Abstract: A vehicle for the exploration of the atmosphere comprising an infra-red and olar montgolfier (hot-air balloon) capable of being piloted reversibly. The vehicle comprises a gas-tight envelope in which the upper part of the envelope is either transparent to or slightly absorbent of infra-red radiation, the outer face of the upper part of the envelope is slightly emissive in the infra-red region of radiation and the inner face of the upper part absorbs infra-red radiation so that ascending forces which act on the montgolfier are only obtained as a result of the heating of the gas contained in the envelope which is produced by the absorption of infra-red radiation.