中文摘要：

小行星探测是当前深空探测的热点之一，探测目标的可接近性又是探测任务首先要解决的问题．根据直接转移轨道方式下太阳系中可以探测到的区域和小行星的空间分布，确认发射能量C3=50km2／s2的直接转移轨道，可以探测大部分主带小行星；使用少量的速度修正还能够实现多目标飞越任务．同时指出，这种多目标的飞越可以达到△V—EGA轨道方案阻中的深空机动同样的效果，经地球引力助推，以较小能量实现小行星伴飞或更遥远小行星的探测；据此提出了一个探测器先飞越多颗主带小行星，然后借助地球引力助推探测更遥远小行星的轨道设计方案，并给出了设计实例．

英文摘要：

The mission designed to visit asteroids has been the hot spot of deep space exploration at present, and the accessibility to the detected targets is the most important issue. The number of asteroids is enormous, and it needs large calculations to evaluate the accessibility of all asteroids. In this paper, we calculate the accessibility to different regions of the solar system by considering direct transfer strategy, which are compared with the distribution of asteroids. By comparison, we find that most of the asteroids in the main belt are accessible using direct transfer strategy with launch energy of C3= 50 km2/s2. If limited fuel is added, the designed trajectory is able to access multiple asteroids. Such multiple flybys lead to the same effect with the orbit maneuver in △V-EGA strategy, accompanying asteroids or exploring the asteroids at further distances by gravity assistance of Earth with lower energy. In the end, an orbit as an example to carry out multiple flybys to the targeted asteroids with the gravity assistance of Earth is shown.