Search

The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that can enhance the sciencereturn of planetary missions. By shadow tracking the spacecraft signal using radio telescopes from VLBI networks,the PRIDE technique provides precise open-loop Doppler and near-field VLBI observables (Duev et al. 2012,Bocanegra-Bahamon et al. 2018a) to find the radial velocity of the spacecraft and its position in the plane of thesky. This information is not only important for navigation, but it can also be used for many science applications.One such case is the study of planetary atmospheres by means of radio occultation experiments.

The presence of water has been considered for a long time as a key condition for life in planetary environments. The Cassini mission discovered water vapour in the Kronian system by detecting absorption of UV emission from a background star (Hansen et al. 2006). Prompted by this discovery, we started an observational campaign for search of another manifestation of the water vapour in the Kronian system, its maser emission at the frequency of 22 GHz (1.35 cm wavelength). Observations with the 32 m Medicina radio telescope (INAF-IRA, Italy) started in 2006 using Mk5A data recording and the JIVE-Huygens software correlator. Later on, an on-line spectrometer was used at Medicina. The 14 m Metsähovi radio telescope (TKK-MRO, Finland) joined the observational campaign in 2008 using a locally developed data capture unit and software spectrometer. More than 300 hours of observations were collected in 2006-2008 campaign with the two radio telescopes. The data were analysed at JIVE using the Doppler tracking technique to compensate the observed spectra for the radial Doppler shift for various bodies in the Kronian system (Pogrebenko et al. 2009). Here we report the observational results for Hyperion, Titan, Enceladus and Atlas, and their physical interpretation. Encouraged by these results we started a campaign of follow up observations including other radio telescopes.