Total Electron Content Evaluation for the Development of a Mexican Ionospheric Monitoring System

Abstract

Radio signals experience adverse effects when they travel through the ionosphere. Global Navigation Satellite System (GNSS) experience degradation in their performance as a function of the status of the ionosphere. Total Electron Content (TEC) provides an overall description of the ionosphere status, and some techniques use this parameter to correct the range error on single frequency GNSS receivers. Several agencies around the world generate TEC maps using networks of GNSS receivers and some physics-based ionospheric models. As an example, the USA National Oceanic and Atmosphere Administration (NOAA) operates a system named US-TEC that generate TEC maps for the North America region that have an update every fifteen minutes. Although TEC values are reported for the Mexican territory, the US-TEC network of GNSS receivers does not include equipment placed in this territory. The aim of this paper is to present the results of a study of the TEC values over the Mexican territory that can be used as the basis for the generation of a national ionospheric monitoring system. A comparison of TEC values reported by the NOAA and measurements conducted in several locations of the Mexican territory is presented in this paper for the period 2013 to 2015. The Mexican territory is located near to geographic latitudes with a high level of ionospheric activity and therefore studying their effects on GNSS signals represents an important challenge. TEC measurements were performed using double frequency GNSS receivers located at different latitudes in the Mexican territory. Results of a statistical analysis are presented in order to recognize similarities and differences between the TEC values reported by the NOAA and our measurements. Additionally, results of TEC estimations calculated by two ionospheric models (IRI and NeQuick) over the same region and on different seasons of the year are presented. Results of this analysis can be applied on the generation of a fitted ionosphere model for the Mexican region. Results presented in this paper are the first steps for the development of a regional system which will generate TEC reports in real-time focused on GNSS applications, particularly for air navigation systems.