Towards a Pan-European network for the mitigation of ionospheric threats
2013
Measurements of signals from Global Navigation Satellite Systems (GNSS) offer the
possibility to analyze the spatial and temporal characteristics of the electron density structure in the
ionosphere and plasmasphere.
Dual frequency ground based measurements are well suited to observe horizontal structures of the electron
density and their dynamics whereas space based GNSS measurements can effectively contribute to
explore the vertical structure of the ionosphere-plasmasphere ionization. The current data base, covering
more than one solar cycle, enabled the development of empirical models of ionospheric key parameters
such as the total electron content (TEC), the peak density NmF2 and the corresponding peak density
height hmF2. TEC models can directly be used as correction in single frequency GNSS applications.
Utilizing well established geodetic networks such as that of the International GNSS Service (IGS), it is
discussed how ground based GNSS measurements are used to derive regional and global maps of the
vertical TEC in near real time. Actual TEC maps are used for correcting ionospheric range errors in
operational single frequency applications, e.g. in space based augmentation systems (SBAS) like WAAS in
US and EGNOS in Europe.
However, severe space weather conditions lead to perturbations of the ionospheric plasma which in turn
can affect the performance of GNSS. These perturbations come at a wide range of spatial and temporal
scales and are observed as large scale ionization fronts, medium scale travelling ionospheric disturbances,
plasma bubbles and small scale irregularities causing radio scintillations at the receiver level. These
disturbances can strongly degrade the accuracy, reliability, integrity and availability of the GNSS. This is
especially detrimental for space and ground based augmentation systems which have specific accuracy
and availability requirements.
Therefore an important use of the measurements of GNSS signals is to assess the threat that space
weather can have on GNSS. One possible application is the estimation of the strongest possible influence
of the ionosphere. This can then be used as a safety margin to fulfill the high safety requirements of
aircrafts landing with GNSS and GBAS.
GNSS receivers are a crucial component in countless modern systems, e.g. in telecommunication,
navigation, remote sensing and precision timing. Additionally the demands on these systems with respect
to accuracy, reliability and safety are permanently growing. Considering the fact that the ionospheric impact
cannot be ignored enhanced research activities are required to improve current solutions for correcting or
mitigating the ionospheric impact or at least to provide awareness of current threats. It is reported how the
current EC funded research project TRANSMIT focuses on bringing together young researchers in this field
in order to establish a Pan-European network for Ionospheric Perturbation Detection and Monitoring (IPDM)
in the upcoming years. To highlight essential results of these researchers, a prototype solution is being
prepared to be accessible via internet (http://swaciweb.dlr.de ).
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