ADAPTIVE RADIO ASTRONOMY. CORRECTION OF THE PHASE DELAY AND THE ROTATION OF POLARIZATION 
PLANE USING GPS SOUNDING DATA, REGIONAL IONOSPHERE MAPS AND THE IONOSPHERIC MODELING.
E.L. Afraimovich, YU. V. Yasukevich

VHF and HF radio signals are widely used for observations of the Sun and pulsars. Nowadays 
huge low-frequency radio astronomical arrays (LOFAR, 30-240 MHz; MIRA, 80-300 MHz) are 
being constructed to record pulsars radiation at maximum far distance. Registration of 
solar radio emission intensity at fixed frequencies and in spectral VHF band is very 
important along with others methods of monitoring of coronal mass ejections. In order 
to interpret radio astronomical data it is necessary to take into account the possible 
distortions of these signals in the Earth ionosphere. However in contrast to modern 
navigation systems (GPS, GLONASS, GALILEO), where very accurate reconstruction of 
ionosphere parameters is a built-in function, in present-day radio astronomy a retrieve 
of ionosphere transfer characteristics has not been appropriately worked out yet. It is 
collide with increasing requirements to accuracy of the analysis of radio emission amplitude 
profile and to the angular and polarizing resolution of radio telescopes of new generation. 
We have developed a method and software for calculation of the ionosphere measure of 
rotation (RM), and measure of dispersion (DM). We used the ionosphere model IRI-2001, 
magnetic field model IGRF-10 and values of ionosphere total electron content as deduced 
from GPS measurements. The obtained values of DM and RM were recalculated into characteristics 
of phase delay, Faraday amplitude modulation and polarization changes. We made calculations 
for different levels of geomagnetic activity and for different angular position of radio 
sources as well. Our main idea is to use a signal of navigation satellites (GPS, GLONASS, 
GALILEO) as a testing signal from reference source located at minimal angular distance from 
studied source. Our project opens a way to development of methods and systems of ADAPTIVE 
RADIO ASTRONOMY, adaptive to non-uniform and non-stationary ionosphere - by analogy to known 
systems of adaptive optics which are intended for adaptation optical telescopes to varying 
conditions of optically non-uniform and non-stationary troposphere. The paper is supported 
by the Program of basic researches of Presidium of the Russian Academy of Science No.30 
"Solar activity and physical processes in system the Sun-Earth".