Monitoring ionospheric scintillation on a global scale requires introducing a network of widely distributed geodetic receivers, which call for a special type of scintillation index due to the low ...sampling rate of such receivers. ROTI, as a scintillation index with great potential being applied in geodetic receivers globally, lacks extensive verification in the high-latitude region. Taking the phase scintillation index (σϕ) provided by ionospheric scintillation monitoring receivers as the reference, this paper analyses data collected at 8 high-latitude GNSS stations to validate the performance of ROTI statistically. The data is evaluated against 4 parameters: 1, the detected daily scintillation occurrence rate; 2, the ability to detect the daily occurrence pattern of ionospheric scintillation; 3, the correlation between the detected scintillation and the space weather parameters, including the 10.7 cm solar flux, Ap, the H component of longitudinally asymmetric and polar cap north indices; 4, the overall distribution of the scintillation magnitude. Results reveal that the scintillation occurrence rates, the occurrence patterns of ionospheric scintillations and the correlations provided by ROTI are generally consistent with those given by σϕ, particularly in the middle-high-latitude region. However, the analysis on the distribution of σϕ for different ranges of ROTI shows ROTI cannot achieve accurate scintillation monitoring at the epoch level in all selected stations. The main outcomes of this paper are of importance in guiding the reasonable application area of ROTI and developing a high-latitude ionospheric scintillation model based on geodetic receivers.
Amplitude and phase scintillation indexes (S4 and σϕ) provided by Ionospheric Scintillation Monitoring (ISM) receivers are the most used GNSS-based indicators of the signal fluctuations induced by ...the presence of ionospheric irregularities. These indexes are available only from ISM receivers which are not as abundant as other types of professional GNSS receivers, resulting in limited geographic distribution. This makes the scintillation indexes measurements rare and sparse compared to other types of ionospheric measurements available from GNSS receivers. Total Electron Content (TEC), on the other hand, is an ionospheric parameter available from a wide range of multi-frequency GNSS receivers. Many efforts have worked on establishing scintillation indicators based on TEC, and geodetic receivers in general, introducing various metrics, including the Rate of TEC change (ROT) and ROT Index (ROTI). However, a possible relationship between TEC and its variation, and the corresponding scintillation index that an Ionospheric Scintillation Monitor (ISM) receiver would estimate is not trivial. In principle, TEC can be retrieved from carrier phase measurements of the GNSS receiver, as σϕ. We investigate how to estimate σϕ from time series of TEC and ROT measurements from an ISM in Ny-Ålesund (Svalbard) using Machine Learning (ML). To evaluate its usability to estimate σϕ from geodetic receivers, the model is tested using TEC data provided by a quasi-co-located geodetic receiver belonging to the International GNSS Service (IGS) network. It is shown that the model performance when TEC from the IGS receiver is used gives comparable results to the model performance when TEC from the ISM receiver is utilised. The model's ability to infer the exact value of the scintillation index is bound to Mean Square Error (MSE) = 0.1 radians2 when σϕ≤0.8 radians. For σϕ>0.8 the MSE reaches 0.18 and 0.45 radians2 in operative testing using ISM and IGS measurements, respectively. However, the model’s ability to detect phase scintillation from IGS TEC measurements is comparable to expert visual inspection. Such a model has potential in alerting against phase fluctuations resulting in enhanced σϕ, especially in locations where ISM receivers are not available, but other types of dual-frequency GNSS receivers are present.
In this work, we introduce a new way of improving the sligthly best performing global ionospheric model (GIM) within the International GNSS Service, the UQRG produced by UPC-IonSAT with the TOMION ...dual-layer voxel model solved with ground-based dual-frequency carrier phase GPS data combined with kriging interpolation. This is done by increasing its vertical resolution consistently with the heights of the now involved GNSS and DORIS LEO receivers. This has allowed the synergestic combination of vessel-, LEO- and ground-based measurements, providing an increase of the VTEC accuracy at global scale in large regions with sparse GPS ground-based data. The performance of the new resulting multiTOMION model is illustrated with a first application to one of the infrequent datasets, including the whole day of June 5, 2017, with all the involved input data collocated, in particular the vessel-based GNSS ones. The results show in particular: (1) an overall GIM improvement of 3% in standard deviation versus independent JASON-3 VTEC measurements when LEO- and ground- based GPS data are combined with DORIS measurements. And (2) a local improvement of 6–9% in performance versus observed differences of STEC from independent GPS receivers placed at several hundreds of km far from the vessel.
As a frequently-occurred phenomenon in the high-latitude region, ionospheric scintillations affect the stable service of the positioning navigation and timing service of the Global Navigation ...Satellite System (GNSS), calling for an urgent need of monitoring the scintillations accurately. The monitoring of scintillations usually adopts a special type of receiver, called an ionospheric scintillation monitoring receiver (ISMR), which cannot cover the whole high-latitude region due to its loss distribution. Geodetic receivers are densely distributed, but set at a 30s-sampling-interval usually. It is a controversial issue, namely, the accuracy of the scintillation index extracted from 30s-sampling-interval observations. This paper evaluates the accuracy of two 30s-sampling-interval indices in monitoring scintillations from both the time and space aspects using observations collected in the whole year of 2020. The accuracy in the time aspect is assessed with the phase scintillation index from ISMR as the reference through the following three-pronged approaches, i.e., the accuracy of the daily scintillation occurrence rates in the year 2020, the correlation with space weather parameters, and the variation pattern of the scintillation occurrence rate with the local time and day of the year 2020. The accuracy in space is studied based on the scintillation grid model considering the following two aspects, i.e., the scintillation monitoring performance in a Swarm satellite observation arc, and the statistical scintillation occurrence rate in the whole research region throughout the year 2020. The results of this paper reveal the efficiency of the 30s-sampling-interval scintillation indices in monitoring scintillations and detecting the occurrence patterns in the high-latitude region. The outcome of this paper can provide a basic idea for introducing the widely distributed geodetic receivers to monitor and model the scintillations in the high-latitude region.
With Galileo, the European GNSS (Global Navigation Satellite System) starting early services in 2015, open-area-testing of applications which use the new positioning system gets more and more ...important. This contribution gives an overview on existing test sites like railGATE, automotiveGATE and seaGATE, it highlights the latest addition for dynamic calibration with geodetic precision and finally describes the testing regime of the BONUS project ANCHOR, where multiple test sites are used for maximum benefit in a maritime application.
Ionospheric scintillation causes rapid fluctuations of measurements from Global Navigation Satellite Systems (GNSSs), thus threatening space-based communication and geolocation services. The ...phenomenon is most intense in equatorial regions, around the equinoxes and in maximum solar cycle conditions. Currently, ionospheric scintillation monitoring receivers (ISMRs) measure scintillation with high-pass filter algorithms involving high sampling rates, e.g. 50 Hz, and highly stable clocks, e.g. an ultra-low-noise Oven-Controlled Crystal Oscillator. The present paper evolves phase scintillation indices implemented in conventional geodetic receivers with sampling rates of 1 Hz and rapidly fluctuating clocks. The method is capable to mitigate ISMR artefacts that contaminate the readings of the state-of-the-art phase scintillation index. Our results agree in more than 99.9% within ± 0.05 rad (2 mm) of the ISMRs, with a data set of 8 days which include periods of moderate and strong scintillation. The discrepancies are clearly identified, being associated with data gaps and to cycle-slips in the carrier-phase tracking of ISMR that occur simultaneously with ionospheric scintillation. The technique opens the door to use huge databases available from the International GNSS Service and other centres for scintillation studies. This involves GNSS measurements from hundreds of worldwide-distributed geodetic receivers over more than one Solar Cycle. This overcomes the current limitations of scintillation studies using ISMRs, as only a few tens of ISMRs are available and their data are provided just for short periods of time.
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