## 1 Introduction  
Transient luminous events (TLEs) are a result of electrical discharge phenomena that occur in the upper atmosphere. Since the first TLE recording, accidently captured in the year 1989 [1], researchers have made various efforts to observe TLEs on a variety of platforms such as ground-based facilities [2; 3; 4], aircrafts [4; 5; 6], space shuttles [7; 8], satellites [9; 10; 11], and the International Space Station [12; 13]. From these studies, TLEs are categorized into five groups such as sprite, blue jet, halo, elf, and gigantic jet. Figure 1 illustrates the different types of TLEs. Sprites are large-scale TLEs that typically occur in the upper stratosphere and mesosphere regions (altitude of 40 to 90 km) and move rapidly downwards at speeds of up to 10,000 km/s [14]. It resembles a reddish-orange colored carrot with tendrils below. Sprites sometimes accompany halos which are quick extending glows with diameters of 40 to 70 km. Elves are similar to halos but the diameter of elves is greater than 100 km while they occur in the thermosphere region (altitude of 80 to 100 km) [15]. Finally, blue jets are relatively small and slow-moving TLEs as compared to sprites. They propagate from the top of thunderclouds towards an altitude of 40 km [5; 6]. Table 1 summarizes the properties of respective TLEs. Researchers have tried to understand the underlying principles of TLEs occurrence and the relevant effects by obtaining and analyzing scientific data from diverse sources. Several attempts are still underway to collect the relevant data from space [16]. A scientific platform in orbit for TLE research has advantages in many aspects: a daily global coverage, simultaneous monitoring over large-scale storm areas, and a diminished atmospheric influence on the emitted radiation [21]. In addition to these advantages in observing from the orbiting platform, using a CubeSat constellation enables multi-point simultaneous measurements over a large area of the globe, thus enabling a greater temporal coverage of the observation for short-lived events such as TLEs. References [22; 23; 24; 25; 26] present the activities employing small satellites on the purpose of Earth observation. A CubeSat is a miniaturized satellite that is specified by a multiple of single unit (1U). For a 1U CubeSat, the volume is 1 cubic cm (10 cm \(\times\) 10 cm \(\times\) 10 cm) and the weight is no more than 1.33 kg [27; 28]. Because the CubeSat system is intended to be developed within a rather short time period at reduced cost using commercial off-the-shelf (COTS) parts [29], a small research institute or an individual research team can have a satellite constellation system for scientific purpose with a small budget as compared to conventional multi-satellite constellation. The VisionCube is a 2U CubeSat developed by Unmanned Systems Control Lab at Korea Aerospace University, whose scientific mission aims at detecting the occurrence of TLEs in the upper atmosphere and obtaining the corresponding digital images taken with a complementary metal-oxide-semiconductor (CMOS) image sensor. The VisionCube is currently scheduled to be launched in the third quarter of 2018. The planned orbit of VisionCube is a Sun-synchronous orbit with an inclination of 97.69\({}^{\circ}\) and an altitude of 575 km. The other orbit parameters such as the argument of perigee and \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type** & **Duration (ms)** & **Size (km)** & **Velocity (km/s)** & **Altitude (km)** \\ \hline Blue jets & up to 250 & 3–20 & 12 & 20–40 \\ Gigantic jets & less than 1 & 20–30 & 70–90 & \\ Sprite & 1–10 & 25–50 & 10,000 & 40–90 \\ Elves & less than 1 & over 300 & 100,000 & 84–87 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The properties of Transient Luminous Events (TLEs) [17; 18; 19]. Figure 1: Representation of transient luminous events (elf, sprite, and blue jet) [20]. Elves are flat, round TLEs and occur in the thermosphere. Sprites are large-scale TLEs that mostly appear in the mesosphere.