The Venus Balloon prototype undergoing inflation tests at JPL. Autonomous Aerobots like these are being tested for exploration of Titan and Venus. Future Titan and Venus in situ missions are two of the top three priorities in the 2005 Solar System Exploration Roadmap. The choice of an in situ platform is motivated by the dense clouds that completely cover Titan and Venus and thereby limit observations from orbit. The SSE Roadmap recognizes that there are tremendous opportunities for the application of aerial mobility technology to the exploration of both worlds. In particular, the thick atmosphere at Titan and Venus enables the use of compact, self-propelled buoyant vehicles that can access virtually any point of the planet over multi-month time scales with minimal consumption of scarce onboard electrical power. Depending of the level of autonomy incorporated, such an aerobot (robotic balloon) vehicle could acquire a wide spectrum of scientific data ranging from simple aerial imaging to acquisition of surface samples and onboard composition analysis. Even the simpler aerobot technology of drifting (unpropelled) balloons can yield valuable science, especially if the vehicle incorporates long duration flight and/or altitude control capability to do atmospheric profiling and ground approach for surface sampling. Pictures from the Huygens probe dramatically illustrate the utility of low altitude (
