RU2734108C1 - Method of determining coordinates of radio-frequency radiation sources - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to radio direction-finding, specifically to determining location of radio-frequency sources (RFS). In the method of determining coordinates of radio-frequency sources located in a given region of the Earth, emitting a periodic sequence of signals, in a given region of the Earth, a spatial multi-position system for determining coordinates by means of receiving equipment of one spacecraft (SC) or aircraft (AC) moving in space and conducting monitoring of the specified area of the Earth. That is ensured by calculating the arrival time of the same individual fragments of the emitted periodic signal sequence in the receiving equipment of the spacecraft (or aircraft) by interpolation in time of said fragments received at spaced points of the spacecraft orbit (or AC). Then, receiving equipment of one spacecraft is used to process signal fragments and, as per difference between actual pulses arrival times and calculated pulses positions on time axis, determining the coordinates of the radio-frequency source on the surface of the earth by a radio-dimensional method.

EFFECT: technical result consists in simplification of the process of determining spatial coordinates of an object using a system of space or aircraft radio-electronic probing of the surface of the Earth.

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Description

The invention relates to the field of radio direction finding, namely, to determine the location of objects - sources of radio emission (IRI).

The main method for locating the IRI is direction finding. This method has a high resolution, reliability and efficiency when processing large streams of signals received from the entire radio visibility range, but it does not have very high accuracy characteristics, especially when the SIR is removed from the sub-satellite point.

а значение Δt выбирают в пределах от 30 до 6000 с. Запоминают упомянутые значения Q и соответствующие им моменты времени t_i. Вычисляют размер максимальной пеленгационной базы (ПБ), причем ПБ являются различные пары точек орбиты спутника, запоминают его. Группируют попарно все возможные сочетания ПБ на интервале упомянутых Q значений с шагом n=ΔT/Δt, где ΔT - временной шаг формирования ПБ. Сравнивают размеры ПБ в сгруппированных парах с пороговым значением, выделяют пары ПБ, в которых обе ПБ не короче порогового значения. Измеряют угол между ПБ в выделенных парах ПБ, сравнивают измеренный угол с пороговым значением. Выбирают пары ПБ, в которых измеренный угол не менее порогового значения, и для каждой из выбранных пар ПБ интегрируют на соответствующем каждой ПБ интервале времени запомненные значения доплеровского сдвига несущей частоты сигнала для трассы «ЗС - спутник». Определяют разностно-дальномерным способом местоположение ЗС. Далее запоминают координаты ЗС, усредняют запомненные координаты, а результат усреднения определяют как окончательное местоположение ЗС. Недостатком способа является высокий уровень погрешности при определении координат. На практике сложно обеспечить приемлемую точность данных измерений угла между ПБ в выделенных парах ПБ.Known "Method for determining the location of a satellite earth station by a relayed signal" (patent RU 2172495 C1, priority from 06/05/2000, IPC G01S 5/00, G01S 5/06). In the method, a signal from the desired earth station (ES) is received at the receiving earth station (WGS), the values of the Doppler shift of the signal carrier frequency are measured for the entire path "ZS - satellite - MES" at the appropriate times t _i with a step of Δt, and they are processed. On the basis of the processing, the values of the Doppler shift of the signal carrier frequency are calculated for the path "ЗС - satellite". The total number Q of the measured values of the Doppler shift of the signal frequency for the path "ЗС - satellite - СЗС" and the calculated values of the Doppler shift of the signal frequency for the path "ЗС - satellite" is selected from the condition

and the value of Δt is selected in the range from 30 to 6000 s. The mentioned values of Q and the corresponding moments of time t _{i are stored} . The size of the maximum direction finding base (PB) is calculated, and the PB are different pairs of satellite orbit points, and it is stored. All possible PB combinations are grouped in pairs on the interval of the mentioned Q values with a step n = ΔT / Δt, where ΔT is the time step of PB formation. The sizes of PB in grouped pairs are compared with the threshold value, pairs of PBs are distinguished in which both PBs are not shorter than the threshold value. Measure the angle between the PB in the selected pairs of PB, compare the measured angle with the threshold value. PB pairs are selected in which the measured angle is not less than the threshold value, and for each of the selected PB pairs, the stored values of the Doppler shift of the signal carrier frequency for the "GS - satellite" path are integrated at the corresponding time interval for each PB. The location of the ES is determined by the differential-ranging method. Further, the coordinates of the ES are stored, the stored coordinates are averaged, and the averaging result is determined as the final location of the ES. The disadvantage of this method is the high level of error in determining the coordinates. In practice, it is difficult to ensure an acceptable accuracy of measurement data for the angle between PBs in selected pairs of PBs.

Known "Angular-time Doppler method for determining the coordinates of an emergency object", adopted by the applicant for a prototype (patent RU 2302645 C1, priority from 16.02.2006, IPC G01S 5/02, H04B 7/185, B64G 3/00, G01C 21/00) ... The implementation of the differential-rangefinder method for determining the coordinates of radio wave radiation sources (RRS) in the prototype is carried out when organizing a single-stage signal reception from RRS using a ballistically coupled constellation of two or three spacecraft or, respectively, a constellation of aircraft. The proposed method consists in measuring the Doppler frequency by a non-query method when the signal from the transmitter of the emergency object appears in the field of view of the receiving antenna of the spacecraft. The proposed method can be used on spacecraft in orbit of an artificial Earth satellite, the edge of the geostationary, stabilized by rotation along the vertical axis. The disadvantages of such systems are: high cost, constant changes in the size of the bases in real flight, problems with the elimination of ambiguity when receiving signals, especially with an increase in the size of the bases, the complexity in organizing the control of observation processes, etc.

Differential rangefinder (RDM) positioning method requires measuring the arrival times (or their differences) of the same signal at three (not necessarily different) points in space along different paths.

In this case, under the assumption that the signal propagates in space in a rectilinear manner at the speed of light, the differences in the signal reception times are recalculated in the difference in the distances from the reception points to the IRI.

However, as a rule, there is only one spacecraft (or aircraft) of this system in the radio visibility zone of the IRI, and in some cases, under conditions of multiple reception of signals from a stationary source, only one receiver located on a moving spacecraft (or aircraft) can be used. quasi-difference-rangefinder "method (quasi-RDM) for determining the location of a radio emission source.

The use of quasi-RDM becomes possible if the emission of radio signals by the source is so regular that, knowing the moments of emission of one or several signals, it is possible to predict with high accuracy the moments of emission of subsequent signals over a long period of time. Based on these predictions, it is possible to "quasi-synchronize" the signals received at different points in time at the spaced points of the spacecraft (or aircraft) trajectory, and to calculate the difference in distances to the ERS corresponding to these points.

The simplest example of regular radiation is a periodic sequence of signals emitted with a constant period T. To determine the moment of emission of the next signal, it is enough to know the moment of emission of one (any) of the previous signals and the number of signals emitted in the interval between them.

In reality, a number of radio electronic devices use signals with interpulse intervals varying according to a certain law (the so-called "period wobble"). In a more complex case, the IRI performs wobbling of the signal repetition period, when the time intervals between adjacent signals are periodically repeated: T ₁ , T ₂ , ..., T _K , T ₁ , T ₂ . Such a sequence can be split into K periodic subsequences, each of which has a period

Thus, the solution to the problem of positioning the RRI with wobbling of the signal repetition period can be reduced to solving a simpler problem focused on the emission of signals with a constant period.

The technical result of the claimed invention is to simplify the process of determining the spatial coordinates of an object using a system of space or aviation electronic sounding of the Earth's surface, while using only one spacecraft (or aircraft) instead of a multi-position bearing with several spacecraft, and creating increasingly simple, cheap, affordable radio-imaging technologies, ensuring their wider application in various practical problems of remote sensing of the Earth.

For this, a method is proposed for determining the coordinates of radio emission sources (IRS) located in a given region of the Earth, emitting a periodic sequence of signals, which consists in the fact that in a given region of the Earth a spatial multipositional coordinate determination system is created in time, characterized in that the spatial multipositional coordinate determination system created by means of the receiving equipment of one spacecraft (SC) or aircraft (AC), moving in space and conducting observation of a given area of the Earth, for this, the time of arrival in the receiving equipment of the SC (or aircraft) of the same individual fragments of the emitted periodic signal sequence is calculated by time interpolation of these fragments received at the spaced points of the spacecraft orbit (or aircraft), the signal fragments are processed by the receiving equipment of one spacecraft, and, according to the difference between the arrival times of real pulses and the calculated positions pulses on the time axis, determine the coordinates of the IRI on the surface of the earth using the radio range method.

A source located on the Earth's surface emits a periodic sequence of signals (possibly with missing fragments of this sequence).

A signal receiver located on board a spacecraft (or aircraft) moves in space and receives signals from a source. At the moments of receiving each signal, the coordinates (latitude, longitude, altitude) of the spacecraft (or aircraft) and the time of signal reception are measured, with a certain accuracy. In this case, either all emitted signals are received (with small gaps associated with errors or reception interference), or individual "bursts" consisting of several successive signals.

It is possible to simulate spaced apart measurements of the reception time of the same signal when using the same spacecraft (or aircraft) if the signal can be interpolated in time (for example, if it has periodic repetitions of the same fragments, so that by determining the times the arrival of these fragments at spaced points of the spacecraft orbit (or aircraft), it is possible to calculate the arrival times of the same signal fragment at these points of the orbit).

The main part of the initial information for the algorithm for determining the position of the IRR is the results of measuring the parameters of the signals received by the equipment installed on the spacecraft (or aircraft) during its flight, as well as navigation data on the location of the spacecraft (or aircraft) at the moments of receiving signals.

Another part of the initial information is a set of parameters that make it possible to select from the entire set of received signals signals from the same IRI. First of all, it is a set of radio technical parameters inherent to the IRI. It is also possible that there is a priori information about the area of its location. In particular, this information can be obtained as a result of radio direction finding, produced by processing data from the same observation session, or one of the preceding ones.

In any case, the boundaries of the observation area are set, within which the radio emission source is deliberately located.

The method for determining the spatial coordinates of radio emission sources consists in creating a spatial multi-position system in time due to the movement in the orbit of one spacecraft (or aircraft). The spacecraft (or aircraft) monitors the given area of the Earth, receives and processes the signals from the IRR. Next, the differences between the arrival times of real pulses and the calculated positions of the pulses on the time axis are calculated, where the pulses should have been if the spacecraft (or aircraft) did not move relative to the IRR.

The information received on the spacecraft (or aircraft) during the flight can be processed both on board the spacecraft (or aircraft) and at the ground complex for receiving and processing the transmitted information.

FIG. 1 shows a diagram of the creation in time of a spatial multi-position system by a group of several spacecraft.

Figure 2 shows a diagram of the creation in time of a spatial multi-position system by one spacecraft. Here:

1. Position of the spacecraft at time t ₁ - SC (t ₁ ).

2. The position of the spacecraft at time t ₂ - SC (t ₂ ).

3. The position of the spacecraft at time t ₃ - SC (t ₃ ).

4. The source of radio emission - IRI.

The claimed method for determining the spatial coordinates of an object is carried out as follows (Fig. 2):

- a spatial multi-position system is created in time due to the orbital motion of one spacecraft (or aircraft);

- the time differences of arrival Δt _i are calculated between the real pulses and the calculated positions of the pulses on the time axis, where the pulses should have been if the spacecraft (or aircraft) did not move relative to the IRR;

- the calculated values of the path differences Δt _i are used in the same way as in the traditional RDM.

To implement RDM using software, it is necessary to select the class of IRI, the signals of which have a periodic structure, to learn to identify fragments of the same IRR spaced in time of radiation (using coordinates obtained by the direction finding method and radio technical parameters of signals), and also to evaluate the calculation errors Δt _i by the formula

where T is the pulse repetition period;

n _i is an integer number of periods T that have passed over the interval [t _i t _{i + 1} ].

The calculated values of the path differences Δt _i are used in the same way as in the traditional RDM.

Formula (1) is determined by the accuracy of knowledge of T and the value of n. This class includes some subscribers of satellite communications systems and some radar stations.

Let us consider the possibilities of specifying the coordinates for pulsed ERS based on the results of signal reception in one session of the spacecraft (or aircraft) observation. In case of target planning of observation, the set of observations for a session of the same IRI is a group of signal fragments received at times t ₁ , t ₂ , ... t _n ∈ [t _n.s. t _c.c. ], here

- t _n.s. - start time of the observation session;

- t _c.c. - time of the end of the observation session.

A fragment of the signal of a pulsed IRI with the number i (i = 1, 2, ...) is a burst of a number of pulses, and let t _i be the time of reception of the first of them.

For each group of pulses using the direction finding method, an estimate of coordinates (latitude, longitude), radio technical parameters of the signal are determined: carrier frequency, pulse duration, time intervals between them, etc. This information is sufficient to group the flow of signal fragments according to belonging to one radiation source ...

A fairly large part of modern IRI has a certain periodicity of radiation, which consists in sending a group of pulses with a constant, strictly specified sequence of intervals between them T ₁ , T ₂ , ..., T _K. In this case, with known values of T ₁ , T ₂ , _... , T _K , it becomes possible to calculate the time interval between the emissions of the same pulses in different packs received at different points in space (in those where the spacecraft or aircraft was at the time of reception).

Thus, when realizing the determination of the reception time of signal fragments with an accuracy of 10 ^-5 s, the intervals between pulses of about 10 ^-7 s, and the accuracy of the positioning of the center of mass of the spacecraft (or aircraft) of the order of 300 m by using the differential-rangefinder method, it is possible to refine the coordinates of the pulsed SIR, operating with periodic radiation of packets of pulses, up to a value of the order of a few kilometers at a distance from the sub-satellite point up to 3000 km, which the direction finding method cannot provide.

The algorithm for specifying the coordinates of pulsed IRI should consist of the following stages:

1. Identification of signals of IRR belonging to one source, received at different times t _i , t _j , is carried out according to the following criterion

Here:

- вектора измеренных координат i-ого и j-ого сигналов;

- vectors of measured coordinates of the i-th and j-th signals;

Q _i , Q _j - correlation matrices of the measured coordinates of the i-th and j-th signals;

- пороговое значение для идентификации сигналов от одного ИРИ

- threshold value for identifying signals from one IRI

ϕ _i , ϕ _j - latitude;

λ _j , λ _j - longitude.

2. By correlation processing of all sequences {T ₁ ⁱ , T ₂ ⁱ , ... T _K ⁱ }, the repetition period of the bursts of pulses T _∑ is estimated.

для

отождествившихся отметок по формуле3. The averaged coordinates are determined

for

identified marks by the formula

4. Calculated:

до точек расположения КА (или ЛА) в моменты времени t₁, t₂, …, t_n приема идентифицированных между собой сигналов

где x_i y_i, z_i - координаты КА (или ЛА) в момент измерения i-ого фрагмента сигнала; а х₀, у₀, z₀ - декартовы гринвичские координаты точки

;- distances d ₁ , d ₂ , ..., d _n from the point

to the points of location of the spacecraft (or aircraft) at times t ₁ , t ₂ , ..., t _{n of} receiving signals identified among themselves

where x _i y _i , z _i - coordinates of the spacecraft (or aircraft) at the time of measurement of the i-th signal fragment; а х ₀ , у ₀ , z ₀ - Cartesian Greenwich coordinates of the point

;

- values Δt` _i = (d _i -d _i-1 ) / c;

- приема одноименных импульсов в точках пространства x_i, y_i, z_i;- values δt _i = t` <sub>i</sub> -t` _i-1 -Δt` <sub>i</sub> , where t` _i , t` _i-1 are the times of reception of pulses corresponding to the intersection of sequences {T ₁ ⁱ , T ₂ ⁱ , ... T _k ⁱ } ∩ {T ₁ ^i-1 , T ₂ ^i-1 ,… T _m ^i-1 }, and the moments

- reception of pulses of the same name at points in space x _i , y _i , z _i ;

- the number of bursts of pulses emitted between times t _i , t _i-1 , n _i = δt _i / T _∑ (in this case, n must be a positive integer);

- the value of the repetition period of bursts of pulses T _∑ is specified according to the formula T _∑ = (∑n _i δt _i ) / ∑n _i ² .

5. The hypothetical times of reception of the first of the received bursts of pulses at points in space x _i , y _i , z _{i are} calculated.

6. The equation is solved

- вектор измеряемых параметров;Where

- vector of measured parameters;

- вектор оцениваемых параметров;

- vector of the estimated parameters;

- вектор навигационных параметров;

- vector of navigation parameters;

R - correlation matrix of the measured parameters vector;

- функция зависимости истинных значений измеряемых параметров от

- the function of the dependence of the true values of the measured parameters on

, а в качестве измерений - вектор, составленный из разностей t^{^} _i-t^{^} ₁. Итерации выполняются до тех пор, пока

где ε выбирается исходя из реальных возможностей местоопределения (ε≈10^-5).Moreover, the coordinates of the point are used as the zero approximation

, and as measurements - a vector composed of the differences t ^{^} _i -t ^{^} ₁ . Iterations are performed until

where ε is chosen based on the real possibilities of positioning (ε≈10 ^-5 ).

As a result, its location is determined by the updated coordinates of the IRI.

Claims (1)

A method for determining the coordinates of radio emission sources (IRI) located in a given region of the Earth, emitting a periodic sequence of signals, which consists in the fact that in a given region of the Earth a spatial multi-position coordinate determination system is created in time, characterized in that a spatial multi-position coordinate determination system is created by means of a receiving equipment of one spacecraft (SC) or aircraft (AC), moving in space and observing a given area of the Earth, for this purpose, the time of arrival at the receiving equipment of the SC (or aircraft) of the same individual fragments of the emitted periodic sequence of signals is calculated by interpolation by the time of these fragments, received at the spaced points of the spacecraft orbit (or aircraft), are processed by the receiving equipment of one spacecraft signal fragments and, according to the difference between the arrival times of real pulses and the calculated pulse positions on the time axis , determine the coordinates of the IRI on the surface of the earth by the radio range-finding method.

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