GESA -Georreferenciacion Satelitaria- is a laboratory
belonging to the Faculty of Astronomical and
Geophysical Sciences of La Plata National University.
It is a branch of the Astrometry Department
specialized in Space Geodesy researches, covering
realization of the International Terrestrial Reference
Frame; tide gauges control by GPS for sea level rise
studies; model Earth rotation irregularities; and EC
imaging from beacon satellite observations. This talk
outlines the results achieved by GESA in the last of
the topics previously mentioned.
GESA developed the so-called La Plata Ionospheric
Model (LPIM). It is an algorithm to retrieve TEC
information from dual-frequency beacon satellite
signals, based on a thin-layer ionosphere
approximation and a spherical harmonics expansion for
global TEC interpolation. Several systematic biases
that affect GPS- and TOPEX-based TEC are also
discussed in this talk.
Finally, a model to retrieve EC distribution from GPS
observations is described. It uses the NeQuick
ionspheric model to describe the electron density
profile and GPS observations for updating the pick
parameters. Comparisons between EC derived from our
model and from ionozonde observations will be also presented.