Scintillation Climatology from a Software Defined Radio Receiver over Antarctica

Abstract

Software-Defined Radio (SDR) Global Navigation Satellite System (GNSS) receivers for operational Ionospheric Scintillation Monitoring (ISM) have faced challenges and were deemed failures by many research projects. The need for a highly stable oscillator and a robust real-time signal-tracking capability have been the main challenges. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) led a project called DemoGRAPE (Demonstrator of GNSS Research and Application for Polar Environment) to deploy an SDR GNSS Receiver in SANAE IV Antarctica station, which has been continuously operating since January 2016. The SDR receiver was designed by the Navigation Signal Analysis and Simulation (NavSAS) group in collaboration with the Joint Research Centre (JRC) of the European Commission.  The system deploys the SDR in parallel to a Septentrio PolaRxS ISM receiver. The two receivers are fed by the same receiving antenna (i.e., they share the same field of view and, hence, cross the same portion of the ionosphere) such that they receive quasi-identical signals except for the independent effects of their front-ends. The SDR produces as output a log file, equivalent to the ISM record produced by PolaRxS, that contains the amplitude and phase scintillation indexes. In addition to this, the SDR system records the raw digital samples of the GNSS signal when the internal algorithm of the receiver detects scintillation presence. These data can be used to replicate the scintillation event in the laboratory and perform dedicated post-processing of the raw signal itself. The system has been in operation for over seven years now, spanning more than half a solar cycle. It has recorded several geomagnetic storm events as well as abundant data in quiet conditions. To the best of our knowledge, this is the longest dataset of this nature (co-located PolaRxS and SDR  receivers). We compare the performance of the two receivers by analyzing the scintillation climatology maps obtainable from both receivers' data. Here, the climatology is obtained using the well-established Ground Based Scintillation Climatology (GBSC) technique from the data provided by the two different receivers.  The study shows that the SDR climatology maps under disturbed geomagnetic conditions are equivalent to those obtained from the PolaRxS receiver. Under quiet conditions, the SDR shows more scintillation events than the PolaRxS. Carefully inspecting the differences in the scintillation occurrence between the two receivers, they seem not to happen randomly but mainly concentrated along the expected (climatological) position of the auroral oval. This means that the SDR application for space weather monitoring could be possible and that the SDR could be utilizable as an informative tool by the ionospheric scintillation community.