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This paper describes a new algorithm to determine the attitude of micro-/nano-satellites using an Earth sensor. For recent micro-/nano-satellites, the requirements for attitude determination accuracy are becoming more stringent, despite its limited volume. Since Earth sensors have the advantage of smaller size, some studies have presented using them as attitude sensors; however, they could not achieve fully automatic processing in real-time. Therefore, we have developed an algorithm that effectively combines geometrical consideration and image recognition technology, thus realizing high autonomy, robustness, and real-time processing. The validity of this algorithm is confirmed through ground experiments. The algorithm operates at a rate of 0.2 Hz and achieves an accuracy of 0.1-1 deg, which is similar to the accuracy of a coarse sun sensor. Furthermore, it is capable of determining the three-axis attitude using only an Earth sensor and a GNSS receiver for position information. This study proves that the bus equipment required for attitude determination systems in micro-/nano-satellites can be reduced, thereby contributing to increased design freedom.

A conceptual design of a wide-field near UV transient survey in a 6U CubeSat is presented. Ultraviolet is one of the frontier in the transient astronomy. To open up the discovery space, we are developing a 6U CubeSat for transient exploration. The possible targets will be supernova shock-breakouts, tidal disruption events, and the blue emission from NS-NS mergers in very early phase. If we only focused on nearby/bright sources, the required detection limit is around 20 mag (AB). To avoid the background and optical light, we chose a waveband of 230−280 nm. As an imaging detector, we employ a delta-doped back-illuminated CMOS. In addition to delta doping, the multi-layer coating directly deposited on the detector enables both a high in-band UV QE and the ultra-low optical rejection ratio. Taking into account these specifications, even an 8 cm telescope can achieve the detection limit of 20 mag AB for a FoV larger than 60 deg 2. We also designed the satellite bus system for this mission by utilizing commercially available cubesat components satisfying the mission requirements.

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