# A Simulation of Contact Graph Routing for Mars-Earth Data Communication
## 1 Introduction
The development of DTN has a wide range of analyses in Intelligent Transportation Systems, which includes Vehicular Delay-Tolerant Networks, or VDTN. In [7], the basic routing process in DTN is classified according to the methods used to identify destinations and whether or not message replication is employed: One copy as opposed to several copies are forwarded, flooded, and randomly forwarded according to the various kinds of information that are available. The authors surveyed the development of opportunistic forwarding for VDTN, which is based on various forwarding methods, including social-based forwarding, mobility prediction, geographical forwarding, and incentive-based and congestion control. In the context of deep space communication, DTN is designed to work in scenarios where end-to-end connectivity is not always available and lengthy and erratic delays are common [8]. DTN has demonstrated its effectiveness through innovative techniques that ensure connectivity in challenging terrestrial communication scenarios, such as natural catastrophes. Recent research on the architecture of present and future deep space communication systems, the environmental difficulties associated with deep space communication, different DTN architecture implementations and demonstrations, and the verification of associated routing strategies over the Deep Space Relay network are all covered. There are many relay satellites in space that are available for our approach. In this paper, we simulate the four most commonly observed by NASA due to their reliable storingand forwarding capabilities. MRO (Mars Reconnaissance Orbiter), TGO (Trace Gas Orbiter), Mars Odyssey, and MAVEN (Mars Atmosphere and Volatile Evolution) are of the LEO orbit type and are not always immediately above the rovers. Their altitudes range from 500 to 2000 km. TGO and MAVEN have non-elliptical orbits, so they represent the furthest and closest points from the surface of Mars, with Mars being the location of the Perseverance and Curiosity rovers. See [9; 10] for detailed information. First proposed in [11], the Contact Graph Routing (CGR) architecture is used in DTN protocols to implement the concepts and methods for routing between ground elements and spacecraft in deep space and near-Earth orbit. Based on [3; 12], CGR combines several non-trivial algorithm modifications, time-dynamic scheduling, space operations ideas, and certain graph models. A contact plan outlining the anticipated resources that the space network will have for data transmission may be used to express the future connectedness of the assets in space networks. These circumstances led to the development of time-evolving abstractions, new graph models, and algorithm modifications for the Contact Graph Routing (CGR) framework [12]. The communication between Mars and Earth begins with Earth contacting the rovers on Mars, which is in the form of commands or requests, for example, asking an instrument to take an image or to resend some data; then, the Mars rovers carry out the commands. Mars and Earth are roughly 54.6 to 401 million kilometers apart. When Earth and Mars are on the same side of the Sun, and Earth is close to its perihelion and Mars is at perihelion, the shortest distance, known as perihelic opposition, occurs. This occurs approximately every 15 to 17 years, and is an extremely uncommon occurrence. When Earth and Mars are on opposite sides of the Sun and both are at or close to their aphelion, or the furthest from the Sun, this is known as Superior Conjunction at Aphelion [13; 14]. The protocol used in the communication is the bundle protocol (BP), which is a network-layer protocol in the DTN architecture; instead of assuming continuous connectivity like TCP/IP, it bundles data into \"bundles\" (similar to packets), stores them when necessary, and forwards them opportunistically--whenever a communication path becomes available. The core concepts behind the bundle protocol are as follows.