## 1 Introduction  
Presently, new key enabling technologies have precluded the emergence of novel space-based applications that can satisfy current environmental, and socio-economic demands. The Horizon 2020 Operational Network of Individual Observation Nodes (ONION) project [1] identified the needs of the Earth Observation (EO) community to define the evolution of the EU Copernicus system in the 2020-2030 time frame. Specifically, applications to monitor the marine weather forecast, and marine fishery pressure are the most demanded ones to cover the Arctic changes, followed by the hydric stress monitoring (i.e., soil moisture) as a proxy of desertification, or crop yield. Moreover, the increase of climate disasters has accentuated the need for continuous monitoring and prediction [2]. As pointed out in [3], these applications can only be achieved with low latency and sub-metric spatial resolution observations. The consequence of having a satellite constellation equipped with the required instruments that provide these measurements would entail the increase of the data volume generated. Additionally, broadband telecommunicationsservices have experienced a boost in recent years with the emergence of the 5G paradigm in the aerospace domain to achieve global coverage and seamless integration with terrestrial networks [4; 5]. This feature is remarkable when new applications with Wireless Sensor Networks (WSN) [6] are conceived for remote areas of the globe, such as the Arctic region, the open oceans, or other large inhabited regions [7]. To achieve this goal, the connectivity between space and ground segments must be improved. Therefore, the increase of downlink opportunities is essential to enhance the downlink capacity in future missions. Distributed Satellite Systems (DSS) have emerged as an effective solution to meet these new demands. DSS are described as an ensemble of satellites that share a common objective. As presented in [8; 9], different DSS architectures have been described in recent years. Some of these architectures proposed the use of satellite-to-satellite communications [10]. In this context, a satellite could communicate with a ground station using the downlink contact of another satellite, increasing thus the overall downlink opportunities. The Federated Satellite System (FSS) concept [11; 12] aims at addressing this situation by promoting collaborations between satellites to share unused resources, such as memory storage or downlink opportunities. These collaborations, called federations, are established sporadically and opportunistically depending on the availability of the resources to be shared. The federation is established through Inter-Satellite Links (ISL), which are point-to-point communication links between satellites [13]. Due to the satellite movement, an ISL is characterized by existing only during a lapse of time, impacting the stability of the federation. To overcome this situation, the Internet of Satellites (IoSat) paradigm [14] expands this concept to a multi-hop scenario. In this context, satellites agree to be involved in a sporadic and temporal network, called Inter-Satellite Network (ISN). This kind of network is created from a decision of the intermediate satellite, and only when a federation must be established. The creation of a federation is related to the availability of the resources that can be shared. In this context, these resources can be shared as services that a satellite provides to another satellite. However, these services are not continuously available, existing opportunities to consume them only during lapses of time. This opportunistic nature of the federations poses new communications challenges, such as intermittent connections or mechanisms to fairly share or trade the resources. Previous work [15] presented the Opportunistic Service Availability Discovery Protocol (OSADP) which provides a mechanism to know the available services among the satellites that can be requested to create a federation.