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Projects / Programmes source: ARIS

Electron density structures in the upper atmosphere and their effects on satellite navigation systems

Research activity

Code Science Field Subfield
1.06.05  Natural sciences and mathematics  Geology  Geophysics 

Code Science Field
P500  Natural sciences and mathematics  Geophysics, physical oceanography, meteorology 
Keywords
ionosphere, inhomogenities in electron density, scintillations, satellite navigation sistems
Evaluation (rules)
source: COBISS
Researchers (1)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  27791  PhD Biagio Forte  Geology  Head  2007 - 2008  55 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  1540  University of Nova Gorica  Nova Gorica  5920884000  14,198 
Abstract
A radio wave propagating through the ionized part of the upper atmosphere may experience irregular fluctuations in its amplitude and phase: the fluctuations characteristics depend on the radio frequency, magnetic and solar activity, time of day, season of the year and magnetic latitude of the observation point in the case of satellite-to-ground links. These fluctuations, known as scintillations, are responsible for signal degradation and services disruption (particularly in the case of satellite navigation applications, such as GPS and Galileo). Received radio signal components show irregular ("stochastic") fluctuations of amplitude and phase. If other parameters of received signals like polarization, angles of arrival, etc., are considered, they also show scintillation effects. All scintillation effects strongly depend on the frequency of the signal component considered. The principles of wave propagation lead to the conclusion that scintillating signals must have encountered irregular fluctuations of the refractive index somewhere along the propagation path. Since satellite to ground radio links use frequencies which are well above the maximum electron plasma frequency of the ionosphere, irregular fluctuations of signal amplitude and phase can be produced by electron density inhomogeneities in the ionosphere or by irregular fluctuations of neutral gas densities in the troposphere/stratosphere height range for even higher operational frequencies. In the following we restrict to ionospheric irregularities. These depend on magnetic and solar activity, time of day, season of the year and magnetic latitude of the observation point. The properties of the ionospheric irregularities change with time and most of them are drifting. The irregularities producing radio wave scintillations are predominantly in the F layer at altitudes ranging in altitude from 200 to 1000 km with the primary disturbance region for high and equatorial latitude irregularities between 250 and 400 km of altitude. There are times when E-layer irregularities, between 90 and 100 km, produce scintillation, particularly sporadic-E and auroral E. Nowadays, the scientific attention is mainly focused on the effects these irregular fluctuations can have on satellite based navigation systems. Therefore a lot of analyses about ionospheric scintillation effects on signals from the satellites of the Global Navigation Satellite Systems (GNSS) have been carried out. Special Global Positioning System (GPS) scintillation monitors have been arranged by using commercial GPS receivers for this purpose. A similar interest is raising for the new European satellite navigation system, i.e. Galileo, which is being developed jointly by the European Union (EU) and the European Space Agency (ESA). The objectives of the proposed research activities include the refinement of the radio propagation problem in the strong scattering regime, the investigation on plasma turbulent structures responsible for ionospheric scintillations in order to assess their impact on Galileo receivers and to improve their design and performance, the setup of a radio propagation model, remote sensing of small scale irregularities with special emphasis to those developing at high magnetic latitudes.
Significance for science
This project will strengthen the scientific activities and studies connected with the design of GNSS receivers. Also, it will allow for significant advancements in the remote sensing of plasma density irregularities by using GPS scintillation monitors. Such a project contained topics and results which will be very important in future years, when the solar activity will increase to its maximum levels, jeopardizing GNSS services wordlwide. This is very relevant to future ESA scientific programmes and, in this respect, the UNG would become a worldwide leading institution in upper atmosphere sciences.
Significance for the country
This proposed project will have relevant benefits to satellite based navigation, surveillance, surveying, and telecommunication services by providing updated information on the disruptions caused by the ionosphere and thus on the services reliability in the Alpine-Adriatic region. The activities connected with the proposed project will be useful to companies dealing with electronics, radio receivers’ development, and telecommunications. In the framework of the proposed project, this type of companies could be well cooperating with UNG in bidding for ESA tenders, as Slovenia has recently become an ESA cooperating country. For ESA related projects, the scientific expertise provided by the candidate and the UNG have to be coupled with technological infrastructures and capabilities of interested companies. Such a synergy, will clearly apply to FP7 related calls, as well, where the already established cooperation of scientific groups with small and medium enterprises (SME) is very important. The proposed scientific project will also strengthen the cooperation between Slovenia and ESA not only for Galileo related issues, but also for Earth observation missions as well as for future ESA missions still in the design phase
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