<h2>AAS 95-425</h2><h2>The Low-Thrust Flyby Guidance and an Extended Optimal Spacing Rule</h2><h4>J. Kawaguchi,  T. Fujimura and H. Matsuo, Institute of Space and Astronautical Science, Kanagawa, Japan</h4><h2> Abstract </h2>A new extended spacing law governing the mid-course correction points is given for electrically propelled interplanetary missions.  The problem treated here is how much chemical fuel is required in order to cancel out the potential electric and impulsive correction errors.  A generalized spacing rule that determines the optimal correction points is derived.  In addition, simple analytical fuel estimate is presented.  Numerical illustrations include Monte Carlo simulation as well as the return flight from the asteroid back to the Earth, demonstrating the newly developed spacing rule.<br><br>