## 5 ESTCube-Luna Preliminary Mission Requirements and Platform Design Solutions  
### System Engineering  
As detailed in the previous sections, the ESTCube-LuNa mission is required to perform novel E-sail propulsion experiments in lunar orbit. The E-sail experiments are designed to provide force measurements and estimates in thrust and torque modes. Although Section 4 \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Initial** & **Initial** & **Escape** & & & \\
**Pericentre** & **Semimajor** & **Time** & & & \\
**Altitude [km]** & **Axis [km]** & **[days]** & & & \\ \hline
500 & 5593.5 & 485 & 275 & 71 & 33.26\% \\ \hline
1500 & 8093.5 & 327 & 194 & 51 & 28.07\% \\ \hline
3000 & 11843.5 & 269 & 118 & 33 & 20.29\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of the ESTCube-LuNa escape manoeuvre from the Moon’s orbit. Figure 9: Sketch of the inertial reference frame, the E-sail spin axis, and control angles \(\zeta,\psi\). provides results for a potential lunar escape manoeuvre, the baseline ESTCube-LuNa mission is designed with a fixed E-sail spin plane, which in turn is not well suited for complex trajectory manoeuvres. The ESTCube-LuNa E-sail experiment sets the following top-level **mission requirements** for the platform and operations:  
1. Launch and operate in lunar orbit. 2. Operate DSN-free by developing alternative solutions for communications and navigation without the access to space agency DSNs. 3. Withstand three years of operations in the lunar orbit environment: solar and cosmic particles, radiation and large temperature fluctuations between sunlit and shadowed sides. 4. Perform and monitor the spin manoeuvres and E-sail tether deployment using reaction wheels, attitude thrusters and sensors as well as the tether camera. 5. Operate and characterise the E-sail performance by charging the tether and measuring changes in orbit, spin rate, tether deflection angle and surrounding plasma environment. 6. Ensure sufficient power production during E-sail tether deployment and operations. 7. Estimate the ESTCube-LuNa position using optical navigation and triangulation of the Moon, the Earth and the Sun. 8. Estimate the ESTCube-LuNa attitude by combining the navigation solution with Sun sensors, inertial measurement unit (IMU) and star tracker (the tether camera can double as a star tracker when the spin rate is low, such as after tether deployment). 9. Transmit telemetry and commands via a wide-beam antenna. 10. Transmit data and perform ranging with narrow-beam antennas. The ESTCube-LuNa spacecraft hosts the E-sail payload, the tether camera (TC), ranging experiment (RE) and Langmuir probes (LPs). As detailed in the following subsections and shown in Figure 10, the ESTCube-LuNa platform consists of the communication system (COM), electrical power system (EPS), on-board computer (OBC) as well as the attitude and navigation system (ANS). Based on the ESTCube-2 architecture, the Avionics stack includes the COM, EPS and OBC, while the new ANS is introduced to connect and control six cameras and eight thrusters. Figure 10: An exploded view of ESTCube-LuNa showing the preliminary volume allocation of payloads and subsystems inside the nanospacecraft. The side with thruster, LPs and navigation camera control boxes requires careful system engineering to place thrusters, control electronics, harness and wiring to LPs and TCN cameras. Communications is one of the primary challenges when bringing cubesats from LEO to cis-lunar and deep space. Typically, deep space networks (DSNs) of space agencies are used for communications, even for cubesats, as in the case of NASA's Artemis 1. For ESTCube-LuNa, we are designing communications and navigation from scratch, without assuming access to DSNs, and in this paper, we present the preliminary solutions and considerations.