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Successful Launch of ESA's Herschel and Planck
rgarbacz writes "Today at 13:12 GMT, the ESA launched successfully new and long-awaiting spacecraft: Herschel, the infrared telescope with a 3.5m mirror, and Planck, the CMB mapper. The spacecraft were carried by the Ariane-5, which lifted off from Kourou in French Guiana. They will stay in L2 to perform the research. This launch is one of the most expensive and important missions of the European Space Agency. Planck will measure the CMB with an accuracy more than 10 times better than the previous mission, WMAP. Because of this high sensitivity, both spacecraft are cooled to temperatures close to absolute zero by on-board liquid helium; staying in L2 is very helpful to maintain this state. Both spacecraft are designed to observe the Universe at its infancy: Herschel by observing the first stars and galaxies (whichever came first), and Planck by scrutinizing the first photons that were set free, making up the cosmic microwave background radiation."
even if it is ten times more accurate than before, I think we have a long way to go.
Planck will measure CMB with accuracy below 1%
Uhm. Is this technical terminology that I simply don't understand, or just a typo? Because I can understand a '1% margin of error', and I can sort of understand 'accurate to 1%'... but something which is below 1% accurate?
If only I could get away with that in my job.
Herschel is supposed to complete its mission in three years, Planck in only 15 months. After the helium supplies have evaporated, their missions end. They won't be repaired / serviced, because they are too far away to be easily reached with a shuttle. That's what local news here say.
I hope I didn't brain my damage.
Wiki Entry for Lagrange Point
Oh god, that woman is John Romero!
Lagrange point. Location where the gravitic pulls of some objects cancel each other out. In this case, it's Earth and Moon.
Lagrange point 2, one of the 5 locations in space around an orbiting body where the gravity wells from the major surrounding bodies cancel each other out, providing a sort of "still point" in space.
http://en.wikipedia.org/wiki/Lagrange_point
Ah how, how, how, how....
It seems like the summary writer didn't understand TFA. Quoting from ESA:
The older measurements that Planck is trying to improve already are accurate to 0.1%.
It seems like someone got confused with the coincidence that the temperature of the universe, 2.7 K, is about 1% of the temperature of freezing water, 270 K.
First emotion: Wow! Far out: L2 is 1.5 million km from Earth beyond the orbit of the moon ( so no space shuttle service missions here... ). But before I looked it up I had completely forgotten that Mars is at best still another 53 million km and then imagining the billions of lightyears Herschel will be able to "see"... I have to buy another ticket for "Star Trek" to lose this image of an invisibly tiny blue spec in a black void in my head...
It's really awesome this thing launched succesfully. My professor of astronomy and his department worked ten years on Herschel. I'm really happy for him.
I hope the sattelite gives us a lot of useful information or at least some beautiful pictures
As long as there are slaughterhouses, there will be battlefields.
Well, that's because the space is too hot.
Even without the sun.
They are trying to measure the CMB. If you are not colder than outer space, most of the radiation would just come from the telescope itself...
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
Plural of "spacecraft" is "spacecraft".
But the plural should be spacecreft!
Spacecruft?
As maintainer of RTEMS, I am very proud that both spacecraft are running our free real-time operating system on at least the Spacecraft Management Unit (SMU). These are both important missions which promise to provide us with new insights.
"In order to study the coolest places in the Universe the Herschel instruments must be cooled to just above absolute zero. A large cryostat surrounds the instruments maintaining an operational temperature of 1.7 K for a nominal mission lifetime of 4 years." ESA has some great info on their site.
I hope I didn't brain my damage.
Because what they're trying to measure is, in some senses, the temperature of space itself - the ~3K CMB. So they need the detector to be colder than that.
Isn't there some way to use one or more of the three forms of heat transfer to keep the instruments cold enough to work without having to rely on a limited source of helium?
No. The radiative coolers (can't really use conduction or convection in space) will keep the craft cold enough for the low frequency instrument to work, even after the helium* runs out, but to get the 0.1K that the high frequency instrument needs, there's no (good) alternative to this active cooler.
* Well, not after the helium in its own refrigerators runs out. But it's not actively venting that, so we only have leakage to worry about there.
I am trolling
I realize we, as in all space agencies, use helium or something else to keep these instruments cold, but why can't we use the coldness of space to do the same thing?
Space isn't really "cold", or rather, the terms "cold" and "hot" lose much of their meaning when you're talking about incredibly low densities like you have in space.
If you have an atmosphere then you transfer heat by radiation and conduction. You can cool your instruments by putting them in the shade (so they don't get the radiated energy from the sun) and ensuring the atmosphere is cool so that it will conduct the heat away. The atmosphere on Earth is actually not a great conductor, but because it is a fluid you can keep the air moving so that as soon as some of the heat has been conducted to the surrounding air you move that (warmer) aid out of the way and replace it with cool air - this can be done naturally by convection or by forcing the air to move with a fan.
In space you have practically no atmosphere, so the heat transfer is almost entirely by radiation - your instruments are essentially in a giant vacuum flask. Your satellite needs to reflect away the energy radiated by the sun, and the cosmic microwave background radiation, etc. and also radiate away its own heat (remember, these satellites contain lots of electronics and like all electronics they will generate heat). This is a pretty tall order - surfaces that radiate well are also really good at absorbing energy. - I imagine it's much cheaper and lighter to send up a load of liquid helium and dissipate the heat by letting it boil away.
http://blog.nexusuk.org
Space radiates. If we were to put a black body in space at absolute zero, after a while it would be about 2.7 Kelvin. This is because of the cosmic microwave background (which is what they're trying to measure here).
If you have a distractor (radiation from the craft itself) as big as the thing you're trying to measure, you won't get good results.
To put it another way- heat is full of microwaves (the same as are in your kitchen appliance) which heats up everything in space to a certain point (2.7 Kelvin, if it's a black something). If you simply rely on "the coldness of space" to cool you down, that's as cool as you're going to get.
That's still EXTREMELY cold, but for this particular mission it's not cold enough. This mission is to measure said background radiation, meaning that in order to do it's job it must be colder than that extremely low temperature that is "the coldness of space".
Actually, it's the Earth and the Sun. It's on the Earth-Sun line, behind the earth (from the sun's point of view), and orbits the sun once a year. They put it here because it's easier to shield the satellite from both the Sun and Earth.
The L2 point for the Earth-Moon system is on the Earth-Moon line, behind the moon, and orbits the earth once evry 29.5 days.
HCG 50a = 2MASX J11170638+5455016
11h17m06.4s +54d55m02s
There is a huge technical problem that many of the above posters have ignored. To use "space" as a heat sink requires you to conduct that head to space. However, space is very close to vacuum and thus it is near impossible to conduct heat away. The other option is to radiate heat away this requires that you have something which is very efficient at radiating in the peak frequency for the nominal temperature of the radiator. To make a long story short you cannot use radiative cooling to cool something to near zero in space because you are being bathed by 2.7k blackbody radiation.