In September this year, the Wide-field Infrared Survey Explorer (WISE) space telescope was reactivated to begin its new mission (NEOWISE) to search for and classify potentially hazardous Near-Earth Objects, like the one which exploded above the Russian city of Chelyabinsk earlier this year, injuring thousands. WISE was originally mothballed after it’s supply of cryogenic coolant ran out early in 2011, marking the end of its original mission to map the entire sky in the far infra-red spectrum. However, its reduced sensitivity is still good enough to detect tiny objects in our own Solar System, and the decision was made to keep the spacecraft alive on a new mission to discover and categorise NEO’s. That mission was performed so succesfully that NASA has decided to run it again, in the hope of mopping up the remaining NEO’s and identifying candidate asteroids for NASA’s Asteroid Watch program. “The WISE mission achieved its mission’s goals and as NEOWISE extended the science even further in its survey of asteroids. NASA is now extending that record of success, which will enhance our ability to find potentially hazardous asteroids, and support the new asteroid initiative,” said John Grunsfeld, NASA’s associate administrator for science in Washington. “Reactivating WISE is an excellent example of how we are leveraging existing capabilities across the agency to achieve our goal.”

Asteroids are generally dark, rocky objects, which don’t reflect much sunlight. They’re also small enough that we can’t directly measure their size. We infer their size by measuring their brightness, but this means that if they’re more or less reflective than we thought then our estimates could be out by a long way. The vast majority are so small and dim that finding them has always been more a matter of luck than skill. But all objects in the Solar System are warmed by the Sun, and this means they radiate infra-red light. The sophisticated inra-red sensors in WISE’s 16 inch telescope are easily able to find and track these objects, making it an ideal instrument for cataloguing and studying these previously elusive bodies, and accurately gauging their physical properties.

“The data collected by NEOWISE two years ago have proven to be a gold mine for the discovery and characterization of the NEO population,” said Lindley Johnson, NASA’s NEOWISE program executive in Washington. “It is important that we accumulate as much of this type of data as possible while the WISE spacecraft remains a viable asset.”

The Asteroid Watch initiative has the ambitious goal of defending the Earth from dangerous asteroid impacts. Although there are currently no known asteroids likely to collide with Earth at any time in the next few centuries, the is still the chance of a previously undiscovered asteroid lurking – a fact brought home by the totally unexpected Chelyabinsk impact, when a small asteroid escaped detection and collided with Earth, exploding in the upper atmosphere with the force of a large nuclear bomb. Asteroid Watch was founded on the sobering fact that even if we’d known about the Chelyabinsk impactor in advance, we could not have done anything about it. The goal is to develop methods and technologies to destroy the asteroid, deflect it, or otherwise render it harmless. To do this, the long-term plan is to identify a suitable asteroid, send out a spacecraft to capture it, bring it back home, and park it in Earth orbit for further study. This all starts with the data that NEOWISE is now returning.

“The team is ready and after a quick checkout, we’re going to hit the ground running,” said Amy Mainzer, NEOWISE principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “NEOWISE not only gives us a better understanding of the asteroids and comets we study directly, but it will help us refine our concepts and mission operation plans for future, space-based near-Earth object cataloging missions.”

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