The relation between space geodetic measurements and ionosphere
models is twofold: (1) the geodetic measurements can be evaluated to
derive parameters of physical, empirical or analytical ionosphere
models and (2) models are used to correct the electromagnetic signals
for the ionospheric effects. In other words ionospheric signals such
as electron density or vertical total electron content are either the
target functions or interpreted as disturbing signals.

Space geodetic techniques such as GNSS (ground- and
satellite-based), DORIS, VLBI, satellite altimetry or the GPS radio
occultation missions (e.g Formosat-3/COSMIC, TerraSAR-X, ...) can
provide valuable information on the electron density. The potential
for ionospheric sensing using these techniques has improved
considerably over the last few years as a result of technological
advances, larger ground networks and developments of appropriate
models and algorithms. Accurate ionospheric estimates and retrievals
based on these techniques may significantly improve our understanding
on the physical and dynamic characteristics of electron density and
space weather at various scales. Consequently, contributions on
physical modeling of the ionosphere are highly appreciated. Studies on
the combination of various observation techniques as well as the
development of a full error model are also welcome. Furthermore,
contributions including near real-time developments and applications,
e.g. by introducing Kalman filtering procedures, are appreciated.