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GAVDOS: Establishment of a European radar altimeter calibration and sea level monitoring site for JASON-1, ENVISAT and Euro-GLOSS (EC)

Period: December 2001 till December 2004
Status: Completed

Thesaurus term: Sea level records
Geographical term: Greece, Crete [Marine Regions]

Institute  Top 
  • Hellenic Centre for Marine Research; Institute of Oceanography, more, partner

"The primary objective of this project is the establishment of an absolute sea level monitoring and altimeter calibration facility on the isle of Gavdos, south of the island of Crete, Greece. The GAVDOS project will determine consistently and reliably (1) the altimeter biases and drifts for each of these missions and (2) the bias among different missions. It will also determine the mean sea level and the earth's tectonic deformation field in the region of Crete, Greece.
When the project becomes operational, continuous altimeter measurements of similar quality and reliability and over long time periods will be ensured. It will also supply useful data for global change, geophysics, geodynamics, geodesy, oceanography and seismology.
Scientific objectives and approach: The purpose of this permanent facility is (a) to conduct comparative laser distance measurements between the facility and satellite radar altimeters; (b) to ensure the unbiased establishment of the Mean Sea Level (MSL), as realised by the globally distributed altimeter measurements; and (c) to monitor any altimeter errors. Using this facility, errors from instruments, orbital biases, drifts, delays, etc., are decreased, quantified and monitored. Thus, we improve the accuracy of the oceanographic products, orbit determination, sea-state bias and other issues of algorithm refinements, achieving a global MSL monitoring system with an accuracy of a few mm.
In this experiment, the radar measurements from satellites are to be combined with the satellite ephemeris, the geodetic position of the facility, and the ties between reference points of instruments at the facility. Further, on-site tide-gauge measurements, the determination of a high-resolution regional geoid, hydrodynamic levelling, direct altimeter transponder observations and continuous Global Positioning System (GPS) measurements are planned. Observations for ultra precise orbit determination will be also carried out, using the DORIS (Doppler Orbitography by Radiopositioning Integrated on Satellite) positioning system and Satellite Laser Ranging.
Expected impacts: This integrated facility due to its nature and its open ocean location is appropriate and will be available for use within RTD programmes dedicated in forecasting the Mediterranean and monitoring climate change. Also, the system will be capable for monitoring extreme events (storm surges, floods, etc.) in the proximity. The proposed facility will underpin research relevant to the European component of the global observing systems for climate and oceans and operational forecasting of environmental constraints on offshore activities .

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