is operating in a continuous mode, it makes it possible to minimize the EPR conversion error associated with the unknown color.

When a laser source operates in a repetitively pulsed mode, the use of time filtering of the laser signal from a mixture with a continuous signal of solar radiation makes it possible to simplify the design of the focal assembly of the receiving system, namely, to reduce the number of photodetectors from three to two.

Consider the implementation of the proposed method for determining the intensity of laser radiation, schematically presented in figures 1-3.

In FIG. 1 shows a scheme for determining the intensity.

In FIG. 2 shows the scheme of the focal node for continuous LI.

In FIG. 3 shows the scheme of the focal node for repetitively pulsed LI.

Positions in figures 1-3 are marked: 1 - laser location station; 2 - space object observed in solar illumination at phase angle Ψ; 3 - Sun; 4 - receiving system; 5 - mirror; 6 - turntable; 7 - lens; 8 - focal node; 9 - spectral separation system; 10 - signal photodetector; 11 - background photodetector; 12 - photodetector visualization TO.

LLS (1) is an optoelectronic system that illuminates the CO with laser radiation, while the wavelength of laser radiation λ ₁ is in the range from 500 nm to 900 nm, the average energy intensity of laser radiation is at least 400 W / arcsec ² .

The space object (2) is illuminated by the Sun (3) and is an artificial satellite of the Earth, belonging to the category of space debris, and in orbit with an altitude of 600 km to 1000 km.

The receiving system (4) is an optical-electronic system for detecting the radiation reflected from the SO and consists of a mirror (5), a turntable (6), an objective (7) and a focal assembly (8).

The mirror (5) is flat, has a light aperture diameter of at least 0.7 m, and a reflection coefficient at wavelength A) of at least 80%.

The turntable (6) is a motorized mirror frame (5) that allows you to rotate the mirror (5) around the horizontal and vertical axes.

As a lens (7), a telescope lens with a light diameter of the entrance aperture of at least 400 mm, a relative aperture of 1:10, a radiation transmittance at a wavelength of λ ₁ of at least 80%, an average radiation transmittance in the range from 400 nm to 1000 nm not less than 60%.

The focal assembly (8) consists of a spectral separation system (9) and photodetectors. The spectral separation system (9) is a set of mirrors with a dielectric coating, light filters, lenses and fiber optic bundles. With continuous LI, the spectral separation system (9) distributes the radiation collected by the lens (7) between photodetectors (10), (11) and (12). In case of repetitively pulsed LI, the spectral separation system (9) distributes the radiation collected by the lens (7) between photodetectors (10) and (12).

The spectral separation system (9) provides:

- for the signal photodetector (10): the working spectral range with an effective width of not more than Δλ ₁ =3 nm, including the wavelength λ ₁ ; field of view in the range of 20…40 arcsec; total transmittance of elements (5)-(7)-(9) at wavelength λ ₁ not less than 20%;

- in the case of continuous LI for the background photodetector (11), the operating spectral range with an effective width of not more than Δλ ₂ =20 nm, including the wavelength λ ₂ and not including the wavelength λ ₁ ; field of view in the range of 20…40 arcsec; total transmittance of elements (5)-(7)-(9) at wavelength λ ₂ not less than 20%; the total residual transmittance of elements (5)-(7)-(9) at wavelength λ ₁ is not more than 0.01%.

- for visualization photodetector KO (12): field of view in the range of 200..300 arcsec; average over the range 400…1000 nm transmittance of elements (5)-(7)-(9): not less than 20%; the total residual transmittance of elements (5)-(7)-(9) at wavelength λ ₁ is not more than 0.01%.

The signal photodetector (10) is a photon counting module based on an avalanche diode in the Geiger mode and has the following characteristics: diameter of the receiving area: not less than 100 µm; photon detection efficiency at wavelength λ ₁ : not less than 40%; dark count rate: no more than 100 s ^-1 ; dead time: no more than 50 no. The signal photodetector (10) receives radiation through an optical fiber bundle.

The requirements for the background photodetector (11) coincide with the requirements for the signal photodetector (10).

The CR visualization photodetector (12) is a video camera with a resolution of more than 0.4 megapixels, a frame rate of more than 25 s ^-1 and a detectability that allows the receiving system (3) to visualize stars of the spectral type G0 with magnitude m _v < 6 at an exposure time of not more than 40 ms at an elevation angle of the Sun not more than -15°.

The outputs of photo receivers (10), (11) are connected to the inputs of frequency counters (not shown in the figure) of the HAMEG HM8123 type, interrogated by the computer via a serial interface.

The method for determining the intensity of laser radiation on a space object is implemented as follows. First, depending on the temporal nature of the laser radiation as part of the laser location station (1), the removal L of the receiving system (4) is selected.

Then, depending on the wavelength of laser radiation λ ₁ for the spectral separation system (9) of the focal node (8), an optical element is selected that provides spectral selection of laser radiation and sets the width and position of the working spectral range for the signal photodetector (10) and using a spectrophotometer measure spectral dependence of the directional transmittance of a given element, then calculate the equivalent spectral width Δλ ₁ using the formula (1):

where τ(λ) is the spectral dependence of the directional transmittance.

Next, the optical element is mounted in the spectral separation system (9) of the focal node (8).

In the case of continuous LI for the spectral separation system (9), an optical element is selected that sets the position of the spectral operating range of the background photodetector (11) centered on the wavelength λ ₂ determined based on the condition (λ ₁ -λ ₂ )/λ ₁ ≤5% . Next, this optical element is mounted in the spectral separation system (9).

Next, the receiving system (4) is mounted at a distance L from the laser location station (1). With a repetitively pulsed LI, the distance L should not exceed 10 km, and with a continuous LI, the distance L is determined from the condition 100 m≤L≤10 km.

Next, choose a CO that reflects radiation only diffusely, with a phase function Ф(Ψ) that differs minimally from the phase function of the ball:

Examples of such SOs are spent rocket stages with the following NORAD identifiers: 16910, 26960, 41791. To determine the phase function Ф(Ψ) of a particular SO, the open database of the MMT9 multichannel monitoring telescope of the Kazan (Volga region) Federal University is used [3].

Next, such a time interval is chosen in advance at which the phase angle Ψ of the solar illumination of the SC does not exceed 10°, while the elevation angle of the Sun (3) does not exceed -15°, while the angular size of the SC should be less than the LR divergence estimated from above, while KO range should not exceed 2000 km. The angular size of the SO is defined as the ratio of its linear size to the range.

Then, using a laser location station (1), the space object (2) is illuminated with laser radiation. Further, with the help of a turntable (6) and a mirror (5), the optical axis of the telescope (7) is directed to the CO, the CO is detected in the image given by the CO visualization photodetector (12). Next, the image of the TO is held within the field of view of the photodetectors (10), (11) and the rate of their counting of the frequency meters is recorded.

Then, the intensity of laser radiation at the CO is calculated according to the formula:

- спектральная интенсивность солнечного излучения на КО, определяемая согласно источнику [2]; Ф - фаза, рассчитываемая по формуле (1); отношение

в формуле (3) определяется в зависимости от временного характера ЛИ. В случае импульсно-периодического ЛИWhere

- spectral intensity of solar radiation on SO, determined according to the source [2]; Ф - phase calculated by formula (1); attitude

in formula (3) is determined depending on the temporal nature of the LI. In the case of repetitively pulsed LI

и

- скорости счета сигнального фотоприемника в фазе одновременной регистрации солнечного и лазерного излучения и в фазе регистрации только солнечного излучения соответственно. Значения

и

определяются по показаниям частотомера с учетом паспортных счетных характеристик фотоприемника (10).Where

And

- the count rate of the signal photodetector in the phase of simultaneous detection of solar and laser radiation and in the phase of registration of only solar radiation, respectively. Values

And

are determined according to the readings of the frequency meter, taking into account the passport counting characteristics of the photodetector (10).

In the case of continuous radiation

и

- скорости счета сигнального и фонового фотоприемника, определяемые по показаниям частотомеров с учетом паспортных счетных характеристик фотоприемников (10) и (11).Where

And

- counting rates of the signal and background photodetectors, determined from the readings of frequency meters, taking into account the passport counting characteristics of photodetectors (10) and (11).

находят с помощью приемной системы (4) после зондирования КО, для чего дополнительно проводят серию из 10 наблюдений звезд спектрального класса G0 со звездной величиной M_v=3…7 и рассчитывают коэффициент балансировки по формуле:Included in (5) balancing factor

are found using the receiving system (4) after sounding the SO, for which a series of 10 observations of stars of the spectral type G0 with magnitude M _v = 3 ... 7 is additionally carried out and the balancing coefficient is calculated by the formula:

- символ усреднения;

- скорости счета сигнального фотоприемника (10) и фонового фотоприемника (11), реализуемые при наблюдении звезды с номером j.Where

- symbol of averaging;

are the count rates of the signal photodetector (10) and the background photodetector (11) implemented when observing a star with number j.

To date, the enterprise has carried out computational and theoretical studies confirming the feasibility of the presented method for determining the intensity.

List of sources used

1. A. A. Kovalev, A. A. Lieberman, S. A. Moskalyuk, and S. V. Seregin, Tech. Measurement of the transmittance of laser radiation by the atmosphere over a long path. Measuring equipment No. 8, 2008. - S. 33-37

[2] G. Thuillier, M. Hersé, D. Labs, T. Foujols, W. Peetermans, D. Gillotay, P.C. Simon and H. Mandel The solar spectral irradiance from 200 to 2400 nm as Measured by the solspec spectrometer from the Atlas and Eureca missions

[3] Site http://mmt.favor2.info/satellites

Claims (5)

1. A method for determining the intensity of laser radiation on a spherical space object, including probing a space object with laser radiation with a divergence known in order of magnitude and a generated laser source operating in a continuous or repetitively pulsed mode, while choosing a space object with a phase function that is minimally different from phase function of a diffusely reflecting ball, while all structural elements of a space object reflect radiation only diffusely, and its linear dimensions do not exceed the diameter of the laser radiation profile on the space object, while the space object is illuminated by the Sun so that between the direction from the space object to the Sun and the direction from a space object to a laser source, a minimum phase angle Ψ is provided that does not exceed 10°, after which the intensity of the laser and solar radiation reflected from the space object is recorded, for which on the Earth's surface at a distance When L from the laser source, a receiving system is installed that registers the reflected laser radiation and the reflected solar radiation, and the intensity is determined by calculation

laser radiation source on a space object according to the formula

Where

- the magnitude of the spectral intensity of solar radiation on the CR at the wavelength of the LI; Δλ ₁ - equivalent width of the working spectral range of the photodetector, registering the reflected LI; Ф - phase of solar illumination of KO;

is the intensity of the reflected LI on the Earth,

- the intensity of the reflected solar radiation on the Earth in the spectral range of the photodetector, which registers the reflected LR. 2. The method according to claim 1, characterized in that when the laser source is operating in continuous mode, the distance L is selected from the condition 100 m ≤ L ≤ 10 km, and the reflected solar radiation is recorded in the spectral range centered on the wavelength λ ₂ determined by based on the condition

3. The method according to claim 1, characterized in that when the laser source is operating in a repetitively pulsed mode, the distance L is selected from the condition 0 m ≤ L ≤ 10 km, and the reflected solar radiation is recorded in the spectral range centered on the wavelength λ ₁ , and for the selection of a repetitively pulsed laser signal from a mixture with a continuous signal from reflected solar radiation, time filtering is used.

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