IPB

Welcome Guest ( Log In | Register )

9 Pages V   1 2 3 > »   
Reply to this topicStart new topic
WISE, a mission that will find ALL the neighbours
ngunn
post Aug 27 2009, 08:31 PM
Post #1


Senior Member
****

Group: Members
Posts: 3064
Joined: 4-November 05
From: North Wales
Member No.: 542



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/
Go to the top of the page
 
+Quote Post
Gsnorgathon
post Aug 27 2009, 11:37 PM
Post #2


Member
***

Group: Members
Posts: 247
Joined: 23-January 05
From: Seattle, WA
Member No.: 156



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!
Go to the top of the page
 
+Quote Post
Mongo
post Aug 27 2009, 11:46 PM
Post #3


Member
***

Group: Members
Posts: 610
Joined: 13-June 04
Member No.: 82



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
Go to the top of the page
 
+Quote Post
stevesliva
post Aug 27 2009, 11:48 PM
Post #4


Senior Member
****

Group: Members
Posts: 1156
Joined: 14-October 05
From: Seattle
Member No.: 530



Is it harder to control the torques from Liquid Helium? Does it slosh a little more an fight gyros?
Go to the top of the page
 
+Quote Post
ngunn
post Aug 28 2009, 10:35 AM
Post #5


Senior Member
****

Group: Members
Posts: 3064
Joined: 4-November 05
From: North Wales
Member No.: 542



A handy free article on solid hydrogen:

http://www.tvu.com/PEngPropsSH2Web.htm
Go to the top of the page
 
+Quote Post
Juramike
post Aug 28 2009, 02:36 PM
Post #6


Senior Member
****

Group: Moderator
Posts: 2676
Joined: 10-November 06
From: Pasadena, CA
Member No.: 1345



"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!


--------------------
Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
Go to the top of the page
 
+Quote Post
elakdawalla
post Aug 28 2009, 04:11 PM
Post #7


Bloggette par Excellence
****

Group: Admin
Posts: 4259
Joined: 4-August 05
From: Pasadena, CA, USA, Earth
Member No.: 454



QUOTE (Mongo @ Aug 27 2009, 03:46 PM) *
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


--------------------
My blog - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
Go to the top of the page
 
+Quote Post
nprev
post Aug 28 2009, 07:18 PM
Post #8


Senior Member
****

Group: Moderator
Posts: 6828
Joined: 8-December 05
From: Los Angeles
Member No.: 602



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!


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
SteveM
post Sep 3 2009, 03:15 AM
Post #9


Member
***

Group: Members
Posts: 236
Joined: 5-February 06
Member No.: 675



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
Go to the top of the page
 
+Quote Post
Guest_PhilCo126_*
post Oct 27 2009, 07:24 PM
Post #10





Guests






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
Go to the top of the page
 
+Quote Post
dtolman
post Nov 12 2009, 04:54 PM
Post #11


Junior Member
**

Group: Members
Posts: 58
Joined: 20-April 05
Member No.: 291



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.
Go to the top of the page
 
+Quote Post
Greg Hullender
post Nov 12 2009, 09:54 PM
Post #12


Senior Member
****

Group: Members
Posts: 1009
Joined: 29-November 05
From: Seattle, WA, USA
Member No.: 590



QUOTE (dtolman @ Nov 12 2009, 08:54 AM) *
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
Go to the top of the page
 
+Quote Post
ngunn
post Nov 12 2009, 10:26 PM
Post #13


Senior Member
****

Group: Members
Posts: 3064
Joined: 4-November 05
From: North Wales
Member No.: 542



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.
Go to the top of the page
 
+Quote Post
nprev
post Nov 12 2009, 10:31 PM
Post #14


Senior Member
****

Group: Moderator
Posts: 6828
Joined: 8-December 05
From: Los Angeles
Member No.: 602



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.


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
Greg Hullender
post Nov 13 2009, 04:21 AM
Post #15


Senior Member
****

Group: Members
Posts: 1009
Joined: 29-November 05
From: Seattle, WA, USA
Member No.: 590



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
Go to the top of the page
 
+Quote Post

9 Pages V   1 2 3 > » 
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 16th April 2014 - 10:19 AM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is a project of the Planetary Society and is funded by donations from visitors and members. Help keep this forum up and running by contributing here.