STRATOSPHERIC BALLOON BASES IN THE WORLD

The Seychelles is a group of about 115 islands which lie 1600km off the coast of east Africa. The three central islands -Mahé, Praslin and La Digue- are granite, while the outlying islands are coral atolls. Unlike most similar islands, the Seychelles are not volcanic - they seem to be the peaks of a huge underwater plateau that was torn away from Africa.

The islands were uninhabited when the British East India Company were the first visitors to the archipelago in 1609. Thereafter, they became a favorite pirate haven. The French claimed the islands in 1756 and administered them as part of the colony of Mauritius. The British gained control of the islands through the Treaty of Paris (1814) and changed the islands' name from the French Séchelles to the Anglicized Seychelles.

The Seychelles became self-governing in 1975 and independent on June 29, 1976. They have remained a member of the Commonwealth of Nations.

As the islands are located in the center of the Indian Ocean, a zone of special interest for atmospheric scientist whom study the behavior of wind patterns and their influence in the monsoonal activity, starting in the late seventies Seychelles served several times for launch stratospheric balloons. The great majority -if not all- of these launches were performed by the french space agency CNES or the National Center for Atmospheric Research and involved a subtype of stratospheric balloon called superpressure balloons, much smaller than their stratospheric cousins and with the remarkable capability to perform long durations flights maintaining a constant flight level.

After an impasse of almost two decades CNES showed again interest to launch balloons there. Thus in in the early 2000's cooperation with Seychelles in the scientific ballooning was initiated, in the frame of the VASCO program dedicated to study the atmosphere/ocean interaction over the Indian Ocean. Contacts between CNES and the National Meteorological Services of Seychelles, were established leading to perform the first two launch campaigns in 2006 and 2007 for the VASCO program involving small superpressure balloons drifting at about 1000 m altitude, and "Aeroclippers" a new type of hybrid vehicle buoy-balloon, stabilized at 40 m altitude through a "guide rope" able to perform simultaneous measurement at the ocean surface and in the air.

The balloon launches took place in January and Febraury both years from the seaside at the Southern end of the Victoria airport, an aerial station originally built by the English in 1972 with only one runway of 2987 meters. At left we can see an aerial image of the launch site and the hangars loaned to airport authorities to be used as integration halls by the teams participating in the operations.

After these two first campaigns, in 2008 took place the Scout-O3 effort devoted to study the Upper Stratosphere and Lower Stratosphere at equatorial latitudes, funded by European Union, CNES, and several scientific institutes in Europe. This program used "Montgofières Infrarouges" (MIR), another concept of long duration stratospheric balloon by CNES, which as a special feature performs daily naturally vertical excursion in the lower stratosphere. The choice of the launch site for SCOUT-O3 was difficult. The site of Mahé was at the right latitude (5°S), however it was considered quite challenging to conduct these flights from such an island, because it is under the direct influence of the sea and often in the middle of powerful convective systems. But, given the quality of the relationship established for the previous VASCO project, it was finally proposed to launch from Mahé. Thus, three MIR and two superpressure balloons were launched from Victoria Airport in February 2008.

This first stratospheric balloon campaign, with five successful launches served to validate the Mahé site as a possible place for conducting such activity.