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Terms of
Reference
As a result of many years of research the climatology of
the ionosphere is today quite well known. However, variations of the solar
activity and emissions of plasma from the solar corona change the conditions
of the Sun-Earth environment and can dramatically disturb the ionospheric
mean conditions. The development of sophisticated high technological systems
for navigation, telecommunication, space missions, etc., created the need
of predicting the meteorological conditions of the space around the Earth,
giving rise to a branch of knowledge that today is called space weather. Disruptions
of the ionosphere caused by massive solar flares can interfere with or even
destroy communication systems, Earth satellites and power grids on Earth.
A stringent application of ionospheric models would be to provide real-time
corrections and integrity information for aircraft navigation and precision
approach.
Ionospheric models are important for many space geodesy
observing techniques to correct the delay caused by the ionosphere on the
propagation of electromagnetic wave, typical applications being single-frequency
GPS and GLONASS positioning or real time ambiguity resolution. The EarthÕs
ionosphere has been studied for more than one hundred years using different
observational techniques. A large contribution to the knowledge of the bottom-side
ionosphere was done by a global network of 100-200 vertical incidence ionosondes,
that started operation during the International Geophysical Year 1957-1958.
Incoherent backscatter radars were used after 1958 to extend the exploration
of the ionosphere to its topside. In 1957 the space age began enabling topside
ionosondes onboard satellites, observations of Faraday rotation on transionospheric
signals emitted by geostationary satellites, Doppler method with rockets and
satellites and in situ techniques aboard spacecrafts.
Using large data bases of classical observations covering
different geographical regions and different solar and geomagnetic conditions,
several empirical ionospheric models were established. Among them, the International
Reference Ionosphere (IRI) is probably the most widely used. IRI is continuously
revised and updated through international cooperative effort of different
type sponsored by the Working Group created by the Committee on Space Research
(COSPAR) and the Union of Radio Sciences (URSI). Today ground-based and space-based
GPS observations, and in a less extent observations of other space geodetic
dual-frequency observing techniques, e.g., satellite altimetry, bring an unprecedented
opportunity for ionospheric studies and may well revolutionize science and
technology of the ionospheric meteorology. They provide high quality ionospheric
information, with global coverage, simultaneity and time continuity and are
easy and free available for ionospheric scientists.
Steering
Committee
Michael
Schmidt (Germany) - Chair
Susan
Skone (University of Calgary, Canada) - Vice-Chair
Objectives
A first valuable step toward exploiting the GPS potentiality for ionospheric
studies was already done by the IGS in 1998 by the creation of the Ionosphere
Working Group. In the framework of this group, five centers are computing
and making accessible on a regular basis several GPS-derived ionospheric products,
mainly two-dimensional worldwide grids of vertical total electron content.
We believe that the efforts to maintain a regular service for processing GPS
data to form VTEC maps should be continued, but we are convinced that the
effort should be pursued to fully exploit such amount of high quality data
and to maximize the benefits for the scientific community. Therefore, we propose
the creation of a study group on Ionospheric Modeling and Analyses, in co-operation
with IGS and possibly with COSPAR, to support the already existing Ionospheric
Working Groups.
The principal objectives of the Study Group may be summarized as follows:
- To establish a scientific link between geodetic and aeronomy experts
in order to maximize the benefit of the ionospheric information provided
by geodesy.
- To analyze the ionospheric products derived from GPS and other space
techniques and to explore the better use for scientific and practical purposes.
- To study possible improvements of the existing products.
- To propose new products that could be obtained from ionospheric information
of GPS and other space techniques.
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