This paper describes the results of development work on a small mobile robot carried out within the framework of ESA's Technological Research and Development Program. The purpose of the vehicle is to deploy instruments or sensor heads, acting as an 'extended robotic arm' rather than covering large distances on various types of terrain, while maximizing the mass allocation for scientific equipment. Even with this limited mobility it becomes possible to expand the investigated area by several orders of magnitude compared to the capabilities of a purely lander-mounted payload. Applications of the vehicle could be the projected European mission to Mars, called 'Mars Express', to be launched in 2003, and future European missions to the Moon as well as potential international missions.