RU2313477C1 - Determination of coordinates of emergency object by elevation angle and time doppler method - Google Patents

Abstract

FIELD: space engineering; operation of spacecraft flying in orbit of artificial earth satellite, but for geostationary orbit, which are stabilized by rotation along vertical axis, as well as ground reception points.

SUBSTANCE: system used for realization of this method includes emergency object transmitter, onboard equipment of spacecraft and ground equipment of reception point. Onboard equipment of spacecraft includes horizon sensor, receiving antenna, comparison unit, receiver, Doppler frequency meter, blocking oscillator, two AND gates, two rectifiers, pulse generator, pulse counter, switching circuit, magnetic memory, transmitter, transmitting antenna, modulating code shaper, RF generator and power amplifier. Ground equipment of reception point includes receiving antenna, RF amplifier, two mixers, standard frequency unit, phase doubler, three narrow-band filters, phase scale-of-two circuit, phase detector, Doppler frequency meter, computer and recording unit. Proposed method consists in search of such space position of space object by receiving antenna when Doppler frequency of received signal is equal to zero. Measurement at this moment of angle between mechanical axle of receiving antenna and horizon axis is carried out referring to onboard receiving unit.

EFFECT: extended functional capabilities; enhanced accuracy of determination of spacecraft orbit elements; reduction of time required for search of emergency object.

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Description

The proposed method relates to space technology and can be used on spacecraft located in the orbit of an artificial Earth satellite, in addition to the geostationary, 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 No. 2155352, 2158003, 2040860, 2059423, 2174092, 2193990, 2201601, 2206902, 2226479, 2240950; US patents No. 4161730, 4646090, 4947177; Skubko R.A. et al. Sputnik at the helm. - L .: Shipbuilding, 1989, p.168 and others).

Of the known methods and systems closest to the proposed one is the "Angle-time Doppler method for determining the coordinates of an emergency object" (RF patent No. 2174092, B64G 1/10, 1999), which is selected as a prototype.

According to the known method, 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 method 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 method 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 method by clarifying the elements of the orbit of the spacecraft as it passes above the ground receiving point.

The problem is solved in that according to the angle-time Doppler method for determining the coordinates of an emergency object located on the Earth’s surface, using a spacecraft stabilized by rotation along the vertical axis, which consists in the fact that when the signal from the transmitter of the emergency object appears on the band viewed from the spacecraft on the surface of the Earth, the Doppler frequency is measured by a non-query method, the spatial position of the spacecraft is found at the moment when the Doppler frequency The received signal is equal to zero, the angle between the mechanical axis of the receiving antenna of the spacecraft and the axis of the horizon sensor is measured at this time, the coordinates of the sub-satellite point are calculated at the time of this measurement, and the measurements are made twice and the coordinates of two sub-satellites points and two measurements of the angle between the mechanical axis of the receiving antenna of the spacecraft and the axis of the horizon sensor determine the location of the emergency object on the Earth’s surface, a modulating code is generated on board the spacecraft containing information about the angle between the mechanical axis of the receiving antenna of the spacecraft and the axis of the horizon sensor, manipulate it with the phase of high-frequency oscillations, form a complex signal with phase manipulation, amplify it by power, radiate it into the air, receive it at the ground receiving paragraph when passing over it a spacecraft, convert the received complex signal with phase shift keying in frequency using the voltage of the first reference frequency, isolate the intermediate frequency voltage, multiply and divide its phase by two, isolate the harmonic oscillation of the intermediate frequency, use it to synchronously detect the received complex signal with phase manipulation at the intermediate frequency, isolate a low-frequency voltage proportional to the modulating code, and use it to determine the location of the emergency of an object on the Earth’s surface, at the same time the harmonic oscillation of the intermediate frequency is converted in frequency using m second voltage reference frequency oscillation isolated Doppler frequency value is determined, the sign and the value zero Doppler frequency and use them to update the elements of the spacecraft's orbit.

The geometric arrangement of the spacecraft 1, the pulsed infrared sensor 2 of the horizon and the receiving antenna 3, located on the same 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 a system that implements the proposed method 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, a matching circuit And 8, the second input of which is connected to the second the output of the receiver 5, the coincidence circuit And 9, the second input of which is connected to the second output of the blocking generator 7, a valve 10, the second input of which is connected through the pulse counter 13 to the outputs of the horizon sensor 2 and the pulse generator 12, mu switching 14, magnetic storage device 15, driver 21 of the modulating code, phase manipulator 23, the second input of which is connected via the high-frequency generator 22 to the second output of the switching circuit 14, power amplifier 24 and transmitting antenna 17. High-frequency generator 22, phase manipulator 23 and a power amplifier 24 forms a transmitter 16.

The ground equipment of the receiving station 25 includes 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. To the output of the second narrow-band filter 34, a second mixer 36 is connected in series, the second input of which is connected to the second output of the reference frequency unit 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.

The essence of the proposed method consists in finding 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 KA 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 receiving 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, which 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 a distance report is conducted. 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

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 speed ratio

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 method is 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 equal to 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)

where U _c , f _c , φ _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)

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 borders 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

where f ₁ = f _c ± F _d ,

F _d - Doppler frequency offset due to the motion of the SC 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

.

.

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)

Where

To ₁ - gear ratio of the mixer;

- промежуточная частота;

- intermediate frequency;

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)

Where

K ₂ is the transmission 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_с 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

those. spectrum width Δf _{2 of the} second harmonic of the signal is N times smaller than the spectrum width Δf _{from 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)

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)

Where

To 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 at 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 axis of the horizon, the location of the emergency object is determined.

At the same time, harmonic oscillation u ₄ (t) (Fig.

Where

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

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

Where

F _p = ± F _d + F _o ,

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 определяются элементы орбиты КА.Knowing the velocity V and the wavelength λ, as well as measuring the derivative

in the computing unit 39, the spacecraft orbit elements are determined.

The method allows you to uniquely determine the coordinates, reduce the search time of 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 method 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 method is expanded.

Claims (1)

An angular-temporal Doppler method for determining the coordinates of an emergency object located on the Earth’s surface using a spacecraft stabilized by rotation along the vertical axis, namely, when a signal from the transmitter of an emergency object appears on a strip viewed from the spacecraft on the Earth’s surface, the Doppler frequency is measured without a query method, find the spatial position of the spacecraft at the moment when the Doppler frequency of the received signal is zero, measure it moment of time, the angle between the mechanical axis of the receiving antenna of the spacecraft and the axis of the horizon sensor with reference to the flight time, calculate the coordinates of the sub-satellite point at the time of the specified measurement, while the measurements are carried out twice and the coordinates of the two sub-satellite points and two measurements of the angle between the mechanical axis of the receiving the antennas of the spacecraft and the axis of the horizon sensor determine the location of the emergency object on the surface of the Earth, characterized in that on board the spacecraft They form a modulating code containing information about the value of the angle between the mechanical axis of the receiving antenna of the spacecraft and the axis of the horizon sensor, manipulate it with the phase of high-frequency oscillations, form a complex signal with phase manipulation, amplify it by power, radiate it, and receive it at the ground receiving point when passing through above it a spacecraft, the received complex signal is converted with phase shift keying in frequency using the voltage of the first reference frequency, the voltage between frequency, sequentially multiply and divide its phase into two, isolate the harmonic oscillation of the intermediate frequency, use it to synchronously detect the received complex signal with phase manipulation at the intermediate frequency, select a low-frequency voltage proportional to the modulating code, and use it to determine the location of the emergency object by of the Earth’s surface, at the same time the harmonic oscillation of the intermediate frequency is converted in frequency using the voltage of the second reference frequency oscillation isolated Doppler frequency value is determined, the sign and the value zero Doppler frequency and use them to update the elements of the spacecraft's orbit.

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