Tele-operated rovers offer huge application potential in the areas of emergency support, surveillance and security, in particular if they are small and easy to transport. In this context, the MERLIN outdoor rovers have been designed for robust operations in harsh outdoor environments at a total mass below 20 kg. The MERLIN rover system design aspects are described, including the rover on-board data processing and the sensor configuration. Special emphasis is on the remote operations assistance system, composed of the human-machine interface for appropriate presentation of relevant data at the tele-operator workplace and the autonomous reaction capabilities coordinated by the on-board data handling system.