A 150-foot (45-meter) asteroid hurtled toward Earth’s backyard, destined on Friday to make the closest known flyby for a rock of its size.

NASA promised the asteroid would miss Earth by 27,600 km, avoiding catastrophe. But that’s still closer than many communication and weather satellites; scientists insisted these, too, would be spared.

Asteroid 2012 DA14, as it’s called, is too small to see with the naked eye even at its closest approach around after 2 p.m., Montreal, over the Indian Ocean near Sumatra.

The best viewing locations, with binoculars and telescopes, are in Asia, Australia and eastern Europe. Even there, all anyone can see is a pinpoint of light as the asteroid zooms by at 28,000 kmph.

(VIDEO: NASAs Live streaming channel. There will be other programming before and after asteroid coverage) 

As asteroids go, DA14 is a shrimp. The one that wiped out the dinosaurs 65 million years ago was about 10 km across. But this rock could still do immense damage if it struck, releasing the energy equivalent of 2.4 million tonnes of TNT and wiping out 1,950 sq. km.

Scientists are certain it won’t impact Earth. And chances are extremely remote it will run into any of the satellites orbiting 36,000 km up.

Most of the solar system’s asteroids are situated in a belt between the orbits of Mars and Jupiter, and remain stable there for billions of years. Some occasionally pop out, though, into Earth’s neighbourhood.

The flyby provides a rare learning opportunity for scientists eager to keep future asteroids at bay and a prime-time advertisement for those anxious to step up preventive measures.

“We are in a shooting gallery and this is graphic evidence of it,” said former Apollo astronaut Rusty Schweickart, chairman emeritus of the B612 Foundation, committed to protecting Earth from dangerous asteroids.

Mr. Schweickart noted that 500,000 to 1 million sizable near-Earth objects asteroids or comets are out there. Yet less than 1 per cent fewer than 10,000 have been inventoried.

DA14 discovered by Spanish astronomers last February is “such a close call” that it is a “celestial torpedo across the bow of spaceship Earth,” Mr. Schweickart said in a phone interview on Thursday.

Astronomers organised asteroid-encounter parties for Friday and experts just about everywhere were giving flyby rundowns.

NASA’s deep-space antenna in California’s Mojave Desert was ready to collect radar images, but not until eight hours after the closest approach given the United States’ poor positioning for the big event.

Scientists at NASA’s Near-Earth Object programme at California’s Jet Propulsion Laboratory estimate that an object of this size makes a close approach like this every 40 years. The likelihood of a strike is every 1,200 years.

If a killer asteroid was, indeed, incoming, a spacecraft could be launched to nudge the asteroid out of Earth’s way, changing its speed and the point of intersection. A second spacecraft would make a slight alteration in the path of the asteroid and ensure it never intersects with the planet again, Schweickart said.

Photo: NASA