DORIS (geodesy)

Doppler Orbitography and Radiander Integrated by Satellite or, in French, Orbital Determination and Satellite Integrated Radiagnosis ( DORIS ) is a French satellite system used for the determination of satellite orbits (eg TOPEX / Poseidon ) and for Positioning .

Principle

Ground-based radio beacons emit a signal which is picked up by receiving satellites. This is in reverse configuration to other GNSS , in the qui transmitters are space-borne and receivers are in majorité near the area of the Earth. A frequency shift of the signal which is caused by the motion 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

DORIS stations in Australia : [1]

  • Yatharagga – Active
  • Orroral Valley Tracking Station – No longer active.
  • Mount Stromlo Observatory – Currently active, replaced

Space segment

The best known satellites equipped with DORIS receivers are the altimetry satellites TOPEX / Poseidon , Jason 1 and Jason 2 . 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. [2]

Positioning

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

References

  1. Jump up^ Australia, c \ = AU \; o \ = Australia Government \ or Geoscience (15 May 2014). “Doppler Orbitography and Radiander Integrated by Satellite” . www.ga.gov.au . Geoscience Australia . Retrieved 24 June 2017 .
  2. Jump up^ “Doris-Equipped Satellites” .
  3. G. Seeber: Satellite Geodesy . De Gruyter-Verlag, 2. Auflage (590 p.), Berlin 2003

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