RU2368550C1 - Elevation-time doppler system for detection of emergency object coordinates - Google Patents

Abstract

FIELD: transportation.

SUBSTANCE: system comprises transmitter (20) of emergency object, spacecraft (SC) and ground control station. SC has body, comprises infrared horizon detector (2) and board equipment. Equipment includes receiving antenna (3), comparison device (4), receiving device (5), the first metre (6) of Doppler frequency, blocking-generator (7), circuits "AND" (8), (9), valves (10), (11), pulse generator (12), pulse counter (13), switching circuit (14), memorizing device (15), transmitter (16), transmitting antenna (17), time device (18), setting generator (19), high frequency amplifier (28), the second heterodyne (29), the second mixer (30), amplifier (31) of the second intermediate frequency, amplitude detector (32), switch (33), modeling code shaper (34), phase manipulator (35) and power amplifier (36). Ground control station comprises high frequency generator (21), the first heterodyne (22), the first mixer (23), amplifier (24) of the first intermediate frequency, the first power amplifier (25), duplexer (26), transceiving antenna (27), the third power amplifier (37), the third heterodyne (38), the third mixer (39), amplifier (40) of the third intermediate frequency, phase doubler (41), the first (42), second (44) and third (47) narrow band filters, phase divider in two (43), phase detector (45), the fourth mixer (46), the second metre (48) of Doppler frequency and computing unit (49).

EFFECT: expansion of system functional resources by provision of control over information sending from SC to ground control station and specification of SC orbit elements.

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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 the ground control station.

A known method and system using spacecraft to determine the location of emergency objects (RF patents Nos. 2.027.195, 2.040.860, 2.059.423, 2.158.003, 2.174.092, 2.177.437, 2.201.601, 2.206.902, 2.240.950; US patents Nos. 4.161.730, 5.860.842; German patents Nos. 4.311.473, 4.322.288; Skubko R.A. et al. Sputnik at the helm. - L .: Shipbuilding, 1989. -168 S. and others).

Of the known methods and systems, the closest to the proposed system 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.

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

At the same time, a signal transmitter with high frequency stability is located at the emergency facility. On board the spacecraft is a measuring device that incorporates a highly stable frequency standard, the frequency of which is equal to the frequency of the emergency transmitter or differs from it by a strictly fixed value. Comparison of the frequency of the received oscillations with the frequency of the reference makes it possible to establish the magnitude of the Doppler frequency shift and determine the radial velocity from it.

However, the potential capabilities of the known system are not fully utilized. This system can also be used to control the discharge of information from the spacecraft to the ground control point and to clarify the elements of the orbit of the spacecraft.

An object of the invention is to expand the functionality of the system by controlling the discharge of information from the spacecraft to the ground control point and clarifying the elements of the orbit of the spacecraft.

The problem is solved in that the proposed elevation-time Doppler system for determining the coordinates of an emergency object, containing, in accordance with the closest analogue, a transmitter of the emergency object and a spacecraft, the axis of rotation of which is deviated from the local vertical, consisting of a housing, 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, and on-board equipment containing the receiving device is properly connected to the receiving antenna, the second input of which is connected to the first output of the master oscillator, the first 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 circuit And, the second input of which is connected to the second the output of the receiving device, the second circuit And, 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 through the pulse counter to the output of the pulse infrared an alternating horizon sensor and a pulse generator, a switching circuit, a storage device, a transmitter, the second input of which is connected to the second output of the switching circuit, and a transmitting antenna, while 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 the output of the second circuit And, and the output is connected to the input of the switching circuit, differs from the near analogue in that it is equipped with a ground control point, consisting of series-connected generators a high frequency torus, a first mixer, the second input of which is connected to the output of the first local oscillator, an amplifier of the first intermediate frequency, a first power amplifier, a duplexer, the input-output of which is connected to a transceiver antenna, a third power amplifier, a third mixer, the second input of which is connected to the output of the third a local oscillator, an amplifier of the third intermediate frequency, 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 amplifier of the third intermediate frequency, and the computing unit, from the fourth mixer in series connected to the output of the second narrow-band filter of the fourth mixer, the second input of which is connected to the second output of the high-frequency generator, the third narrow-band filter and the second Doppler frequency meter, the output of which is connected to the second input of the computing unit, the spacecraft’s onboard equipment is equipped with a high-frequency amplifier, a second local oscillator, a second mixer, a second intermediate-frequency amplifier, and an amplitude detector, the transmitter being made in the form of a key sequentially connected to the output of the memory device, the second input of which is connected to the output of the amplitude detector, modulator code generator, the second input of which is connected to the second output of the switching circuit, a phase manipulator, the second input of which is connected to the output of the amplifier the intermediate frequency, and the second power amplifier, the output of which is connected to the transmitting antenna, a high-power amplifier is connected in series to the output of the receiving antenna a frequency eye, a second mixer, the second input of which is connected to the output of the second local oscillator, an amplifier of the second intermediate frequency and an amplitude detector.

The geometric layout of the spacecraft and the emergency object are presented in figures 1 and 2. Structural diagrams of the spacecraft onboard equipment and ground control point are presented in figure 3. A frequency diagram explaining the process of converting signals by frequency is shown in FIG. 4.

Timing diagrams explaining the operation of the system are shown in Fig.6. The dependence of the Doppler frequency on time is shown in Fig.5.

The equipment located on board the spacecraft, the axis of rotation of which is deviated from the local vertical, contains a housing 1, an infrared sensor 2 of the horizon, placed on one axis opposite to the receiving antenna 3, the mechanical axis of which does not coincide with the axis of rotation of the spacecraft, and connected in series to the receiving antenna 3, a receiving device 5, the second input of which is connected to the first output of the master oscillator 19, a Doppler frequency meter 6, the second input of which is connected to the second output of the master oscillator 1 9, a braked blocking generator 7, circuit I 8, the second input of which is connected to the second output of the receiving device 5, circuit I 9, the second input of which is connected to the output of the blocking generator 7, the first valve 10, the second input of which is connected through the pulse counter 13 with the output of the horizon sensor 2 and the pulse generator 12, a switching circuit 14, a magnetic storage device 15, a key 33, a modulating code driver 34, the second input of which is connected to the second output of the switching circuit 14, a phase manipulator 35, the second input of which is connected to the output an amplifier 31 of a second intermediate frequency, a second power amplifier 36 and a transmitting antenna 17, 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 circuit And 9, and the output is connected to the second input of the circuit 14 switching, to the output of the receiving antenna 3, a high-frequency amplifier 28, a second mixer 30, a second input of which is connected to the output of the second local oscillator 29, an amplifier 31 of a second intermediate frequency and amplitude detectors are connected in series ctor 32, the output of which is connected to the second input of the key 33. The key 33, the generator 34 of the modulating code, the phase manipulator 35 and the second power amplifier 36 form a transmitter 16.

The equipment located at the ground control point contains a high-frequency generator 21 connected in series, a first mixer 23, the second input of which is connected to the output of the first local oscillator 22, an amplifier 24 of the first intermediate frequency, a first power amplifier 25, a duplexer 26, the input-output of which is connected to transceiver antenna 27, third power amplifier 37, third mixer 39, the second input of which is connected to the output of the third local oscillator 38, amplifier 40 of the third intermediate frequency, phase doubler 41, first narrow-band filter p 42, a phase divider 43 into two, a second narrow-band filter 44, a phase detector 45, the second input of which is connected to the output of the amplifier 40 of the third intermediate frequency, and a computing unit 49 connected in series to the output of the second narrow-band filter 44 is a fourth mixer 46, the second input of which connected to the second output of the high-frequency generator 21, a third narrow-band filter 47 and a second Doppler frequency meter 48, the output of which is connected to the second input of the computing unit 49.

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. A receiving antenna is selected such that the axis of the radiation pattern coincides with the mechanical axis of the antenna. 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 3.

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 receiving device 5. At the output of the circuit And 8 is zero. The coincidence circuit And 9 is closed, at its outputs also zero. A pulsed infrared sensor 2 of the horizon at the moment of intersection of the spacecraft path generates a pulse, which resets the counter 13 pulses. From the output of the generator 12 pulses, the pulses are fed to the counter 13. The valves 10, 11 are closed.

When a signal appears from the transmitter 20 of the emergency object in the strip of the earth’s surface viewed by the radiation pattern of the receiving antenna 3, a signal appears at the output of the receiving device 5. At the output of the circuit And 8 is one.

When the value of the Doppler frequency is reached at the output of the meter 6 equal to zero, the comparison device 4 opens and the braked blocking generator 7 starts, at the outputs of the circuits And 9, a unit appears. Valves 10, 11 open. In this case, the mechanical axis of the receiving antenna 3 is at the point of the beam. At this moment, the value of the angle α is measured between the axis of the horizon sensor 2 and the position of the mechanical axis of the receiving antenna 3. The measurements are tied to the on-board temporary devices 18 and recorded in the magnetic storage device 15 through the switching circuit 14 in the form of the number of pulses in the counter 13.

The coordinate of the sub-satellite point at the time of measurement is calculated. Measurements are taken at least two times. The coordinates of two sub-satellite points and two measured angles α ₁ and α ₂ between the mechanical axis of the receiving antenna 3 KA and the axis of the sensor 2 horizon determines the location of the emergency object.

When triggered by a pulse sensor 2 horizon, the system returns to its original state.

When the spacecraft appears in the reception area at the ground control point, a high-frequency generator 21 is turned on, which generates a high-frequency oscillation (Fig. 6, a)

where U _s , ω _s , φ _s , T _s - amplitude, carrier frequency, initial phase and duration of the oscillation.

This oscillation is fed to the first input of the first mixer 23, the second input of which is supplied with the voltage of the first local oscillator 22

At the output of the mixer 23, voltages of combination frequencies are generated. The amplifier 24 is allocated the voltage of the first intermediate (total) frequency

Where

K ₁ - gear ratio of the mixer;

ω _pr1 = ω _s + ω _g1 = ω ₁ - the first intermediate (total) frequency;

φ _pr1 = φ _s + φ _g1 ,

which after amplification in the power amplifier 25 through the duplexer 26 enters the transceiver antenna 27, is broadcast on the frequency ω ₁ = ω _CR1 , is captured by the receiving antenna 3 KA and through the high-frequency amplifier 28 is fed to the first input of the second mixer 30, to the second input of which voltage of the second local oscillator 29 is applied

At the output of the mixer 30, voltages of combination frequencies are generated. The amplifier 31 is allocated the voltage of the second intermediate (differential) frequency (Fig.6, b)

Where

_np2 ω = ω _z2 -ω _pr1 = ω ₂ - second intermediate (difference) frequency;

_WP2 cp = φ _pr1 -φ _r2,

which is fed to the input of the amplitude detector 32 and to the first input of the phase manipulator 35. The amplitude detector 32 selects the voltage envelope U _pr2 (t), which is fed to the control input of the key 33 and opens it. In the initial state, the key 33 is always closed. In this case, information about the value of the angles α ₁ , α ₂ and the measurement time recorded in the magnetic memory 15, through the public key 33 is fed to the input of the shaper 34, where the modulating code M (t) is generated (Fig.6, c).

This code is fed to the second input of the phase manipulator 35, the output of which forms a complex signal with phase manipulation (PSK) (Fig.6, g)

where φ _k (t) = {0, π} is the manipulated component of the phase that displays the law of phase manipulation in accordance with the modulating code M (t) (Fig.6c), 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);

τ _e , N - the duration and number of chips that make up a complex signal of duration T _s (T _s = Nτ _e ). This signal is amplified by power in the power amplifier 36 and radiated by the transmitting antenna 17 at a frequency ω ₂ = ω _pr2 ± Ω _d , is captured by the transceiver antenna 27, and through the duplexer 26 and the power amplifier 37 is supplied to the first input of the third mixer 39

where Ω _d - Doppler frequency shift;

the plus sign corresponds to the approximation of the receiver and the transmitter, the minus sign deletes, i.e. the sign determines the direction of the radial velocity vector.

The second input of the third mixer 39 is supplied with the voltage of the third local oscillator 38

The output of the mixer 39 is formed voltage Raman frequencies. The amplifier 40 is allocated the voltage of the third intermediate (differential) frequency (Fig.6, d)

Where

_PR3 ω = ω -ω _{z3 np2} = ω _s - third intermediate (difference) frequency;

_PR3 cp = φ _r3 -φ = φ _{with WP2}

This voltage is a complex QPSK signal at the third intermediate frequency ω _pr3 and is supplied to the first (information) input of the phase detector 45 and to the input of the phase doubler 41.

At the output of the phase doubler 41, a harmonic voltage is generated (Fig.6, e)

Where

K ₂ - transfer coefficient of the multiplier (as a doubler 41

phase, a multiplier is used, at the two inputs of which the same voltage is applied u _pr3 (t)),

in which phase manipulation is already absent, since 2φ _k (t) = {0.2π}.

The spectrum width Δf _{c of the} complex QPSK signal is determined by the duration τ _{e of} its elementary premises (Δf _c = 1 / τ _e ). Whereas the width of the spectrum Δf _{2 of} its second harmonic is determined by the signal duration T _s (Δf ₂ = 1 / T _s ). Therefore, when the phase is multiplied by two broadband QPSK signals, its spectrum collapses N times (Δf _s / Δf ₂ = N).

The harmonic voltage u ₃ (t) is allocated by a narrow-band filter 42 and is fed to the input of a phase divider 43 into two, the output of which is a harmonic voltage (Fig.6, g)

This voltage is allocated by a narrow-band filter 44 and is supplied to the first input of the fourth mixer 46 and to the second (reference) input of the phase detector 45. At the output of the latter, a low-frequency voltage is generated (Fig.6, h)

Where

K ₃ - the transfer coefficient of the phase detector,

proportional to the modulating code M (t) (Fig.6, c). This voltage is supplied to the first input of the computing unit 49.

At the second input of the mixer 46, a high-frequency oscillation u _c (t) is supplied from the second output of the generator 21. A low-frequency voltage is generated at the output of the mixer 46

Where

which is proportional to the Doppler frequency shift, is allocated by a narrow-band filter 47 and fed to the input of the Doppler frequency meter 48. The measured value of the Doppler frequency is fed to the second input of the computing unit 49.

In the computing unit 49, the coordinates of two sub-satellite points and two measured angles α ₁ and α ₂ uniquely determine the location of the emergency object.

In the computing unit 49, spacecraft orbit elements are also calculated. Doppler frequency is determined based on the ratio

Where

λ _s is the working wavelength;

r is the current distance between the spacecraft and the ground control point.

If you count the time from the moment of the spacecraft passage of the traverse point, then the current distance is (Fig. 5)

where r ₀ is the shortest distance between the spacecraft and the ground control point;

V is the speed of the spacecraft in orbit.

Substituting (2) in (1) gives

The dependence of the Doppler frequency on time, calculated by the formula (3) under the condition that V = 7.9 km / s, r ₀ = 500 km and λ _s = 3 m, is shown in Fig. 5 (a, b)

As can be seen, this dependence is a monotonically decreasing function of time, and with an unlimited increase in the absolute value of t, both branches of this curve tend to the same, but different in sign, limit.

и тогда (фиг.5)In a linear section near the inflection point

and then (figure 5)

Differentiating (4) with respect to time, we can find the expression for the derivative of the Doppler frequency

From the last expression it follows that knowing the velocity V and the wavelength λ _s , as well as measuring the derivative F ' _d , we can find the shortest distance

These calculations are carried out in computing unit 49. Thus, the proposed system, in comparison with the prototype and other technical solutions of a similar purpose, provides control of the dumping of information from the spacecraft to the ground control point and refinement of the orbit elements of the spacecraft. In this case, the interrogation method for measuring the radial velocity of the spacecraft is used, a feature of which is the need for decoupling the interrogation and response signals, which is achieved by spacing them in frequency.

Since with the interrogation method for measuring radial velocity, the reference oscillations of the receiver mixers and the transmitter signal are generated by a high-frequency common oscillator 21, only the frequency drift of this generator during propagation of the signal to the spacecraft and vice versa significantly affects the measurement accuracy. The high short-term stability of the frequency of the generator 21 is provided easier than the high long-term stability of the reference generators in non-demanding systems. Therefore, in query systems, the same measurement accuracy as in non-query systems can be obtained using simpler (quartz) oscillators. Thus, the functionality of the system is expanded.

Claims (1)

An angular-temporal Doppler system for determining the coordinates of an emergency object, containing a transmitter of an emergency object and a spacecraft with an axis of rotation deviated from the local vertical, including a housing, a pulsed infrared horizon sensor, located on the same axis with the receiving antenna opposite to it, and the mechanical axis of the antenna does not coincide with the axis of rotation of the spacecraft, and on-board equipment containing a receiver in series connected to the receiving antenna, the second input of which o connected to the first output of the master oscillator, the first 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 circuit And, the second input of which is connected to the second output of the receiver, the second circuit And, the second input which is connected to the second output of the blocking generator, the first valve, the second input of which is connected through the pulse counter to the outputs of the pulsed infrared horizon sensor and the pulse generator, the communication circuit, remembering its device, a transmitter, the second input of which is connected to the second output of the switching circuit, and a transmitting antenna, while 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 AND circuit, and the output is connected to the input switching circuit, characterized in that it is equipped with a ground control station containing a high-frequency generator in series, a first mixer, the second input of which is connected to the output of the first local oscillator , an amplifier of the first intermediate frequency, a first power amplifier, a duplexer, the input-output of which is connected to the transceiver antenna, a third power amplifier, a third mixer, a second input of which is connected to the output of the third local oscillator, an amplifier of the third intermediate frequency, a phase doubler, the first narrow-band filter, divider phases into two, a second narrow-band filter, a phase detector, the second input of which is connected to the output of the amplifier of the third intermediate frequency, and a computing unit, as well as connected in series to the second narrow-band filter ode is the fourth mixer, the second input of which is connected to the second output of the high-frequency generator, the third narrow-band filter and the second Doppler frequency meter, the output of which is connected to the second input of the computing unit, while the spacecraft onboard equipment is equipped with a high-frequency amplifier, the second local oscillator, the second mixer, the amplifier of the second intermediate frequency and the amplitude detector, and the transmitter is made in the form of series-connected to the output of the storage a key device, the second input of which is connected to the output of the amplitude detector, the generator of the modulating code, the second input of which is connected to the second output of the switching circuit, a phase manipulator, the second input of which is connected to the output of the amplifier of the second intermediate frequency, and a second power amplifier, the output of which is connected to the transmitting an antenna, while a high-frequency amplifier, a second mixer, the second input of which is connected to the output of the second local oscillator, are connected in series to the output of the receiving antenna Torah intermediate frequency and amplitude detector.

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