Besides the obvious answer... "very carefully"!
Wouldn't it be "embarrassing" if instead of being trapped in the moon's orbit, it came after the Earth!
"uh... didn't expect that outcome."
POTUS: "Really? Naturally, you have a backup plan on how to blow the thing up before it reaches us."
NASA Chief: "Well you see, Madame President, that was just one the points of the experiment, to study ways to mine these for minerals in space station construction, to learn how to deflect asteroids and how to blow them up before they hit Earth."
NASA Chief: The "how to blow them up" experiment is scheduled to begin in 3 years."
POTUS: But the asteroid is expected to make impact in 3 days!!"
"Yeah... like I said, we really didn't expect that outcome or we might have started with the "exploding asteroid experiment" as soon as we captured it last year.