有效渐开线起始圆直径 start of active profile diameter
如果说对于大型的行星的挑战不能一蹴而就，研究者常常从小一点的开始，比如直径6到30英尺的小行星。
And if the challenges for a large asteroid seem too daunting researchers could always start with a smaller asteroid perhaps six to 30 feet across.
Braun博士最开始采用的材料正是他在自然纳米技术杂志所描述的那样，是由直径为百万分之一米紧密排列的聚苯乙烯小球组成。
His starting material, as he describes in a paper in Nature Nanotechnology, is made of closely packed polystyrene spheres about a millionth of a metre in diameter.
照片由美国航天局“黎明号”探测器拍摄，该探测器自上月起就在该直径达330英里的岩石天体轨道上运行并传送回团队刚刚开始关注的大量不可思议的表面细节信息。
The images were taken by NASA's Dawn spacecraft, which began orbiting the 330-mile-wide rocky body last month and beaming back incredible surface details that the team is only beginning to pore over.
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