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Prof Hiroshi Yamakawa

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Hiroshi Yamakawa was born in Geneva, Switzerland in 1965. He received master's degree of engineering in 1990 and Ph. D in 1993 both from the University of Tokyo. He became a research associate and an associate professor at the Institute of Space and Astronautical Science in 1993-2003, and an associate professor at Japan Aerospace Exploration Agency in 2003-2006. He engaged in mission design of numerous Earth-orbiting scientific satellite projects as well as in lunar and interplanetary missions. He also engaged in the navigation, guidance, and control systems of the solid propellant rocket, M-V, and liquid propellant reusable sounding rocket, RVT. He was a study manager and a project manager of the Euro-Japan collaborative mission to Mercury "BepiColombo" from 2000 through 2006. He was a visiting scientist at NASA JPL in 1997-1998 and at ESA ESTEC in 2002. He moved to Kyoto University in 2006 as a professor of the Research Institute of Sustainable Humanosphere, a professor of the Graduate School of Engineering (cooperating chair) and a deputy director of the Unit for Synergetic Studies of Space. He was appointed as secretary general at the Secretariat of Strategic Headquarters for Space Policy, Cabinet Secretary, Government of Japan in July 2010 through July 2012. He was assigned member of the Committee for National Space Policy, Cabinet Office in July 2012. His academic interest lies in orbital mechanics (spacecraft formation dynamics, solar sail dynamics, Halo orbits), trajectory optimization (interplanetary trajectory design, low-thrust trajectory optimization), and space propulsion (magnetic sail, solar sail, Coulomb force, Lorentz force orbit control).


Reaching Asteroids
Reviewing spacecraft transfer trajectories from the Earth to asteroids including the Hayabusa mission, two types of asteroid transfers are discussed: one is to make rendezvous with the asteroid and the other is to impact the asteroid with large relative velocity. The use of solar electric propulsions and solar sails are discussed. For the latter case, some detailed discussions will be given to the optimal interplanetary trajectories for impulsive deflection of potentially hazardous asteroids under velocity increment uncertainties.

Moving Asteroids
Vairous ideas of orbital deflection methods of potentially hazardous asteroids are discussed. Some detailed discussions on the combinatorial use of gravity and electrostatic forces applicable for small asteroids will be provided. The latter half of the lecture will investigate the possibility of an asteroid survey mission enabled by advanced solar sailing technology. The discussion focuses not on the solar sail spacecraft itself but on its orbital dynamics to realize the missions. A novel near-earth asteroid flyby survey mission with a lightweight solar sail spacecraft to increase the observability is discussed.

Tackling Space Debris
Reviewing various methods to decrease orbital debris, the lecture investigates the possible methods of decreasing or changing the altitude of space debris by Lorentz force which is an interaction between the Earth geomagnetic field and the current induced by, for example, electrodynamic tether attached to space debris. Approximated equations of motion for the altitude variation are derived. The motion of a satellite utilizing the geomagnetic field around space debris is also discussed for observation of and rendezvous with space debris. Analytical approximations for the relative motion in Earth orbit are obtained. The sequential quadratic programming method is applied to solve the orbital transfer problem.

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