Ionosphere/Plasmasphere sounding with ground and space-based GNSS observations

Applying a methodology developed and tested in previous studies, the contribution from the ionospheric and plasmaspheric regions to the total electron content (measured by ground receivers) is analyzed. The method is based in the electron density profiles retrieved from radio occultations observed with low Earth orbit satellites, combined with an accurate empirical modeling of the topside-ionosphere electron density. The results of a climatological study of the fractional electron content from the ionospheric region are presented for a year of low solar activity. It is shown that a simple parametric model can be used to reproduce the electron content variations in the ionosphere and the plasmasphere between sunrise and midday, the period of the day showing the largest electron content variability.Peer ReviewedPostprint (author's final draft

Navegando con satélites : (o cómo posicionarse con GPS y Galileo con errores de pocos centímetros, en tiempo-real y a escala continental)

Peer Reviewe

Synthetic events description, generation and characterization report

Preprin

Confirming geomagnetic Sfe by means of a solar flare detector based on GNSS

Solar Flares (SF) refer to sudden increases of electromagnetic radiation from the Sun lasting from minutes to hours. Irradiance in the Extremely Ultra-Violet (EUV) or X band is enhanced and it can produce a sudden over-ionization in the ionosphere, which can be tracked by several techniques. On the one hand, this over-ionization increases the ionospheric delays of GNSS signals in such a way as can be monitored using measurements collected by dual-frequency GNSS receivers. On the other hand, this over-ionization of the ionosphere is the origin of electrical currents which, in turn, induce magnetic fields which can be monitored with ground magnetometers. In this work we propose the use of a GNSS Solar Flare Monitor (GNSS-SF) for its utility to confirm the presence of ionospheric ionization which is able to produce Solar Flare Effects (Sfe) in geomagnetism. A period of 11 years (2008–2018) has been analyzed and contingency tables are shown. Although most of the GNSS-SF detections coincide with SF and most of the Sfe have a detected origin in the ionosphere, there are some paradoxes: sometimes small flares produce disturbances which are clearly detected by both methods while other disturbances, originated by powerful flares, go by virtually unnoticed. We analyzed some of these cases and proposed some explanations. We found that suddenness in the variation is a key factor for detection. Threshold values of the velocity of change to remove the background noise and the use of the acceleration of change instead of the velocity of change as the key performance detector are other topics we deal with in this paper. We conclude that the GNSS-SF detector could provide warnings of ionization disturbances from SF covering the time when the Sfe detectors are “blind”, and can help to confirm Sfe events when Sfe detectors are not able to give a categorical answer.Peer ReviewedPostprint (published version

Navegando con satélites : (o cómo posicionarse con GPS y Galileo con errores de pocos centímetros, en tiempo-real y a escala continental)

Peer Reviewe

Fast-PPP assessment in European and equatorial region near the solar cycle maximum

Oustanding Student Poster Award, European Geosciences Union General Assembly, 2014Award-winningPostprint (published version

Multi-satellite cycle-slip detection and exclusion using the noise subspace of residual dynamics

Real-time detection of cycle-slips on undifferenced carrier-phase measurements is an important task to properly exclude wrong phase trackers from precise positioning algorithms. The detection is especially challenging in high-dynamic mobile scenarios, where traditional approaches (as those based on single-channel polynomial fitting) may easily lead to false positives. Using a multi-channel formulation of the problem, the proposed technique takes benefit of the available data redundancy (high number of tracked satellites) in order to ameliorate the false positives. This robustness is accomplished by adaptively estimating the orthogonal subspace spanned by the polynomial time-varying residuals obtained from all available channels (treated as a vector process), and using that subspace to form efficient channel combinations with cancelled satellite-receiver dynamics. The main advantage of the multi-channel approach is that wrong measurements can be discarded without needing any positioning estimate nor phase-ambiguity solver, thus improving the accuracy, reliability and integrity of positioning. The performance improvement is shown by means of theoretical analysis and computer simulations.Peer ReviewedPostprint (published version

The GPS Toolkit: world class open source software tools for the GNSS research community

The ”GPS Toolkit” (GPSTk) project is an advanced GNSS Open Source Software (GOSS) suite initiated by the Applied Research Laboratories of the University of Texas (ARL:UT), aiming to provide a world class GNSS library computing suite to the satellite navigation community. The objective of this work is to show how the GPSTk suite may be used to rapidly and easily develop, implement and test advanced GNSS data processing applications in a flexible way. The main characteristics and modules of the GPSTk are also presented, as well as the current trends in its development. Results from the GNSS data processing carried out with the examples introduced in this work are shown, as well as a brief comparison with an established GPS software package such as BRUS.Peer Reviewe