We present a technique for determination of ionospheric parameters based on automatic interpretation of ionograms of ionosphere vertical sounding (VS). Ionograms are interpreted using the points with significant amplitudes that were detected after the secondary data processing, results of modelling the VS signal height-frequency characteristic (HFC) being used. We developed algorithms to extract HFC tracks of signals reflected from E, F1 and F2-layers. These algorithms are based on the analysis of signal amplitude characteristics and plotting distribution histograms of points falling into the HFC model mask when the latter is moved over the ionogram. The algorithm to detect tracks of signals reflected from sporadic layers is implemented separately. From the resultant VS HFC, one can estimate ionospheric parameters and calculate electron density profile.
KEYWORDS: Reflection, Einsteinium, Algorithm development, Beam path, Signal processing, Signal detection, Wave propagation, Signal to noise ratio, Radio propagation, Modeling
We consider the algorithms for interpreting data of ionosphere oblique sounding (OS) by using continuous chirp signal. Ionograms are interpreted using the points with significant amplitudes that were detected after the secondary data processing, results of modelling the OS signal distance-frequency characteristic (DFC) being used. We developed hybrid algorithms to extract DFC tracks of signals reflected from F1 and F2-layers. These algorithms are based on the analysis of signal amplitude characteristics and plotting distribution histograms of points falling into the DFC model mask when the latter is moved over the ionogram. Algorithms to extract tracks of signals reflected from sporadic layers are given a separate consideration. Using the results of ionogram interpretation, one can detect the maximum observed frequencies of signal propagation modes on radio path.
We present a method to determine spatial distribution of the ionospheric electron density based on data of vertical (VS), oblique (OS), and backscatter (BS) sounding with a continuous chirp signal. Initial data represent the results of automatic processing and interpretation of ionograms, from which we calculate the height-frequency characteristics (HFC) of vertical sounding in the points selected on the sphere. From HFC tracks, we determine the ionospheric parameters and calculate the electron density profiles. This allows reconstruction of electron density spatial distribution within the sector of backscatter sounding and the region of HF radio paths. The resultant ionospheric parameters are used to correct ionospheric model IRI.
The methods for determining and correction of ionosphere parameters by real-time data of vertical and backscatter data sounding (VS and BS) by continuous chirp signal are presented. The input data are forecast ionosphere parameters and processing and interpretation results for VS and BS ionograms: VS height-frequency characteristic (HFC) and the leading edge of backscatter signal. On the base of the leading edge of BS signal one can calculate VS HFC for given points on the sphere in the sounding sector. On the base of HFC tracks the counting of ionosphere parameters is carried out. On the base extrapolation of the ratio of real to forecast values of ionosphere layer critical frequencies with account of layer geometrical parameters the correction of ionosphere parameters in given sphere points is carried out.
We present the application of the periodicity search technique for the solution of extrapolation problem for time series when the advance time of the forecast is 24 hours. This technique doesn't demand an equidistance of counting, has a little sensitive to missing data and can be used as the short-term forecast for several days ahead with background of 5 days. The considered technique has been used on the data obtained by chirp sounding network of ISTP SB RAS during the periods of strong and weak solar activity.
KEYWORDS: Backscatter, Wave propagation, Diagnostics, Data modeling, Data processing, Signal processing, Image processing, Image compression, Data compression, Interference (communication)
We present techniques and algorithms for processing and interpretation of backscatter ionosphere sounding ionograms received on chirp ionosonde. The processing of experimental ionograms is carried out on the basis of basic data filtration with the subsequent compression by method of the cellular automaton. The interpretation technique for ionograms is based on use of modeling results for frequency dependences on the minimum group way in the mode of the long-term forecast and results of experimental data processing. We also present the results of operative diagnostics of HF radio channel on the base of current backscatter sounding data.
The paper deals with techniques and algorithms of near real-time diagnostic software for estimating ionospheric parameters at a radio path midpoint based on data obtained from oblique sounding by a continuous chirp signal. We conducted a statistical analysis of precision characteristics of automatic determination of the critical frequency f0F2 at the path midpoint, using chirp ionosonde data.
The work is devoted to experimental check of operative technique for calculation of F2-layer parameters in path's midpoint
(critical frequency and peak height) using oblique sounding data. In this work experimental data obtained in 2003-2006 by FMCW-ionosounder in Irkutsk (over different paths with different length and orientation) were used. The IRI
data and experimental vertical sounding data (nearest to path's midpoint) were used for verifying of calculated values.
Experimental oblique sounding data recalculation into the path's midpoint parameters was performed on the basis of the
modified Smith method without consideration of Earth's magnetic field.
Oleg Berngardt, Victor Grozov, Nikolai Ilyin, Vladimir Kurkin, Andrey Medvedev, Sergei Ponomarchuk, Konstantin Ratovsky, Boris Shpynev, Alexander Voronov
We present a solid information system for storing, accessing and collecting of Earth upper atmosphere sounding data
produced by radiophysical instrument complex of Institute of Solar-Terrestrial Physics SB RAS. At present complex
consists of Irkutsk incoherent scatter radar unique in Russia, four frequency modulated current waves ionosounders
(FMCW) operating in vertical, oblique-incidence and backscattering sounding modes and two digital ionosounders
DPS-4. We suggest a technique for unification of heterogeneous data into united format and secondary processing with
unified technology based on international techniques of geophysical parameters determining. We discuss a structure of
united information system with Web access which allows us to integrate our radiophysical data into worldwide network
of geophysical data.
Ionospheric observations are necessary as for research scientific problems as for practical purposes. Different
ionospheric stations (AIS, Chirp-ionosounders, digisondes) are used widely for obtaining of information about ionosphere
condition at the concrete time moments. The methods of ionogram registration of ionospheric stations can be distinguished,
but ionogram processing and interpretation methods can be generally described by common regulations and
manuals. Creation of unified universal program apparatus for interpretation of ionograms and application it independently
from ionospheric stations type is logical in such situation. "SAO-Explorer" included in digisonde DPS-4 set is suggested
as such apparatus. It allows carrying out complete processing of ionosphere vertical sounding ionograms, to obtain
prediction meanings and to calculate electron density profile using International Reference Ionosphere IRI model
also. By the example of Kamchatka's automatic ionosphere station it was shown that the data reformatting into the digisonde
format and their following processing with a help of the program complex <> sufficiently facilitate
and accelerate the interpretation process of vertical sounding ionograms. By such a way were prepared and processed the
ionograms obtained during the period of 7-11 of November 2004. During this period the powerful magnetic storm generated
the powerful negative ionosphere disturbance, which made worse the ionosphere structure. Here are shown the results
of observations at the Petropavlovsk-Kamchatski and at the other VS-stations (Irkutsk, Yakutsk, Norilsk).
The powerful magnetic storm 29-31.10 was superposition of two strong magnetic storms from solar flares 28.12 (X17.2) and 29.10 (X10.0). Ionosphere response to the magnetic storm in Irkutsk (52°N, 104°E) was investigated by means of a complex of radiophysical facilities of ISTP SB RAS including digisonde DPS-4m FNCW-ionosonde and incoherent scatter 9IS) radar. In the work the main attention is given to the analysis of distinction in the data received on three various facilities.
KEYWORDS: Signal processing, Data acquisition, Antennas, Data processing, Physics, Receivers, Data conversion, IRIS Consortium, Knowledge management, Switches
Analysis of the behavior of main ionospheric parameters allows us to study the physical processes in the ionosphere and develop empirical and semi-empirical the ionosphere models (IRI) with applications to the various geo- and radio-physical problems. Vertical-incidence sounding ionosondes provide the key source of information about ionospheric parameters. The worldwide network of ionosondes includes over 120 stations. On the other hand, sounding techniques using chirp-signals (linear-frequency-modulated signals) are also under development mainly for oblique-incidence sounding paths. With a small receiver-transmitter separation on the order of 100 km, weakly oblique-incidence sounding is very similar in its information capabilities to vertical-incidence sounding. Furthermore, the constraint imposed on maximum duration is removed in the case of weakly oblique sounding thus making it possible to use chirp-signals with a long baseline and to signicantly improve the signal/noise ratio. It is therefore of interest to estimate the matching weakly oblique-incidence sounding data with vertical-incidence sound (VS) data acquired by sounders, such as digisonde DPS-4. This paper presents the results derived from comparing the weakly oblique-incidence sounding data with the main vertical-incidence ionospheric parameters obtained with digital ionosonde DPS-4. The comparisons are made for the ionosheric E- and F-regions, for both quiet and disturbed ionospheric conditions. Our study reported in this paper has shown that the recorded ionospheric parameters for the ionosondes of both types are similar in their values for both quiet and disturbed days.
Of decisive importance in diagnosing the ionospheric channel is the use of vertical-incidence sounding (VS) ionograms. The ionogram processing problem involves identifying characteristic points corresponding to actual signal modes, followed by approximating them in the form of traces. Within the framework of this problem, it is necessary to take the following steps: (1) to carry out a preprocessing of ionograms; (2) a compression of the data resulting in a substantial reduction in their amount and the identification of the times of arrival of the signal; and (3) a combination of the points, thus identified, into traces and referencing them to particular propagation modes. The solution of the first problem is achieved through use of statistical techniques for processing images. The cellular automaton is proposed in order to solve the second problem. The third problem is tackled by implementing Hopfield's method of artificial neural networks. As a consequence of the complicated character of the VS ionograms and due to the presence of scattered signals, errors are possible both when determining the times of arrival of signals and, especially, when combining them into traces. To solve this problem we suggest that use should be made of predicted values of critical values (foE, foF2) and heights h'F of regular layers obtained from a real-time version of the ionospheric model. An analysis of results made on the basis of the data from the ISTP chirp-sonde (Irkutsk) showed that this approach yields good results.
Knowledge of the state of the ionospheric radio channels is of great importance for both ionospere research and radio wave propagation predictions. Diagnostic of ionospheric radio channels is carried out by the analysis of ionograms. An efficient method of ionogram processing is proposed. It uses an artificial neural network (ANN) with the mean field theory updating scheme. Because of a complex character of ionospheric traces with quite a heavy background, a modified rotor model of Hopfield network is used. To speed up the convergence of the ANN evolution, a special initial ANN configuration is constructed in a vicinity of the global minimum of the ANN energy function. It is done by applying a special angular histograming within a sliding window, whose size is determined by the average local track curvature. Our model was tested on ionograms obtained on the chirp- ionosonde (ISTP, Irkutsk). Result analysis shows the efficiency of our approach and its prospects for the solution of the ionograms processing problems.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.