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."

Comments

Re:SuperAccurate

[Anonymous Coward]

The correct term would be inaccuracy. Calling it accuracy is misleading, but very common.

Re:Another Job well Done

[whathappenedtomonday]

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.

Re:L2?

[Morphine007]

Wiki Entry for Lagrange Point

Re:L2?

[Ornedan]

Lagrange point. Location where the gravitic pulls of some objects cancel each other out. In this case, it's Earth and Moon.

Blame rgarbacz

[mangu]

It seems like the summary writer didn't understand TFA. Quoting from ESA:

Planck is designed to 'see' the microwaves and, in practice, it will detect them by measuring temperature. That temperature is already known to be about 2.7K (which is very cold, about 270C, near absolute zero). It has been measured to be 2.726K all over the sky to three decimal figures. This degree of accuracy in the measurement may seem good enough, but much more precise measurements are needed.

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:Another Job well Done

[imsabbel]

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

[whathappenedtomonday]

"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.

Re:Another Job well Done

[m50d]

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?

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.