The amount of orbital debris tracked by the US SpaceSurveillanceNetwork jumped from 9, 949 cataloged objects in December 2006 to 16, 094 in July 2011, the National Research Council said.
The Space Fence program is a multi-phase acquisition leading to the delivery of up to three globally positioned S-band radars capable of interoperation with the SpaceSurveillanceNetwork.
太空护栏计划是一个多阶段的采购项目，交付3个全球定位S波段雷达系统，能够完成空间监测网互操作。
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America already has the world's most developed space monitoring system with a network of radars and telescopes. But its surveillance is patchy.