WISE, a mission that will find ALL the neighbours Options

[ngunn]

I'm used to reading excellent articles by Emily, but this one I found to be of truly extraordinary interest:

http://www.planetary.org/blog/article/00002070/

[Gsnorgathon]

Yes. And the funny thing is, my mind was being all boggled by the implications of the mission, and then I got to the bit about 15kg of solid hydrogen. Holy cow!

[Mongo]

I wonder why they chose solid hydrogen instead of liquid helium for the coolant. My best guess would be that the mass of the helium tank would be too great for the WISE mass budget (the Herschel spacecraft seems to be basically a giant liquid helium tank with attached optics and electronics), plus liquid helium might be slightly overkill for the wavelengths it will study.

Bill

[stevesliva]

Is it harder to control the torques from Liquid Helium? Does it slosh a little more an fight gyros?

[ngunn]

A handy free article on solid hydrogen:

http://www.tvu.com/PEngPropsSH2Web.htm

[Juramike]

"macroscopic crystals characterized by different nuclear spin states"

Whoa! This takes Pasteur separating chiral crystals to a whole new level. That is just plain bizarre!

[elakdawalla]

I wonder why they chose solid hydrogen instead of liquid helium for the coolant. My best guess would be that the mass of the helium tank would be too great for the WISE mass budget (the Herschel spacecraft seems to be basically a giant liquid helium tank with attached optics and electronics), plus liquid helium might be slightly overkill for the wavelengths it will study.

Bill

Sounds like you're right, and there's one other advantage. From Bill Irace: "Our detectors do not require He temp (1.5 K) and solid Hydrogen (6.5 K) has about 7X the specific heat as liquid He: ergo lower weight system."

--Emily

[nprev]

Huh. I'd always thought that hydrogen needed to be highly pressurized to freeze; guess I was confusing that with what's needed to achieve its 'metallic' phase. Pretty ingenious, and as you said in your blog, Emily, this looks to be an exciting mission!

[SteveM]

I know it's really premature to begin talking about what to do after WISE sublimates all it's solid hydrogen before it's even launched. Nonetheless, I imagine there must be some contingency planning for a WISE warm mission analogous to that of Spitzer. See the discussion of Spitzer beginning at this link.

Among the things NASA mentions is the detection of asteroids during the Spitzer warm mission. WISE warm might be able to continue its asteroid survey.

Steve M

[Guest_PhilCo126_*]

Wide-field Infrared Survey Explorer
WISE preparation for launch from Vandenberg Air Force Base ;
http://mediaarchive.ksc.nasa.gov/search.cfm?cat=216
Launch scheduled 7th December 2009

[dtolman]

The latest Sky and Telescope has a nice article on this - I was astonished that they gave even odds to finding a brown dwarf CLOSER than Alpha Centauri.

[Greg Hullender]

I was astonished that they gave even odds to finding a brown dwarf CLOSER than Alpha Centauri.

Given that smaller stars are more numerous than larger ones, I'd have thought it almost a certainty they'd find a number of brown dwarves closer than Alpha Centuri. What I'm wondering is whether a brown dwarf inside the Oort Cloud might be responsible for otherwise-difficult-to-explain things like the orbit of Sedna.

--Greg

[ngunn]

I'm somewhere between evens and 'almost a certainty' but I agree that their statement of the odds is probably on the cautious side of what they are actually thinking. I say this because they will be able to detect objects below the small end of what we normally think of as brown dwarfs.

[nprev]

I too wouldn't be surprised if there were one or more brown dwarfs closer than the Alpha Centauri system. However, I'm also pretty confident that orbital anomalies in the extreme outer Solar System could just as easily be explained by the nearby passage (within 1 light-year) of stars and/or brown dwarfs, which has doubtless happened more than once over geological time.

Would definitely be interesting if we do have a very nearby neighbor, though. Might take decades of observation to determine whether such an object was just passing by or actually associated with the Sun.

[Greg Hullender]

I suppose I should say that, after LCROSS and the mystery of the incredible plume, I'm all in favor of NASA making conservative predictions but being prepared to record spectacular results.

It's funny; there's not a lot of buzz about WISE, but between brown dwarves and optically-dim Earth-crossing asteroids, it promises to deliver an incredible wealth of information.

If they manage the extended mission, they'll have two shots of each object, six months apart. Since their resolution is 2.75 seconds of arc per pixel, that ought to give them a good clue as to which objects at least MIGHT be associated with the sun. Too much or too little change in position would mean it's either going to fast or located too far away.

--Greg