# Development of a Novel Deployable Solar Panel and Mechanism for 6U CubeSat of STEP Cube Lab-II
## 2 The STEP Cube Lab-II CubeSat's Overview
### Satellite's Configuration and Design Descriptions  
Figure 2a,b demonstrate the STEP Cube Lab-II mechanical configurations at the solar panel stowed and deployed states, respectively. The CubeSat's mechanical dimensions and total weight are 366 mm (\(X\)-axis) \(\times\) 117.8 mm (\(Y\)-axis) \(\times\) 238.5 mm (\(Z\)-axis) and 9.6 kg, respectively, which are within the 6U standard. The CubeSat mainly consists of COTS components enclosed in domestically developed structures, while a few interface boards and mechanical subsystems were designed and assembled by the team. The primary payload comprises three optics and sensor pairs: EOC, BBIRC, and LWIRC, which are designed to operate in staring mode and are capable of capturing images and videos nearly simultaneously from the three cameras. The performance specification of the EOC of spectral 0.38-0.94 um wavelength range is a 10 m ground sampling distance (GSD), which covers an area of 40 km \(\times\) 40 km swath width. The GSD and swath width of the BBIRC and LWIRC were 350 m and 220 km \(\times\) 160 km, respectively. The maximum estimated observation times for the multi-band still imaging mode and dual-IRC video mode on the Korean peninsula during an orbit period are 5.85 s and 10 s, respectively. All commands for uplink as well as the downlink of images and telemetry will be performed using the ultra-high frequency (UHF) amateur band at a frequency of 1200-9600 bps. Additionally, the communications between CubeSat and ground stations for data transmission are accomplished by an S-band antenna with a capacity greater than 8 Mbps. For the redundancy of the satellite communication system, communication between the satellite and ground stations can be accomplished through the iridium communication network, which also enables satellite orbital determination through the iridium GPS navigation data. Furthermore, the satellite's attitude control is accomplished by the three-axis attitude control method by the application of the XACT-15 attitude determination and control system (ADCS) [20]. To optimize the in-orbit power generation capability from the fixed-type deployable solar panels, the attitude of STEP Cube Lab-II will be set in such a way that deployable solar panels always point toward the sun direction by a 90-degree roll maneuver of the CubeSat from the nadir-pointing attitude through the ADCS, except for the periods of mission operation \begin{table}
\begin{tabular}{c c c} \hline \hline
**Items** & **Specifications** \\ \hline Satellite name & STEP Cube Lab-II \\ \hline Size (mm) & 366 (\(X\)) \(\times\) 117.8 (\(Y\)) \(\times\) 238.5 (\(Z\)) \\ \hline Weight (kg) & 9.6 \\ \hline \multirow{4}{*}{Orbital parameter} & Orbit: Sun-synchronous orbit & \\  & Altitude: 700 km & \\  & Orbital inclination angle: 98.2 deg. & \\  & Local time of descending node (LTDN): 16:00 p.m & \\ \hline \multirow{4}{*}{Mission payload} & Primary payloads: & \\  & EOC, BBIRC, LWIRC & \\ \cline{2-3}  & & Secondary payloads: & \\  & PDHS and PDTS, VMLA, P-HRM, SADA & \\ \hline \multirow{4}{*}{Camera performance} & Camera & EOC & BBIRC & LWIRC \\ \cline{2-3}  & GSD (m) & 10 & 350 & 350 \\ \cline{2-3}  & Observation width (km) & 40 \(\times\) 40 & 220 \(\times\) 160 & 220 \(\times\) 160 \\ \cline{2-3}  & Wave length range (um) & 0.38–0.94 & 3–14 & 9–12 \\ \hline \multirow{4}{*}{Observation mission time (s)} & Multi-band still imaging mode: 5.85 & \\  & BBIRC and LWIRC video mode: 10 & \\ \hline Ground station contact & 7.5 Minutes (Average) & \\ \hline \multirow{4}{*}{Communication system} & Uplink & UHF band: 1200 bps Audio frequency shift keying (AFSK) \\ \cline{2-3}  & \multirow{2}{*}{Downlink} & UHF band: 9600 bps Gaussian minimum & S-band: \(\rightarrow\)8 Mbps \\ \cline{1-1}  & & shift keying (GMSK) & 16-ary amplitude and phase shift keying (16-APSK) \\ \hline \multicolumn{2}{c}{Attitude control system} & \multicolumn{2}{c}{3-axis Attitude control method} \\ \hline Mission life & \multicolumn{2}{c}{1 Year} \\ \hline \hline \end{tabular}
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