On Monday, once Yeomans' office had confirmed the incoming asteroid, he called NASA headquarters in Washington DC, which publicized the impact about seven hours before it occurred. If, however, the incoming object had been 50 to 100 times bigger than it was, the warnings would have been very different. "We would have found out several days sooner," Yeomans says, and arrangements would have been made to get people out of the area of impact.
... astronomer Peter Brown of the University of Western Ontario in London, Canada, was able to confirm that the space rock hit the atmosphere at around 02:45 GMT on Tuesday, within minutes of the predicted time and at the predicted location. Brown used data from a Kenya-based array of seven microbarometers, which record atmospheric sound waves to monitor countries' compliance with the Comprehensive Nuclear Test Ban Treaty. The infrasound signals show that the asteroid hit the atmosphere with an energy equivalent to detonating one to two kilotonnes of TNT. "We can infer from that energy that 2008 TC3 was about three metres in diameter," Brown says.