Abstract: A stratospheric balloon comprising on the one hand an external flexible envelope (1) having a natural shape and made of transparent synthetic material and presenting an air inlet and, on the other hand, an internal screen (2) made of visible and infrared energy collecting material and having the shape of a surface generated by a mobile generatrix parallel to the longitudinal symmetry axis of the external envelope. The internal shield is connected to the envelope (1) by attachments arranged at the upper part of the envelope at a distance from the longitudinal axis of the latter, and extending longitudinally freely inside the envelope (1) without contacting it.

Abstract: The invention relates to a process for stabilizing at altitude a stratospheric balloon between the upper and lower levels through a plurality of diurnal and nocturnal cycles. The process comprises providing the stratospheric balloon (1) of the open, variable volume type a with a thermal trapping hood (7) arranged in the vicinity of its upper pole piece (4). This hood has reflecting properties from the side oriented toward the interior of the balloon and preferably thermal insulating properties, and its surface comprises between 1% and 15% of the total surface area of the balloon when full, preferably between 2% and 5%. In the full state, it does not appreciably alter the thermal balance of the balloon, while at lower levels at reduced states of inflation, it limits the energy loss from the bulb by reflecting toward the exterior and avoids an irreversible descent of the balloon.