The University of Maryland (UMd) and Arizona State University (ASU) are collabora- tively developing and testing robotic technologies and operating protocols to increase the ability of humans to perform extended science missions on the Moon and Mars. In past years, the UMd Space Systems Laboratory (SSL) has developed fully functional pressure suits for Earth-based simulations, along with space-qualified dexterous robotic systems. In parallel, ASU has developed a number of instruments for in situ geological sampling and examination which would dramatically increase the scientific yield of future human explo- ration missions. These technologies are being integrated for the lunar exploration scenario by the joint development of a field assistant robot for EVA exploration: the Robotic Assist Vehicle for Extravehicular Navigation, or RAVEN. RAVEN is a minimally-sized robotic rover to assist in the human science mission. Con- ceptually, this robot is similar in size and functionality to the Modular Equipment Trans- porter (MET) used on Apollo 14, but is self-propelled to eliminate the considerable impact on crew physiological workload induced by the requirement to manually pull the MET through the regolith. The rover is used to carry tools and instruments for the astronauts, as well as collected samples. A UMd manipulator arm has been provided to add dexterous capabilities to the robot, and to expand the range of potential human/robot task allocations during the exploration mission. This paper details the design and development of RAVEN, leading to its initial field trials in the Arizona desert near ASU in September, 2010. During these trials, RAVEN will perform three separate exploration functions: surveying the exploration site prior to the human EVA; accompanying and assisting the humans during their geological sortie; and performing directed activities at the field site after the humans have returned to their lander, rover, or habitat. Metrics have been established to measure the scientific produc- tivity of the overall system, and to test various approaches to human/robot interaction to maximize science data return. In the basic design scenario, the RAVEN rover would be deployed early in an Apollo-like surface stay, and would be capable of self-tended recharging from the landing vehicle and a combination of autonomous, locally controlled, and ground-controlled activities. The rover would be capable of independently performing an extended traverse to survey the coming EVA route, categorizing the exploration sites geographically and aiding in detailed EVA planning. Following a quick recharge, RAVEN will be ready to accompany the crew on the human exploration phase, autonomously staying close to the humans while transporting materials needed for the EVA operations and science data collection. One of the critical de- sign requirements is that the rover must be capable of meeting or exceeding human traverse velocities, while being able to navigate on the same terrains chosen for human ambulation. During the EVA, RAVEN will support the crew by providing data relay, video monitoring, and a variety of viewpoints (e.g., telephoto, microscopic, and data visualization) not avail- able during the Apollo era, fed directly into head-mounted and suit-mounted displays built.