GEODETIC ACTIVITY AT IRA

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 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. Details and results in: Sarti et al. 2010; La Delfa et al. 2012.

Fig 1 - Relative geodetic velocity vectors in the Italian
               area Fig 1 - Relative geodetic velocity vectors in the European area obtained with VLBI observations spanning the 1990-2010 period. (from Sarti et al. 2010).


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.  2011.

LOCAL TIES

The two co-location sites of Medicina and Noto are an important facility of the national and international permanent geodetic network. They are a challenge in terms of maintenance and management of geodetic co-location sites, tie vector estimation and all related aspects (see e.g. Sarti et al 2013a).


GRAVITATIONAL FLEXURES OF VLBI TELESCOPES

Local tie vector surveying and the comprehensive monitoring campaigns of the VLBI telescope structures at Medicina and Noto led us into a detailed study of the signal path variations and phase shifts induced by gravitational flexures, thus addressing the long term goal of reducing biases in VLBI observations. A correction model was developed for both telescopes (Sarti et al. 2009) and fine tuned on the and tested in a VLBI data re-processing that highlighted how gravitational-related deformation impact the accuracy of VLBI-derived positions to a non-negligible extent (Sarti et al. 2011).

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 two Operative Units 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 (DICAM), Modena, Reggio Emilia (DIEF). Details and results in: Sarti et al. 2013b.