NASA's New 'Intruder Alert' System Spots An Incoming Asteroid

A large space rock came fairly close to Earth on Sunday night. Astronomers knew it wasn't going to hit Earth, thanks in part to a new tool NASA is developing for detecting potentially dangerous asteroids.

The tool is a computer program called Scout, and it's being tested at NASA Jet Propulsion Laboratory in Pasadena, Calif. Think of Scout as a celestial intruder alert system. It's constantly scanning data from telescopes to see if there are any reports of so-called Near Earth Objects. If it finds one, it makes a quick calculation of whether Earth is at risk, and instructs other telescopes to make follow-up observations to see if any risk is real.

NASA pays for several telescopes around the planet to scan the skies on a nightly basis, looking for these objects. "The NASA surveys are finding something like at least five asteroids every night," says astronomer Paul Chodas of JPL.

But then the trick is to figure out which new objects might hit Earth.

"When a telescope first finds a moving object, all you know is it's just a dot, moving on the sky," says Chodas. "You have no information about how far away it is. "The more telescopes you get pointed at an object, the more data you get, and the more you're sure you are how big it is and which way it's headed. But sometimes you don't have a lot of time to make those observations.

"Objects can come close to the Earth shortly after discovery, sometimes one day, two days, even hours in some cases," says JPL's Davide Farnocchia. "The main goal of Scout is to speed up the confirmation process."

The rock that whizzed past Earth tonight was discovered on the night of Oct. 25-26 by the NASA-funded Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) on Maui, Hawaii. Within a few hours, preliminary details about the object appeared on a Web page maintained by the Minor Planet Center at the Smithsonian Astrophysical Observatory. Scout did a quick analysis of the preliminary details and determined that the object was headed for Earth but would miss us by about 310,000 miles.

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