Over the past few years, many research projects have begun to focus on swarms of mobile unmanned systems (e.g., drones, ground robots) globally referred as UMS. These systems, because of the many sensors and actuators they can embed, are suitable for autonomous missions in 3D (Dull, Dirty and Dangerous) environments for instance. However, embedding a large number of capabilities in all of members of a swarm is expensive in terms of cost, weight and energy consumption. Thus, it is usually more efficient to embed only a single or a few capabilities within each UMS. It then becomes necessary to provide a discovery mechanism built into the swarm in order to allow its members to share their capabilities and to collaborate for achieving a global mission. These shared capabilities are called services. In this paper, we propose a new service discovery system called AMiRALE for Asynchronous Missions Relay for Autonomous and Lively Entities dedicated to highly volatile, autonomous and mobile swarms of UMS. Our solution is independent of both nodes’ mobility and connectivity patterns. Moreover, it supports heterogeneous swarms and degraded conditions of operation (i.e., message loss, UMS loss and disconnected network). It is also totally decentralized and enables both discovery and service usage. We provide a description of the theoretical model of our AMiRALE system as well as several simulation results obtained from a park cleaning scenario.