PPP Carrier Phase Residual Stacking for Turbulence Investigations

Microwave space-geodetic observations such as Global Navigation Satellite Systems (GNSS) or Very Long Baseline Interferometry (VLBI) are delayed in the neutral atmosphere. In order to improve the quality of these techniques for precise applications like reference frame realisation, we need to get more knowledge about the temporal and spatial refractivity variations in the neutrosphere. In addition to the annually to hourly long periodic variations, which can be considered within the adjustment process, micro-scale meteorological phenomena in the range of minutes to sub-seconds affect space-geodetic observations as well. Thus, induced phase fluctuations of wavefronts passing through the turbulent medium form a significant error source for electromagnetic wave propagation.In order to identify high-frequency atmospheric effects, we analysed 1 Hz high-rate GPS observations from the continuous operating GNSS station at the Geodetic Observatory Wettzell and derived post-fit carrier phase residuals for several days with a Kalman-Filter based Precise Point Positioning (PPP) approach. Since undifferenced carrier phase observations contain a superposition of several effects, the computed power-law behaviour of the residuals might not follow the theoretically predicted stochastical behaviour for refractivity fluctuations. Hence, the influence of multipath was identified. A residual stacking was performed, and the reduced residuals were analysed with regard to turbulence characteristics.