Satellites guide ship through South Pacific's watery desert   IFREMER research vessel L'Atalante anchored in front of Ranga Roa on Easter Island during the BIOSOPE cruise.   The BIOSOPE transect in the South Pacific from Papeete in France's Tahiti to Concepcion in Chile. Each point identifies a station where hydrological and biogeochemical measurements as well as, in most cases, optical measurements.   Deployment of LICOR spectroradiometer allowing the measurement of spectral upwelling and down-welling irradiance. In addition this radiometer is coupled to a natural fluorescence sensor which measures upward radiance at 685 nanometres which is due to phytoplankton sun-induced fluorescence, and reflects in some way its photosynthetic activity. The deployment is performed in coincidence with a satellite overpass.   An example of marine phytoplankton. This is Emiliania huxleyi coccolithophore. From Tahiti to Chile     Map of the surface chlorophyll concentration in the vicinity of the Marquises Archipelago. This image is a composite of MERIS and MODIS-T data. Such images were produced and provided daily by ACRi-ST; they allowed the location of some stations to be accurately selected and were helpful in deciding the ship's course. In this particular case, the station located at 141 degrees West, 8.2 degrees south was chosen for a three day station because of the significant extension of chlorophyll concentrations above 0.5 mg m-3.   Map of the surface chlorophyll concentration corresponding to the second part of the cruise, from Easter Island to the Chilean coast. The map illustrates the large range of surface chlorophyll concentration explored, which encompasses more than two orders of magnitude.   Detailed map of chlorophyll concentration in the upwelling zone off the Chilean coast. This map allowed the location of a station at 73 degrees 30 minutes West, 33 degrees 50 minutes South to be selected for detailed investigations. Release date: 1 March 2012