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DORIS (satellite system)

French civilian geopositioning system

Field	Value
image	Doris-system.jpg
image_caption	The DORIS antenna and receiver installed onboard OSTM/Jason-2 satellite
country	France
type	Civilian
status	Operational
operator	CNES
satellites_nominal	0 (ground transmitters only)
first_launch

DORIS is a French satellite system used for the determination of satellite orbits (e.g. TOPEX/Poseidon) and for positioning. The name is an acronym of "Doppler Orbitography and Radiopositioning Integrated by Satellite" or, in French, Détermination d'Orbite et Radiopositionnement Intégré par Satellite.

Principle

Ground-based radio beacons emit a signal which is picked up by receiving satellites. This is in reverse configuration to other GNSS, in which the transmitters are space-borne and receivers are in majority near the surface of the Earth. A frequency shift of the signal occurs that is caused by the movement of the satellite (Doppler effect). From this observation satellite orbits, ground positions, as well as other parameters can be derived.

Organization

DORIS is a French system which was initiated and is maintained by the French Space Agency (CNES). It is operated from Toulouse.

Ground segment

The UHF transmitting antenna of DORIS ground station at [[Dionysos, Greece

The ground segment includes about 50-60 ground stations, equally distributed over the Earth and ensure a good coverage for orbit determination. For the installation of a beacon only electricity is required because the station only emits a signal but does not receive any information. DORIS beacons transmit to the satellites on two UHF frequencies, 401.25 MHz and 2036.25 MHz.

Australian ground segments

There are two active DORIS stations in Australia:

Yatharagga - active
Orroral Valley Tracking Station - no longer active
Mount Stromlo Observatory - currently active, replaced Orroral Valley Tracking station installation

Space segment

The best known satellites equipped with DORIS receivers are the altimetry satellites TOPEX/Poseidon, Jason-1, OSTM/Jason-2, Jason-3, and Sentinel-6 Michael Freilich. They are used to observe the ocean surface as well as currents or wave heights. DORIS contributes to their orbit accuracy of about 2 cm.

Other DORIS satellites are the Envisat, SPOT, HY-2A and CryoSat-2 satellites.

Positioning

Apart from orbit determination, the DORIS observations are used for positioning of ground stations. The accuracy is a bit lower than with GPS, but it still contributes to the International Terrestrial Reference Frame (ITRF).

References

(15 May 2014). "Doppler Orbitography and Radiopositioning Integrated by Satellite". Geoscience Australia.
"Doris-Equipped Satellites".
"ITRF2014". IGN.

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

satellite-navigation-systems spacecraft-instruments

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