The method of detection, measurement of the phase velocity and the direction of arrival of ionospheric disturbances

 

(57) Abstract:

The use of the invention: systems for remote control of nuclear and other explosions, warning of missile launches, monitoring of seismic activity. The essence of the invention: time series of total electron content obtained using a spatial grid of dual-frequency receivers of signals of satellite navigation systems GLONASS/GPS with an aperture size corresponding to the far zone of the source of disturbances, filtered to identify variations of the total electron content corresponding to the response of the ionosphere to the influence of the source, obtained after filtering the signals shift in time by the value ofiand coherently summarize, achieving the maximum amplitude of the total signal, the decision about the detection of perturbations are in the excess of the total signal threshold level, and direction of arrival and magnitude of the phase velocity of the wave perturbations are solution of the system of equations describing in the chosen coordinate system the family of planar wave fronts, separated from each other by a distance determined relative time shiftsisignals separate priemnik is of the direction of arrival of ionospheric disturbances. 2 Il.

The invention relates to electrical engineering and can be used in systems for remote control of nuclear and other explosions, warning of missile launches, monitoring of seismic activity.

Known methods observations of ionospheric disturbances caused by anthropogenic and natural sources, based on registration delays of signals of satellite navigation systems GLONASS/GPS. Using multiple receivers GLONASS/GPS dual band perform latency of the navigation signals of GLONASS/GPS on the measured delays determine the value of the total electron content on the highway "receiver - navigation artificial satellite of the Earth." Filter rows total electron content for the individual receivers in the selected range of periods of oscillations and the presence of a signal above the specified level, register indignation caused by powerful ground explosions [1], runs spacecraft [2]. These methods are low sensitivity.

The closest to solving the problem is a method of determining the direction of arrival and the velocity of the ionospheric vozmoshnost it is with the help of lattice, consisting of three spatially separated dual-frequency receivers of signals of satellite navigation systems GLONASS/GPS receive time series fluctuations in the total electron content in the ionosphere of the Earth for a line receiver navigation artificial satellite of the Earth." By filtering the rows of the total electron content for individual receivers produce perturbations that contains the response of the ionosphere to the influence of the source. The parameters of motion of the wave front perturbations are determined by the values of mutual delay fluctuations of the total electron content registered at three points. Due to the fact that at the specified method decision about the detection of the perturbation is accepted by the analysis of the signal of each receiver separately, without taking into account the information of the other two receivers, and to determine the direction of arrival of wave perturbations using the minimum required number of receivers n= 3, the prototype method is characterized by low detection sensitivity and insufficient accuracy of measurement of the angle of arrival of the signal, especially at high level of ionospheric perturbation.

The aim of the invention is to increase chuvstvitelnostyu this is due to the fact, for the implementation of the proposed method is used grille with a large number n (n >> 3) spatially separated ground-based dual-frequency receivers of signals of satellite navigation systems GLONASS/GPS. The aperture of the lattice L is chosen so that to satisfy the condition of the far zone where

L is the maximum distance between receivers;

R is the estimated distance to the source of the disturbance;

- wavelength perturbations [3, 4, 5].

The signals obtained by filtering the rows of the total electron content for the individual receivers of the lattice, delay timei(i - number of the receiver) relative to the signal of one of the receivers is selected as the reference signal and coherently summed together. The decision about the detection of perturbations is taken when exceeding the total signal of a predetermined threshold. Direction of arrival and magnitude of the phase velocity of the wave perturbations are solution of the system of equations describing in the chosen coordinate system the family of planar wave fronts, separated from each other by a distance determined relative time shiftsisignals to individual receivers, which provide maximumamount receivers, projection pogonocherini points of the rays of the receiver and navigation artificial Earth satellite", the family of the phase fronts of the perturbation of the total electron content. In Fig.2 depicts the variations of the total electron content obtained for individual receivers corresponding to the response of the ionosphere to the influence of the perturbation source, and the total signal of all receivers.

Research a number of authors found that the response of the ionosphere to the powerful influence of anthropogenic (nuclear and chemical explosions, space launches) and natural (earthquakes, volcanic eruptions) sources are propagating in the direction of the source of the shock-acoustic waves. The distribution of the shock-acoustic waves leads to the perturbation of the total electron content in the ionosphere. The perturbation of the total electron content has a wavelength between 100 and 200 km, the period T of 200-300 C, the amplitude of the 1015-1016e/m2[3, 4, 5].

Each of the GLONASS/GPS registration phase delay L1and L2navigation signals with carrier frequency f1= 1575.42 MHz, f2= 1227,6 MHz on the track "receiver - navigation artificial satellite of the Earth."

Fluctuations in the values of total electron content contain low-frequency components caused by the movement of the navigation artificial Earth satellite, the latitudinal-longitudinal and diurnal course of the total electron content and high-frequency oscillations of I(t) caused by the perturbation of the total electron content in the propagation of the shock-acoustic waves from the source. To highlight these fluctuations in the ranks of the total electron content of the output of each receiver is fed to the input of the filter with a bandwidth corresponding to the bandwidth of the shock-acoustic waves. The feedback received I(t) belong to the projections 2 (Fig.1) on the horizontal plane points in the ionosphere, corresponding to the intersection of the beam receiver navigation artificial satellite of the Earth surface at the height of the layer maximum F2the ionosphere. Coordinates (xi; yithe specified point is found by knowing the coordinates of the receivers and navigateto filters the signals Ii(t) 3 (Fig.2) delay timeithe relative signal of the reference receiver I0(t) 4 (Fig.2) and then summarize. Valuesichoose so as to maximize the amplitude of the total signal Ic(t) 5 (Fig.2). When exceeding the total signal of a predetermined threshold, the decision about the discovery of the source of disturbance. The threshold value is determined by the criterion of detection. If the aperture of the lattice L and the distance to the source of the perturbation R such that the condition of the far zone, the front shock-acoustic waves in the area of the grid of receivers can be considered flat. Valuesidetermine distancesibetween the phase fronts of shock-acoustic waves, having a form of parallel lines passing through the point (xi; yi), wherei=iV; V is the phase velocity of the wave disturbance.

Distanceiare defined relative to the phase front, passing through the point with coordinates (x0; y0) corresponding to the reference receiver. Let the Cartesian coordinate system is set so that its origin coincides with the point (x0; y0), the axis of the Shelter system is directed to the North, and the Ox axis to the East (Fig. 1). Then the equation fasoft direct;

K = tg;

= 180- where

the azimuth of the wave vector of the ionospheric perturbations, measured from North in a clockwise direction.

Distanceifrom point (xi; yi) to a straight line with parameters a, b, passing through the point (x0;0), is defined by the equation

< / BR>
where xi= xi-x0; yi= yi-y0.

In this case, the unknown phase wave velocity perturbation V and the parameters a and b can be found from the system of equations

< / BR>
< / BR>
.................

< / BR>
The system of equations for three unknowns, V, V - solve numerically, by any known method [6]. The azimuth of arrival of ionospheric perturbations in the given coordinate system is determined from the expression

< / BR>
LITERATURE

1. Calais E. , Minster, B. J., M. A. Hofton, Hedlin, M. A. H. Ionospheric signature of surface mine blasts from Global Positioning System measurements.//Geophys. J. Int. 1998. V. 132. P. 191-202.

2. Calais, E. , J. B. Minster GPS detection of ionospheric perturbations following a Space Shuttle ascent. //Geophys. Res. Lett. 1996. V. 23. P. 1897-1900.

3. Afraimovich, E. L. , Kosogorov E. A., Plotnikov A. C. Detection using GPS-arrays of shock-acoustic waves generated during rocket start. Proceedings of the VI international scientific-technical conference "Radiola is sey R. S., Taranenko N. Y., Wu G. The blast wave of the Shuttle plume at ionospheric heights. // Geophys. Res. Lett. 1994. V. 21. P. 2737-2740.

5. Blanc, E. , Jacobson, A. R. Observation of ionospheric disturbances follwing a 5-kt chemical explosion. 2. Prolonged anomalies and stratifications in the lower thermosphere after shock passage. // Radio Science. 1989. V. 24. P. 739-746.

6. Bakhvalov N. C., Zhidkov N. P., Kobelkov, M. Numerical methods. - M.: Nauka, 1987.

The method of detection, measurement of the phase velocity and the direction of arrival of ionospheric disturbances based on data analysis of the total electron content in the ionosphere of the Earth, which are the result of processing the signals received dual-frequency receivers of satellite navigation systems GLONASS/GPS, located in the nodes of the grid aperture, satisfying the condition of the far zone, with the subsequent formation time series of the total electron content and filtering in the range of periods of oscillations corresponding to the response of the ionosphere to the influence of the source of ionospheric perturbations, characterized in that use grid number n (n > 3) spatially separated receivers, and the signals obtained after filtering the time series of the total electron content, coherently summed with time shiftsithat provide maximum ary signal threshold level, and the direction of arrival and the phase velocity of the ionospheric disturbance is determined from the solution of a system of equations describing in the chosen coordinate system the family of planar wave fronts, separated from each other by a distance determined relative time shiftsithat signals to individual receivers.

 

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