Installation and configuration of an ionospheric scintillation monitoring station based on GNSS receivers in Antarctica

Abstract

Global Navigation Satellite Systems (GNSSs), such as the US Global Positioning System (GPS), The Russian GLONASS or the European Galileo, are space-based navigation systems. GNSSs enable a generic user located anywhere on the Earth to determine in real time his Position, Velocity and Time (PVT), by means of a Radio Frequency (RF) electro-magnetic signal, the Signal-In-Space (SIS), transmitted by a constellation of satellites orbiting around Earth. Uninterrupted Positioning, Navigation, and Timing (PNT) solution is determined by GNSS receivers, which continuously process the SIS from the satellites in view. GNSS receivers are part of the GNSSs ground segment. They are a suboptimal implementation of a maximum likelihood estimator of the SIS propagation time. The PNT solution is indeed based on the computation of the SIS Time Of Arrival (TOA), according to the satellite and receiver local clocks. This is achieved thanks to the presence of a different Pseudo Random Noise (PRN) spreading code in the modulated SIS broadcast by each satellite. In the GNSS receiver, the incoming signal is correlated with a local replica of signal code, obtaining the time difference information. The time difference is then transformed into a range information by multiplying it by the speed of light in the vacuum. However, since the receiver clock is not synchronized with the transmitters clock, this measure suffers of time bias, which is considered as an additional unknown in the navigation solution. Finally, the user position is determined on an Earth centred reference system with a process denoted trilateration, by exploiting the range information computed by the receiver and the information contained in the SIS navigation message, such as satellite ephemeris [Kaplan et al., 2005].