Tracking of GLONASS satellites by VLBI radio telescopes

Övrigt konferensbidrag, 2010

Several tests to observe signals transmitted by GLONASS (GLObal NAvigation Satellite System) satellites have been performed using the VLBI (Very Long Baseline Interferometry) technique. The radio telescopes involved in these experiments are Medicina and Onsala. The satellites transmit artificial radio signals that were considered in a similar way as natural radio signal that are emitted by natural radio sources. The signal strength of satellite signals is much stronger than the signal strength of natural radio signals, so in order to avoid overload of the telescope frontends, corresponding signal attenuation was applied. Observations at the stations were performed using the standard Mark4 VLBI data acquisition rack and Mark5A disk-based recorders. The goals of the observations were to develop and test the scheduling, signal acquisition and processing routines to verify the full tracking pipeline, foreseeing the cross-correlation of the recorded data on the baseline Onsala-Medicina. The natural radio source 3C454.3 was used as a calibrator before the beginning of the satellite observation sessions. We present results of a detailed analysis of the signal recorded at the Onsala telescope together with a first attempt of cross-correlation of data recorded on the baseline Onsala–Medicina. Further plans to perform new GNSS observations are in preparation, and a study to develop the VLBI delay model for GNSS observations with astronomical VLBI telescopes is in progress.