| definition |
- [Source: ESA/Earthnet Online,
http://envisat.esa.int/instruments/doris/ ]
The Doppler Orbitography and Radio-positioning Integrated by Satellite instrument is a microwave tracking system that can be utilized to determine the precise location of the ENVISAT satellite. Versions of the DORIS instrument are currently flying on the SPOT-2 and Topex-Poseidon missions.
DORIS operates by measuring the Doppler frequency shift of a radio signal transmitted from ground stations and received on-board the satellite. The reference frequency for the measurement is generated by identical ultra-stable oscillators on the ground and on-board the spacecraft.
Currently there are about 50 ground beacons placed around the globe which cover about 75% of the ENVISAT orbit. On board measurements are performed every 7 - 10 seconds. Precise Doppler shift measurements are taken using an S-band frequency of 2.03625 GHz, while a second VHS band signal at 401.25 MHz is used for ionospheric correction of the propagation delay.
On the ground, DORIS data is used to create precise orbit reconstruction models which are then used for all satellite instruments requiring precise orbit position information. In addition, DORIS operates in a Navigator mode in which on-board positioning calculations are performed in real-time and relayed to the ground segment.
Group: Instrument_Details
Entry_ID: DORIS
Group: Instrument_Identification
Instrument_Category: Earth Remote Sensing Instruments
Instrument_Class: Passive Remote Sensing
Instrument_Type: Positioning/Navigation
Instrument_Subtype: Radio
Short_Name: DORIS
Long_Name: Doppler Orbitography and Radiopositioning Integrated by Satellite
End_Group
Group: Associated_Platforms
Short_Name: CRYOSAT-2
Short_Name: ENVISAT
Short_Name: JASON-1
Short_Name: OSTM/JASON-2
Short_Name: SPOT-2
Short_Name: SPOT-3
Short_Name: SPOT-4
Short_Name: TOPEX/POSEIDON
Short_Name: SPOT-5
Short_Name: CRYOSAT
End_Group
Group: Spectral_Frequency_Information
Wavelength_Keyword: Radio
Number_Channels: 2 Channels
Spectral_Frequency_Coverage_Range: 401.25 MHz and 2036.25MHz
End_Group
Online_Resource: http://envisat.esa.int/instruments/doris/
Online_Resource: http://www.aviso.oceanobs.com/en/doris/index.html
Sample_Image: http://www.aviso.oceanobs.com/typo3temp/pics/98d5269f70.jpg
Creation_Date: 2007-04-16
Group: Instrument_Logistics
Data_Rate: 330 bps
Instrument_Start_Date: 2002-01-15
Instrument_Owner: France/CNES
End_Group
Group: Instrument_Logistics
Instrument_Start_Date: 1992-09-23
Instrument_Stop_Date: 2005-10-09
End_Group
End_Group
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