Planck instrument loses its cool

January 17, 2012
Artist's impression of Planck. Credit: Background image: ESA, ESO and STECF. Planck image: ESA/AOES Medialab.

( -- After an impressive two and a half years of operation, Planck's High Frequency Instrument has finally exhausted its onboard coolant gases and reached the end of its very successful mission. Meanwhile the Low Frequency Instrument, which does not need to be super-cold, will continue taking data with unprecedented sensitivity at longer wavelengths.

Planck’s primary mission is to observe the Cosmic Microwave Background – the afterglow of the Big Bang. Despite an original mission lifetime of a year, the spacecraft has continued working for almost three years, and has mapped the sky nearly five times. The expansion of the Universe means that the Cosmic Microwave Background is brightest when seen in microwave light, with wavelengths between 100 and 10,000 times longer than visible light. To measure such long wavelengths Planck’s detectors have to be cooled to very low temperatures, with the heart of the High Frequency Instrument (HFI) being the coldest place in space.

Professor George Efstathiou, at University of Cambridge and the Planck Survey Scientist, said “Planck is giving us the best ever view of the , and while the High Frequency Instrument is coming to the end of its mission we have a wealth of data to analyse over the coming months and years.” Although Planck is an international project, led by the European Space Agency, there is strong involvement from scientists in the UK. Scientists at University of Cambridge, Imperial College, University of Manchester and Cardiff University have been involved in the design, construction and operation of Planck and its instruments for over a decade, and are now heavily involved in analysis of the data. In addition, one of three refrigeration systems was designed and built at the Science and Technology Facilities Council’s Rutherford Appleton Laboratory near Harwell, Oxfordshire.

The detectors of the Instrument (HFI) only work properly when cooled to very low temperatures, and for the duration of the mission have been cooled to 0.1 degrees above absolute zero (-273.15 Celsius) – making them the coldest known place in space! The refrigerator that keeps them cold relies on helium gas, and it is this that has finally been exhausted.

Planck satellite. Credit: ESA.

Cardiff University researchers, led by Professor Peter Ade, have been heavily involved in the design, build, testing and operation of HFI for over ten years. “We put as much Helium-4 and Helium-3 gas onboard as we could squeeze in and are therefore delighted that the HFI has operated for almost three times its nominal mission lifetime”, explained Professor Ade. “This is a testimony to the expertise of the scientific and technical teams who designed, built and operated Planck and its scientific instruments.” With the loss of cooling gases the detectors will gradually warm rendering them unusable for scientific purposes. Following a salvo of final tests the HFI instrument will be switched off, although it will remain at a chilly 269 Celsius providing a reference source for the LFI which will continue to operating for at least another year.

Planck’s second instrument, the Low Frequency Instrument (LFI), does not need to be as cold, though is still at a nippy -255 Celsius. Astronomers from Jodrell Band Centre for Astrophysics, at the University of Manchester, have played a key role in LFI. “The Low Frequency Instrument will now continue operating for another year”, said Richard Davis, of the University of Manchester. “During that time it will provide unprecedented sensitivity at the lower frequencies.” It is the combination of both instruments that makes Planck so powerful, and gives cosmologists the best ever view of the Universe on the largest scales.

First light survey superposed on an all-sky map. Credit: ESA, LFI & HFI Consortia (Planck), Background image: Axel Mellinger.

The scientists involved in Planck have been busy understanding and analysing the data since Planck launched in May 2009, with UK efforts being led by the Cambridge Planck Analysis Centre, based at the University of Cambridge. "The fact that Planck has worked so perfectly means that we have an incredible amount of data," explained Prof Efstathiou. "Analysing it takes very high-performance computers, sophisticated software, and several years of careful study to ensure that the results are correct. In fact, the preparation for this work started years before Planck was even launched". Detailed information about the early Universe is now being extracted from the Planck data, with the first cosmology results expected in early 2013.

Professor Andrew Jaffe, from Imperial College London, is also involved in the analysis through the London Planck Analysis Centre, and said “In the last two and a half years, Planck has collected incredible data directly from the early Universe which we are currently decoding. We are honoured to have the chance to continue to work with members of the Planck team, in the UK and abroad, and to use Planck’s data to understand the Universe on the very largest scales.”

One of the major tasks is identifying which bits of the map are showing light from the early Universe, and which parts are due to much closer objects, such as gas and dust in our galaxy, or light from other galaxies. While the cosmologists consider these “foreground” objects to be an annoyance that need to be removed for some astronomers they are already providing major astronomical results.

“A side effect of studying the distant Universe is that you get to see everything in the foreground,” said Dr. Clive Dickinson, from the University of Manchester. “The wavelengths Planck observes make it ideal for studying star formation, both in our own galaxy and in others, and having such detailed maps of the entire sky at such a wide range of wavelengths provides a treasure trove of information.” Astronomers have been pouring over the data and have already confirmed the existence of two additional components of the interstellar medium – the gas and dust from which stars form. There are more results on these foregrounds expected to be released during 2012.

“It has been a privilege to be part of the Planck team”, concluded Prof Efstathiou. “The satellite has performed flawlessly since launch and has returned data of exceptional quality. I am sure that we will soon have exciting science results on the early Universe.”

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5 / 5 (1) Jan 17, 2012
Have to wonder just how cold is space that they had to cool the instrument lower than the normal temperature of space.
5 / 5 (5) Jan 17, 2012
AFAIK the average temperature of space is about 3K.
5 / 5 (3) Jan 17, 2012
In the solar system the "average temperature" is a little above 3K because of solar radiation reflected from dust. The only place you'd find below 3K, even in theory, is the interior of some cold, dense gas/dust clouds, and I don't know whether we have any way of directly measuring that. Open interstellar space is very close to 3K, and can't be lower than the cosmic microwave background temperature.
1 / 5 (12) Jan 17, 2012
We put as much ... ... onboard as we could squeeze in...

This is a short come of design. Endless cooling is optimal.
The retrieval of the object was given zero thought too.
One year operational life spans are unacceptable.
No retrieval is unacceptable.
Uncontrolled reentry is unacceptable.
The ratio of unacceptable to acceptable conditions is 10:1.
And you will heard nothing but pride from any space
4.6 / 5 (11) Jan 18, 2012
I don't see you as being the Poo Bah of what is acceptable.

It is a need of budget. Would you care to triple the budget next time?

Your position on this is unacceptable.

1.7 / 5 (3) Jan 18, 2012
the observed lifetime of this instrument, when compared to the calculated age of the Universe, is, well - Planckian in dimension... Funny, eh?
5 / 5 (9) Jan 18, 2012
This is a short come of design. Endless cooling is optimal.
The retrieval of the object was given zero thought too.
One year operational life spans are unacceptable.
No retrieval is unacceptable.
Uncontrolled reentry is unacceptable.

C'mon hush.
- If retrieval and refilling is more costly than building a new one it's perfectly acceptable. this thing is in high elliptic orbit and we have no way to service anything there.
The telescope cost 600 million Euros. A shuttle launch costs 450 million dollars on average (and we don't have a shuttle anymore) - and that would get you only to low earth orbit, too.

- A lifespan sufficient for the mission is acceptable (in this case the mission was more than fulfilled. They did 5 surveys instead of the two in the design specs)

- Uncontrolled reentry is perfectly acceptable if it contains no parts that will survive the fall.

The ratio of unacceptable to acceptable conditions is 10:1.

Your ratio or nutcase to rationality is 10:1
1 / 5 (10) Jan 18, 2012
I care to grant no further space exploration until all space debris is removed. Anyone who can afford to make junk, can afford to remove the junk as well.

Hold any nation hostage to a unaffordable budget that can not afford to remove their space garbage.

My position on this will save lives. Your position places nauts (is there one letter too many in this word?) during space travel at the stake of garbage, budget and your attitude.

C1, insignificance as measured with time is not a measure for human endeavor, existence, value, or loss.

The need of budget is the measure of all things.
A Universe and all it's attributes are insignificant compared to a need of budget. This is Ethelred's lesson to be learned.
All else is unacceptable...yes, that funny.

5 / 5 (10) Jan 18, 2012
I care to grant no further space exploration until all space debris is removed.

Good thing then, that no one listens to your opinion on this.

Hold any nation hostage to a unaffordable budget that can not afford to remove their space garbage.

And WHO would (or could) do that?

I agree that space debris is not a good idea, and that we should refrain from gratuitously creating any. But that's as far as it goes. The new space code of conduct will go some way to realize this (and other) goals.
It waits to be seen whether anyone will feel compelled to stick to it. Currently space debris is only a threat to stuff that is in orbit - not anyone on the ground.

Space debris is there (to stay) fo some time. When we have the technology to go into space cheap then we can think about cleannig up. Right now going there at all is what we can do. Let's worry about niceties when we have the leisure to do so.

1 / 5 (7) Jan 18, 2012
'Niceties' The nuclear industry garbage.
You can't even do on the ground what is nice.
I expect extinction from your attitude.

And WHO would (or could) do that?

Always the person that poses the question.
1 / 5 (6) Jan 19, 2012
There are 20,000 satellites in orbit. Four percent are operational.
The greatest and next maximum CME will take out the remaining 4%.
So what satellite can withstand any amount of CME? None.
Not a single satellite builder has anything against this except excuses and prophylactics.

Thanks. For the mess and 'niceties' you provided our generation. As payback we will provide you the leisure you failed to implement.
4.5 / 5 (8) Jan 20, 2012
Somebody has issues that aren't based in reality.

1 / 5 (6) Jan 20, 2012
Somebody is in denial.
4.4 / 5 (7) Jan 21, 2012
Yes. Someone is denying the facts of the damage rate caused by satellites.

The greatest and next maximum CME will take out the remaining 4%.
Sorry, but I thought it was Hennis Dove that is from the future and should know when the next AND greatest Coronal Mass Ejection will be.

Do you use tarot cards, a ouji board, or is that you have a secret Sundiver Project. We have had satellites up for over fifty years now. That is more than two full Solar cycles. And YOU have secret information that the NEXT CME will be greatest.

Its gotta be a sundiver. Do you use David Brin's X-ray refrigeration laser idea? How much is the royalty on that kind of thing anyway?

not rated yet Jan 22, 2012
:::Currently space debris is only a threat to stuff that is in orbit - not anyone on the ground.:::

Actually, that is no longer true, the older larger space trash is starting to come down, the COPV's in particular are very good at surviving reentry, only a matter of time before somebody gets hit.

1 / 5 (1) Jan 22, 2012
"No retrieval is unacceptable." - Yahoodie

Well, there was the shuttle, but America is bankrupt and can't afford to build a replacement.

Besides, they have been busy building the white elephant space station which has proven itself to be useless.

It's the American way.

not rated yet Jan 22, 2012
This seems odd, as I have just read an article about the shutting down of another HEATER on the Voyager spacecraft, thus causing the instrument to operate at -38 degrees Celcius. While the average temps in space might be 3K, it's sure as hell not uniform. Perhaps in Earth orbit being constantly exposed to the sun cooks the spacecraft pretty good, but far away from it things are pretty damn cold.
5 / 5 (3) Jan 23, 2012
This seems odd, as I have just read an article about the shutting down of another HEATER on the Voyager spacecraft, thus causing the instrument to operate at -38 degrees Celcius.

The Voyagers have a nuclear power source which keep them somewhat cozy.
It's hard to get rid of heat in space (there's no convection, just radiation losses)

Planck did surveys of the CMB with a resolution down to a millionth of a degree. for that you need ultra-stable cooling of your sensors or the readings will be off.
The instruments were cooled down to a temperature of a tenth of a degree above absolute zero (i.e. much lower than the background temp of space). You need to get colder than space because otherwise you never know if that photon you just captured is from the CMB or just produced by your own instruments.

Obviously such cooling takes coolant/power...and eventually that runs out.

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