Dr. Pascal Willis
International DORIS Service
Web site at the LAREG
Geodetic Data Information System.
DORIS is a dual-frequency Doppler system that can be included as a host
experiment on various space missions, Spot2 Spot3, Spot4, Topex/Poseidon and
Spot 5 in the future.
On contrary to most navigation systems, DORIS is based on an uplink device: the receiver is on board the satellite while the transmitters are on the ground. This creates a naturally centralized system, in which the complete set of observations is downloaded from the satellite to the ground centre, from where they are distributed after unified editing.
The system at the present time started operation in 1990. Its permanently tracked network includes 50 beacons evenly distributed on the Earth, including stations on all major tectonic plates.
The geocentric positioning results obtained in 1998 have a precision of 2 cm, and daily polar motion determinations have a precision of about 1-2 milliarcseconds.