International DORIS Service (IDS)

Project Description
After a decade of fully operational functioning, the DORIS space
geodesy system has demonstrated its capabilities for
orbitography and navigation of the satellites and also ground
location. It plays a key rule in the Topex/Poseidon altimetric
mission for oceanography providing in association with the Laser
technique a 2 cm accuracy in the radial component of the
orbit. DORIS and Laser are renewed as the nominal orbitographic
system for the Jason mission (end of 2000).

DORIS also provides with Diode navigator on Spot 4 (1993), an
orbit in real time within a few meters. It's a world first at
this level of precision.

Since 1994 and thanks to its more than fifty permanent beacon
network, DORIS contributes to the IERS activities for the
realization and maintenance of the ITRS (International
Terrestrial Reference System). 3D positions and velocities of
the reference sites at a cm and mm/yr accuracy lead to
scientific studies (investigations) in the fields of global and
regional tectonics. Two recent DORIS results appear very
encouraging for the future. One concerns a seasonal effect of
earth surface fluid mass redistribution (oceanic water,
atmospheric masses, snow, ...) on the relative positions of the
earth mass and earth figure centers. Another concerns vertical
displacement of the crust monitored near tides-gages. This
information is of major interest for the topic of sea level
variations and correlation to the Global Change.

Such as the other space geodesy techniques GPS, VLBI, SLR, there
is a strong demand among the scientific community to create an
International DORIS Service, so called IDS. The CSTG, commission
for international co-ordination of space techniques for geodesy
of the International Association Geodesy (IAG) and the IERS
directing board decided in July 1999 to initiate a DORIS Pilot
Experiment. Its objective is to assess the need and feasibility
of an International DORIS Service.

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