East-Siberian Center for the Earth's Ionosphere Research (SDC ESCEIR)

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Mathematical modelling and information support subdivision

SW radiosignal characteristics long-term prediction

The algorithm and appropriate program for decametric radiosignal propagation conditions prediction for paths from 500 to 9000 km have been developed at ISTP SB on the basis of normal wave method (AltyntsevaB.I,Iliyin N.V., Kurkin V.I. and others //Decameters channel simulation on the base of normal wave method. //Tekhnika sredstv svyasi.SS series. M.:Ekos, 1987. Issue.5. P.28-34) and refraction integral method(Kiyanovski M.P., Prudkovski A.G.,Kotovitch G.V. and others. Refraction integral method for two-dimensional non-homogenious ionosphere and its application to radio runs calculations //Tekhnika sredstv svyasi. SS series. M.:Ekos, 1987. Issue5. P.4-13). Oblique sounding signal characteristics are calculated for a given set of transmitting and receiving antennas, thus allowing us to choose antennas with different actual parameters.

The incident field characteristics calculation program package functional diagram ("Prognosis") is presented in the figure. The package work is directed by program "Manager", which has the following modes:

• Radioline calculation;
• Catalogues correction;
• Calculation results display.

The "radioline calculation" mode specifies in the interactive mode radio path geometric parameters (geographical location DB), prediction date, working frequency range, transmitting and receiving antennas (antenna DB), transmitter power, and solar activity indices correction. Geometry adjustment of the path of interest can be set in two ways:

• from transmitting point coordinates, radiation azimuth and distance;
• from transmitting and receiving points coordinates.

The frequency range can also be set in two ways:

• the frequency step is set automatically, high (MUF mode F2 of smallest multiplicity) and low frequency range boundary (F2 layer minimum critical frequency along the propagation path) are calculated by software;
• the high and low frequency range boundaries and frequency step are set manually.

Solar activity indices are chosen automatically from the prediction date from the database. The operator can correct values of indices or set them a new. If there is a need for multiple calculations, then current settings can be saved in a special configuration file.

After initial data setting "Manager" requests the file name for calculation results, creates working files on the working device with initial data, and transfers the control to the operational system for program modules initiation (through the batch-file). Upon completion of the calculation of the characteristics (MUF, DFC, AFC of propagation modes), the control is transferred to "Manager", thus storing results in the calculation results database with operator's confirmation.

The "catalogues correction" mode can form and correct catalogues (databases) of the solar activity, real antennas and geographical locations database.

The "results display" mode can display calculation results by transferring the control to Norton Commander.

On the basis of the OS signals characteristics calculation algorithm we have developed single algorithms for calculating real-time signal characteristics: MUF propagation modes calculation at a selected point of the Earth-ionosphere waveguide, signal focusing zones locations in the waveguide (Kurkin V.I.,Ponomartchuk S.N. SW signal focusing zone locations in Earth-ionosphere waveguide. /Issledovaniya po geomagnetismu, aeronomii i phisike Solntsa.M.:Nauka. 1989. Issue88. P.193-199). The illuminated zone boundary on-line calculation for working frequencies grid allows to create simpe algorithm for the BSS signals DFC calculation (Kurkin V.I.,Savkov S.S. On given distance MAF and BSS signals DFc calculations for smoothly non-honogenious radio runs. //Issledovaniya po geomagnetismu, aeronomii i phisike Solntsa.M.:Nauka. 1987.Issue77. P.48-52). The program package functional diagram for BSS signals DFC calculations is virtually the same as for OS signals characteristics calculation. Sounding path setting is determined from transmitting point coordinates, distance and azimuth .We can carry out BSS signals DFC calculation from the main sounding azimuth as well as from the backward direction.