The Near-Earth Object Observation Program, commonly called "Spaceguard, " also plots the orbits of these objects to determine if any could be potentially hazardous to our planet.

近地天体观察项目，常被叫做“太空警卫”，也对这些天体绘制了轨道图来判断其中是否有天体可能对我们的星球有潜在危险。

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But even if Spaceguard does succeed, another problem remains smaller asteroids, of the size believed to have caused a huge explosion above Tunguska, in Russia, in 1908.

ECONOMIST: A large asteroid sweeps by Earth. Where are the others?

Any NEO that is going to hit the Earth will swing near our planet many times before it hits, and it should be discovered by comprehensive sky searches like Spaceguard.

FORBES: We Probably Wouldn't Even See A Doomsday Asteroid Until It Was Too Late