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Benjamin Männel
Type of contribution: oral

Observing GNSS L-band signals: ionospheric corrections by co-located GNSS measurements

Benjamin Männel, ETH Zurich Markus Rothacher, ETH Zurich

As an alternative and complement to ground-based co-location of the space geodetic techniques, the use of co-location in space is gaining more and more interest. As a result of dedicated hardware developments in the last years it became possible for a few VLBI telescopes to track the GLONASS L1 signal. This opens up the possibility to analyze observations of GLONASS satellites simultaneously tracked by VLBI, GNSS and SLR at co-located fundamental sites. Also comparisons between single-technique solutions and combined estimations of common parameters are feasible. We will present a method, named L4R approach, to correct the ionospheric delay for a single-frequency VLBI satellite observation using the co-located GNSS phase measurement to the same satellite. We will discuss our method in detail concerning network effects (baseline lengths), different GNSS (GPS and GLONASS) and the possibility to resolve the GNSS phase ambiguities. For validation purposes we tested our method by using GNSS and VLBI data from 2013. In a first step we applied the GNSS-based ionospheric delay corrections to an L1 GNSS processing and compared the residuals and station coordinate repeatibilities against a dual-frequency solution. In a second step we compared ionospheric delay corrections derived by VLBI observations (R1 and R4 sessions) against our GNSS-based ionospheric delay corrections. Based on the insights obtained from these studies we will highlight the potential applications and limits of the L4R approach.