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NASA WISE Telescope Starts Taking Pics
coondoggie writes "NASA said its Wide-field Infrared Survey Explorer spacecraft successfully popped the cover off its infrared telescope and began 'celestial treasure hunt' mission of sending back what will be millions of images of space. The WISE lens cap served as a safety system keeping the ultra-sensitive lens and telescope system safe until the spacecraft positioned itself correctly in orbit. The cap also served as the top to a 'bottle' that chille the instrument and detectors. This cryostat is a Thermos-like tank of solid hydrogen."
I understand that WISE is particularly well suited for finding asteroids (its an infra-red telescope so can pick up warm objects and its a survey scope). If this telescope finds an asteroid with our name on it with enough time to do something about it, it will make all the money spent on the space program by all the countries of the world seem like spare change.
(I wonder if this is first post. If so, it'll be my first.).
Thermos like. Or, if you don't want to step on anyone's trademarks, a Vacuum Flask. You can even see a picture of WISE's cyrostat at Wikipedia
Uuum, first of all: Why would you not be sure that they really need it? Do you think they sent it up there just for fun??
From what I know, 4K is way too hot / above the wanted temperature. Which is closer to 0.5K (dunno the exact temperature, but it’s a quick search).
Any sufficiently advanced intelligence is indistinguishable from stupidity.
Yes, they do need the hydrogen to keep things chilly. The vacuum is a nice insulator, but can't prevent all the heat from all that sunshine hitting the satellite (and other sources) heating things up- including those very, very sensitive detectors. Noise from heat is the enemy, which is why they've gone through so much trouble to keep the detectors cold and safe in a covered 'Thermos' until ready to serve.
The hydrogen is a nice heat sink in addition to the natural vacuum flask provided by Space, and is allowed to slowly boil off, carrying away what heat that makes it through. It's also why there's a definite time limit on the main part of the mission and effective lifetime; once they hydrogen is gone, the detectors begin to heat up, heat noise ruining all that lovely sensitivity.
I suspect that they'll continue to get some results after the liquid hydrogen is gone but, much like similar previous missions, the "warm" part of the mission will not achieve anywhere near the same results as the first "cold" portion.
Space, being a vacuum, does not dissipate heat all that well.
The operating temperatures will be 30–34K for the 3.3 & 4.7 m detectors, 7.8 ± 0.5K for the 12 & 23m detectors and 17K for the optical system, which are achieved using a two stage solid hydrogen cryostat providing a minimum mission lifetime of 7 months allowing for a single full coverage of the entire sky.
Update on The Wide-Field Infrared Survey Explorer (WISE).
and surely the hydrogen will now boil off?
Exactly what they want. As the hydrogen melts and boils off, it removes heat which keeps noise down and image quality up. When the hydrogen finally boils off, it'll greatly reduce the value of the telescope since the internal components will heat up. That's probably when they'll end the mission.
TFA specifies that the hydrogen will run out about ten months into the mission (including a month for systems check-out).
Allegedly real newspaper headline from 1998:
Man Struck by Lightning Faces Battery Charge
in a covered 'Thermos' until ready to serve.
Am I the only one to notice that a Thermos Bottle (aka Dewar flask) insulated with solid hydrogen isn't, by definition, a Thermos Bottle, since a Thermos Bottle requires a vacuum and solid hydrogen isn't?
"I don't know, therefore Aliens" Wafflebox1
Doubtful. One thing you can be pretty sure of is that a mission that uses cryogenic expendables won't last much longer than planned. The tanks are built to a certain size and filled to brimming; working out how long that'll last is fairly straightforward. You might get perhaps 50% longer than calculated if you're very lucky (more likely you'll get less), but no way will it last five times longer.
As an example, the Spitzer Space Telescope was planned for 5 years before the cryogens ran out: it lasted roughly 6.3 years.
Kepler and Corot are the missions which have been launched and will be searching for exoplanets over the next few years. WISE and Herschel are the missions that have been launched, which are not targeted at exoplanets, but instead in the IR region. WISE tends to be focused as a total sky survey mission in the near-IR while Herschel is focused more on the mid-far IR at more specific targets.
Combined they potentially give use the ability to begin the search for Matrioshka Brains. IMO, one of the primary problems with astronomy and astrophysics is that the physicists (and most physics based research activities) start with the assumption that the "Universe is dead". But what if thats not true? What if it is in fact quite "alive"? This makes things horribly more complex for the physicists and astronomers because "life", esp. advanced intelligent life, can stretch the boundaries of what is determined by the laws of physics. Even more difficult -- for a complete "Theory of Everything" it probably means the physicists and astronomers are going to have to enter into serious discussions with the biologists and sociologists (to determine the characteristics that advanced civilizations might possess.
The Kepler and Corot missions, because they are focused on stellar photometry (brightness) can detect transients of other objects in front of stars. So they may be able to provide some limits on the abundance of various "dark objects" orbiting between our solar system and those stars (the planet searches are obviously looking for repeats, but the data, once public could be scanned for transient occultations (i.e. one time apparent occultations which indicate something between us and the star, be it a nearby asteroid or a more distant Matrioshka Brain). Freeman Dyson has suggested that the study of stellar occultations would be useful (presumably recognizing that not every stellar occultation indicates a planet around the star -- some might represent intervening objects transiting across the field of view. Know the size of the object being viewed, and one can set limits on sizes/distances of what is being viewed). (And Jupiter Brains or Matrioshka Brains clearly fall outside of the realm of classical (read acceptable to the "realm of comfortability" of most astrophysicists). [I have been to several conferences of gravitational microlensing astronomers -- this statement is made on the basis of direct experience -- they think in terms of hard data and they will only reluctantly acknowledge ideas which conflict with those in which they have been trained).
Now the WISE and Herschel missions are more interesting from the perspective that they begin to allow us to ask the fundamental question of "What is the rate at which Stars go dark?", i.e. what is the rate at which civilizations migrate from a pre-Kardashev type I level civilization (where we are now) to a Kardashev type II level civilzation (which does not require but is significantly enabled by the development of mature molecular nanotechnology [in the robust Drexler/Merkle/Freitas framework]. So the possible development rate could be measured in anything from months (which is feasible within our solar system, to decades, to centuries (solar system development has varying degrees of "difficulty")). And one measures that rate at that which a solar system goes "dark", with a slow conversion of visible light radiation (an undeveloped star) into an IR star (that being intelligently harvested) (i.e. the star effectively goes "dark"). We are just posed on this transition point ourselves, so it is not unworthy of study or discussion. Perhaps most importantly, the currently launched missions enable the setting of limits on the abundance of Advanced Extraterrestrial Civilizations. And it is useful to