An asteroid 1.7 miles long will pass close by the Earth on 31 May, according to Nasa scientists.
Scientists plan to use the Near Earth Object (NEO) event to help them prepare to land on a lump of space rock in four years' time as part of an asteroid defence planning project.
Nasa scientist Lance Benner said: "Whenever an asteroid approaches this closely, it provides an important scientific opportunity to study it in detail to understand its size, shape, rotation, surface features, and what they can tell us about its origin.
"We will also use new radar measurements of the asteroid's distance and velocity to improve our calculation of its orbit and compute its motion farther into the future than we could otherwise."
Earth's upcoming brush with an extra-terrestrial object should not cause any problems, unlike the meteor that exploded over Russia earlier this year.
The asteroid, known as 1998 QE2, will fly 3.6 million miles above the Earth's surface.
The event will be 1998 QE2's first appearance near our planet, and scientists have little idea what it will look like.
They will track it using Nasa's enormous Deep Space Network antenna, which is 230 feet wide.
"It is tremendously exciting to see detailed images of this asteroid for the first time.
"With radar we can transform an object from a point of light into a small world with its own unique set of characteristics.
"In a real sense, radar imaging of near-Earth asteroids is a fundamental form of exploring a whole class of solar system objects."