Maddalena Errico

Assessment of the possible contribution of space ties on-board GNSS satellites to the terrestrial reference frame

The realization of the international terrestrial reference frame (ITRF) is currently based on the data provided by four space geodetic techniques. The accuracy of the different technique-dependent materializations of the frame physical parameters (origin and scale) varies according to the nature of the relevant observables and to the impact of technique-specific errors. A reliable computation of the ITRF requires combining the different inputs, so that the strengths of each technique can compensate for the weaknesses of the others. This combination, however, can only be performed providing some additional information which allows tying together the independent technique networks. At present, the links used for that purpose are topometric surveys (local/terrestrial ties) available at ITRF sites hosting instruments of different techniques. In principle, a possible alternative could be offered by spacecrafts accommodating the positioning payloads of multiple geodetic techniques realizing their co-location in orbit (space ties). In this paper, the GNSS–SLR space ties on-board GPS and GLONASS satellites are thoroughly examined in the framework of global reference frame computations. The investigation focuses on the quality of the realized physical frame parameters. According to the achieved results, the space ties on-board GNSS satellites cannot, at present, substitute terrestrial ties in the computation of the ITRF. The study is completed by a series of synthetic simulations investigating the impact that substantial improvements in the volume and quality of SLR observations to GNSS satellites would have on the precision of the GNSS frame parameters.

Space geodetic activities, from the early days to present, with focus on the northeastern Adriatic

Abstract It has become of greatest importance to monitor and understand how the dynamics of the System Earth works. Geodesy has gone far beyond the provision of a static knowledge of the Earth’s geometric and physical parameters and with the development of high-accuracy satellite and space techniques and increased measurement capability, this discipline is now providing observations of changes in the Earth’s shape, gravity field and rotation which are essential for Earth system science. In a short historical excursus of the main space geodetic techniques, we review achievements in the determination and study of Earth’s crustal deformation and sea-level change/variations. Focus is given to geodetic research activities developed in northeastern Italy.