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DORIS Observation Centre


How the analysis centre operates

Since 1994, LEGOS has been one of IERS' (International Earth Rotation Service) DORIS analysis centres.

LEGOS proposed its services to IDS (International Doris Service) as an analysis centre in 2000. The analysis centre has been running since June 2002.

In collaboration with CLS, LEGOS/GOHS contributes to the production of high-precision geodesic products (industrial contract with CLS).

Work carried out and main findings

DORIS is a satellite-borne radiopositioning system based on measurements of Doppler shifts between signals transmitted by beacons from the ground DORIS network (approx. 50 beacons), and received on board satellites by the DORIS receiver payloads.

The geodetic products of DORIS data analysis are: satellite orbit, 3D position of each beacon, as well as other geodesic parameters (horizontal and vertical velocity of the beacons, geocentre movement and movement of the Earth's rotation pole).

Since December 2001, 3 satellites with DORIS payloads have been put into orbit: Jason-1, Envisat and Spot-5. They all have on board a new generation of DORIS receivers compared to receivers onboard Topex/Poseidon and Spot-2-3-4. An impact study of these new DORIS systems on calculated geodesic products has shown an improvement in precision. DORIS data from 6 satellites collected from 1993 to 2004 were reprocessed in 2004 using an improved configuration (modified software, modified computing strategy, use of new orbit calculation models, etc.). The corresponding geodesic products (monthly and weekly time series of DORIS beacon coordinates and velocities, pole coordinates, geocentre and orbit) were supplied to IDS at the end of 2004.

International collaboration

DORIS data analyses are part of an international effort. In its role as the analysis centre for one of the 4 basic IERS techniques, the DORIS CLS/LEGOS observation centre constantly interacts with the other analysis centres (in the United States, France, Russia, etc.) and help develop new analysis centres by offering technical support (for example, by installing DORIS data processing algorithms).

DORIS geodesic products are used regularly by many foreign research workers, in combination with Laser, VLBI and GPS-based geodesic products.

En 2008 ce centre d'analyse va participer aux tests de qualibration d'une solution DORIS combinée entre les differents centres, en vue d'une soumission à l'IERS pour la réalisation de l'ITRF-2008.

For a list of all the products supplied by the analysis center, consult the web site at :

Performances DORIS

Performance trends of the DORIS system since 1994 at the LEGOS Analysis Centre, as assessed by IERS.


Contacts : J.F. Crétaux, S. Daillet-Rochette

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