VLBI tracking of the Huygens Probe in the atmosphere of Titan

We present results of an assessment study of VLBI (Very Long Baseline Interferometry) observations of the Huygens probe during the probe's descent through the atmosphere to the surface of Titan. The aim of the study was to assess the feasibility of a direct receipt, detection and VLBI processing of the probe's S-band radio signal. The direct receipt of the probe signal by Earth-based tracking stations was not foreseen in the original mission scenario but has proven to be possible owing to recent developments in radio astronomy, and particularly in VLBI. We analyze the power budget of the "Huygens-Earth" radio link, the potential accuracy of the VLBI determination of the probe's coordinates in the atmosphere of Titan, and some scientific applications of these measurements. We also discuss prospects for VLBI tracking of future deep space missions using the next generation Earth-based radio telescopes, in particular the Square Kilometer Array (SKA).