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DORIS - Determination d'Orbite et Radiopositionement Integre par Satellite

OSTM/Jason-2
The DORIS instrument onboard Jason-2 will provide real-time location and precise orbit determination. DORIS measurements are also used for geophysical studies, in particular through the International DORIS Service (IDS). DORIS is a dual-frequency instrument able to determine atmospheric electron content. This function complements the dual-frequency altimeter function. Additional information on the DORIS instrument is available on the AVISO site.
Jason-1
The DORIS instrument onboard Jason-1 provides real-time location and precise orbit determination. DORIS measurements are also used for geophysical studies, in particular through the International DORIS Service (IDS). DORIS is a dual-frequency instrument able to determine atmospheric electron content. DORIS orbitography beacons transmit signals at two separate frequencies (2036.25 MHz and 401.25 MHz) to the satellite. The receiver onboard the satellite analyzes the received signal frequencies to calculate its velocity relative to Earth. This velocity is fed into orbit determination models to derive the satellite's position on orbit to within two centimeters on the radial component. Additional information on the DORIS instrument is available on the AVISO site.
TOPEX/Poseidon
The DORIS antenna is connected to the DORIS receiver inside the Instrument Module. The function of the receiver is to listen for signals from ground stations. By using the Doppler shift of these signals the satellite's position can be determined. Currently, the CNES DORIS system has about fifty ground beacons distributed evenly around the globe. DORIS measurements are taken about every ten seconds. Combining the DORIS information with that of the Laser Ranging System gives TOPEX/Poseidon an unprecedented precision orbit determination capability.