# Analysis of the Most Relevant Factors for Routing in Internet of Space Things Networks
## 1 Introduction  
Inter-satellite networking has the potential to make a significant impact in modern society by enabling voice, data, and remote sensing applications in underserved areas [1, 2] and deep space missions [3, 4, 5]. In the last decade, nanosatellite standards such as CubeSat [6, 7, 8] have focused on developing smaller, highly efficient, and cost-effective satellite platforms [9] using commercial off-the-shelf (COTS) components. For instance, CubeSats are satellites built with cubic modules denoted as \"units\" (U) of 10 \(\times\) 10 \(\times\) 10 cm\({}^{3}\) each. Thus, the development costs of CubeSats are lower compared to other satellites [10]. Furthermore, although CubeSats were initially envisioned as an educational and research tool, currently there is a huge interest in developing commercial applications based on this kind of platform [11]. Nanosatellites (e.g., CubeSats) are commonly deployed in low earth orbits (LEO) [12]. With the increasing number of LEO spacecraft, there is a growing interest in developing inter-satellite networking solutions and applications [13, 14], leading to the introduction of the Internet of Space Things (IoST) paradigm. In IoST networks, the nodes can be satellites (e.g., picosatellites, CubeSats, microsatellites, small satellites), ground stations, or terrestrial transceivers whose primary mission (function) is not necessarily the retransmission (relay) of packets within an IoST network. Thus, one of the main paradigms proposed for IoST networking involves the formation of ad hoc inter-satellite networks. In an ad hoc IoST network, satellites assume the role of nodes and participate in networking tasks (e.g., packet relay) on a temporary or intermittent basis (depending on each satellite's primary mission) [15, 16]. Therefore, in an IoST deployment, satellites can play the role of both network infrastructure in space and as sensors of the physical world [10]. IoST networks have the potential to provide an in-space backhaul for connectivity in places far from the reach of terrestrial telecommunication coverage such as jungles, forests, open oceans, and polar areas [17; 18]. Thus, IoST networks can enable the deployment of applications such as early warning systems for natural disasters, ecosystem monitoring, marine species monitoring, and marine weather monitoring (among others) in remote regions where no other communication options are available. However, for the IoST paradigm to be a reality, designing and developing novel networking mechanisms is necessary to deploy effective IoST networks [19]. As the nodes in IoST networks are satellites, they will exhibit high mobility and constrained energy resources [20; 21]. Furthermore, the nodes in an IoST network can be microsatellites [22], nanosatellites (e.g., CubeSats) [7], or picosatellites [23]. In that case, low processing capabilities and low storage capacity should be considered essential node characteristics. Additionally, in ad hoc IoST networking, a satellite might have a primary mission not directly related to its possible role as a node in the network [24]. Therefore, its participation in networking tasks (e.g., packet relay) might be limited to idle periods within its primary mission. These issues pose significant challenges to designing inter-satellite networking protocols for IoST applications. Thus, flexible, reconfigurable, and opportunistic networking protocols are required to fulfill the potential offered by ad hoc IoST networks [25]. Mobile ad hoc networks (MANETs) offer flexible and opportunistic communication among mobile nodes forming a network without the need for coordination from a central entity [26; 27; 28; 29]. Communication between two nodes of a MANET is carried out if (a) they are located within their radio coverage or (b) there is one or more intermediate nodes able to relay the information from one node to the other.