GEODETIC ACTIVITY AT IRA

Involved IRA Scientists and Collaborators: P. Sarti, M. Negusini.

Since the end of the 1980s both Medicina and Noto radiotelescopes regularly participate in Geodetic VLBI observations. In both sites there are co-locations with permanent International GNSS Service (IGS) Global Positioning System (GPS) equipment. The IRA is a member of the International VLBI Service (IVS) since 1998, when the service was established to ensure coordination and promotion of VLBI-based astrometric and geodetic investigations.  Twelve IRA staff members are affiliated to IVS (see Associate Members list at the page of IVS) to work and contribute on different technological and scientific VLBI-related issues. The observational activity is part of the scientific research which is carried out on some selected aspects of geodetic investigation based on VLBI as well as on other space geodetic techniques.

CRUSTAL DEFORMATION

VLBI-based monitoring of the deformation field in Europe and in Mediterranean area is a long lasting scientific activity of the geodetic group. It has recently been expanded with GPS data processing aiming at defining a more detailed, though complementary, picture of the geodetic deformation field (see Figure 23 - link Figure 23). Details and results in: Tomasi, Rioja & Sarti 1999.

Fig 23 - Relative geodetic velocity vectors in the Italian area obtained subtracting Wettzell ITRF velocity to the GPS-estimated vectors. The map also contains information concerning the main tectonics features of the area (from Di Martino et al. 2007).

TROPOSPHERIC WATER VAPOUR

The IRA contributes to the IVS project IVSTROP through regular processing of geodetic VLBI observations used to study and monitor the tropospheric water vapour content. See for results: Heinkelmann et al.  2007.

LOCAL TIES

The two co-location sites of Medicina and Noto are a remarkable resource in the national as well as the international geodetic network. They represent a challenge in terms of maintenance and management of geodetic co-location sites, eccentricity vectors estimation and all related aspects (e.g. geodetic reference point definition, reference system transformation, local ground control network stability, gravitational deformation of large VLBI telescopes, etc. (see Sarti 2007).

An indirect approach for the computation of the eccentricity vectors has been developed at IRA, in cooperation with the Dept. of Engineering (DISTART - Topography) of the University of Bologna. The method is nowadays acknowledged as one which meets the International Earth rotation and Reference systems Service (IERS) requirements for the estimations of the eccentricity vectors. In addition, since 2004 the IRA participates in the activities of the IERS Working Group 2 on local ties and co-location sites. Details and results in: Dawson  et al.  2007; Sarti  et al. 2004.

ANTARCTIC GEODESY

The IRA is involved in Antarctic geodetic investigations in the Northern Victoria Land within the framework defined by PNRA (Progetto Nazionale di Ricerca in Antartide). The IRA leads an Operative Unit whose aims are to study the content and evolution of tropospheric water vapour using the GPS technique and to compute the regional crustal deformation using the GPS solutions. The Antarctic activities are developed in cooperation with the Istituto di Scienze dell' Atmosfera e del Clima (ISAC) of the National Research Council and with the Universities of Bologna (DISTART), Modena, Reggio Emilia (DIMEC) and the Politecnico of Bari (DAU). Details and results in: Capra et al. 2007; Negusini et al. 2005.