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Swift
2013-Dec-26, 05:31 PM
NEOWISE is the re-tasked IR telescope WISE, now being used for hunting NEOs (Near Earth Objects). NASA has posted the first image, and the BA himself has blogged about it.

LINK (http://www.slate.com/blogs/bad_astronomy/2013/12/20/neowise_nasa_s_asteroid_hunter_is_back_in_business .html)


Astronomers have released the first few images from the now-revived NEOWISE, and its already turning up space rocks. The picture above shows a star field with the asteroid 872 Holda, seen as the series of red dots moving across the sky as NEOWISE took a set of exposures. Holda is big, about 42 kilometers (26 miles) across, and orbits the Sun between Mars and Jupiter, safely away from Earth.

Nicolas
2013-Dec-27, 09:47 AM
Can someone explain how it can work now if it ran out of coolant in 2011?

In any case, this is beautiful recycling!

Swift
2013-Dec-27, 02:19 PM
I think NASA can (http://solarsystem.nasa.gov/missions/profile.cfm?Sort=Chron&StartYear=2010&EndYear=2019&MCode=WISE)


After completing its prime science mission, the spacecraft ran out of the frozen coolant that keeps its instrumentation cold. However, two of its four infrared cameras remained operational. These two channels were still useful for asteroid hunting, so NASA extended the NEOWISE portion of the WISE mission by four months, with the primary purpose of hunting for more asteroids and comets, and to finish one complete scan of the main asteroid belt. The spacecraft was then placed in hibernation in case another science opportunity arose.

Beginning in September 2013, WISE will be revived with the goal of discovering and characterizing near-Earth objects (NEOs). NASA anticipates WISE will use its 40-cm (16-inch) telescope and infrared cameras to discover about 150 previously unknown NEOs and characterize the size, albedo and thermal properties of about 2,000 others.


From the WISE wikipedia page (http://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer#Spacecraft):

WISE surveyed the sky in four wavelengths of the infrared band, at a very high sensitivity. Its detector arrays have 5-sigma sensitivity limits of 120, 160, 650, and 2600 microjanskies (Jy) at 3.3, 4.7, 12, and 23 micrometers (aka microns).[19] This is a factor of 1,000 times better sensitivity than the survey completed in 1983 by the IRAS satellite in the 12 and 23 micrometers (micron) bands, and a factor of 500,000 times better than the 1990s survey by the Cosmic Background Explorer (COBE) satellite at 3.3 and 4.7 micrometers.[19] On the other hand, IRAS could also observe 60 and 100 micron wavelengths.[20]

Band 1 – 3.4 micrometers (microns) – broad-band sensitivity to stars and galaxies
Band 2 – 4.6 micrometers – detect thermal radiation from the internal heat sources of sub-stellar objects like brown dwarfs
Band 3 – 12 micrometers – detect thermal radiation from asteroids
Band 4 – 22 micrometers – sensitivity to dust in star-forming regions (material with temperatures of 70–100 kelvins)

Nicolas
2013-Dec-29, 08:51 PM
Thanks, but it's still not 100% clear to me. The 2 instruments that still work, do they not need cooling by design or do they work now outside of their designed cooled state? If the latter, how does that influence the detectable range?

Swift
2013-Dec-29, 09:37 PM
Thanks, but it's still not 100% clear to me. The 2 instruments that still work, do they not need cooling by design or do they work now outside of their designed cooled state? If the latter, how does that influence the detectable range?
I don't know. There are certainly IR detectors they do not need cryogenic cooling. I suspect that a detector that need such cooling would not work at all without, but I don't know for sure.

antoniseb
2013-Dec-30, 03:08 PM
Thanks, but it's still not 100% clear to me. The 2 instruments that still work, do they not need cooling by design or do they work now outside of their designed cooled state? If the latter, how does that influence the detectable range?

The instruments that still work do not require refrigeration. They are looking at IR wavelengths shorter than what requires special cooling aside from simply keeping the reflecting surface out of direct sunlight.

samkent
2013-Dec-31, 06:19 PM
I thought the coolant was needed to increase the sensitivity not to allow operation.
Comets and asteroids are much warmer than the distant objects they origionally looking for.
Hense no cooling needed.

If I'm wrong please correct me.

ToSeek
2014-Jan-07, 05:23 PM
WISE operated at 4 different wavelengths: 3.4 and 4.6 microns with one set of detectors, and 12 and 22 microns with another. If the latter detectors are not cooled, then the thermal radiation from the detectors themselves overwhelms any signal they might pick up. You can run them if they're not cooled, but you're not going to get any useful data. I believe the shorter wavelength detectors can still be run but won't be as sensitive.