Jun'ichiro Kawaguchi

Insitute of Space and Astronautical Science, Japan will launch Muses-C spacecraft in 2002. The purposes of the mission is sample return of an asteroid. We will outline the Muses-C mission, focusing on the interplanetary flight with ion propolsion, interplanetary telecommunications, sampling technology, etc. In addition, our perspective of spacecraft technology for space sciences will be described.

This paper deals with the post flight analysis on the attitude control problem of the M-3SII-8/EXPRESS flight, which occurred at the midcourse of its second stage powered phase. The results of the post-flight modal analysis, executed for the second stage entire vehicles of the M-3SII series, shows peculiarity of the EXPRESS flight in structure and control interactions of the vehicle. The loop gain from the control command to the first order bending oscillation of the vehicle, indicating the extent of the flexibility effect, is definitely enhanced compared with those of the previous flights, which combined with the instability of the mode to yield the dynamical coupling between the structural oscillation of the degree and the attitude control. An increase in the payload mass compared to the rest of the flights is considered a principal contribution to the difference in modal characteristics. The mechanism of the growth of the oscillation amplitude, even within the control dead band, is also mathematically disclosed, which is featured by the magnitude of the disturbance. A transition from the disturbance governed (dynamic) cycle into a static cycle triggered the resonance type phenomenon. The static limit cycle, which happened to be formed in the middle of the second stage flight, caused the frequent and long durational injections, resulting in the excess energy supply into the oscillating system. Thus the magnitude of the oscillation gradually increased to finally exceed the control dead band, leading to a divergence type response. The numerical simulation has been conducted under the system parameters evaluated through the flight data and given its endorsement to all the point. The paper also describes an effective measure to avoid the problem.

This report summarizes the future trend in the weight of scientific satellites in Japan which will be launched or programmed in the late twentieth century. Among the several missions contained in this report, particular interest is directed to the interplanetary probes and astronomical observatory satellites. In the estimation of spacecraft weight, each component is systematically estimated based on the satellites which have already been launched or designed. Major result is that 3 ton LEO payload capabidity is needed in future transporter in order to accomplish the missions mentioned here.