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TOP > Report & Column > The Forefront of Space Science > 2011 > The Challenge for Ultra-Small Satellites : Aiming at Great Innovation in Space Science

The Forefront of Space Science

The Challenge for Ultra-Small Satellites : Aiming at Great Innovation in Space Science
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Current development of 50kg-class satellite TSUBAME

Figure 5. 50kg-class satellite TSUBAME

Figure 6. Scenes of environmental test of TSUBAME
Under vibration test (left) and just before thermal-vacuum test (right)

At present, the Matunaga Lab is researching and developing a 50kg-class satellite TSUBAME to observe earth and celestial bodies (Fig. 5) in cooperation with the Kawai Lab of University of Tokyo and the Kimura Lab of Tokyo University of Science. In order to conduct observation of sudden gamma-ray burst events in relation to the mystery of the creation of the universe (Kawai Lab: gamma-ray detector and X-ray polarimeter) and observation of the earth with visible-light camera (Kimura Lab: small optical camera), we aim to develop an ultra-small satellite which is designed to simultaneously perform both high-speed attitude change and high-accuracy directional control using Control Moment Gyro (CMG). In particular, we are developing the CMG system jointly with Tamagawa Seiki Co., Ltd. It features an ultra-small actuator, making it the world’s smallest and most power-saving attitude controller, yet it has the capability to generate high-power torque. On the other hand, the satellite power is 100W-class. Since the power is very high compared to its weight and size, advanced bus technology is required. Thus, the satellite is a very ambitious one. At present, we are developing a flight model and plan to launch it around December 2012. Fig 6 shows scenes of the environmental tests.

Great potential of ultra-small satellite

Ultra-small satellite R&D is valuable mainly for the following reasons:
(1) Practical education of aggressive space-system engineering and human resource development
(2) Rapid demonstration in space of advanced technologies at component and equipment level. Effective tactics to upgrade significantly TRL (Technology Readiness Level).
(3) Implementation of science missions and actual application missions by ultra-small satellite (constellation)
(4) Discovery and development of new space engineering and high-value-added business fields

The key point of all the above is that ultra-small satellites are at the level that allows failure. This, of course, does not mean that you can fail mission intentionally. The utmost diligence for absolute success are required because, once the satellite is launched in a one-shot deal, it has to be operated without direct operation and handling. Even if inevitable trouble occurs and the mission fails in spite of all best efforts, the project stays within the permitted budget.

Examples of successful operation of ultra-small satellites developed using the upsize design concept in laboratory level is limited to up to several kg in Japan. In the 50kg–class, there were several successfully operating satellites based on the downsize design concept using know-how of medium- to large-scale satellites of governmental agencies and space manufacture. From this year, some projects including the University of Tokyo’s 35kg-class satellite and our own 50kg-class satellite will aim at successful development based on the upsize design concept.

Even with satellites of the same size, the degree of difficulty varies greatly depending on the mission. The difference is similar to the “propeller or jet?Equestion with aircraft. There are still significant issues to be resolved including: “How far can we progress based on the upsize design concept originated from laboratory levelE “Should we stick to the downsize design conceptE “Where is the boundary for both conceptsEand “How should the design concept evolve?E

With the use of ultra-small satellites, we can deepen and systematize space-system engineering in the true sense. Accordingly, we expect to facilitate practical problem finding and resolution in space engineering, and to generalize the knowledge obtained. I believe that the era when we routinely launch more than five ultra-small satellites a year in Japan will come soon. At that time, revolutionary change will occur in space science.


Cubesat EYou too can launch a satellite (Nikkei Science, September 2011)
open new window University Space Engineering Consortium (UNISEC)
open new window UNISEC Space Takumi Journal

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