GALOCAD project “Development of a Galileo Local Component for the nowcasting and forecasting of atmospheric disturbances affecting the integrity of high precision Galileo applications” aims to ...perform a detailed study on ionospheric small- and medium-scale structures and to assess the influence of these structures on the reliability of Galileo precise positioning applications. GPS-derived TEC (total electron content) is obtained from the Belgium Dense Network (BDN), consisting of 67 permanent GPS stations. An empirical 3-D model is developed for studying these ionospheric structures. The model, named LLT model, described temporal variations of TEC in latitude/longitude frame (46°,
52°)N and (−1°,
11°)E. The spatial variations of TEC are modeled by Tchebishev base functions, while the temporal variations are described by a trigonometric basis. To fit the model to the data, the observed area is divided into bins with (1°
×
1°) geographic scale and 6
min on time axis. LLT model is made flexible, with varying number of coefficients along each axis. This allows different degree of smoothing, which is the key element of the present approach. Model runs with higher number of coefficients, capturing in details medium-scale TEC structures are subtracted from results obtained with smaller number of coefficients; the latter represent the background ionosphere. The residual structures are localized and followed as they travel across the observed area. In this way, the size, velocity, and direction of the irregular structures are obtained.
The knowledge transfer project called "Magnetic Valley" that was launched in 2009 is presented below. This project is funded by the Belgian government to investigate and develop products and services ...that will improve the socio-economic development in the area around the "Centre de Physique du Globe de l'IRM".
The paper reviews the current state of GNSS-based detection, monitoring and forecasting of ionospheric perturbations in Europe in relation to the COST action ES0803 “Developing Space Weather Products ...and Services in Europe”. Space weather research and related ionospheric studies require broad international collaboration in sharing databases, developing analysis software and models and providing services. Reviewed is the European GNSS data basis including ionospheric services providing derived data products such as the Total Electron Content (TEC) and radio scintillation indices. Fundamental ionospheric perturbation phenomena covering quite different scales in time and space are discussed in the light of recent achievements in GNSS-based ionospheric monitoring. Thus, large-scale perturbation processes characterized by moving ionization fronts, wave-like travelling ionospheric disturbances and finally small-scale irregularities causing radio scintillations are considered. Whereas ground and space-based GNSS monitoring techniques are well developed, forecasting of ionospheric perturbations needs much more work to become attractive for users who might be interested in condensed information on the perturbation degree of the ionosphere by robust indices. Finally, we have briefly presented a few samples illustrating the space weather impact on GNSS applications thus encouraging the scientific community to enhance space weather research in upcoming years.
Ground‐based ionosphere sounding measurements alone are incapable of reliably modeling the topside electron density distribution above the F layer peak density height. Such information can be derived ...from Global Positioning System (GPS)‐based total electron content (TEC) measurements. A novel technique is presented for retrieving the electron density height profile from three types of measurements: ionosonde (foF2, foE, M3000F2, hmf2), TEC (GPS‐based), and O+‐H+ ion transition level. The method employs new formulae based on Chapman, sech‐squared, and exponential ionosphere profilers to construct a system of equations, the solution of which system provides the unknown ion scale heights, sufficient to construct a unique electron density profile at the site of measurements. All formulae are based on the assumption of diffusive equilibrium with constant scale height for each ion species. The presented technique is most suitable for middle‐ and high‐geomagnetic latitudes and possible applications include: development, evaluation, and improvement of theoretical and empirical ionospheric models, development of similar reconstruction methods utilizing low‐earth‐orbiting satellite measurements of TEC, operational reconstruction of the electron density on a real‐time basis, etc.
The NEtlander Ionosphere and Geodesy Experiment (NEIGE) of the Netlander mission to Mars will measure Doppler shifts affecting the radio links between ground stations and an orbiter. The experiment ...has two complementary scientific objectives which are the monitoring of the structure and dynamics of the ionosphere of Mars and the precise determination of Mars orientation parameters. The horizontal variation of the Total Electron Content (TEC) of the ionosphere will be derived from the so-called “geometric-free” combination of the Doppler shifts which affect radio links at two frequencies (in the UHF and S bands) between the Netlander microstations on the Mars surface and the data-relay orbiter. We describe a new method for retrieving the horizontal profile of the absolute value of the TEC. Simulations have allowed to evaluate the precision in the determination of the TEC using this method. We show that the daytime TEC can be retrieved with a precision of
5×10
13
m
−2
for a nominal accuracy of
0,1
mm/
s
on the orbital pseudo-velocity, which represents a relative precision of a few percent. A preliminary analysis of the sensitivity of the TEC to the physical parameters which control the ionosphere has been performed. For this purpose, we have used a new one-dimensional ionospheric model based on the solution of coupled kinetic, fluid and MHD equations. This model describes the suprathermal electron component, the thermal plasma component as well as the induced horizontal magnetic field. The code which provides the vertical electron density profile has been used to study the variation of the TEC with the solar zenith angle and with the induced magnetic field at the top of the ionosphere. In particular, we show that NEIGE will allow to diagnose the penetration into the daytime ionosphere of an induced magnetic field.
The netlander ionosphere and geodesy experiment Barriot, J.-P.; Dehant, V.; Folkner, W. ...
Advances in space research,
01/2001, Volume:
28, Issue:
8
Journal Article, Conference Proceeding, Web Resource
Peer reviewed
The NEtlander Ionosphere and Geodesy Experiment (NEIGE) of the Netlander Mission to Mars has two series of scientific objectives: (1) to determine Mars orientation parameters in order to obtain ...information about the interior of Mars and about the seasonal mass exchange between atmosphere and ice caps; and (2) to determine the total electron content (TEC) and the scintillation of radio signals in order to study the large- and small-scale structure of the ionosphere of Mars. These two sets of information will be derived from measurements of amplitudes and Doppler shifts of radio links at UHF and X-band between the Netlander microstations on the Mars surface and an orbiter and between this orbiter and the Earth (at X-band).
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