DORIS SYSTEM
CLS Expertise How DORIS works Applications Argos, Altimetry and DORIS News

Tracking satellites in orbit DORIS calculates satellite orbits extremely accurately. It is one of the keys to the succes of the TOPEX/POSEIDON mission. The ocean is a fascinating sight. Seen from the shore, its waves and tides give some idea of the complex motion taking place at the surface. Accross a basin, currents cause sea level variations of up to a meter, while unequal mass distributions in the Earth's core produce variations of tens meters. The TOPEX/POSEIDON satellite calculates height variations to within just a few centimeters, allowing scientists to study climatic events like El Niño. A world first Until recently, The DORIS system provided satellite orbits in delayed time only. With the DIODE navigator on SPOT-4, launched in March 1998, it now also provides orbits in real time, to within a few meters.

Locating beacons on the ground Marking out the boundaries of a local oil concession, routing a new national highway, observing global variations in mean sea level, all rely on reference networks of geodetic control points. For needs like these, DORIS supplies absolute coordinates with sub-20-centimeter accuracy within 48 hours, or with centimeter accuracy from several months of measurements. A permanent observation network can also measure motions as small as a few millimeters per year. DORIS is one of four space geodesy techniques used by the International Earth Rotation Service to maintain the International Terrestrial Reference System.

Operational location, anytime, anywhere The main purpose of the DORIS instruments on the SPOT satellites is to provide location data. This service is well suited to remote regions where geodetic networks and infrastructure are lacking. Its applications are geodesy, geotechnicsand geophysics. CLS provides remote access to your platform location.

DORIS was designed and set up by: the French space agency (CNES), the French mapping and surveying agency (IGN) the (LEGOS/GRGS) space geodesy research laboratory

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