**1. Introduction**

During the last years, unmanned aerial vehicles (UAVs) have been used in a wide variety of applications, such as in agriculture [1], civil protection [2], infrastructure, inspection and maintenance [3], and light shows [4]. Their uses are not limited to the Earth's surface, but extend to space environments as well, where they could be used for ad hoc missions [5]. When considering applications in a marine environment, different types of robots can be involved. Generally, a set of underwater and surface vehicles allow the execution of complex tasks, such as monitoring wide areas or cooperative collaboration for a mutual goal. For instance, in [6], an autonomous robotic team composed of underwater and surface vehicles was considered for geotechnical survey purposes. By considering aerial agents also, a wider variety of missions can be designed, such as the protection and security of marine areas, or humanitarian search and rescue activities [7]. The landing of aerial agents requires ad hoc procedures [8], and when working in complex conditions, this is often performed by a human operator. In fact, in marine applications, the sea conditions could alter the pose of the landing target, and could determine the success or the failure of the landing procedure itself. Therefore, in fully autonomous missions, the landing maneuvers of an aerial agent must be robust to difficulties and reliable.

On the basis of the previous works [9,10], we aimed to provide an efficient, reliable, and modular solution to autonomously land a quadrotor on a catamaran in a marine environment.
