Successful Launch of ESA's Herschel and Planck 121
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."
Re:SuperAccurate (Score:4, Informative)
The correct term would be inaccuracy. Calling it accuracy is misleading, but very common.
L2? (Score:3, Informative)
FFS (Score:1, Informative)
Plural of "spacecraft" is "spacecraft".
English, do you speak it?
Re:Another Job well Done (Score:5, Informative)
Re:L2? (Score:5, Informative)
Re:L2? (Score:5, Informative)
Lagrange point. Location where the gravitic pulls of some objects cancel each other out. In this case, it's Earth and Moon.
Re:L2? (Score:3, Informative)
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....
Blame rgarbacz (Score:5, Informative)
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.
Re:FFS (Score:3, Informative)
"new and long awaiting spacecrafts....both spacecrafts are cooled...Both spacecrafts are designed"
Plural of "spacecraft" is "spacecraft".
English, do you speak it?
Actually Herschel and Planck are _two_ of the most expensive and important missions. But maybe we are being too hard on the author of this piece, who may not have english as his native language.
Indeed, the working language of ESA is something known as "franglais". It sounds like french and has grammar like french, but uses mostly english words. From experience, a communication like the article summary is actually pretty good by ESA standards...
Re:Another Job well Done (Score:1, Informative)
During the launch commentary they mentioned that the scopes are launched with a 3 year supply of helium. I'm pretty sure repair missions to L2 would be pretty impractical.
Re:L2? (Score:3, Informative)
Re:Another Job well Done (Score:5, Informative)
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...
Re:Another Job well Done (Score:5, Informative)
Re:Another Job well Done (Score:4, Informative)
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.
Re:Another Job well Done (Score:4, Informative)
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.
Re:Another Job well Done (Score:3, Informative)
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?
According to this PDF [nationalacademies.org] the Planck mission does not use liquid helium coolant (although Herschel does). Also the upcoming James Webb telescope will not use it.
Re:L2? (Score:1, Informative)
Re:Another Job well Done (Score:4, Informative)
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.
Re:Free Software On Both (Score:1, Informative)
The NASA/GSFC Solar Dynamics Observatory (SDO) also uses RTEMS on some of its support processors. The main processor on SDO runs the closed source VX/Works OS.
Re:L2? (Score:4, Informative)
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.