The benefits of combined processing of observations from different Global Navigation Satellite Systems

The Galileo GNSS and the modernisation of the existing GPS and GLONASS systems will offer many exciting opportunities and challenges in the field of geosciences in the next decade. However, in order to obtain any positive effects on our geodetic and geophysical estimates the different GNSS systems will have to be observed by multi-system receivers that track all systems on all available frequencies. Furthermore, these receivers should not introduce any biases between the tracked GNSS observations. In addition to this we need analysis software that can efficiently handle these multi-system and multi-frequency observations in one single estimation process. Over the last two years ESOC has put a significant effort into its Napeos processing software. This software is now capable of combined processing of SLR, DORIS, GPS, GLONASS, and GIOVE data. It is routinely used for a large number of tasks within ESOC, e.g., for IGS, ILRS, and IDS reprocessing for the ITRF2009.