GGOS-SIM2: A simulation study on the benefits of co-locating the space geodetic techniques on one satellite

Abstract:

Project GGOS-SIM-2, successor of project GGOS-SIM, funded by the German Research Foundation (DFG), is a cooperation of the Helmholtz Centre Potsdam German Research Centre for Geosciences GFZ and the Technische Universität Berlin (TUB). Its aim is to find out by simulations, whether and how the requirements imposed for the Terrestrial Reference Frame (TRF) of the Global Geodetic Observing System (GGOS) can be met. These are 1 mm accuracy and 1 mm per decennium long-term stability. The current international TRF, the ITRF2014, does not achieve these goals. GGOS-SIM-2 is focused in particular on the potential of so-called space ties co-locating the different space-geodetic techniques, i.e. DORIS, GNSS, SLR, and VLBI, on the same satellite. We are in the convenient and beneficial situation that our in-house precise orbit and parameter estimation software EPOSOC is able to handle all four techniques. We give a brief description of how the space-geodetic observations are being simulated.

The simulation allows to quantify the effect of random and systematic errors in the observations on geodetic results like the orbits and the TRF. The observations are simulated with accuracy and availability figures based on experience with Precise Orbit Determination (POD) of real observations to existing missions. The simulation scenarios comprise the formerly proposed space missions GRASP (NASA) and E-GRASP (ESA), and a suite of other possible orbital characteristics aiming in particular at enhancing the possibilities to observe on long baselines with VLBI. From the simulated observations, technique specific TRFs are derived and compared to TRFs that were combined via the space ties. The effects on the TRFs are quantified in terms of changes in origin and scale, and in changes and standard deviations of the resulting ground station coordinates and Earth rotation parameters.