Long-duration robotic missions on lunar and planetary surfaces ͑for example, the Mars Exploration Rovers have operated continuously on the Martian surface for close to 3 years͒ provide the opportunity to acquire scientifically interesting information from a diverse set of surface and subsurface sites and to explore multiple sites in greater detail. Exploring a wide range of terrain types, including plains, cliffs, sand dunes, and lava tubes, requires the development of robotic systems with

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... ity enhanced beyond that which is currently fielded. These systems include single as well as teams of robots. TRESSA ͑Teamed Robots for Exploration and Science on Steep Areas͒ is a closely coupled three-robot team developed at the Jet Propulsion Laboratory ͑JPL͒ that previously demonstrated the ability to drive on soil-covered slopes up to 70 deg. In this paper, we present results from field demonstrations of the TRESSA system in even more challenging terrain: rough rocky slopes of up to 85 deg. In addition, the integration of a robotic arm and instrument suite has allowed TRESSA to demonstrate semi-autonomous science investigation of the cliffs and science sample collection. TRESSA successfully traversed cliffs and collected samples at three Mars analog sites in Svalbard, Norway as part of a recent geological and astrobiological field investigation called AMASE: Arctic Mars Analog Svalbard Expedition under the NASA ASTEP ͑Astrobiology Science and Technology for Exploring Planets͒ program.