Isn't space cold, near absolute zero.. so why do they need to cool it.. shouldn't they be heating it?

'The cryostat will be filled with super-fluid helium, which clocks in at just two degrees above absolute zero. There is a further cooling stage in the focal plane units, ESA says, which keeps the instruments at just a third of a degree above absolute zero.'

imagine what an overclocker could with that sort of cooling

With the Ariane 5's track record they could take the opportunity to build diplomatic bridges with the US by pulling the launch forward a tad to July the 4th.

TeeCee

Space, although mighty chilly, isn't at absolute zero, especially in this bit near the sun. On average, interstellar space is around 3K, and IIRC where Herschel is going to sit is around 6-8K.

You could say space was at absolute zero - indeed an object sitting in the shade in space would be approaching that temperature. However, space is also very hot. Because there is no matter in space at all, the only way to vent heat is via radiation - on earth we can use air cooling to lose heat. An object in direct sunlight in space can reach hundreds of degrees very quickly.

There is two reasons that the telescope has to be at 0K. The first will be heat generation - digital sensors turned on for the long periods of time that these will be heat up, and heat means noise. By keeping them cooled near 0K, any heat generation can easily be taken away from the sensors and electronics.

The second issue is not dependant on the temperature that the optics etc are at - they could probably be at any temperature between 0K and 300K - but that, if left alone and unprotected, they would cycle between almost 0K and hundreds of K regularily. The heating and cooling would destroy any glass or electronics very, very quickly. By keeping everything at absolute zero, there is no heat cycle.

I don't know if I've covered all the reasons, and without a source and more information I may be wrong on some points, but there is certainly a lot of factors that have to be considered in space cooling that are just not issues on earth - with limited supplies of gas etc, you can't simply energise particles and vent them, and there is nothing to exchange heat with.

Darn .. beat me to it ..

If you can keep the environment that cool .. and shift the heat from the chip efficiently enough .. what then is the limit that the chip will work at ..?

When in the shade space is very cold, but without an atmosphere to protect from the sun it can get boiling hot too! And remember they're trying to measure infra-red radiation, i.e. heat coming from very very far away, so they need their apparatus as cold as possible.

Space is cold, but only about 2.7K (remains of the big bang, we think) and you have to consider the heat from the Sun on some of the craft, and the heat needed for the electronics around the sensor to work. So it seems odd, but sticking a cooler in there is needed, particularly if you want lower temps than the areas of space you are looking at.

Space, if it has a temperature would be at the 4K of the microwave background. Perhaps more to the point is that the instrumentation must be constantly chilled to ward off the experiment-ruining heating of the sunshine the observatory must bathe in to generate power.

What about when the sun shines on it? I think you will find that there are extremes of temperature to worry about....

I think you'll find that radiation from that big, hot sun at the heart of our solar system does a very good job of heating things up.

kill themselves or destroy expensive pc/parts?

Big thing out there called the sun. The suns rays will be hitting the poor little telescope without the protection of the atmosphere, This leads to massive changes in temperature, hence the need for cooling. As a whole (as in the whole universe) its near absolute zero, but then the universe is a pretty big place.

-- Isn't space cold, near absolute zero..

Temperature doesn't work the way you think it does.

Space is near vacuum, and thus is a really lousy conductor with very low specific heat. In such media, temperature is probably better thought of in terms of particle velocity distribution rather than thermodynamic temperature and enery transfer is dominated by radiation, not by kinetic interaction with massive particles. However, if one must be reduce things to a number, it's actually quite hot where the spacecraft will operate - certainly a lot hotter than the 300 mK mentioned in the article.

-- imagine what an overclocker could with that sort of cooling

Conventional CMOS doesn't function properly below ~220 K.

How does that work then ... ? 'Shall we scan HIC 91262 and look for signs of gravitational effects on the outerlying stars or .... or maybe just have a smoke, glass of wine and slip on some jamiroquai ...'

Having messed about with the IR telescope on the roof of the Physics building at Queen Mary College in the Mile End Road a few years ago during my degree I can tell you that the IR detectors must be cold to work. We used liquid nitrogen then, but the telescope we were using wasn't all that sensitive.

When you have to do the BBC thing and predict news instead.

However, The temperature of space is peculiar. Some parts are allegedly 100 million degrees, if some boffins are to believed. Which they shouldn't, of course, as they've doubtless forgotten about synchrotron radiation.

"You could say space was at absolute zero"

No you can't. It's at least 3K. That is the temperature of the CMB in intergalactic space; the temperature is higher within a galaxy, and even more so within a solar system.

Which is where this probe is designed to be and operate from.

" there is no matter in space at all, "

No matter in space at all? I hardly consider four hydrogen atoms per cubic metre to be "no matter ... at all", and that's the intergalactic medium; within a galaxy you can expect quite a bit more. In fact, just to be pedantic, all the matter in the universe is "in space" ...

... none of it being anywhere else, after all! :-)

The sun wont shine on it, it is to be placed in the earths shadow at Lagrange point 2, see http://en.wikipedia.org/wiki/Lagrange_point#L2

would it be better to simply place the satelite in the shade of the earth permanently to better safeguard its safety and accuracy?

Simple explanation: it’s detecting infrared radiation. If the detector and the parts around it were not cooled to near absolute zero, they would be emitting infrared radiation themselves. This would lower the sensitivity and mess up the results.

They could indeed site the telescope at the 2nd Lagrange point, unless it would interfere with the Wilkinson Microwave Anisotropy Probe which is already sited there (how much elbow room is there at L2?). The site is partially shielded from the Sun, lying about 100,000km beyond where the Earth’s umbra peters out