Collisions in space: A retrospective overview of ISAS studies

A chronological review of studies in ISAS concerning collisions in space is presented. The collision probability in space with artificial orbiting bodies was estimated, and a Space Traffic Control System was proposed, in 1971. The design of a space station for safety against collision hazards was discussed in 1972. A trajectory optimization technique for low-thrust multiple rendezvous mission in order ti sweep space debris around the earth was developed in 1977. In 1984, the collision probability was reestimated using space bedris data accumulated for more than a decade. Several experimental projects in ISAS, such as hypervelocity impact experiments using a railgun system, sampling and measuring of alumina particles in exhaust plume of solid-propellant propellant rocket motors, and a result of analysis on the behavior of such alumina particles in orbit are also introduced.     

Hayabusa—Its technology and science accomplishment summary and Hayabusa-2

Hayabusa performed five descents last November, among which two touching-down flights were included. Actually Hayabusa made three touching-downs and one long landing on the surface of Itokawa during those two flights. This paper summarizes how series of descents were planned and operated. The contents focus their attention on the correction maneuvers planning as well as what kind of terminals with what kind of software tools were actually built and used. The project team had distilled and accumulated their experiences through the rehearsal flights and accomplished this difficult mission. This paper presents the entire story about it.     

Orbital design and technological feasibility of Halley mission

Missions to Halley's comet in 1985–1986 are discussed. They include pre-perihelion encounter, post-perihelion encounter, the utilization of Venus swing-by, one round mission in which the spacecraft goes the round of the Sun before the encounter and missions to the point beneath the perihelion of Halley's orbit. Technological feasibility of the small spacecraft is also discussed on the basis of the use of the improved version of M-3S launch vehicle.     

Cosmic dust measurements in lunar orbit

On 15th February 1992, ISAS space engineering satellite HITEN was successfully inserted into an elliptical orbit around the moon with perilune between some 100 km and 8000 km and apolune of about 50.000 km. On board was a small scientific experiment designed to detect cosmic dust particles, MDC - Munich Dust Counter. During a period of more than one year, until Hiten's hard landing on the moon surface at 10th of April 1993 (UTC), measurements of impact velocity, mass and crude flight direction of micrometeoroid particles have been performed. In total 150 cosmic dust impacts were detected and evaluated. From these measurements, the impact rate versus time and the dust flux versus distance from the moon are derived. The evidence of moon ejecta and some indications of particles which are orbiting the moon will be discussed. The spatial distribution of the measured particles is shown in lunarcentric as well as in heliocentric coordinate systems. The directional distribution is also given, showing the different populations of cosmic dust particles. Finally, the gathered data will be compared with previous results from measurements in the vicinity of the Earth and in the geomagnetic tail region.