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.
A small, deep-space probe, Shinen2, was developed under collaboration with the Kyushu Institute of Technology and Kagoshima University. The Shinen2 was launched by an H-2A rocket as a piggyback space probe with the JAXA's (Japan Aerospace Exploration Agency) asteroid probe, Hayabusa2, in 2014. The outer shape of the Shinen2 has a quasi-spherical diameter of 50 cm, and a mass of approximately 18 kg. An example of a deep-space probe to explore beyond the moon beyond has not been developed by any university, and no private companies exist. There are many technical aspects for the development of a small spacecraft to explore deep space. One is deep-space communication. The purpose of this development is to substantiate new deep-space communication methods used by amateur radio communications without the deep-space network of JAXA, NASA (National Aeronautics and Space Administration) or ESA (European Space Agency). The other subject is the realization of autonomous control of space probes. A communication control computer, a power control computer and a system control computer were equipped in Shinen2. The system control computer is called the Shinen2 control unit (SCU), and can control the total system of the Shinen2. Many satellites have been developed to orbit the earth. We have obtained a lot of experience, such as how computers are destroyed by radiation. There are no cases which explore deep space using a small spacecraft. The radiation measures are unknown for small satellites in deep space. This paper describes the methods of the total system control and measures radiation in deep space.
Micro satellites must survive severe mechanical conditions during their launch phase. One design requirement for rockets is the stiffness requirement, i.e. the natural frequencies requirement. In the early stages of satellite development, presumption of the natural frequency of a satellite may be difficult.
The material used for the structure of many micro satellites is an aluminum alloy. The structure subsystem occupies a large portion of the satellite mass, and the elastic modulus of this aluminum alloy is larger than that of other subsystems. Therefore, the mechanical property of the aluminum alloy cannot be used to represent the mechanical property of the whole satellite. The density of an actual satellite differs from the density of the aluminum alloy. Therefore, when estimating the minimum natural frequency, the size and the elastic modules of an actual satellite structure must be used. When using an actual satellite structure, the estimated minimum natural frequencies of the lateral direction and the longitudinal direction during the ascent phase are in agreement with the measured values acquired by the vibration tests.
In order to shorten a process of satellite development, this paper describes a practical method for estimating the natural frequency of a cube-shaped micro satellite
This paper is a modified version of the previous paper [1] using new measurement results.
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