Probably, scientific inquiry has each purpose originally and to realize it somehow or other is the royal road. However, when we need a large amount of budgets and many resources like space science, in order to lead the space science in the world, we have to arrange examination of the purposes and the realization means from various directions, and unite actually and the method of making the purpose gradual or giving a realization priority.
It was decided upon new "Road Map for Space Science and Exploration" as this arrangement examination in 2013. The Institute of Space and Astronomical Science (ISAS) will set solar system exploration with "the engineering subject conquest and technology acquisition by small missions with high mobility, and the radicalized missionís purpose" as one of the pillars of action for another 10 years. And free exploration activity will be developed in further ten years using the acquired knowledge.
Road Map for Space Science and Exploration, and the Epsilon rocket
The key of "small missions with high mobility" is practical use of the Epsilon rocket. However, far bigger energy than the launch to an orbit around the earth is required for exploration, i.e., a launch of the flying object to an interplanetary space, and important observation equipment may not be carried by the capability of present Epsilon.
Then, it is necessary to improve in capability of Epsilon.
Epsilon is solid fuel rocket which belongs to the rocket development of ISAS.
ISAS and Space Transportation Program are cooperating and conducting maintenance, improvement, reinforcement, etc. By launching as ISAS, if reinforcement of capability is required, we cannot miss this time when various examination is conducted. Moreover, reinforcement requires an additional budget, and considering rocket lineup of Japan, skyrocketing request can not be passed.
If Scientific Satellites Cluster is premised on practical use of Epsilon as the base which considers long-range plan, we have to clarify the launch capability required value of space science before capability reinforcement type development. On the other hand, since Epsilon is regarded as the basic rocket, also in order for our country to maintain it, it is required to raise industrial competitiveness, and it is necessary to examine giving proper launch capability to the needs of small satellites market. And Scientific Satellites Project Cluster is large quantity frame of continuous demand, and we consider using this rocket well as "the transport rocket which gets experience", and "the base of rocket development."