Abstract. Since 2012, the Radiophysical Research Institute and the Lobachevsky State University at Nizhny Novgorod, Russia and the Ventspils International Radio Astronomy Centre at Irbene, Latvia are making radio interferometric experiments on study of ionosphere parameters in a quiet (natural) state of medium and research of artificial turbulence of the ionosphere, heated by the emission from the SURA facility. Remote diagnostics of the ionosphere is implemented using a method of radio sounding by signals of navigation satellites in combination with the Very Long Baseline Interferometry (VLBI) method. As a result of spectral and correlation analysis, interferometric responses of the two-element (RRI-UNN) and three-element (RRI-UNN-Irbene) interferometers were received by observations of 12 satellites of the navigation systems GLONASS and GPS. Here the first results are reported.

The RT-32 radio telescope at Irbene has been used in the VLBI experiments for studying the ionosphere by its transradiation with the signals from Navstar GPS and GLONASS satellites. The VLBI station at Irbene is equipped with a modular receiver system operating on 1.6 GHz and consisting of off-the-shelf RF components (Mini Circuits Ltd.). In the secondary focus of RT-32 a four-helix antenna array is installed. The implemented receiver system has successfully been employed in the experiments as a part of multi-element radiointerferometer, with interferometric echoes registered from all the observed satellites.

Radiotelescope RT-32 is a fully steerable 32-m parabolic antenna located at Irbene and belonging to Ventspils International Radio Astronomy Centre (VIRAC). Currently, the work on upgrading and repair of its receiving hardware and data acquisition systems is of high priority for the VIRAC.One of the main scientific objectives for the VIRAC Radioastronomical observatory is VLBI (very long baseline interferometry) observations in centimetre wavelengths in collaboration with world VLBI networks, such as European VLBI network (EVN), Low Frequency VLBI network (LFVN), and others.During the last years the room in the secondary focus of telescope was reconstructed, and several new receivers were installed. Currently, RT-32 observations are carried out in four different bands: 92 cm, 18 cm, 6 cm, and 2.5 cm. First three of them are already successfully employed in diversified VLBI experiments. The receiver on 2.5 cm band has only one linear polarized chain and is used mainly for the methanol maser single dish observations.The apparatus system of RT-32 is equipped with two independent VLBI data acquisition systems: TN-16, and DBBC in combination with MK5b. Both systems are employed in interferometric observations depending on the purpose of experiment and the enabled radiotelescopes.The current status of RT-32, the availability of its receiving and data acquisition units for VLBI observations and the previous VLBI sessions are discussed.