Strateole-2 uses CNES superpressure balloons to collect in-situ observations in the lower stratosphere.
Strateole-2 balloons are 12-m and 13-m diameter spherical balloons, made of plastic. They are closed and filled with helium. At float altitude, the helium pressure inside the balloon is larger than that of the air outside, hence their denomination. Strateole-2 balloons carry up to 50 kg of equipment, which is evenly distributed between science instruments and safety devices.
Superpressure balloons can fly for very long time in the stratosphere, the flight duration being ultimately determined by helium leak or diffusion through the balloon envelop. The target flight duration for Strateole-2 is 3 months.
Superpressure balloons fly on constant-density surfaces in the atmosphere. They are advected by winds, and thus almost perfectly follow the motion of air masses. Observations performed on superpressure balloon flights are hence called quasi-Lagrangian. This unique characteristics of superpressure balloon flights allows to address scientific issues that are otherwise tackled with either difficulties or arguable assumptions.
Three superpressure balloon flights have even already been achieved from Seychelles Islands during the Pre-Concordiasi campaign (2010).