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The Forefront of Space Science

Examination of the exploration using the Epsilon rocket
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What is made by the required capability?

Even if the assumed capability is realized in Epsilon, there is no meaning which will be required, if there are no missions that the space probe side has meaning scientifically. Then, the things that we should do next is to estimate outline "being able to do", and while the meaning of request is shown, we should urge the project proposal from science community. Now we have been considering estimation for outline, succeeding the meeting which drew the required capability to Epsilon.

By the way, even if we do not have to wait for examination, two or more exploration mission proposals are considered in Japan. At first it seems that it will be appropriate to this examination to compensate from the area which they do not cover. We have analyzed from navigation technology and viewpoint of the destination. It shows as table 1. First of all, we have decided to examine from the possibility of gravity astronomical exploration and asteroid exploration.

Table 1
Table 1.  Classification of currently proposed missions [Click to see larger image.]
Since it is "acceleration" means to change the technical composition of the deep space probe, the vertical axis was classified according to the technical form.


We have fixed the following three points as the indicator in examination. (1) Find out the limit, although it is challenge. Just exceed the limit is also acceptable. (2) It should suggest that the fixed area of the solar system can be covered. (3) It is possible to utilize the current knowledge of ISAS, and it will be connected 20 years.

First of all we have to start with consideration how far can it go and what can do with the technology of the space probe in the near future. As a result, the following knowledge was arranged. (A) If it is able to go to Mars and Venus, going to Jupiter in orbit mechanics is also possible. However, we do not know if we can build practical space probe with the viewpoints of electric power, communication, etc. (B) After launching space probe to SEL and moving to the suitable place of potential area and then launching it to the destination. It is possible to send the larger space probe to the target heavenly body. (C) The space probe which does complicated work may insufficient launch capability. In order to compensate this problem, two or more space probes should be launched with two or more rockets, and we can get good result by those cooperation operation.

About the missions in two or more space probes, explanation is somewhat required. In order to realize the same thing, there is also method of enlargement of satellite and two-set launch by H-II A except Epsilon. However, if we launch separately using low price rocket, launch time and an orbit can be divided and we can get the advantage of being assembled missions gradually. And it is compatible with good characteristic and of Epsilon that high launch frequency and simple launching pad may be good enough. It can be said that success of Epsilon is going in the direction divided into two or more bodies from the current technique of having stuffed various sensors and functions into one space probe.

A concrete examination of how to build the space probe which realizes these has just started. However, we already know the following subjects. First of all, the SPRINT bus which is the base of the present small scientific satellites, such as Small scientific satellite Platform for Rapid Investigation and Test EA "Hisaki", is still too heavy to use. This is caused by that the design is turned to secure for standardization and flexibility. Therefore, based on the new trial production and experiment which pursue the weight saving of each part step by step, and are conducted as constant research activities in the engineering system, we have to cause the technical innovation of the design. In addition, when summarizing them as space probe design, we have to prepare for selecting configuration required for the mission requirement carefully, and reconstructing the whole from zero. And probably, it should have common factor as much as possible with the technology used with science or missions other than exploration, in order to maintain exploration missions group continuously.

A future motion

Since we understand that space probe seems possible to use as vehicle, it is the stage considered in the form of an example about outline. Since it is closely involved with the hope of various scientific fields from now on, it is impossible to advance examination carelessly only from narrow range and viewpoint of ISAS. Moreover, missions will be required for engineering and scientific innovative spirit. Then, we are going to extract the information which helps to propose and evaluate actual missions by discerning the execution scale in the review session supposing some samples considered to be adapted for various purposes. In the near future, I hope that we can show you the image which considers that several years are necessary to build one mission and there is already no time in deciding the reinforcement specification of Epsilon.

(Masanobu Ozaki)

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