# In-Orbit Results and Attitude Analysis of the SNUGLITE CubeSatellite
## 2 Materials and Methods
### Attitude System of SNUGLITE  
#### 2.3.1 Attitude System Configuration  
The attitude system of the SNUGLITE was programmed to maintain the +z direction of the body-frame, as described in Figure 1, pointing to the nadir-direction and the +x direction of the body-frame aligned along-track with the orbit. The LQG-based attitude system was designed using coarse sun-sensors, a 3-axis magnetometer and a 3-axis gyroscope as sensors, and 3-axis magnetorquers as actuators [16; 19]. A triple-axis MEMS MPU-3300 gyroscope by InvenSense and an HMC5843 low-cost three-axis magnetometer by Honeywell are utilized. Five SLCD-61N8 photodiodes are attached to the solar panels at +x, -x, +y, -y, and -z sides to work as coarse sun-sensors. The dipole momentum of the utilized magnetorquers is approximately 0.038 Am\({}^{2}\), and three magnetorquers are integrated into the solar panels at each axis. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Data** & **Description** & **Type** \\ \hline time & \begin{tabular}{c} “YY/MM/DD HH:MM-SS” in UTC (GMT) \\ \end{tabular} & 6 \(\times\) unsigned char \\ GPS (Global Positioning & positioning flag (”0”: TLE (two line element set), \"1”: GPS) & unsigned char \\ System) receiver & \
\begin{tabular}{c} “X, Y, Z” position in Earth-centered Earth-fixed (ECEF) (cm) \\ \end{tabular} & 3 \(\times\) signed int \\
\begin{tabular}{c} “X, Y, Z” velocity in ERTC (Ens) \\ \end{tabular} & 3 \(\times\) signed int \\  & battery status flag (”0”: initial, \"1”: under-voltage, \"2\": \\  & safe-mode, \"3”: nominal, \"4\": full) & unsigned char \\  & battery voltage (mV) & unsigned short \\ power system & battery current (mA) & unsigned short \\  & power-supply-switch flags for each module & unsigned char \\  & current consumption for each power-supply-switch (mA) & 6 \(\times\) unsigned short \\  & solar-panel input voltage: \(\textasciasciitifax{}\) x, \(\textasciitifax{}\) y, \(\textasciitifax{}\) Z \(\textasciitifax{}\) (mV) & 3 \(\times\) unsigned short \\  & solar-panel input current: \(\textasciitifax{}\) x, \(\textasciitifax{}\) y, \(\textasciitifax{}\) Z \(\textasciitifax{}\) (mA) & 3 \(\times\) unsigned short \\  & estimated attitude: \"00, 41, 42, 43\" & 4 \(\times\) float \\  & estimated gyro bias: \"roll pitch, yaw\" (rad/s) & 3 \(\times\) float \\ attitude system & estimated angular rate: \"roll, pitch, yaw\" (rad/s) & 3 \(\times\) float \\  & gyroscope measurements: \"roll pitch, yaw\" (rad/s) & 3 \(\times\) float \\  & attitude convergence flag and sun/close flag & unsigned char \\  & attitude variance: \"q0, 41, q2, q3\" & 4 \(\times\) float \\ mode & current operation mode (”0”: init-mode, \"1\": standby mode) & unsigned char \\  & elapsed time of operation mode (min) & signed int \\  & solar panels (deg. Celsius) & 5 \(\times\) unsigned char \\ temperature & onboard computer (deg. Celsius) & 2 \(\times\) unsigned char \\  & power module (deg. Celsius) & 4 \(\times\) unsigned char \\  & UHF module (deg. Celsius) & 2 \(\times\) unsigned char \\ deployment status & antenna release status flag and boom release status flag & unsigned char \\  & number of trial for antenna release & unsigned char \\  & number of trial for boom release & unsigned char \\ \hline \hline \end{tabular}  
* There is no solar panel for +Z surface (nadir-direction).  
\end{table} 
Table 2: Full beacon data. The block diagram for the SNUGLITE attitude system is shown in Figure 3. Position, velocity, and time were input into DE405 and IGRF12 models to generate reference vectors of the sun vector and the magnetic field vector. DE405 is NASA's Development Ephemeris, and IGRF12 is a model of the International Geomagnetic Reference Field. Measurements from the coarse sun-sensors, magnetometer, and gyroscope, were compared to the reference vectors for attitude estimation. The 3-axis magnetorquers acted as the actuators for the SNUGLITE CubeSat. Sensing cannot be conducted when the magnetorquers are in operation, because both attitude determination and control utilize magnetic information.