# A Simulation of Contact Graph Routing for Mars-Earth Data Communication
## 3 Algorithms of the Model
Through running the simulation multiple times, the results show consistently that about 96.4% data is successfully delivered to Earth. The running time of the algorithm is about 8.02 s.

## 5 Conclusions

In this paper, we construct a simulation of a Contact Graph Routing method for Mars and Earth data communication using two rovers, four relay-store-carry satellites, and three DSN antennas on Earth. Using the assumed window contacts, the successful rate of delivery is very high. However, we are aware that this rate is heavily dependent on the condition of the contact windows. The example in Table 3 shows well-distributed times for the contact windows; therefore, the rate could be worse if the only satellite that is open for \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Dep/Arr** & **Time** & **Routes** & **Total** & **Info** \\  & & & **Data** & \\ Dep & 21:22-21:31 & CR-TGO & 11,840 & \\ Dep & 21:46-21:49 & PR-ODY & 5632 & \\ Dep & 21:50-21:58 & PR-MVN & 30,848 & \\ Dep & 21:59-22:31 & - & - & No contact \\ Arr & 22:43 & TGO-SPN & 1180 & Figure 5(c) \\  & & ODY-SPN & 5632 & \\  & & MVN-SPN & 30,848 & \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Case 4: Selection of satellite. Figure 6: Case 4: (a) Sending data at 21:49, (b) sending data at 21:50, (c) receiving data at 22:43.

connection for a long amount of time is Odyssey, where the rovers would have to deliver their data to this satellite since they have no other choice. The number of satellites that are used can be increased in the algorithm by increasing the number of middle nodes. If we want to have ten relay satellites, we define nodes 3 up to 12 to be the relay satellites, so in total there are 15 nodes, where there are two initial nodes for the rovers (nodes 1 and 2), and the last three nodes represent the DSN antennas (nodes 13, 14, and 15). There is not much modification needed, except increasing the dimensions of the matrix \(x\) and related vectors. We emphasize that the addition of nodes gives increasing numbers of rovers, satellites, or DSN antennas. The algorithm has utilized the optimized number of groups, which is three. It is not wise to increase this number because the travel time will significantly increase too. More numbers of rovers and satellites with different contact windows could increase the possibility of data delivery more continuously during the day. The arrangement of satellites to be chosen as a route, or as a path that will be taken by a data packet, is ready to be prioritized in order. In this algorithm, the larger the storage capacity, the more likely it is to be chosen. The order of arrangement can be augmented by adding the probability that the satellite will have a contact window opened shortly or a pre-defined specific time interval. For future research, we could consider using the CGR method on other forms of DTN, including Vehicular Delay-Tolerant Networks (VDTNs). This would give various potential benefits, such as semi-predictable mobility that improves performance through predictive routing, lower overhead (less flooding in contrast to methods based on epidemics), effective scheduling (forwarding matched contacts to contact availability), and delay awareness (able to give priority to the earliest delivery, which is helpful for data that are time-sensitive). A deep analysis would be needed for this potential development. Conceptualization, B.S. ; methodology, K.A.S. and N.S. ; software, B.S. ; validation, B.S., K.A.S., and N.S. ; formal analysis, B.S. ; investigation, B.S. and N.S. ; resources, B.S. ; data curation, B.S. ; writing--original draft preparation, B.S. ; writing--review and editing, B.S. and N.S. ; visualization, B.S. and N.S. ; supervision, K.A.S. ; project administration, B.S. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.