Seapso V cruise was conducted in January 1986. It started on the 13th from Nuku'Alfa (Kingdom of Tonga) and ended in Papeete (French-Polynesia) on the 28th. The main objectives of this cruise were to gather new data on two well defined problems in order to: 1-understand the tectonic processes of the subduction of an aseismic ridge (the Louisville ridge) and 2-Test of a unique method of detecting, locating and evaluating uncharted seamounts by analysis of Seasat satellite altimetric data.