RU2328416C1 - Elevation doppler system for emergency object positioning - Google Patents

Abstract

FIELD: space-system engineering.

SUBSTANCE: system can be used on the earth satellite vehicle in orbit except geostationary centers which are stabilised by rotation along the vertical axis, and the ground reception centers. The system contains an emergency object transmitter, spacecraft equipment and ground reception center equipment. Spacecraft equipment includes a horizon sensor, receiving antenna, comparison device, receiver, Doppler frequency meter, blocking-generator, two gating circuits, two valves, pulse generator, pulse counter, plug board chart, and magnetic storage device, transmitter, transferring antenna, modulation code generator, high-frequency generator and power amplifier. The ground reception center equipment includes reception antenna, high-frequency amplifier, two mixers, calibration frequency block, phase doublet, three narrowband filter, scale-of-two phase circuit, phase detector, Doppler frequency meter, computing unit and registration block.

EFFECT: it enlarges functional possibilities of the system.

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Description

The proposed system relates to space technology and can be used on spacecraft in the orbit of an artificial Earth satellite, except for the geostationary one, stabilized by rotation along the vertical axis, and at ground receiving points.

Known methods and systems for determining the coordinates of an emergency object (RF patents Nos. 2.155.352, 2.158.003, 2.040.860, 2.059.423, 2.174.092, 2.193.990, 2.201.601, 2.206.902, 2.226.479, 2.240 .950; US patents Nos. 4.161.730, 4.646.090, 4.947.177; Skubko R.A. et al. Sputnik at the helm. - L .: Shipbuilding, 1989, p.168 and others).

Of the known methods and systems, the closest to the proposed one is a system that implements the "Angular-temporal Doppler method for determining the coordinates of an emergency object" (RF patent No. 2.174.092, B64G 1/10, 1999), which is selected as a prototype.

According to the known system, a search is made for such a spatial position of the satellite’s receiving antenna in the presence of the fact of operation of the transmitter of the emergency object when the Doppler frequency of the received signal is zero. At this point, measure the angle between the axis of the receiving antenna and the axis of the horizon sensor. The coordinates of the sub-satellite point of the spacecraft path at the time of measurement are calculated. Measurements are carried out twice. The coordinates of two sub-satellite points and two measurements of the specified angle determine the location of the emergency object.

The known system provides an unambiguous definition and increase the accuracy of calculating the coordinates of an emergency object located on the Earth’s surface, as well as expanding the area of the viewing surface and increasing the signal-to-noise ratio in the receiving radio line.

However, the known system does not fully realize its potential capabilities. It can also be used to clarify the elements of the orbit of the spacecraft as it passes over the ground receiving point.

An object of the invention is to expand the functionality of the system by clarifying the elements of the orbit of the spacecraft as it passes above the ground receiving point.

The problem is solved in that the elevation-time Doppler system for determining the coordinates of the emergency object, containing, in accordance with the closest analogue, the transmitter of the emergency object, onboard equipment of the spacecraft and ground equipment of the receiving station, while the axis of rotation of the spacecraft is deviated from the local vertical, the spacecraft consists of a body, a pulsed infrared horizon sensor, placed on one axis opposite to the receiving antenna, the mechanical axis of which is not coincides with the axis of rotation of the spacecraft, the spacecraft's onboard equipment consists of a series-connected receiving antenna, a receiver, the second input of which is connected to the first output of the master oscillator, a Doppler frequency meter, the second input of which is connected to the second output of the master oscillator, a comparison device, a blocking generator , the first matching circuit, the second input of which is connected to the second output of the receiver, the second matching circuit, the second input of which is connected to the second output of the blocking generator, the first gate, the second input of which is connected through the pulse counter to the output of the pulse generator and the horizon sensor, the switching circuit and the magnetic storage device, the transmitter and the transmitting antenna are connected in series to the second output of the switching circuit, the temporary device and the second valve are connected in series to the third output of the master oscillator, the second input of which is connected to the second output of the second coincidence circuit, and the output is connected to the second input of the switching circuit, differs from the closest analogue m, that the on-board transmitter is made in the form of a high-frequency generator, a phase manipulator connected in series to the second output of the switching circuit, the second input of which is connected to the output of the magnetic storage device and the power amplifier connected to the transmitting antenna through the modulating code generator, and the ground-based equipment of the receiving station is made in the form of series-connected receiving antenna, high-frequency amplifier, first mixer, the second input of which is connected to the first output of the standard unit frequencies, an intermediate amplifier, a phase doubler, a first narrow-band filter, a phase divider into two, a second narrow-band filter, a phase detector, the second input of which is connected to the output of the intermediate-frequency amplifier, a computing unit, and a recording unit, and the second one is connected in series to the output of the second narrow-band filter a mixer, the second input of which is connected to the second output of the reference frequency unit, a third narrow-band filter and a Doppler frequency meter, the output of which is connected to the second input of the calculation solid block.

The geometric arrangement of the spacecraft 1, the pulsed infrared sensor 2 of the horizon and the receiving antenna 3, located on one axis opposite the sensor 2 of the horizon, is shown in figure 1. The principle of determining the Doppler frequency shift of the spacecraft transmitter is illustrated in figure 2. The dependence of the Doppler frequency on time is shown in Fig.3. The structural diagram of the system is presented in figure 4. Timing diagrams explaining the operation of the system are depicted in figure 5.

The system comprises a transmitter 20 of the emergency facility (emergency ARB beacon), spacecraft onboard equipment and ground receiving equipment.

The spacecraft on-board equipment contains a receiving antenna 3 in series, a receiver 5, the second input of which is connected to the first output of the master oscillator 19, a Doppler frequency meter 6, a comparison device 4, a braked blocking generator 7, the first matching circuit AND 8, the second input of which is connected to the second output of the receiver 5, the second coincidence circuit AND 9, the second input of which is connected to the second output of the blocking generator 7, the first valve 10, the second input of which is connected through the pulse counter 13 to the outputs of the horizon sensor 2 and the generator An ora of 12 pulses, a switching circuit 14, a magnetic storage device 15, a modulating code driver 21, a phase manipulator 23, the second input of which is connected to the second output of the switching circuit 14 by a high-frequency generator 22, a power amplifier 24 and a transmitting antenna 17. High-frequency generator 22 , the phase manipulator 23 and the power amplifier 24 form a transmitter 16.

A temporary device 18 and a second valve 11 are connected to the third output of the master oscillator 19, the second input of which is connected to the second output of the second matching circuit 9, and the output is connected to the second input of the communication circuit 14.

The ground equipment of the receiving station 25 contains a receiving antenna 26 connected in series, a high-frequency amplifier 27, a first mixer 28, the second input of which is connected to the first output of the reference frequency unit 29, an intermediate frequency amplifier 30, a phase doubler 31, a first narrow-band filter 32, a phase divider 33 two, a second narrow-band filter 34, a phase detector 35, the second input of which is connected to the output of the intermediate frequency amplifier 30, a computing unit 39 and a recording unit 40. The second mixer 36, the second input of which is connected to the second output of the reference frequency block 29, the third narrow-band filter 37 and the Doppler frequency meter 38, the output of which is connected to the second input of the computing unit 39, is connected in series to the output of the second narrow-band filter 34.

The principle of the proposed system is to search for such a spatial position of the receiving antenna 3 KA, stabilized by rotation along the vertical axis, if there is a fact of operation of the transmitter 20 of the emergency object, when the Doppler frequency of the received signal is zero, the measurement at this point in time of the angle between the mechanical axis of the receiving antenna 3 SC and the axis of the horizon with reference measurements to the on-board temporary device 18. The measurements are recorded in the magnetic storage device 15 and transmitted over the air to the ground paragraph 25. The coordinate of the sub-satellite point at the time of measurement is calculated. Measurements are taken at least two times. The coordinates of the two sub-satellite points and the two measured angles between the mechanical axis of the receiving antenna 3 KA and the axis of the horizon determines the location of the emergency object.

The principle of determining the parameters of the spacecraft’s orbit using the Doppler unquestioning system, in which a transmitter is located on board the spacecraft and a measuring device is located on Earth, is illustrated in FIGS. 2 and 3.

Doppler frequency is determined based on the ratio

where λ is the working wavelength,

r is the current distance from the spacecraft to the ground receiving point (0).

может быть направлен под любым углом к линии радиосвязи. Связь радиальной составляющей V_r с модулем V находится при задании конкретного закона движения КА, определяющего вид функции r=r(t).Spacecraft motion vector

can be directed at any angle to the radio link. The connection of the radial component V _r with the module V is determined by specifying a specific law of motion of the spacecraft that determines the form of the function r = r (t).

Let the observed trajectory of the spacecraft S ₁ -S ₂ not pass through the ground receiving point O, relative to which the distance is counted. The shortest distance between the receiver and the transmitter when the latter is at the point S ₀ is r ₀ (figure 2). This is the so-called traverse point. The time is counted from the moment t = 0, corresponding to the passage of the spacecraft through the point S ₁ . The distance between S ₁ and S _{0 is} denoted by l ₀ , the moment of passage of the point S ₀ - by t ₀ .

The time dependence of the Doppler frequency has the following form:

where the plus sign corresponds to the condition 0≤t≤t ₀ (rapprochement), and the minus sign corresponds to the condition t ₀ <t≤∞ (deletion).

The indicated expression shows that the Doppler frequency depends on both V and λ, as well as t, r ₀ and l ₀ . Moreover, the dependence on time is nonlinear (Fig. 3).

In a linear section near the inflection point

and then

Differentiating this expression with respect to time, we can find an expression for the derivative of the Doppler frequency:

не зависит от начала наблюдений (l₀).It is seen that the value

independent of the start of observations (l ₀ ).

, можно найти кратчайшее расстояниеIt follows from the last expression that, knowing the velocity V and the wavelength λ, as well as measuring the derivative

, you can find the shortest distance

The values of V and r ₀ calculate the elements of the orbit of the spacecraft.

A feature of the non-request method of measuring radial velocity is the need to use frequency standards. Provided that the error in measuring the radial velocity should not exceed a tenth of a meter per second, the permissible relative instability of the frequency standards during the entire time the system operates should not exceed 10 ^-10 . Such high requirements for frequency stability are satisfied by quantum frequency standards.

, равное отношению скорости

, не превышает 10^-4. В этих условиях выделение доплеровского сдвига при однократном преобразовании частоты требует использования контуров с очень высокой, практически недостижимой добротностью.In the receiver of a non-requesting radial velocity measurement system, frequency conversion is performed twice. It is necessary because the relative value of the Doppler shift

equal to the ratio of speed

does not exceed 10 ^-4 . Under these conditions, the separation of the Doppler shift during a single frequency conversion requires the use of circuits with a very high, almost unattainable quality factor.

The proposed system works as follows.

The translational motion of the spacecraft, the axis of rotation of which is deviated from the local vertical, ensures the movement of the scanning line of the radiation pattern of the receiving antenna 3 and sequential viewing of the strip on the Earth's surface along the orbit of the spacecraft. The SC rotation frequency is selected from the condition of viewing the Earth's surface without a gap. To eliminate the ambiguity, the mechanical axis of the receiving antenna 3 KA is shifted relative to the axis of rotation by an angle β equal to the width of the radiation pattern of the receiving antenna.

In the initial state, before the signal from the transmitter 20 of the emergency object hits the radiation pattern of the receiving antenna 3, there is no signal at the output of the receiver 5. At the output of coincidence circuits And 8, 9 is zero. The pulse sensor 2 of the horizon at the moment of crossing the spacecraft path generates a pulse, which resets the counter 13 pulses. Valves 10 and 11 are closed.

When a signal appears from the transmitter 20 of the emergency object in the visible band on the Earth’s surface, meter 6 starts measuring the Doppler frequency using an inapplicable method. When the Doppler frequency reaches a value of zero, the mechanical axis of the receiving antenna 3 is at the point of the beam. At this moment, the angle between the axis of the horizon sensor 2 and the position of the mechanical axis of the receiving antenna 3 (angle α) are measured. The measurements are tied to the on-board temporary device 18.

When the value of the Doppler frequency is reached at the output of the meter 6, which is equal to zero, the comparison device 4 opens and the braked blocking generator 7 starts, at the outputs of the matching circuit And 9 a unit appears. Valves 10 and 11 open. Information about the value of the angle α (the number of pulses recorded in the pulse counter 13) and the measurement time is recorded via the switching circuit 14 to the magnetic storage device 15 and fed to the input of the shaper 21 of the modulating code, where the code M (t) is generated (Fig.5, b), which is fed to the first input of the phase manipulator 23. At the second input of the latter, a high-frequency oscillation is output from the output of the high-frequency generator 22 (Fig. 5, a)

u _c (t) = U _c cos (2πf _c t + φ _c ), 0≤t≤T _c ,

where U _c , f _c , φ _c , T _c is the amplitude, carrier frequency, initial phase, and duration of the high-frequency oscillation.

At the output of the phase manipulator 23, a complex signal with phase shift keying (QPSK) is generated (Fig. 5, c)

u ₁ (t) = U _c cos (2πf _c t + φ _k (t) + φ _c ), 0≤t≤T _c ,

where φ _k (t) = {0, π} is the manipulated phase component that displays the phase manipulation law in accordance with the modulating code M (t) (Fig. 5, b), and φ _k (t) = const for kτ _e < t <(k + 1) τ _e and can change abruptly at t = kτ _e , i.e. at the boundaries between elementary premises (K = 1, 2, ..., N-1);

τ _e , N is the duration and number of chips that make up the signal of duration T _c (T _c = Nτ _e );

which after amplification in the power amplifier 23 with the help of the antenna 17 is radiated into the air. When passing the SC over the ground receiving point 25, the specified signal is captured by the receiving antenna 26. At the output of the receiver 27, in this case, a signal appears

u ₂ (t) = U ₂ cos (2πf ₁ t + φ _k (t) + φ _c ), 0≤t≤T _c ,

where f ₁ = f _c ± F _∂ ,

F _∂ - Doppler frequency offset due to the motion of the spacecraft relative to the ground receiving station, which is fed to the first input of the first mixer 28, the second input of which is supplied with the voltage of the first reference frequency from the first output of the block 29 of the reference frequencies

u _e1 (t) = U _e1 cos (2πf _e1 t + φ _e1 ).

At the output of the mixer 28, voltages of combination frequencies are generated. The amplifier 30 is allocated the voltage of the intermediate (differential) frequency (figure 5, g)

u _pr (t) = U _pr cos (2πf _pr t + φ _k (t) + φ _pr ), 0≤t≤T _c ,

;Where

;

To ₁ - gear ratio of the mixer;

f _ave = f ₁ -f _A1 = f _c -f ± _∂ F _A1 - an intermediate frequency;

_straight φ = φ _c -φ _A1,

which is fed to the information input of the phase detector 35 and to the input of the phase doubler 31. At the output of the latter, harmonic oscillation is formed (Fig. 5, e)

u ₃ (t) = U ₃ cos (4πf _pr t + 2φ _pr ), 0≤t≤T _c ,

Where

K ₂ - transfer coefficient of the multiplier.

It should be noted that the phase doubler 31 is a multiplier, at the two inputs of which the PSK signal of intermediate frequency u _pr (t) is supplied.

, тогда как ширина спектра Δf_c ФМн-сигнала определяется длительностью τ_э его элементарных посылок

, т.е. ширина спектра Δf₂ второй гармоники сигнала в N раз меньше ширины спектра Δf_c входного сигнала

.Since 2φ _k (t) = {0.2π}, phase manipulation is already absent in the indicated oscillation. The width of the spectrum Δf _{2 of the} second harmonic is determined by the duration T _{c of the} signal

, while the width of the spectrum Δf _c FMN signal is determined by the duration τ _{e of} its elementary premises

, i.e. spectrum width Δf _{2 of the} second harmonic of the signal is N times smaller than the spectrum width Δf _{c of the} input signal

.

Therefore, when the phase of the QPSK signal is doubled, its spectrum “folds” N times.

The harmonic oscillation u ₃ (t) is allocated by a narrow-band filter 32 and is fed to the input of a phase divider 33 into two, the output of which is a harmonic oscillation (Fig. 5, e)

u ₄ (t) = U ₄ cos (2πf _pr t + φ _pr ), 0≤t≤T _c ,

which is allocated by a narrow-band filter 34 and fed to the reference input of the phase detector 35.

Therefore, the reference voltage necessary for the synchronous detection of the PSK signals and the operation of the phase detector is extracted directly from the received PSK signal.

At the output of the phase detector 35, a low-frequency voltage is generated (Fig. 5, g)

u _n (t) = U _n cosφ _to (t),

,Where

,

K ₃ - the transfer coefficient of the phase detector,

proportional to the modulating code M (t) (Fig. 5, b), which is fed to the first input of the computing unit 39. In the computing unit 39 along the coordinates of two sub-satellite points and two measured angles α ₁ and α ₂ between the mechanical axis of the receiving antenna of the spacecraft and The horizontal axis determines the location of the emergency facility.

At the same time, the harmonic oscillation u ₄ (t) (Fig. 5, f) from the output of the narrow-band filter is supplied to the first input of the second mixer 36, the second input of which is supplied with the voltage of the second reference frequency

u _e2 (t) = U _e2 cos (2πf _e2 t + φ _e2 ),

where f _e2 = f _c -f _e1 -F ₀ ,

F ₀ is the frequency of the stand, which is introduced to determine the sign of the Doppler shift F _∂ .

At the output of the second mixer 36, an oscillation is formed

u _p (t) = U _p cos (2πF _p t + φ _p ),

;Where

;

φ _p = φ _pr -φ _e2 ;

F _p = ± F _∂ + F ₀ ,

which is allocated by the narrow-band filter 37 and is fed to the input of the Doppler frequency meter 38.

Depending on whether F _p > F ₀ or F _p <F ₀ , the sign of the Doppler shift, and therefore the direction of the radial velocity, is determined.

, в вычислительном блоке 39, определяют элементы орбиты КА.Knowing the velocity V and the wavelength λ, as well as measuring the derivative

, in the computing unit 39, determine the elements of the orbit of the spacecraft.

The system allows you to unambiguously determine the coordinates, reduce the search time for an emergency object, increase the area of the Earth’s viewing surface by scanning the receiving radiation pattern, increase the signal-to-noise ratio of the radio line by using a receiving antenna with a narrow radiation pattern.

Thus, the proposed system in comparison with the prototype allows you to specify the elements of the orbit of the spacecraft during its passage above the ground point. Thus, the functionality of the system is expanded.

Claims (1)

Carbon-temporal Doppler system for determining the coordinates of an emergency object, containing the transmitter of the emergency object, the onboard equipment of the spacecraft and the ground equipment of the receiving station, while the axis of rotation of the spacecraft is deviated from the local vertical, the spacecraft consists of a body, a pulsed infrared horizon sensor located on one axis opposite the receiving antenna, the mechanical axis of which does not coincide with the axis of rotation of the spacecraft, onboard space equipment The apparatus consists of a series-connected receiving antenna, a receiver, the second input of which is connected to the first output of the master oscillator, a Doppler frequency meter, the second input of which is connected to the second output of the master oscillator, a comparison device, a blocking generator, the first matching circuit, the second input of which is connected with the second output of the receiver, the second matching circuit, the second input of which is connected to the second output of the blocking generator, the first valve, the second input of which is connected to the pulse counter the output of the pulse generator and the horizon sensor, the switching circuit and the magnetic storage device, a transmitter and a transmitting antenna are connected in series to the second output of the switching circuit, a temporary device and a second valve are connected to the third output of the master oscillator, the second input of which is connected to the second output of the second matching circuit, and the output is connected to the second input of the switching circuit, characterized in that the on-board transmitter is made in the form of series connected to the second output Commutation switching of a high-frequency generator, phase manipulator, the second input of which is connected to the output of a magnetic storage device and a power amplifier connected to a transmitting antenna through a modulating code generator, the ground-based equipment of the receiving station is made in the form of a receiving antenna, a high-frequency amplifier, and a first mixer the second input of which is connected to the first output of the reference frequency block, an intermediate frequency amplifier, a phase doubler, a first narrow-band filter, a phase divider into two, a second narrow-band filter, a phase detector, the second input of which is connected to the output of an intermediate-frequency amplifier, a computational unit, and a registration unit, and a second mixer is connected in series to the output of the second narrow-band filter, the second input of which is connected to the second output of the reference frequency unit, a third narrow-band filter and a Doppler frequency meter, the output of which is connected to the second input of the computing unit.

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