Watching the skies for large asteroids that could pose a hazard to Earth is a global endeavor. So, to test their operational readiness, the international planetary defense community will sometimes use a real asteroid’s close approach as a mock encounter with a “new” potentially hazardous asteroid. The lessons learned could limit, or even prevent, global devastation should the scenario play out for real in the future.
Click here for original story, Planetary defense exercise uses asteroid Apophis as hazardous asteroid stand-in
Source: Phys.org