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Ten-Koh is a 23.5 kg, low-cost satellite developed to conduct space environment effects research in low-Earth orbit (LEO). Ten-Koh was developed primarily by students of the Kyushu Institute of Technology (Kyutech) and launched on 29 October 2018 on-board HII-A rocket F40, as a piggyback payload of JAXA’s Greenhouse gas Observing Satellite (GOSAT-2). The satellite carries a double Langmuir probe, CMOS-based particle detectors and a Liulin spectrometer as main payloads. This paper reviews the design of the mission, specifies the exact hardware used, and outlines the implementation and operation phases of the project. This work is intended as a reference that other aspiring satellite developers may use to increase their chances of success. Such a reference is expected to be particularly useful to other university teams, which will likely face the same challenges as the Ten-Koh team at Kyutech. Various on-orbit failures of the satellite are also discussed here in order to help avoid them in future small spacecraft. Applicability of small satellites to conduct space-weather research is also illustrated on the Ten-Koh example, which carried out simultaneous measurements with JAXA’s ARASE satellite.

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In CubeSats, because the size is limited, the estimation of the incident solar energy according to the orbital parameters and satellite attitude is more critical for the design process of the electrical power system. This estimation is helpful either for sizing of the power sources and energy storage or for defining the operation modes of the CubeSat with the energy available. This paper describes the kinematic and dynamic equations to derive the CubeSat attitude; similarly, the mathematical models of solar cells and batteries are also derived to calculate the energy harvested and stored. By determining the attitude of a 3U CubeSat over one orbit, we estimated the incident solar energy and thus the energy generated by the solar cells and energy stored in batteries when a direct energy-transfer architecture is used. In addition, these estimations where performed for three orientation scenarios: nadir-pointing, Sun-pointing and free-orientation. The estimated incident average solar energy for the three scenarios indicated that the Sun-pointing and free-orientation scenarios harvest more energy than the nadir-pointing one. This estimation is also helpful to predict the state of charge of the batteries in standby mode, allowing for determination of the time required for charging the batteries and, hence, the operating modes of the CubeSat. We expect to include the consumed energy while considering all of the operating modes of the satellite as well as different orbital parameters.

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