Ionospheric Perturbations and Their Impact on GNSS - Investigated by DLRs High-Rate Receiver Chain

Abstract

Global Navigation Satellite Systems (GNSS) such as GPS, Galileo or Glonass provide good positioning results for a lot of applications. However, they can be heavily disturbed by space weather hazards. Severe temporal and spatial changes of the electron density in the ionosphere can lead to strong GNSS signal fluctuations in phase and amplitude – so-called scintillations. Processes leading to such ionospheric perturbations are ionization fronts, Travelling Ionospheric Disturbances (TIDs), plasma bubbles and plasma turbulences. Since a guaranteed performance is crucial for precise positioning and safety of life applications, it is necessary to monitor this thread. This can be done by multi-frequency measurements of GNSS signals. From these measurements signal amplitude and signal phase scintillation indices can be derived. These indices are a characteristic measure of occurring scintillations, should they surpass a certain threshold. Additionally, these multi-frequency measurements offer the unique opportunity to probe the electron density structure of the global ionosphere-plasmasphere system. As the ionosphere is a dispersive medium, multi-frequency measurements allow for a tomography of the ionosphere. Thus maps of the total electron content (TEC) of the ionosphere can be derived, which are strongly related to the ionospheric impact on GNSS applications. Our contribution will be twofold. First, we will explain the setup of the DLR high-rate receiver chain, the so called Experimentation and Verification Network (EVnet). The EVnet - developed by DLR's Institute of Communications and Navigation - is an infrastructure component for the near-real-time reception, processing and distribution of any kind of GNSS data to the EVnet user community. The network as shown in the figure includes, among others, stations in Kiruna, Neustrelitz, Munich, Toulouse, Tenerife and Bahir Dar. The data can be distributed over the Internet or any local area networks by specific EVnet services. It is designed as a one-stop shop system and products can be directly derived at the stations. These products can then be distributed or disseminated via a web service such as the Space Weather Application Center – Ionosphere (SWACI). Second, we will show, how ionospheric perturbation can be observed in real-time with the EVnet along its associated stations. In particular, we will show the propagation of scintillations at high-latitudes as well as those at equatorial latitudes in stations such as Kiruna and Bahir Dar.