An Aerobot For Global In Situ Exploration of Titan J. L. Hall, V. V. Kerzhanovich, A. H. Yavrouian, J. A. Jones, C.V. White, B. A. Dudik, G. A. Plett, J. Mennella and A. Elfes Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA, USA, 91109. Abstract This paper describes the design and component testing of an aerobot that would be capable of global in situ exploration of Saturn’s moon, Titan, over a 6 to 12 month mission lifetime. The proposed aerobot is a propeller-driven, buoyant vehicle that resembles terrestrial airships. However, the extremely cold Titan environment requires the use of cryogenic materials of construction and careful thermal design for protection of temperature-sensitive payload elements. Multiple candidate balloon materials have been identified based on extensive laboratory testing at 77 K. The most promising materials to date are laminates comprised of polyester fabrics and/or films with areal densities in the range of 40-100 g/m 2 . The aerobot hull is a streamlined ellipsoid 14 meters in length with a maximum diameter of 3 meters. The enclosed volume of 60 m 3 is sufficient to float a mass of 234 kg at a maximum altitude of 8 km at Titan. Forward and aft ballonets are located inside the hull to enable the aerobot to descend to the surface while preserving a fully inflated streamlined shape. Altitude changes are effected primarily through thrust vectoring of the twin main propellers, with pressure modulated buoyancy change via the ballonets available as a slower backup option. A total of 100 W of electrical power is provided to the vehicle by a radioisotope power supply. Up to half of this power is available to the propulsion system to generate a top flight speed in the range of 1-2 m/s. This speed is expected to be greater than the near surface winds at Titan, enabling the aerobot to fly to and hover over targets of interest. A preliminary science payload has been devised for the aerobot to give it the capability for aerial imaging of the surface, atmospheric observations and sampling, and surface sample acquisition and analysis. Targeting, hovering, surface sample acquisition and vehicle health monitoring and automatic safing actions will all require significant on-board autonomy due to the over two hour round trip light time between Titan and Earth. An autonomy architecture and a core set of perception, reasoning and control technologies is under development using a free-flying airship testbed of approximately the same size as the proposed Titan aerobot. Data volume from the Titan science mission is expected to be on the order of 100-300 Mbit per day transmitted either direct to Earth through an 0.8 m high gain antenna or via an orbiter relay using an omni- directional antenna on the aerobot. 1. Introduction Titan is a world that seems very well-suited to in situ exploration by buoyant, self-propelled robotic vehicles, also known as aerobots. This conclusion results from a combination of factors: 1. It has a dense atmosphere composed of high molecular weight gases. The nominal composition is 95% nitrogen, 2% argon and 3% methane for a mean molecular weight of 27.9. The atmospheric density (ρ) near the surface is 5.4 kg/m 3 . This means that relatively large masses can be floated using modestly sized helium- or hydrogen-filled balloons. 2. The surface of Titan is thought to pose serious problems to surface mobility assets (rovers) because of the likely presence of liquid hydrocarbon lakes and oceans, plus possible “sticky” hydrocarbon sludges on the solid parts of the surface. Flying platforms are not impeded by these obstacles or the more conventional difficulties posed by hazardous terrain in the form of rocks or steep slopes. 3. Titan is completely cloud-covered and therefore surface imaging from orbital or fly-by spacecraft is limited to relatively low resolution radar and infrared maps. An aerial platform can provide high resolution aerial imaging over large surface 1