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Infrared Telescope Lifts Off
An anonymous reader writes "On its Delta 2 Heavy-Lift vehicle, the Space Infrared Telescope (SIRTF) successfully launched to its solar orbit at 1:35 AM (EDT). As a result of the expansion of the Universe, most of the optical and ultraviolet radiation emitted from stars, galaxies, and quasars since the beginning of time now lies in the infrared. How and when the first objects in the Universe formed will be learned in large part from this observatory's infrared observations."
I work at Ball Aerospace... I thought some of you might like to see the BATC stuff.
Umm, d00d, I think you're supposed to understand that light was in those ranges when it was created, but redshift due to the expansion of space and the massive distances this light has travelled have resulted in it shifting down-spectrum into the infrared.
Well, I suppose you know about the red shift due to the general expansion of the universe? The most distant objects in the universe are now receeding away from us at such a massive rate that the visible light they emitted has been so far red shifted as to wind up in the infrared region. There's a Doppler effect for light that causes light from an object moving very quickly away from an observer to reach the observer at a lower frequency than what was transmitted (the red shift), just like a car moving away from you makes sounds at a lower pitch than were it standing still or moving towards you. Because of Hubble's law, the farther away an object is, the faster it's moving away from us, and consequently, the greater the Doppler effect. This infrared probe is designed to view objects that have been so far "red shifted" as to apparently be emitting infrared radiation.
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
Of course, I'm talking about more conventional cryostats. The laser cooling methods that the poster referred to are only relevant for gas phase atoms.
Instead, the telescope launched with 360 liters of liquid helium. It will last 5 years. When the helium is gone, the mission is done. You can read about it here:
Actually, it can get pretty damn hot with the Sun up there. If the satellite were out of the solar system, then it is true that cooling wouldn't be much of an issue. But, with the Sun right next door (astronomically speaking), it's very important that you have good cooling. In fact, this will only be a 2 year mission, due to the fact that the cooling system (liquid helium, I believe) will only last for that long. . .
I couldn't tell if you were experimenting with poor-man's cryogenics or looking for the orange sherbet.
Space is not cold enough to cool down the elements surrounding the camera so that they are essentially "invisible" to it. If you need evidence, take a look at what happened when the cooling on Hubble's IR cam (NICMOS) ran out prematurely. NICMOS was completely useless until it was serviced rather recently, because it was constantly saturated by the infrared light emitted from the surrounding instrumentation.
I'm no physicist, so I may not have the terms right in my explanation, but you definetely need cooling for IR cams in space. NICMOS will prove it to you.
...the beauty of digital cameras is that you don't have to do the exposure all at once. You could pause, re-aim the telescope then begin again.
Actually, the real beauty of digital cameras is that you can do several images slightly offset from each other and drizzle the light around to get a larger image at a higher. That's how Hubble's big images are done.
Dunno if they're going to do this with SIRTF, though.
Exit, pursued by a bear.
Here are some links to other projects that have similar goals - examining expansion of the universe, faraway objects, etc. They also have sophisticated infrared imaging capabilities. The James Webb Space Telescope (formerly Next Generation Space Telescope) is the successor to Hubble, and Supernova/Acceleration Probe which, from what I remember, locates potential supernovae by examining data taken at fixed ground locations then points an orbiting camera at the calculated location to collect radiation data. Really interesting stuff!
FYI: The longest HST single HST observation I found was a GHRS spectrum at 230,414 seconds. The longest NICMOS (infrared) exposure was 3839 seconds. It's rare to do a single long exposure. Most of the time, exposures are split and stacked, usually to clean out the cosmic rays.
Exit, pursued by a bear.
- "Thick" Java Client for proposals, planning and data retieval - yes folks, Java on the desktop does work
- Estimating and visibility servers - many computing drone managed by a J2EE server
- Web services access to all of the public data produced by SIRTF - Perl,
.NET, C++ is doesn't matter you can all get the data
Oh, I forgot the mention.... there is not a single Windows box in the operations system. It's all Unix based because... well you know why don't you?Using a simple pumped He3 system, which we just set up in our lab last week, you can easily reach about 300 mK. You use a pumped He4 bath to surround your insert, keeping it at about 1.5 K, and then pump the He3 with a charcoal sorb, to get to 300 mK. In space, you can use blackbody radiation to cool you to the ambient temperature of space (I forget whwat it is, somewhere between 3 to 7 K), and then use He3 pumping to go colder.
You can also get to about 10 mK if you use a dilution regridgerator, which uses a mix of He3 and He4 and relies on changes of entropy as you add them together, and then separate them out.
However, this all assumes that the highest CCD's need to actually go this low. But if for some reason this is needed, these refridgeration techniques are much more efficient and easier than laser cooling. Laser cooling is when you need to go COLD, like microKelvins.
make world, not war
I worked on this program, and actually, there are many many pains taken to extend this mission. There is a very good chance that the mission will last way longer than 2 years.
You'd be amazed at the meetings debating kinds of black paint.... A lot of tiny details were sweated to optimize this lifetime. Electronics that do the data compression and spacecraft control are all situated way far away from the detectors/dewar so that the heat put off by the electronics will have less warming effect on the dewar.
Anyway, SIRTF is in an earth following orbit, looking AWAY from the sun. By using some clever inter-planetary shielding and controlling the directions that observations are made, they will maximize the lifespan of the cryogen
Indeed. The Hubble Deep Field images were assembled in exactly this way.
By the way, the parent post is modded Funny. Why is that?
~Idarubicin
SCUBA (Submillimeter Common-User Bolometer Array) on JCMT maintains a temperature of about 60mK using a liquid helium dilution refrigerator. It is probably the continuously coldest place that we know of in the universe, since it maintains 60mK for weeks on end.
So no, you don't need laser cooling techniques to get down to these low temperatures for astronomical detectors.