RU93995U1 - HARDWARE-SOFTWARE COMPLEX OF IONOSPHERIC MONITORING - Google Patents

Abstract

 A hardware-software complex for ionospheric monitoring, containing an antenna for receiving radio signals from navigation satellites, the output of which is connected to the input of a dual-frequency receiver of satellite navigation systems of the GLONASS and / or GPS type, characterized in that it is equipped with a processing and display unit, the input of which is connected to the output of a dual-frequency the receiver, while the processing and display unit is configured to determine the difference of the pseudorange ΔD12 by the combination of the pseudorange measured by the two-frequency receiver DF1 and DF2 to the navigation satellite and the phase values ψF1 and ψF2 of the received radio signals, as well as sequentially determining the total electron concentration Le along the satellite – ground point and the altitude profile of the electron concentration of the ionosphere N (z) in the measurement domain by applying an iterative solution procedure inverse problem based on the use of the conjugate gradient method and a priori information about the background state of the ionosphere.

Description

The utility model relates to radio engineering and geophysics, and in particular to means for monitoring the state of the ionosphere and measuring its parameters using spacecraft of global navigation systems. Such means of monitoring and determining the parameters of the ionosphere can be used, for example, to estimate the maximum applicable frequency in order to plan sessions of decameter (short-wave) radio communications; short-term forecasting of catastrophic earthquakes in order to take the necessary measures to prevent possible consequences, etc.

A device is known for measuring the total electronic content of the ionosphere at a single-frequency mode of operation of satellite radio navigation systems (RF Patent for Utility Model No. 76462, publ. 09/20/2008), implemented on the basis of the radio navigation receiver of satellite navigation systems of the GLONASS and / or GPS type (NAVSTAR) and including itself: a receiving antenna connected to the input of the radio frequency block, a radio frequency block connected to the output of the frequency synthesizer and the input of the analog-to-digital processor, the full electronic calculation unit contains connected to the outputs of the analog-digital processor and frequency synthesizer, as well as to the input of the information output device.

The disadvantages of this device are: limited functionality, because the device allows you to determine only the full electronic content of the ionosphere, i.e. integral characteristic of the ionosphere, while the solution of most applied problems in the field of radio communications and geophysics requires knowledge of the altitude distribution of the electron concentration of the ionosphere.

Closest to the proposed device is an ionospheric probe (RF Patent for the invention No. 2042129, publ. 08.20.1995 - [1]), implemented on the basis of dual-frequency navigation equipment for users of satellite navigation systems such as GLONASS and / or GPS (NAVSTAR).

This device includes a series-connected antenna for receiving radio signals from navigation satellites and a dual-frequency receiver of satellite navigation systems such as GLONASS and / or GPS.

The device [1] provides the reception of radio signals from navigation satellites at two coherent frequencies F1 and F2, the determination of the distances to the navigation satellite D _F1 and D _F2 , measured respectively at frequencies F1 and F2, the calculation of the full range difference (D _F1 - D _F2 ) electron concentration L _e along the satellite – ground track and determining the altitude profile of the electron concentration of the ionosphere Ne (h) by solving the inverse Tikhonov problem.

The disadvantages of this device are:

1. A significant error in determining the altitude profile of the electron concentration of the ionosphere Ne (h) due to the fact that to determine the altitude profile of the electron concentration of the ionosphere in the device [1], the method of solving the inverse problem according to Tikhonov is used, which is very sensitive to any measurement errors (A. Tikhonov ., Arsenin V.Ya. Methods for solving ill-posed problems. - M .: Nauka, 1986, p. 11, p. 105; Andrianov V.A., Smirnov V.M. On the accuracy of solving the inverse problem of radio transmission of the Earth's troposphere. // Radio Engineering and Electronics, 1991, No. 6, pp. 1081-1087 - [ 2]), and the reception of radio signals from navigation satellites is accompanied by interference leading to instability of the obtained solutions of the inverse problem by the Tikhonov regularization method and, as a result, significant errors in determining the altitude profile of the electron concentration of the ionosphere Ne (h) (Andrianov V.A., Smirnov V.M. Determination of the altitude profile of the electron concentration of the Earth’s ionosphere from two-frequency measurements of radio signals from artificial Earth satellites. // Radio engineering and electronics, 1993, t. 38. No. 7, p. 1326-1327 - [3]; Andrianov V.A., Armand N.A., Mosin E.L., Smirnov V.M. The use of radio signals from a satellite navigation system for sensing the Earth's ionosphere. Preprint IRE RAS, 1995, No. 5 (605), 24 pp. - [four]).

2. The impossibility of automation in the device [1] the process of determining the parameters of the ionosphere, because due to the indicated instability of the method for solving the inverse problem according to Tikhonov, to obtain (restore) the altitude profiles of the electron concentration of the ionosphere, it is necessary for the operator to participate in the selection of the regularization parameter a in order to minimize the residual modulus of the obtained solution of the inverse problem depending on the errors in determining the initial data (measurements).

The practical implementation of the Tikhonov regularization method in solving the inverse problem of radio illumination of the ionosphere has shown that minimizing the residual modulus is difficult [2-4] and, as a result, automation of the process of determining the ionosphere parameters is practically impossible.

3. Significant time for determining the altitude profile of the electron concentration of the ionosphere Ne (h), since the determination of the altitude profile of the electron concentration of the ionosphere in the device [1] is carried out only with the participation of the operator, the total time for determining the parameters of the ionosphere can reach units of hours. At the same time, it is known (Brunelli B.E., Namgaladze A.A. Ionosphere Physics. - M.: Nauka, 1988, pp. 404-486; E.L. Afraimovich, N.P. Perevalova. GPS monitoring of the upper Earth’s atmosphere. - Irkutsk: State Research Center RVH SB RAMS, 2006, p. 41), that the ionosphere has rather fast (about 10 ... 20 minutes) variations, therefore the prototype device does not provide the required efficiency of determining the ionosphere parameters.

For the same reason, when working on all simultaneously observed navigation satellites (currently the number of simultaneously observed satellites of the two GLONASS and GPS systems reaches 16), the participation of the operator in order to determine in real time the altitude profile of the electron concentration of the ionosphere Ne (h) is physically impossible.

4. A limited range of viewing angles of navigation satellites, at which the device [1] is operational, as a result, a small number of measurements of the electron concentration of the Earth’s ionosphere. The Tikhonov’s regularization method used in the device [1] for solving the inverse problem of radio illumination of the Earth’s ionosphere allows one to obtain a solution of the inverse problem only for a limited range of viewing angles of navigation satellites: acceptable accuracy for practical application of determining the altitude distribution of the electron concentration of the ionosphere is achieved only in the range of zenith viewing angles of satellites 50 ... 80 deg. (elevation angle 10-40 degrees), and at angles close to the zenith (0 ... 50 degrees), the differences in measurements are insignificant and, therefore, the system of equations being solved degenerates [3].

The technical result of the utility model is to increase the accuracy and provide automation of the process of determining the parameters of the ionosphere, as well as reducing the time to determine the parameters of the ionosphere while increasing the number of measurements of the electron concentration of the Earth's ionosphere.

The technical result is achieved due to the fact that the hardware-software complex of ionospheric monitoring, containing an antenna for receiving radio signals from navigation satellites, the output of which is connected to the input of a two-frequency receiver of satellite navigation systems such as GLONASS and / or GPS, according to the proposal, is equipped with a processing and display unit, the input of which connected to the output of the dual-frequency receiver, while the processing and display unit is configured to determine the pseudorange difference ΔD ₁₂ by a combination of and measured pseudorange D _F1 and D _F2 measured by a two-frequency receiver to the navigation satellite and phase values ψ _F1 and ψ _{F2 of the} received radio signals, as well as sequential determination of the total electron concentration _Le along the satellite – ground point and the altitude profile of the ionosphere electron concentration N (z) in the field of measurement by applying an iterative procedure for solving the inverse problem, based on the use of the conjugate gradient method and a priori information about the background state of the ionosphere.

Unlike the known device, the proposed device [1] additionally includes a processing and display unit that determines the altitude profile of the electron concentration of the ionosphere Ne (h) by applying an iterative procedure for solving the inverse problem based on the method of conjugate gradients and a priori information about the background state ionosphere (Smirnov V.M. Solution of the inverse problem of radio illumination of the Earth's ionosphere by gradient methods. // Radio Engineering and Electronics. 2001, No. 1, pp. 47-52 - [5]).

Moreover, this procedure is implemented for measuring the difference of ranges (D _F1 - D _F2 ), obtained as a result of a combination of rangefinder and phase measurements, which allows to obtain the values of the difference of ranges with the accuracy of phase measurements, which have higher accuracy compared to other types of measurements, which is explained by shorter wavelength of this signal relative to the code (rangefinder) signal.

Figure 1 presents the diagram of the proposed hardware-software complex ionospheric monitoring.

Figure 2 presents a view of the altitude profile of the electron concentration of the ionosphere N (z).

The block diagram of the proposed hardware-software complex of ionospheric monitoring is presented in figure 1 and includes: an antenna 1 for receiving radio signals from navigation satellites, a two-frequency receiver 2 of satellite navigation systems of the GLONASS and / or GPS type, as well as a processing and display unit 3. In this case, the output of the antenna 1 is connected to the input of the dual-frequency receiver 2, and the output of the latter is connected to the input of the processing and display unit 3.

Antenna 1 for receiving radio signals from navigation satellites can be made, for example, in the form of an antenna of type GPS-702-GGL (manufacturer NovAtel, Canada).

A two-frequency receiver 2 of GLONASS and / or GPS satellite navigation systems can be implemented, for example, as a ProPak-V3 type receiver (manufacturer NovAtel, Canada).

Block 3 processing and display can be performed, for example, in the form of a standard personal computer.

The proposed device operates as follows.

The signals from navigation satellites emitted at two coherent frequencies F1 and F2 are received by antenna 1 and fed to the input of a dual-frequency receiver 2, in which standard processing of the received signals takes place with the aim of determining the distances to a navigation satellite D _F1 and D _F2 , as well as determining the phase values of the received radio signals (measured at frequencies F1 and F2, respectively).

The output signals of the dual-frequency receiver 2, carrying information about the distances to a navigation satellite D _F1 and D _F2 , measured respectively at frequencies F1 and F2 and the corresponding phase values of the received radio signals, are input to the processing and display unit 3.

The processing and display unit 3 determines the range difference (D _F1 - D _F2 ) from the combination of the performed rangefinder and phase measurements, and also determines the total electron concentration _Le along the satellite – ground point in accordance with the known expression [1].

Considering the value obtained L _e processing unit 3 and determines the display area in the vertical profile measurement ionospheric electron concentration Ne (h) by applying an iterative procedure [5] of the inverse problem solutions based on the use of the conjugate gradient method and a priori information about the ionosphere background condition. At the same time, for example, a long-term ionosphere forecast based on some model of the ionosphere, for example, IRI-2007 (International Reference Ionosphere), can be used as a priori information about the background state of the ionosphere.

In the proposed complex, the determination of the pseudorange difference ΔD ₁₂ by the combination of measurements D _F1 , D _F2 and ψ _F1 , ψ _{F2 is} performed as follows: at each i-th time point after determining the pseudorange to the navigation satellite D _F1 and D _F2 , measured respectively at frequencies F1 and F2, and the corresponding phase values ψ _F1 and ψ _{F2 of the} received radio signals, the pseudorange difference Δ _{D12 is} determined by the formula:

ΔD ₁₂ (i) = (λ ₁ ψ _F1 (i) - λ ₂ ψ _F2 (i)) + (∑ [(λ ₁ ψ _F1 ) (i) - λ ₂ ψ _F2 (i)] + [D _F1 ( i) - D _F2 (i)]) M,

where ∑ is the summation sign over the variable i from 1 to M;

M is the number of time measurements taken into processing;

λ ₁ , λ ₂ - radiation wavelength at frequencies F1 and F2, respectively;

The determination of the total electron concentration _Le along the satellite-ground-track route is carried out according to the formula:

,

where δ is the error of phase measurements (in reality, the error in a linear measure is units of millimeters).

Assuming a spherically layered medium (valid for the Earth’s ionosphere within the observation interval), the pseudorange difference ΔD ₁₂ is related to the height distribution function of the electron concentration of the ionosphere N (z) as follows:

.

where Z ₁ and Z ₂ are the estimated heights of the lower and upper boundaries of the ionosphere, respectively,

ϑ - zenith angle of observation of the satellite from the point of measurement at every i-th point in time,

a is the radius of the Earth,

z is the current height from the surface of the Earth.

The solution of this equation with respect to the unknown (sought) function N (z) belongs to the class of incorrectly posed problems — the determination of the function N (z) from the measured value of the influence of the propagation medium — and is carried out by the conjugate gradient method [5, 6].

In the operator form, this equation can be rewritten as follows

Aφ = U,

where A is an integral operator; φ is a function that describes the distribution of the parameters of the propagation medium (distribution of electron concentration); U is the influence of the medium, in this case the difference of pseudorange.

In this case, the solution of the above equation with respect to the unknown function N (z) is reduced to finding a function φ for which the functional reaches a minimum, the value of which is determined mainly by the error of phase measurements.

The essence of the conjugate gradient method is as follows. Elements φ _{i of the} minimizing sequence are determined as follows. Each subsequent element of the sequence φ _{i + 1} is associated with the previous φ _{i by the} relation φ _{i + 1} = φ _i -α _i p _i , where P _i = -gradϕ (z _i ) + β _i p _i-1 is the direction of the function gradient, p ₀ = -gradϕ (z ₀ ), , is the value of the optimal step along the direction of the gradient, z ₀ is the zero approximation of the solution to the problem (in the general case, z ₀ is an arbitrary admissible point), 〈〉 means the scalar product.

As a priori information on the background state of the ionosphere (as a zero approximation of the solution to the problem), for example, a long-term forecast of the ionosphere based on some model of the ionosphere, for example, IRI-2007 (International Reference Ionosphere), can be used.

Upon reaching the minimum of the functional, the elements φ _{i of the} minimizing sequence represent the desired solution and correspond to the altitude profile of the electron concentration of the ionosphere N (z).

An example of determining the ionosphere parameters is given below.

After the antenna 1 receives radio signals (at two coherent frequencies F1 and F2) and processes them in a two-frequency receiver 2 of GLONASS and / or GPS satellite navigation systems, in block 3, a set of corresponding pseudorange values D _F1 and D _F2 , as well as phase values ψ _{F1, is} determined and ψ _F2 for each navigation satellite within sight of the receiver. An example of the initial data array for one satellite is given in the table.

Table Time, UT hour / min / s Time, sec D _F1, m D _F2 , m ψ _F1 , glad ψ _F2 , glad Elevation, hail Azimuth, hail 17:57:57 64677.0 21750210.307 21750211.683 114298170.044 89063496.902 40 32 17:57:58 64678.0 21750373.143 21750375.054 114299024.913 89064163.034 40 32 17:57:59 64679.0 21750536.662 21750538.744 114299880.412 89064829.642 40 32 17:58:00 64680.0 21750700.511 21750702.151 114300736.564 89065496.749 40 32 17:58:01 64681.0 21750864.181 21750865.602 114301593.350 89066164.408 40 32 17:58:02 64682.0 21751027.577 21751029.209 114302450.872 89066832.603 40 32 17:58:03 64683.0 21751191.263 21751194.277 114303309.205 89067501.426 40 32 17:58:04 64684.0 21751354.477 21751358.009 114304168.226 89068170.779 40 32 17:58:05 64685.0 21751518.052 21751520.914 114305027.841 89068840.615 40 32 17:58:06 64686.0 21751682.495 21751684.014 114305888.153 89069510.984 40 32 17:58:07 64687.0 21751847.377 21751847.534 114306749.144 89070181.865 40 32 17:58:08 64688.0 21752011.458 21752010.962 114307610.897 89070853.370 40 32 17:58:09 64689.0 21752175.143 21752174.563 114308473.283 89071525.368 40 32 17:58:10 64690.0 21752338.698 21752339.803 114309336.345 89072197.887 40 32 17:58:11 64691.0 21752502.602 21752503.532 114310199.969 89072870.891 40 32 17:58:12 64692.0 21752666.664 21752668.409 114311064.338 89073544.406 40 32 17:58:13 64693.0 21752831.128 21752832.557 114311929.355 89074218.459 40 32 17:58:14 64694.0 21752995.984 21752997.243 114312794.974 89074892.972 40 32 17:58:15 64695.0 21753161.651 21753163.611 114313661.305 89075568.018 40 32 17:58:16 64696.0 21753325.777 21753328.607 114314528.453 89076243.713 40 32 17:58:17 64697.0 21753490.996 21753493.553 114315396.396 89076920.039 40 32 17:58:18 64698.0 21753656.430 21753658.290 114316265.154 89077596.988 40 32 17:58:19 64699.0 21753822.548 21753824.158 114317134.608 89078274.488 40 32 17:58:20 64700.0 21753988.240 21753990.231 114318004.706 89078952.467 40 32 17:58:21 64701.0 21754154.307 21754157.077 114318875.529 89079631.023 40 32 17:58:22 64702.0 21754320.593 21754322.762 114319747.023 89080310.117 40 32

Given the set of values of D _F1 , D _F2 , ψ _F1 and ψ _F2 in block 3, the altitude profile of the electron concentration of the ionosphere N (z) is determined in the manner described above.

A view of the altitude profile of the electron concentration of the ionosphere N (z), obtained using the proposed device according to the results of processing the above values of D _F1 , D _F2 , ψ _F1 and ψ _F2 , is presented in figure 2.

Thus, due to the claimed combination of essential features, a technical result is achieved consisting in increasing the accuracy and providing the possibility of automating the process of determining the parameters of the ionosphere, as well as reducing the time for determining the parameters of the ionosphere with an increase in the number of measurements of the electron concentration of the Earth's ionosphere.

Improving the accuracy of determining the parameters of the ionosphere is achieved by:

- use as initial data for determining the altitude profile of the electron concentration of the ionosphere N (z) the results of measurements of the difference of pseudorange ΔD ₁₂ , obtained as a result of a combination of rangefinder and phase measurements and allowing to evaluate the value of the difference of pseudorange ΔD ₁₂ with higher accuracy;

- reducing the error in determining the altitude profile of the electron concentration of the ionosphere N (z) due to the use of the iterative procedure in the proposed device to solve the inverse problem based on the use of the conjugate gradient method and a priori information on the background state of the ionosphere, which is less sensitive to any measurement errors compared to the solution method inverse problem according to Tikhonov [2, 5, 6].

The possibility of automating the process of determining the parameters of the ionosphere is achieved through the use of the proposed iterative procedure for solving the inverse problem, based on the use of the conjugate gradient method, which, unlike the method of solving the inverse problem according to Tikhonov, does not require operator participation in its implementation, because There are standard mathematical approaches to the automatic calculation of function gradients [5, 6].

The reduction of the time for determining the ionosphere parameters is achieved by providing the possibility of automating the process of determining the altitude profile of the electron concentration of the ionosphere N (z) by applying an iterative procedure for solving the inverse problem based on the use of the conjugate gradient method. The proposed device provides in practice a reduction in the time of determining the parameters of the ionosphere from units of hours to 1 ... 2 minutes with the number of simultaneously observed satellites to 12 ... 16, which allows us to provide the required efficiency in determining the parameters of the ionosphere, not only under conditions of mellen, but in conditions of fast variations of the ionosphere.

An increase in the number of measurements of the electron concentration of the Earth's ionosphere is achieved by:

- reducing the time of determining the ionosphere parameters in each region of measurements (for each satellite) by automating the process of determining the altitude profile of the electron concentration of the ionosphere N (z) and, as a result, increasing the number of measurements a unit time;

- expanding the range of viewing angles of navigation satellites, at which the proposed device is operational. The proposed device, unlike the ionospheric probe [1], due to the application of an iterative procedure for solving the inverse problem based on the conjugate gradient method, turns out to be operable in almost the entire range of satellite zenith angles of observation (from 0 degrees to 80 degrees).

Claims (1)

A hardware-software complex for ionospheric monitoring, containing an antenna for receiving radio signals from navigation satellites, the output of which is connected to the input of a dual-frequency receiver of satellite navigation systems of the GLONASS and / or GPS type, characterized in that it is equipped with a processing and display unit, the input of which is connected to the output of a dual-frequency receiver, wherein the processing and display unit configured to determine pseudorange difference ΔD ₁₂ of two-frequency receiver combination measured pseudoranges nd D _F1 and D _F2 to a navigation satellite and ψ _F1 the phase values and ψ _F2 received radio signals, and sequentially determining the total electron concentration L _e along the track "satellite - ground station" and the altitude profile of the electron density of the ionosphere N (z) in the measuring region by applying an iterative procedure for solving the inverse problem, based on the use of the conjugate gradient method and a priori information about the background state of the ionosphere.