# Development of a Novel Deployable Solar Panel and Mechanism for 6U CubeSat of STEP Cube Lab-II
## 5 Experimental Validation
### Thermal Vacuum Test  
A TV test of the VMLSA was performed by exposing six thermal cycles at a \(-40\) to \(60\)\({}^{\circ}\)C qualification temperature range in a \(\phi 1\) m TV chamber with a pressure lower than \(10^{-5}\) torr to verify the solar panel's structural safety and the release function of the P-HRM in the space environment. To measure the specimen's temperature, thermocouples were mounted on the solar panel and electrical interface PCB. In order to determine the stabilized target temperature of the solar panel module, a thermocouple attached to the electrical interface PCB was taken as a temperature reference point (TRP). On the specimen, the target temperature stabilization was achieved by controlling the TV chamber's shroud temperature at the \(1\)\({}^{\circ}\)C per hour rate. However, at the hot and cold plateaus of each cycle, the length of dwell time was fixed to \(1\) h.  
The P-HRM's state of health (SOH) check was conducted by visual inspection at each dwelling time. The solar panel deployment test was performed at \(-20\)\({}^{\circ}\)C during the third cold soak phase, as it is the worst state for triggering the mechanism after satellite ejection into an orbit or trajectory. The solar panel was released without any anomalies \(5.20\) s after the input voltage was triggered in the mechanism. However, owing to the difference in the heating time of the resistor to cut the Dyneema wire, the release time was marginally higher than that in ambient room conditions. In addition, the electrical power dissipation from the power supply wire to the mechanism within the chamber at an extreme cold temperature and the relay time delay of the solar panel deployment signal to the DAQ system are also factors that increase the release time [36]. However, the onboard batteries of CubeSats will have sufficient power to deploy solar panels, as release action is typically carried out at the initial stage of orbital injection. After the solar panel deployment test, the remaining cycles were completed within the qualification temperature range of the solar panel. After accomplishment of the TV test, the solar panel deployment test was performed at \(25\)\({}^{\circ}\)C room environment and the result is presented in Figure 17. The results of the release function tests of the mechanism obtained before and after vibration tests and during the TV test are plotted in the same Figure 17 to compare the release time in each event. The release time of the mechanism after the TV test was \(1.5\) s; the minimal difference in release time compared to that determined before the TV test is due to the thermal overstress of the resistor in six thermal cycles. Thus, these release function test results guarantee solar panel deployment in an orbit environment. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Test**} & \multirow{2}{*}{**Excitation Axis**} & \multirow{2}{*}{**Status**} & **Corresponding Axis** & **Frequency Shift** \\  & & & **1 st Eigenfrequency (Hz)** & **Difference (\%)** \\ \hline \multirow{4}{*}{Sine vibration} & \multirow{2}{*}{\(x\)} & Before & 835.2 & \multirow{2}{*}{0.19} \\ \cline{3-3} \cline{5-5}  & & After & 833.6 & \\ \cline{3-3} \cline{5-5}  & & Before & 602.4 & \multirow{2}{*}{0} \\ \cline{3-3} \cline{5-5}  & & After & 602.4 & \\ \cline{3-3} \cline{5-5}  & & Before & 75.0 & \\ \cline{3-3} \cline{5-5}  & & After & 74.3 & \\ \hline \multirow{4}{*}{Random vibration} & \multirow{2}{*}{\(x\)} & Before & 833.6 & \multirow{2}{*}{0.19} \\ \cline{3-3} \cline{5-5}  & & After & 832.0 & \\ \cline{3-3} \cline{5-5}  & & Before & 602.4 & \\ \cline{3-3} \cline{5-5}  & & After & 602.4 & \\ \cline{3-3} \cline{5-5}  & & Before & 74.3 & \\ \cline{3-3} \cline{5-5}  & & After & 70.7 & \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Results of the VMLSA’s low-level sine sweep (LLSS) tests conducted before and after full-level vibration tests. The solar panel was examined microscopically using optical microphotographs, following all the above-mentioned tests.