JASON-1 calibration campaign at the Ibiza island area

A Spanish/French JASON-1 calibration campaign is being prepared for June 2003 in the area of Ibiza island in the NW Mediterranean Sea. The main objective, with a direct absolute altimeter calibration, is to map with a new designed, building and calibrated GPS catamaran, the mean sea surface MSS/local geoid gradient in the north area of Ibiza island at one crossing point of an ascending and descending satellite track. One part of a descending orbit in the SE of the island is also included. It is expected to have a new tide gauge at Ibiza harbor at that time. This campaign with its associated strategies is expected to have French support (CNES, LEGOS, CERGA and Noveltis) and is based in the experience obtained by three previous campaigns made in March 1999, July 2000 and August 2002 in the Cape of Begur/Llafranc/Palamos area. Direct absolute altimeter calibration was made from direct overflights using GPS buoys with a toroidal design performed at the ICC based in the original design of the University of Colorado at Boulder. The TOPEX Alt-B bias was estimated processing altimeter and GPS data. Other main objective of the campaign was to map GPS buoys the mean sea surface, MSS, along an ascending T/P groundtrack about 15-20 km from the coast, using coastal tide gauge measurements. In this case indirect absolute altimeter calibration is possible for any other altimetric satellite crossing the MSS, with the only requirement that tide gauges are operational during the overflight. Two tide gauges were placed temporally in Llafranc harbor and was used the data from the permanent L'Estartit tide gauge. The MSS provides with a reference for the altimetric measurement. The tide gauge provides with the temporal variable part of the sea level. The purpose of this presentation is to present and first results of the expected new JASON-1 calibration campaign in June 2003 at the Ibiza island area.