## 4 Design Analysis
### Telemetry Analysis  
Communication between the satellite and ground station may be affected by several factors such as signal propagation, space radiation, data rates and modulation techniques. Additionally, many signals are attenuated by amplifiers and antennas that work on increasing gain and reducing noise level. However, many signals and data are still lost during propagation. The link budget analysis accounts for all the gains and losses. The gains and losses are accounted for starting from the transmitter going through the medium (free space, fiber, or cable) until reaching the receiver using the equation below:  
\[P_{RX}=P_{TX}+G_{TX}+G_{RX}-L_{TX}-L_{FS}-L_{FM}-L_{RX}, \tag{2}\]  
where  
\(P_{RX}\) = received power (dBm);  
\(P_{TX}\) = transmitter output power (dBm);  
\(G_{TX}\) = transmitter antenna gain (dBi);  
\(G_{RX}\) = receiver antenna gain (dBi);  
\(L_{TX}\) = transmitter feeder and connector losses (dB);  
\(L_{FS}\) = free space loss or path loss (dB);  
\(L_{FM}\) = many sided signal propagation losses (dB);  
\(L_{RX}\) = receiver feeder connector losses (dB). Light-1 utilizes UHF frequency to uplink commands to the satellite and downlink housekeeping data from the satellite. The UHF link budget for Light-1 is summarized in Table 6. In the table, it can be seen that the uplink and downlink margin are averaged to approximately 20, which is sufficient to create a clear linkage between the satellite and the ground station. The calculation of the UHF link budget has followed the Eb/N0 margin method. The method utilizes the operational parameters information, the satellite's communication system information, and the ground station information to measure the strength of the communication. As CubeSats are evolving with new missions that require higher data rates, \(S-\)band frequency is being used to download data. Light-1 is one such CubeSat. The directivity of \(S-\)band patch antenna requires the calculations to be with respect to different elevation angles, and consequently, different path distances as seen in Table 7. The table shows the variation detected in the link budget margin with changes in the elevation angle of the satellite. The downlink margin is found sufficient at elevation angles higher than \(10^{\circ}\), which is satisfactory to establish clear communication between the ground station and the satellite. Similar to the calculation of the UHF link budget, the \(S-\)band link budget has followed the Eb/N\({}_{0}\) margin method. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multicolumn{5}{c}{**Total Downlinked Data Using Minimum Access Time**} \\ \hline Downlink rate (bps) & 1200 & 2400 & 4800 & 9600 \\ \hline Total download size (MBday) & 0.060 & 0.110 & 0.230 & 0.450 \\ \hline \multicolumn{5}{c}{**Total Downlinked Data Using Average Access time**} \\ \hline Downlink rate (bps) & 1200 & 2400 & 4800 & 9600 \\ \hline Total download size (MBday) & 0.120 & 0.250 & 0.490 & 0.980 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Light-1 data budget. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Uplink** & **Downlink** \\ \hline Maximum Distance (km) & & 2300 \\ \hline Frequency (MHz) & & 435 \\ \hline Data rate (bit/s) & & 2400 \\ \hline Bandwidth (Hz) & & 14,400 \\ \hline Transmitter power (dBW) & 13.97 & 3.000 \\ \hline UHF Tx antenna gain (dBi) & 12.24 & \(-\)2.000 \\ \hline Cable losses (dB) & 2.310 & 0.600 \\ \hline Total losses (dB) & 156.2 & 156.14 \\ \hline UHF antenna gain (dBi) & 2.030 & 12.90 \\ \hline Line losses (dB) & 2.310 & 2.410 \\ \hline System Noise Temperature (K) & 241.5 & 342.9 \\ \hline EIRP & 23.90 & 0.400 \\ \hline System Eb/No & 32.42 & 40.27 \\ \hline Required Eb/No & 14.00 & 18.00 \\ \hline Margin (dB) & 18.42 & 22.27 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Light-1 UHF link budget.