\documentstyle{article}
\title{ The connection between dynamical and radio-sources\\
        reference frames obtained from radar and VLBI     \\
        observations of Phobos-2, Viking-Mars, and        \\
        Pioneer-Venus spacecrafts                           }
\author{N.V.Shuygina \\
Institute of Applied Astronomy, Russian Academy of Science\\
         Zhdanovskaya str., 8, St.Petersburg 197042, Russia}
\begin{document}
\maketitle
\begin{abstract}

      The experience of determination of the link between
radio-sources and dynamical reference frames is presented. To obtain this
connection we used series of Very Long Baseline Interferometry (VLBI)
observations of Phobos-2, Viking-Mars, and Pioneer-Venus spacecrafts 
and angularly nearby quasars. Orbit determination of each spacecraft was
carried out by numerical integration of relativistic equations of motion 
with taking into account all major planet perturbations. The coordinates 
of perturbing planets were calculated by the DE200/LE200 ephemerides. 
So the dynamical reference frame is determined by equator and equinox of 
this ephemeris. The resulting spacecraft orbit was fitted to the VLBI and 
tracing (range and Doppler frequency shift) data by means of weighted 
least squares procedure with the uncertainties of a few kilometer level. 
After precise orbit determination using VLBI measurements only we obtained 
three rotation angles between two reference systems.The radio and ephemeris
dynamical frames were found to be coincident in all three axis to less then
80 milliarcseconds.

\end{abstract}
\end {document}
