Lessons from half a century experience of Japanese solid rocketry since Pencil rocket

50 years have passed since a tiny rocket “Pencil” was launched horizontally at Kokubunji near Tokyo in 1955. Though there existed high level of rocket technology in Japan before the end of the second World War, it was not succeeded by the country after the War. Pencil therefore was the substantial start of Japanese rocketry that opened the way to the present stage.In the meantime, a rocket group of the University of Tokyo contributed to the International Geophysical Year in 1957–1958 by developing bigger rockets, and in 1970, the group succeeded in injecting first Japanese satellite OHSUMI into earth orbit. It was just before the launch of OHSUMI that Japan had built up the double feature system of science and applications in space efforts. The former has been pursued by ISAS (the Institute of Space and Astronautical Science) of the University of Tokyo, and the latter by NASDA (National Space Development Agency). This unique system worked quite efficiently because space activities in scientific and applicational areas could develop rather independently without affecting each other.Thus Japan's space science ran up rapidly to the international stage under the support of solid propellant rocket technology, and, after a 20 year technological introduction period from the US, a big liquid propellant launch vehicle, H-II, at last was developed on the basis of Japan's own technology in the early 1990's. On October 1, 2003, as a part of Governmental Reform, three Japanese space agencies were consolidated into a single agency, JAXA (Japan Aerospace Exploration Agency), and Japan's space efforts began to walk toward the future in a globally coordinated fashion, including aeronautics, astronautics, space science, satellite technology, etc., at the same time. This paper surveys the history of Japanese rocketry briefly, and draws out the lessons from it to make a new history of Japan's space efforts more meaningful.     

Optimum low thrust transfer to geosynchronous orbit

The low thrust transfer for geosynchronous mission has been studied by many investigators from the viewpoint of optimization in case of continuous thrust. This paper discusses the possibility of fuel saving to attain a geosynchronous orbit by introducing coast phases during each revolution. In advance of optimizing the whole transfer mission, optimization during a single revolution is treated, and it is shown that the entrance and the exit of optimal coasting arcs are expressed by a sixth order equation, which, in case of coplanar transfer, degenerates into a cubic equation, with respect to the cosine of true longitude. Then an optimum transfer to a geosynchronous orbit, including coast phases in each revolution, is simulated. Computational results for typical initial conditions are shown to be compared with those for all-propulsion cases.     

Data Processing at KAGUYA Operation and Analysis Center

The functions of KAGUYA(SELENE) Operation and Analysis Center (SOAC) are to operate three satellites: the main orbiter KAGUYA and two small satellites, Relay satellite OKINA and VRAD (VLBI (Very Long Baseline Interferometry) RADio source) satellite OUNA; and to process, archive and provide mission data. SOAC has two main functional areas, “Tracking and Control system” and “Mission Operation and Data Analysis system.” The former is for operational planning of bus and mission instruments including satellite navigation, and for the implementation of those plans and for the evaluation of satellite conditions. The latter is the system that processes, archives and provides mission data, and which principal investigators use to generate higher-level data products. Data up to the end of the operation in June 2009 have been processed and the total amount of Level-2 data products reaches about 50 TB. The data products have been released to the public since November 2009.