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Absolute Calibration: the Closure Equation to Link Altimetric Missions TOPEX/Poseidon, Jason-1 and Envisat results from Corsica and Harvest Calibration Sites

Pascal Bonnefond(1) , Pierre Exertier(1) , Olivier Laurain(1) , Yves Ménard(2) , François Boldo(3) , Eric Jeansou(4) , Gwenaele Jan(4) , Laurent Roblou(4) , Florent Lyard(5) , Bruce Haines(6) , Shailen Desai(6) , George Born(7) , and Steve Gill(8)

(1) OCA-GEMINI, avenue Nicolas Copernic, 06130 Grasse, France
(2) CNES, 18 avenue Edouard Belin, 31055 Toulouse, France
(3) IGN-CNES, 18 avenue Edouard Belin, 31055 Toulouse, France
(4) NOVELTIS, Parc Technologique du Canal, 31520 Ramonville, France
(5) LEGOS, 14 avenue Edouard Belin, 31400 Toulouse, France
(6) NASA/JPL, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
(7) University of Colorado at Boulder, 431 UCB, Boulder, CO 80309-0431, United States
(8) NOAA, 1335 East-West Highway, Silver Spring, MD 20910, United States


The Corsica site, which includes Ajaccio-Aspretto site, Senetosa Cape site, and Capraia (Italy) in the western Mediterranean area has been chosen to permit the absolute calibration of radar altimeters. Thanks to the French Transportable Laser Ranging System (FTLRS) for accurate orbit determination, and to various geodetic measurements of the local sea level and mean sea level, the objective is to measure the altimeter biases and their drifts. The extension of this calibration experiment includes now Capraia island and Ajaccio where dedicated GPS campaigns have been realized respectively in 2004 to measure the geoid slopes under Jason-1, EnviSat/ERS- 1 and 2 and GFO tracks around the island and in 2005 under EnviSat/ERS-1 and 2 ground track close to Ajaccio.

The Arguello Inc. Harvest Oil Platform is located about 10 km off the coast of central California near Point Conception. Attached to the sea floor, the platform sits in about 200 m of water near the western entrance to the Santa Barbara Channel. Harvest served for a decade (1992-2002) as a calibration site for the TOPEX/POSEIDON (T/P) mission, and is serving in a similar capacity for Jason-1. Harvest is a dedicated verification site, and features carefully designed collocations of space-geodetic and tide-gauge systems to support the absolute calibration of the altimetric sea-surface height (SSH).

All the presented analyses have been realized in a joint effort with Harvest calibration site in order to adopt common standards. Results on the TOPEX/Poseidon (SSALT, ALT-A and ALT-B), Jason-1 (POSEIDON-2) and EnviSat (RA-2) altimeters biases will be given along with an analysis of their drifts. Complementary results on the on-board radiometers monitoring using GPS will be presented.


Workshop presentation


                 Last modified: 07.10.03