RU2361363C2 - Earth-moon-earth radio communication system - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to radio communication and may be applied in the systems to provide radio communication at any place worldwide. The mirror diametre is ~20 km. So, it helps to retranslate television signals. The mirror is represented as a set of corner reflectors. The angle of corner reflectors deflection allows for receiving reflected signal in any point of the Earth.

EFFECT: placement of mirror in the central visible part of the moon surface to reflect radio radiation of wave length with centimetre diametre.

4 dwg, 2 tbl

Description

The present invention relates to systems for providing radio communications to remote areas on Earth and is based on the use of the Moon as a natural satellite of the Earth.

A well-known experimental work [1], in which a radio signal from the Earth’s radio transmitter was sent by a directional antenna to the Moon, and a radio signal reflected from the lunar surface was received by the receiver’s receiving antenna, which was more than 1000 km from the transmitter on Earth.

The results of the experimental work [1] are as follows:

- the power loss of the radio signal on the route Earth-Moon-Earth amounted to ~ 190 dB,

- when the diameter of the ground receiving antenna was 12 meters (Orbita station), the echo signal power was ~ 3 · 10 ^-16 W at an input impedance of 75 Ohms, the average level of the echo signal exceeded the receiver thermal noise level by 3 ... 4 dB and amounted to 0.15 μV,

- when the diameter of the Earth’s transmitting antenna is 7 meters, the radio signal was transmitted by the Mars mobile satellite communications station at a frequency of 6 GHz (λ = 0.05 m) at a power of 3 kW,

- the frequency band of the transmitted information signals was below 10 kHz.

The main disadvantages of this communication system [1]:

- limiting the frequency band of the transmitted signals F _c <10 kHz with an echo delay of ~ 2.5 s,

- the large power of the terrestrial transmitter (due to the large losses on the Earth-Moon-Earth highway) served as an excuse for not further developing and improving this radio communication option.

The present invention is directed to the technical solution of the problem of creating a Earth-Moon-Earth radio communication system in which the frequency band of the transmitted signal F _c ≈5 · 10 ⁶ Hz (corresponds to the television frequency band) while reducing the power of the earth transmitter and the possibility of receiving a radio signal anywhere in the Earth .

The known system [1] in its physical essence can be adopted as a prototype.

In accordance with the proposed invention, the Earth - Moon radio communication system (passive repeater) - Earth, which includes an earth radio transmitter with an antenna directed to the center of the moon, and an earth receiver of radio radiation reflected from the lunar surface with an antenna also directed to the moon, are connected to centimeter wavelength range, for which, in the center of the lunar surface visible from the Earth, in a circle with a diameter of not more than 200 km, a mirror is placed to reflect radio emissions, which is made in the form of a circle with a diameter of not more 21 km from its corner reflectors whose reflection coefficient is less than 0.7, differences of the reflected radiation beam from the incident angle of the radio beam γ _Vq is 0,9 °, and the terrestrial transmitter is located so that it is at the Earth's rotation around its axis, in the zone which it is included for communication and which is formed by the square base of the conditional tetrahedral solid angle with the vertex on the mirror, the axis of the solid angle is the Moon-Earth axis, and the angle θ of each plane of the solid angle with the axis is determined by the inequality 0.24 ° ≤θ≤0.26 °, and the acceptance condition is The earth echo reflected from the moon is determined by the inequality

,

,

where K _zer and K _{sp. l} are respectively the reflection coefficients of radio emission from the mirror and from the lunar surface, S _zer is the area of the mirror, S _{sp. l} is the area of the lunar surface, the reflection from which reaches the Earth.

The invention is further explained by reference to the presented system diagrams.

Figure 1. Scheme of reflection of radio emission from the lunar surface.

1 - lunar surface, 2 - radio waves of terrestrial transmitter 3 - diameter D _otr.l sector on the Moon, the surface reflection of which reaches the Earth, 4 and 5 - of diffuse scattering respectively closest to the earth area and on the periphery (edge D _otr.l ), 6 - solid angle 2γ, at which the Earth is observed from the Moon (2γ≈1.8 °). 7 - the height of the spherical sector, 8 - the radius of the moon.

Fig 2. Image of the Moon and the Earth during the formation on the Earth's surface of the working area in which the Earth transmitter operates.

9 - Earth, 10 - conditional tetrahedral solid angle with a vertex on the mirror 11 of the Moon 1, 12 - half of the working area on Earth, in which the Earth transmitter works (the second half is not visible), 13 - the position of the Earth transmitter in the working area on the Earth-axis Moon, 14 - angle θ between the axis of the solid angle of the Earth-Moon and the planes of its faces 15, 16 - Earth-Moon distance.

Fig 3. The position of the working area on Earth from the moon.

12 - the working area in the form of a square - the base of the conditional solid angle 10, 17 - the diameter of the radio beam reflected from the mirror 11 in the plane of the Earth 1, 18 - the area covered by the reflected beam 17 of the Earth 9.

Fig 4. The conditional image of corner reflectors (UO): a) UO from three mutually perpendicular mirrors, b) UO from four mutually perpendicular mirrors formed by three mutually perpendicular surfaces.

Comment. Mutually perpendicular surfaces (planes) can have a triangular or square shape - a dashed line on a).

A sufficiently large number of expensive studies of the radiative-reflective properties of the lunar surface from the Earth and from satellites [2-10], which the authors met, do not allow us to reliably estimate the reflection coefficient of the centimeter wave range from the Moon. This circumstance was the reason for the analysis of the experimental results of [1] in order to clarify the value of K _otr , as summarizing the following factors:

- losses associated with the diffuse nature of the reflection of radio emission from the lunar surface;

- losses caused by the specific nature of reflection from a surface having slopes of 0.05 ÷ 0.1 over a length of 1 m;

- losses associated with the specific absorption of radio emissions by the lunar surface;

- losses associated with the double passage of radio emissions from the earth's atmosphere.

Unfortunately, there are currently no reliable values of these losses in the known literature [2-10].

As shown in figure 1, the spherical shape of the moon 1 creates a time delay between the echo signals from the nearest to the Earth zone of the center 4 of the moon and from its peripheral regions 5 on the diameter D _sp . The time difference Δt = 2h / c (where h is the height of the spherical sector of the Moon 7, s is the speed of light) and determines the frequency band of the echo signal F _c

received on Earth F _c = 1 / Δt = s / 2h.

The diameter of sector 3 on the lunar surface with parameters 7, 3 and a radius R _{l of the} moon 8, reflecting the radio emission of the terrestrial transmitter 2, has the form

Table 1 shows the values of D _sp.l for various values of F _c .

Table 1 F _c Hz 5 · 10 ⁶ 10 ⁵ 5 · 10 ³ 10 ³ D _neg. Km 20,4 175 645 1445

It can be seen that for transmitting a television signal, the reflecting surface on the Moon should have a D _{branch of} not more than 21 km, which is recommended by the authors for the proposed communication system. With a decrease in the diameter of the mirror, a television signal will be confidently transmitted, an increase in diameter reduces the television frequency of the signal. However, it should be noted that a decrease in D _negl results in a decrease in the received power of the echo signal reflected from D _negl .

Essential for the retransmission of the television signal F _c through the moon is the inadmissibility in the circle of reflection of swings with a height of more than 30 meters.

As was revealed in [2, 3, 6, 7, 10], the lunar surface in the center of the visible part in a circle with a diameter of 200 km has a low density, weak undulation, roughness per 1 m with a slope of 0.05 ... 0.1 and significant porosity. It is this circumstance that formed the basis for recommending the location of the mirror on the lunar surface in the central region in a circle with a diameter of 200 km, that is, in any area inside this circle. The nature of the reflection of the radio waves of the centimeter wavelength range is recognized as diffuse (in Fig. 1, 4 and 5), which is written as

where P _N and P _α are the reflection powers, respectively, normal to the surface and reflected at an angle α to the normal (see [7]).

Representing the Moon as an ideal spherical surface, the values of (cosα) ³⁰ for various α are given in Table 2

table 2 α radians 0.016 0.10 0.20 0.30 0.35 0.40 degrees 0.9 5.7 11.5 17,2 20,0 22.9 (cosα) ³⁰ 0.988 0.86 0.52 0.23 0.15 0,085

From table 2 it follows that at α = 0.35 radians (20 °) the maximum power reflected in the direction of the Earth does not exceed 0.15 of P _N. In this case, the diameter of the reflecting sector D _spl is close to ~ 1200 km, at which, as follows from Table 1, the frequency band of the signal F _c is in the range 10 ⁴ ... 10 ³ Hz. This value F _c and was recorded in [1], which indicates that the reflecting region on the moon value close to (1/3) D _n (D _n - Moon diameter), i.e. it is confirmed experimentally diffuse reflection K _{Neg .l} . The reflection coefficient K _adl is determined by the obvious expression

where P _{pad. 1200} is the power of the terrestrial transmitter arriving at the surface of the Moon with a diameter of 1200 km, P _{neg. 1.8} is the _power reflected from the Moon in a diameter of 1200 km, which reaches the Earth, that is, enclosed in a solid angle of 2γ = 1.8 ° in the direction of the earth.

The power density of the terrestrial transmitter in the moon plane is determined by the ratio P _s.p. / S _D.s.p (where P _s.p is the power of the earth transmitter, S _D.s.p is the cross-sectional area of the radio beam of the earth transmitter in the moon plane). Then, taking into account (3), we can write

From (4) it follows that in order to calculate K _otr it is necessary to know the power density of the earth transmitter, i.e., the ratio P _s.p. / S _D.s. .

The directional pattern of the terrestrial transmitting antenna in [1] is calculated according to the well-known dependence [11, 12], in which the diameter of the transmitting antenna D _p.an and the wavelength λ of radio emission for space communication systems are related to the angle of the main lobe by the dependence

where Ψ _0.5 is the angle of the main lobe of the radiation pattern at half power.

For the experimental conditions, λ = 0.05 m, D _p.an = 7 m, Ψ _0.5 = 0.5 ° = 8.7 · 10 ^-3 radians, and the diameter of the radio beam in the Moon’s plane is D _{p / l} (Earth-Moon distance ~ 4 · 10 ⁵ km) is equal to 3500 km. In the experiment, it is possible that the angle of the radiation pattern was increased to better "hit" the moon, however, there is no mention of this.

When calculating K _otr, one can use, for example, two values of D _zp : the first is the calculated in accordance with (5) D ' _{p / l} = 3500 km and the second D'' _{p / l} ~ 35000, which is equivalent to a decrease in the use of the transmitting surface antenna 2 times.

The power of the echo reflected from the Moon, reaching the Earth, defined by expression (4), takes the form

,

,

and the power of this signal received by the receiving antenna with an area S _ave.an at any point on the Earth is determined by the expression

where S _zem - the cross-sectional area of the Earth, S _pr.an - the area of the receiving antenna.

In [1], ΔP _ave.an ~ 3 · 10 ^-16 W, then from (6) the value of K _sp.l turns out to be equal

When the earth transmitter power is at the level of 0.5 radiation pattern P _s.p. = 1500 W, S ₁₂₀₀ = 1.13 · 10 ⁶ km ² , S '_D'z.p = 9.61 · 10 ⁶ km ² , S''_D''s.p = 961.6 · 10 ⁶ km ² , S _land = 127.45 · 10 ⁶ km ² S _AN. = 1.13 · 10 ^-4 km ² we get

K ' _sp . _L = 2 · 10 ^-6 and K'' _sp . _L = 2 · 10 ^-4 .

Thus, the calculated value of K _adl according to [1] turned out to be equal to:

- 2 · 10 ^-6 , if the radiation pattern of the antenna of the earth transmitter is determined by the dependence (5) adopted for the calculation of antennas, and

- 2 · 10 ^-4 , if the effective diameter of this antenna is reduced by 2 times.

In the future, we will use the average value of the coefficient K _otl = 5 · 10 ^-5 .

Limitations of D _s.p. from above are not advisable, since an increase in D _{s.p. is} directly related to the need to increase the power of the earth transmitter. It should be noted that if D _zp ≥D _l (D _l is the diameter of the Moon), then the surface reflecting towards the Earth on the Moon has a circle area of 1200 km in diameter (S ₁₂₀₀ ). If D _zp <D = 1200 km, the diameter of the reflecting surface of the lunar _otr.l D = D _ZP

In accordance with the invention, in the center of the visible part of the moon in a circle with a diameter of 200 km, a mirror is placed to reflect radio emissions of the centimeter wavelength range. It is proposed that this mirror be made in the form of angular reflectors uniformly covering the surface of the moon in the above-mentioned circle of not more than 21 km for relaying a television signal.

It is known [13-15] that corner reflectors reflect the incident radio beam strictly in the direction of the emitter, with strict adherence to the requirement of 90 ° between the reflecting planes. It is also known that non-compliance with this requirement leads to the scattering of the reflected beam from the axis of the corner reflector-emitter. Some tasks that are solved by corner reflectors (UO):

- to create a radar landmark on the ground,

- passive radar beacons (in the desert, taiga, etc.),

- radio towers on complex fairways,

- to create an artificial target (UO is on Lunokhod-1),

- for the prevention of collisions (back "lantern", indicators on roads).

According to the authors, it is technically possible to design corner reflectors with a reflection coefficient of radio emissions from the mirror K _zer ≥0.7 [13, 14]. A higher reflection coefficient is difficult to manufacture, and a lower value will directly reduce the reflected power of the radio emission.

For the problem under consideration, corner reflectors on the lunar surface in the Moon-Earth-Moon radio communication system should be made with the angle of divergence of the reflected radio beam from the axis of the incident beam, which is determined by the equality γ _Yo = 0.9 °. The proposed value of γ _уо = 0.9 ° is explained by the fact that from the surface of the Moon the Earth is observed at a solid angle of 2 γ _уо = 1.8 °. It is clear that at γ _V0 > 0.9 ° a part of the reflected energy goes beyond the Earth. When γ _Y0 <0.9 °, the zone of “coverage” of the Earth by the reflected radio beam will decrease, and thereby the technical result of the invention is not achieved - receiving an echo signal anywhere in the Earth.

The power of the echo signal at the receiving antenna of the Earth with the coincidence of the axis of the mirror - the earth transmitter with the axis of the Earth-Moon will be (see (6)):

- for a signal reflected from the lunar surface from an area of S ₁₂₀₀ (this signal can be received as noise) and received by an earth antenna with a diameter of 12 m (as in [1])

Where

- for a signal on the same antenna reflected from a mirror (20 km in diameter)

что практически может оказаться приемлемым для приема телевизионных программ в любой точке Земли.where the signal-to-noise ratio will be

which may practically be acceptable for receiving television programs anywhere in the world.

In particular, for example, when γ _V0 = 0.7 °, the reflected radio beam covers only half of the transverse area of the Earth. In this case, the ΔP value, _pr.20 = 7.8 · 10 ^-18 · 314 · 0.7 = 17.14 · 10 ^-16 W, and the signal-to-noise ratio = 17.14.

It should also be noted that upon acceptance of K _otr ≈2 · 10 ^-6 , ceteris paribus, the signal-to-noise ratio will be equal to 100.

The calculation shows that with a decrease in the level of intrinsic noise during reception, it is possible to reduce the power of the earth transmitter, for example, by 2 times, with an intrinsic noise level of less than 10 ^-17 W.

The Earth transmitter on the Earth’s surface will move relative to the Moon-Earth axis as the Earth rotates around its own axis. So, when the transmitter is located and turned on at the edges of the Earth, the condition for transmitting radio emission in the direction of the moon worsens due to an increase in the atmospheric layer during the passage of the radio beam, which increases the loss of radiating power. In this case, the radio beam reflected from the mirror on the Moon will “illuminate” only a part of the surface on the Earth, since the angle scattered by the corner reflectors and the radio emission from the mirror - Earth transmitter axis are proposed to be set to 2γ _V0 = 1.8 ° (Earth from the Moon is observed at this angle )

Based on the foregoing, it is proposed to position the Earth transmitter on the Earth so that the radio communication of the Earth-Moon-Earth system is carried out only when it is in a certain working area.

Figure 2 shows the Moon 1 and Earth 9, located on a single axis. The mentioned working area on Earth 9 is formed by the square base of the conditional tetrahedral solid angle 10, the top of which is located on the mirror 11 of the Moon 1. Here only half of the mentioned working area 12 is shown, the earth transmitter 13 in Fig. 2 is shown located on the Earth-Moon axis, which In this case, it coincides with the axis of the mirror - the earth transmitter. The angle 14 θ between the axis of the solid angle 10 and its planes 15 of each face determines the size of zone 12 both vertically and horizontally, taking into account the Earth-Moon distance 16.

It is proposed that the angle 14 θ be set by the inequality 0.24 ° ≤θ≤0.26 °. At an Earth-Moon distance of ~ 4 · 10 ⁵ km, the dimensions of the square base (zone 12) of the tetrahedral solid angle 10 are 3349 × 3349 km ² and 3628 × 3628 km ² .

Figures 3a) and b) show the position of zone 12 on the Earth's surface (view from the moon) and the position of the earth transmitter 13 at the entrance to zone a) and at its exit from zone 12 b), as well as the corresponding positions reflected from the mirror on the moon radio beam 17, "tied" to the axis of the mirror - the earth transmitter. The proposed values of the angle θ provide coverage of the reflected radio beam 18 (its diameter is equal to the diameter of the Earth) of the Earth's surface, equal to ~ 88% (at θ = 0.24 °) and ~ 80% (at θ = 0.26 °).

According to the authors, the radio communication area, which is (80 ... 88)% of the cross section of the Earth, can satisfy many practical communication needs. At θ = 0.24 °, an increase in the Earth's “coverage” zone by the reflected radio beam will be accompanied by a reduction in the communication session (since the transmitter is turned on only in the working zone 12). At θ> 0.26 °, the Earth’s “coverage” zone will decrease with a reflected radio beam. The communication session time in the proposed values of θ is ~ 2 hours.

The calculated K values _otr.l based on experimental data of [1], and the authors proposed mirror reflectance value equal to K _zer ≥0,7, can detect operating conditions of the proposed radio communication system Earth-Moon-Earth, which can be written as

where S _arr.l is the area of the lunar surface, the reflection from which reaches the Earth.

If we assume that the noise P is formed by the echo signal reflected from the Moon from the surface S _spr , then the signal / noise ratio will be equal

Obviously, the proposed radio communication system with a mirror on the lunar surface will prove to be workable if the condition S / P≥3 is fulfilled.

The minimum value of C / P≈3 provides the same selection of a television signal at the Earth's receiving antenna, as well as receiving a telegraph signal in [1].

In Fig. 4, two types of corner reflectors (UO) with faces 19 are shown, in Fig. 4a, the UO consists of three mutually perpendicular planes 20, and in Fig. 4b, the UO consists of four mutually perpendicular planes 20. The planes 20 mirror the incident light beam or radio beam. The reflected beam 21 is reflected strictly in the direction of the source if the angle between the planes is 90 °. For the problem under consideration, it is advisable to have the length of the VO face of 20 ... 30 cm (at a wavelength of radio emission of ~ 3 ... 15 cm).

The number of corner reflectors N _U on the lunar surface in a circle with a diameter of 20 km is calculated from the dependence [13]

,

,

а для плоскостей 20 с квадратной формой равен

где a - длина грани УО, λ - длина волны светового или радиолуча.where S _euo is the effective transverse dimension of the EO, which, in accordance with [13-15] for planes 20 of a triangular shape, is

and for planes 20 with a square shape is

where a is the length of the EO face, λ is the wavelength of the light or radio beam.

This proposal does not consider the implementation of the technical design of placing the mirror in the form of corner reflectors on the lunar surface in a diameter of not more than 21 km.

If many countries of the world are interested in placing such a mirror on the Moon, then such a project can be international and a technical solution for creating a mirror can be found.

Thus, the proposed Earth - Moon radio communication system (passive repeater) - Earth, according to the authors, provides the retransmission of a television signal to any remote areas on Earth. The proposed system will also allow one-way transmission of telephone and telegraph messages.

Daily relaying is possible using a satellite communication system, which will provide a signal to a transmitter that “sees” the Moon, from a transmitter that “does not see” it, and the number of transmitters should be increased to 12.

Literature

1. Gusyatinsky I.A., Weisburg G.M., Zilberman A.R. and others. The transmission of telegraph messages when using reflection from the moon // Electrosvyaz, 1977, No. 4, 26-28.

2. Evang J. Radio wave scattering by the Moon // Foreign Radio Electronics, 1958, No. 12. - 19-25. Ibid: Radio echo from the moon. - 25-31. Reflection of radar signals from the moon at a wave of 10 cm. - 31-36.

3. Horn P. Modern view of the moon. - Translation from German, Moscow: 1976, 29 L, VTsPNTLiD. - Translation of No. -69098.

4. Cherkasov I.I., Shvarev V.V. Primer of the Moon, Moscow: Science 1979.

5. Cherkasov I.I., Ashkheev V.V., Smorodinov M.I. and others. The first results of determining the physico-mechanical properties of the soil of the Moon, M .: Stroyizdat, 1970.

6. Krotikov V.D., Troitsky B.C. Radio emission and the nature of the moon // Uspekh fiz. Sciences, vol. 81 issue 4.

7. Petrovich N.T., Kamnev E.F., Kablukova M.V. Space radio communication. - M .: Owls. radio, 1970.

8. Markov M.N., Grechko G.M. and other IR spectroscopy of the Moon in the range of 1.6-15 microns from the Salyut-5. - M.: USSR Academy of Sciences of the LPI named after Lebedev. - Preprint - 181, 1978.

9. McKew, J.J., Crocker, E.A. The reflecting ability of the moon at λ≈0.86 cm. - M.: VTsPNTLiD. - Translation of No. A-56203, 1978.

10. Markov M.N., Grechko G.M. and other IR spectroscopy of the Moon in the range of 1.6-15 microns from the Salyut-4. - M.: USSR Academy of Sciences, Lebedev Physical Institute. - Preprint No. 7, 1976.

11. Satellite communications and broadcasting. Handbook Ed. L.Ya. Kantora. - M.: Radio and Communications, 1988.

12. Fortushenko A.D., Askinazi G.B., Bykov V.L. et al. Fundamentals of the technical design of communication systems through a satellite. - M.: Communication, 1970.

13. Makovetsky P.V., Vasiliev V.G. Reflection of radar signals. - Lectures. - Leningrad Institute of Aviation Instrumentation, 1975.

14. www.net.ru Makovetsky P.V. A collection of interesting tasks and questions.

15. www.losi.itgo.com Diffraction properties of corner reflectors.

Claims (1)

The Earth-Moon-Earth radio communication system, including an earth centimeter radio transmitter with an antenna directed to the Moon, and an earth receiver of radio radiation reflected from the Moon with an antenna also directed to the Moon, characterized in that in the center of the lunar visible from the Earth surface, in a circle with a diameter of not more than 200 km there is a mirror for reflecting radio emissions, which is made in the form of a circle with a diameter of not more than 21 km from corner reflectors, the reflection coefficient of which is not less than 0.7, and the divergence angle is conjugated γ antenna beam _Vq is 0,9 °, wherein the terrestrial transmitter is located so that when the rotation of the earth around its axis it was in the area in which it is included for communication and which is formed by a square base conditional tetrahedral solid angle with vertex on the mirror axis corporal of the angle is the Earth-Moon axis, and the angle θ of each plane of the face of the solid angle with its axis is determined by the inequality 0.24 ° ≤θ≤0.26 °, and the condition for receiving an echo signal reflected from the Moon on the Earth is determined by the inequality

where K _zer and K _{sp. l} are the reflection coefficients of radio emission from the mirror and the lunar surface, respectively, S _zer is the area of the mirror, S _{sp. l} is the area of the lunar surface, from which reflection reaches the Earth.

Images