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Doppler Orbitography Radiopositioning Integrated by Satellite (DORIS)

Mission Name: EOS-ALT1


The Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) tracking system was provided by CNES for the EOS-ALT series of spacecraft. DORIS was first flown on the French SPOT-2 spacecraft and later the TOPEX/Poseidon spacecraft. The tracking system provided tracking data for precise orbit determination using microwave Doppler techniques. The satellite velocity was precisely measured by the Doppler shifts of two ultra-stable microwave frequencies (2036.25 and 401.25 MHz). The DORIS system consisted of a dual-frequency coherent receiving unit, an ultra-stable oscillator (USO), and a nadir-directed omniantenna. The DORIS radiopositioning system consisted of uplink doppler measurements from signals transmitted from a network of 40 to 50 ground transmitter stations whose positions are known to within a few centimeters. The DORIS system had an altitude accuracy of 5-10 cm. The DORIS on-board receiver consisted of a 2 GHz antenna and a 400 MHz antenna. Doppler measurements were made at the two frequencies every 10 seconds on 9-second intervals (with the free second used for timing). The separation of the two frequencies made it possible to reduce ionospheric effects on the EOS-ALT altimeters. Tropospheric refraction was modeled using ground meteorological data. Meteorological data from the ground stations were collected by the DORIS receiver and sent back to the ground stations via satellite telemetry. The DORIS system was manufactured by Dessault Electronique, CEIS-ESAPCE, CEPE and OSA for the CNES.

Alternate Names


Facts in Brief

Mass: 44.0 kg
Power (avg): 17.6 W
Bit rate (avg): 0.032 bps

Funding Agency

  • Centre National d'Etudes Spatiales (France)


  • Earth Science: Geophysics/Geodesy
  • Space Physics: Ionospheric Studies

Additional Information

Questions or comments about this experiment can be directed to: Coordinated Request and User Support Office.



NameRoleOriginal AffiliationE-mail
Mr. Lee-Lueng FuGeneral ContactNASA Jet Propulsion
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