GNSS data filtering optimization for ionospheric observation

In the last years, the use of GNSS (Global Navigation Satellite Systems) data has been gradually increasing, for both scientific studies and technological applications. High-rate GNSS data, able to generate and output 50-Hz phase and amplitude samples, are commonly used to study electron density irregularities within the ionosphere. Ionospheric irregularities may cause scintillations, which are rapid and random fluctuations of the phase and the amplitude of the received GNSS signals. For scintillation analysis, usually, GNSS signals observed at an elevation angle lower than an arbitrary threshold (usually 15 , 20 or 30 ) are filtered out, to remove the possible error sources due to the local environment where the receiver is deployed. Indeed, the signal scattered by the environment surrounding the receiver could mimic ionospheric scintillation, because buildings, trees, etc. might create diffusion, diffraction and reflection. Although widely adopted, the elevation angle threshold has some downsides, as it may under or overestimate the actual impact of multipath due to local environment. Certainly, an incorrect selection of the field of view spanned by the GNSS antenna may lead to the misidentification of scintillation events at low elevation angles. With the aim to tackle the non-ionospheric effects induced by multipath at ground, in this paper we introduce a filtering technique, termed SOLIDIFY (Standalone OutLiers IDentIfication Filtering analYsis technique), aiming at excluding the multipath sources of non-ionospheric origin to improve the quality of the information obtained by the GNSS signal in a given site. SOLIDIFY is a statistical filtering technique based on the signal quality parameters measured by scintillation receivers. The technique is applied and optimized on the data acquired by a scintillation receiver located at the Istituto Nazionale di Geofisica e Vulcanologia, in Rome. The results of the exercise show that, in the considered case of a noisy site under quiet ionospheric conditions, the SOLIDIFY optimization maximizes the quality, instead of the quantity, of the data.Published2552–25622A. Fisica dell'alta atmosferaJCR Journa

The IDIPOS project: is a multidisciplinary data infrastructure for weather and space weather feasible?

The Italian National Antarctic Programme (PNRA) has long supported scientific and technological activities addressed to the implementation, upgrade and maintenance of infrastructure and instruments supporting geosciences and physical sciences in the polar region. This report describes the first results of the Italian Database Infrastructure for Polar Observation Sciences (IDIPOS) project, which was recently approved by the PNRA. The project aims to study the feasibility of the hardware and software infrastructure for the construction of relational databases of acquisitions from past and current experiments in the polar areas. The study is based on the fundamental characteristics of the infrastructure: its implementation in Italy, with locations across the country, and its integration into the existing and future telematics infrastructure that will be available at the Italian bases. The project proposes a modern and hightech infrastructure dedicated to data treatment, accessibility and archiving, in line with international standards. This infrastructure will allow modern, rapid and reliable treatment of the acquired data. The IDIPOS infrastructure is crucial during the planning phase of scientific and monitoring activities of the PNRA, especially of those included in the Scientific Committe for Antarctic Research (SCAR) projects, the International Polar Year, and the framework of international cooperation. In the first phase of the project, the observations are related to research projects in different PNRA sectors. The infrastructure will be potentially extendable to other observational activities. In this report, the infrastructure is introduced, while highlighting its usefulness for weather and space-weather forecasting for the scientific community and in the framework of Global Navigation Satellite System (GNSS) Research and Application for Polar Environment (GRAPE) in particular

Mars riometer system

A riometer (relative ionospheric opacity meter) measures the intensity of cosmic radio noise at the surface of a planet. When an electromagnetic wave passes through the ionosphere collisions between charged particles (usually electrons) and neutral gases remove energy from the wave. By measuring the received signal intensity at the planet's surface and comparing it to the expected value (the quietday curve) a riometer can deduce the absorption (attenuation) of the trans-ionospheric signal. Thus the absorption measurements provide an indication of ionisation changes occurring in the ionosphere. To avoid the need for orbiting sounders riometers use the cosmic noise background as a signal source. Earth-based systems are not subject to the challenging power, volume and mass restriction that would apply to a riometer for Mars. Some Earth-based riometers utilise phased-array antennas in order to provide an imaging capability.UnpublishedVienna - Austria3.9. Fisica della magnetosfera, ionosfera e meteorologia spazialeope

A Comparative Study of Different Phase Detrending Algorithms for Scintillation Monitoring

Rapid and sudden fluctuations of phase and amplitude in Global Navigation Satellite System (GNSS) signals due to diffraction of the ionosphere phase components when signals passing through small-scale irregularities (less than hundreds meters) are commonly so-called ionospheric scintillation. The aim of the paper is to analyze the implementation and compare the performance of different phase detrending algorithms to improve scintillation monitoring. Three different phase detrending methods, namely, three cascaded second-order high pass filters, six order Butterworth filter conducted by cascading six first-order high pass Butterworth filters, and Fast Iterative Filter (FIF) are considered in this paper. The study exploits real GNSS signals (GPS L1, Galileo E1b) affected by significant phase scintillation effects, collected in early September 2017 at Brazilian Centro de Radioastronomia e Astrofisica Mackenzie (CRAAM) monitoring station and at Adventdalen (Svalbard, Norway) research station. In this study, a software defined radio (SDR) based GNSS receiver is used to process GNSS signals and to implement the aforementioned detrending algorithms

Disentangling ionospheric refraction and diffraction effects in GNSS raw phase through fast iterative filtering technique

We contribute to the debate on the identification of phase scintillation induced by the ionosphere on the global navigation satellite system (GNSS) by introducing a phase detrending method able to provide realistic values of the phase scintillation index at high latitude. It is based on the fast iterative filtering signal decomposition technique, which is a recently developed fast implementation of the well-established adaptive local iterative filtering algorithm. FIF has been conceived to decompose nonstationary signals efficiently and provide a discrete set of oscillating functions, each of them having its frequency. It overcomes most of the problems that arise when using traditional time–frequency analysis techniques and relies on a consolidated mathematical basis since its a priori convergence and stability have been proved. By relying on the capability of FIF to efficiently identify the frequencies embedded in the GNSS raw phase, we define a method based on the FIF-derived spectral features to identify the proper cutoff frequency for phase detrending. To test such a method, we analyze the data acquired from GPS and Galileo signals over Antarctica during the September 2017 storm by the ionospheric scintillation monitor receiver (ISMR) located in Concordia Station (75.10° S, 123.33° E). Different cases of diffraction and refraction effects are provided, showing the capability of the method in deriving a more accurate determination of the σϕ index. We found values of cutoff frequency in the range of 0.73–0.83 Hz, providing further evidence of the inadequacy of the choice of 0.1 Hz, which is often used when dealing with ionospheric scintillation monitoring at high latitudes

Study of MDT calibration constants using H8 testbeam data of year 2004

In year 2004 Atlas performed a long campaign of test beam data taking at the H8 Cern beam. Two sectors of the barrel and endcap regions of the Muon Spectrometer were exposed to the beam and large amount of data were collected in well defined and controlled operating conditions. This allowed a careful study on MDT drift properties. A better understanding of the calibration constants, of their definition and determination and of the criteria for their acceptance has been obtained. Systematic effects and time stability of the constants have also been studied

Adaptive Phase Detrending for GNSS Scintillation Detection: A Case Study Over Antarctica

We aim at contributing to the reliability of the phase scintillation index on Global Navigation Satellite System (GNSS) signals at high-latitude. To the scope, we leverage on a recently introduced detrending scheme based on the signal decomposition provided by the fast iterative filtering (FIF) technique. This detrending scheme has been demonstrated to enable a fine-tuning of the cutoff frequency for phase detrending used in the phase scintillation index definition. In a single case study based on Galileo data taken by a GNSS ionospheric scintillation monitor receiver (ISMR) in Concordia Station (Antarctica), we investigate how to step ahead of the cutoff frequency optimization. We show how the FIF-based detrending allows deriving adaptive cutoff frequencies, whose value changes minute-by-minute. They are found to range between 0.4 and 1.2 Hz. This allows better accounting for diffractive effects in phase scintillation index calculation and provides a GNSS-based estimation of the relative velocity between satellite and ionospheric irregularities

L'osservatorio ionosferico in Artide e Antartide: osservazioni sperimentali e risultati scientifici

The Italian Upper Atmosphere Observatory at polar latitude was firstly established during the Antarctic campaign 1990-1991 to support the telecommunication logistic activity of the National Program for Antarctic Research (PNRA). The Istituto Nazionale di Geofisica e Vulcanologia (INGV), formerly Istituto Nazionale di Geofisica (ING), was involved in this action as the long time experience in HF radar, ionospheric sounding and ionospheric prediction services for radio communication purposes, managing two of the most important and historical ionospheric observatories all over the world: Rome (41.8N, 12.5E) and Gibilmanna (37.9 N, 14.0 E). Since that time, starting from 1993 up to now, several research projects have been carried on focusing on the multi instruments upper atmosphere observations in Arctic and Antarctica with the aim to study the polar ionosphere in different time and space domains, contributing both to the Global Change and to the emerging Space Weather needs. Here we briefly report on the experimental activities as well on the main scientific results obtained highlighting the latest findings in the field of bipolar GNSS (Global Navigation Satellite Systems) ionospheric scintillation measurements and investigation

Measuring GNSS ionospheric total electron content at Concordia, and application to L-band radiometers

In the framework of the project BIS - Bipolar Ionospheric Scintillation and Total Electron Content Monitoring, the ISACCO-DMC0 and ISACCO-DMC1 permanent monitoring stations were installed in 2008. The principal scope of the stations is to measure the ionospheric total electron content (TEC) and to monitor the ionospheric scintillations, using high-sampling-frequency global positioning system (GPS) ionospheric scintillation and TEC monitor (GISTM) receivers. The disturbances that the ionosphere can induce on the electromagnetic signals emitted by the Global Navigation Satellite System constellations are due to the presence of electron density anomalies in the ionosphere, which are particularly frequent at high latitudes, where the upper atmosphere is highly sensitive to perturbations coming from outer space. With the development of present and future low-frequency space-borne microwave missions (e.g., Soil Moisture and Ocean Salinity [SMOS], Aquarius, and Soil Moisture Active Passive missions), there is an increasing need to estimate the effects of the ionosphere on the propagation of electromagnetic waves that affects satellite measurements. As an example, how the TEC data collected at Concordia station are useful for the calibration of the European Space Agency SMOS data within the framework of an experiment promoted by the European Space Agency (known as DOMEX) will be discussed. The present report shows the ability of the GISTM station to monitor ionospheric scintillation and TEC, which indicates that only the use of continuous GPS measurements can provide accurate information on TEC variability, which is necessary for continuous calibration of satellite data

Space weather challenges of the polar cap ionosphere

This paper presents research on polar cap ionosphere space weather phenomena conducted during the European Cooperation in Science and Technology (COST) action ES0803 from 2008 to 2012. The main part of the work has been directed toward the study of plasma instabilities and scintillations in association with cusp flow channels and polar cap electron density structures/patches, which is considered as critical knowledge in order to develop forecast models for scintillations in the polar cap. We have approached this problem by multi-instrument techniques that comprise the EISCAT Svalbard Radar, SuperDARN radars, in-situ rocket, and GPS scintillation measurements. The Discussion section aims to unify the bits and pieces of highly specialized information from several papers into a generalized picture. The cusp ionosphere appears as a hot region in GPS scintillation climatology maps. Our results are consistent with the existing view that scintillations in the cusp and the polar cap ionosphere are mainly due to multi-scale structures generated by instability processes associated with the cross-polar transport of polar cap patches. We have demonstrated that the SuperDARN convection model can be used to track these patches backward and forward in time. Hence, once a patch has been detected in the cusp inflow region, SuperDARN can be used to forecast its destination in the future. However, the high-density gradient of polar cap patches is not the only prerequisite for high-latitude scintillations. Unprecedented highresolution rocket measurements reveal that the cusp ionosphere is associated with filamentary precipitation giving rise to kilometer scale gradients onto which the gradient drift instability can operate very efficiently. Cusp ionosphere scintillations also occur during IMF BZ north conditions, which further substantiates that particle precipitation can play a key role to initialize plasma structuring. Furthermore, the cusp is associated with flow channels and strong flow shears, and we have demonstrated that the Kelvin- Helmholtz instability process may be efficiently driven by reversed flow events