Agence France-Presse “House-sized asteroid will pass by Earth at just above satellite altitude” https://www.theguardian.com/science/2017/oct/10/house-sized-asteroid-will-pass-by-earth-at-just-above-satellite-altitude

NASAでは小惑星(asteroid)2012 TC4の動きを8月以来追跡してきたが*2、2012 TC4は10月12日*3にも地球から44,000米の上空を通過するという。上空36,000米には数百の衛星が集中する静止軌道がある。

As its name suggests, the object was first spotted five years ago when it called on Earth at about double Thursday’s projected distance, before disappearing from view.

It is 15 to 30 metres (50 to 100ft) wide – about the size of the meteoroid that exploded in the atmosphere over Chelyabinsk in central Russia in 2013, with 30 times the kinetic energy of the atomic bomb dropped on Hiroshima.

The resulting shockwave blew out the windows of nearly 5,000 buildings and injured more than 1,200 people*4.

While the Chelyabinsk event caught everyone unawares, TC4 is one of thousands of space rocks whose whereabouts are known.

*1:See http://d.hatena.ne.jp/sumita-m/20171008/1507476912

*2:See Agence France-Presse “Close encounter: asteroid the size of a house set for near miss with Earth” https://www.theguardian.com/science/2017/aug/11/close-encounter-asteroid-2012-tc4-size-of-a-house-near-miss-with-earth

*3:どの時間帯? NASAのある米国フロリダ州の時間?

*4:See Howard Amos “Meteorite explosion over Chelyabinsk injures hundreds” https://www.theguardian.com/world/2013/feb/15/hundreds-injured-meteorite-russian-city-chelyabinsk