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SYFY WIRE Bad Astronomy

WISE Rises From Its Ashes

By Phil Plait

I have some great news about NASA: Next month they will be reactivating the Wide-field Infrared Survey Explorer, or WISE! This observatory orbits the Earth and sees in the far-infrared, well outside what our eyes can detect. This is the domain where cooler objects in space emit light: dust clouds, planets, and asteroids.

WISE was launched in late 2009 and spent 13 months surveying the sky. Since it looks at what we call âthermal infraredâ light, its cameras had to be cooled to keep from interfering with the observationsâyou donât want to have your own telescope glowing brightly! It ran out of coolant in 2011 (as was expected) and was put into hibernation.

And now it gets a second chance at life. And what a chance: NASA has approved an extended three-year mission for WISE. The goal is to map out potentially hazardous near-Earth asteroidsâthat is, space rocks that can hit usâsomething that was part of its mission when it was still active. Two of its four cameras can operate without coolant, and they should be sufficient to do the job.

My pal and astronomer Amy Mainzer is the principal investigator for NEOWISE, the Near-Earth Object part of the WISE mission. Iâm glad for her, because this means sheâs gainfully employed for another three years, but also because sheâs working on NEOCAM, a follow-up mission that will leverage what was learned from WISE to build a next-generation asteroid hunter.

WISE is good at looking for asteroids because of a quirk of nature. Asteroids are dark in visible light, and difficult to detect. But sitting out there in the sunlight causes them to warm up, where they glow in the far IR. WISE is pretty good at seeing these rocks, even though they may be too faint to see with visible-light telescopes. Also, it looks at wide chunks of the sky at one time, allowing it to find more of these objects and make a survey of them. While the mission was active, WISE found 135 NEOs, another 34,000 asteroids between Mars and Jupiter (in whatâs called the Main Belt), and all in all saw nearly 160,000 of the 600,000 known rocks in the solar system (millions more remain as yet unseen)âincluding the very first Earth Trojan asteroid, a rock that shares Earthâs orbit.

In this extended three-year mission, itâs expected to find 150 more asteroids that can approach the Earth. But itâll do more, too. One thing thatâs hard to do is determine how big an asteroid is; you have to know its distance, how bright it appears, and how reflective it is. Seen from the same distance, a shiny rock will be brighter than a dark one. That reflectivity is called the albedo, and itâs hard to measure in visible light. But in infrared itâs far easier, so in its extended mission WISE will be able to determine the sizes of something like 2,000 more asteroids. Thatâs impressive.

So overall Iâm pretty happy with this. The only downside to me is that this is being done in conjunction with NASAâs plans to go to and capture a small asteroid, and I am by no means confident that plan will get long-term (or any) funding by Congress. Iâd hate to think WISE was a political pawn in this game of trying to get funding. [Update (Aug. 22, 2013 at 22:00 UTC): The day after NASA announced this resurrection of WISE, they released new pictures and animations for the asteroid retrieval mission.] WISE deserves to get extended; it was a highly successful mission, doing great work for a relatively small amount of money, and the idea of bringing it back to life to hunt for more asteroidsâespecially as a stepping stone to even better space rock houndsâis well worth it on its own merits.

So while I keep a jaundiced eye on the politics, Iâm very pleased that WISE will get a chance see more photons. Itâs always bittersweet when a mission is shut down, so itâs a reason to celebrate when one gets switched back on. My congratulations to the WISE team!

Now go find some rocks.

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