ESA's Planck Space Telescope takes final look back in time

Posted Oct 25, 2013 by Robert Myles
The European Space Agency (ESA) switched off its Planck space telescope for good at 12:10:27 UT, Thursday. Planck spent over four years peering back in time, studying background radiation from the Big Bang that gave birth to our Universe.
The Cosmic microwave background (CMB) as observed by Planck  is a snapshot of the oldest light in ou...
The Cosmic microwave background (CMB) as observed by Planck, is a snapshot of the oldest light in our Universe, imprinted on the sky when the Universe was just 380 000 years old
ESA / Planck
Launched in 2009, Planck became the ESA’s "time machine," studying the evolution of stars and galaxies from some of the earliest times in the Universe’s history. Planck was able to examine the merest hint of relic radiation — known as the Cosmic Microwave Background (CMB) — and in so doing obtain a picture of the Universe just 380,000 years after the Big Bang. That may sound a long time but current estimates from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) put the age of the Universe at 13.77 billion years. Doing the math, Planck was able to study the Universe when it was a mere infant at less than 0.003 percent of its current age.
As Alvaro Giménez, ESA's Director of Science and Robotic Exploration, put it, “Planck has provided us with more insight into the evolution of the Universe than any mission has before," adding, "Planck's picture of the CMB is the most accurate 'baby photo' of the Universe yet, but the wealth of data still being scrutinised by our cosmologists will provide us with even more details."
Before final instructions for switch-off were sent to Planck by ESA mission controllers at Darmstadt, Germany last Wednesday, back in August 2013, the Planck space telescope had been nudged into a long term stable parking orbit around the Sun. Once Planck’s remaining fuel was used up it was switched off for good.
Planck’s switch-off was tinged with “much sadness” said Steve Foley, the Planck Spacecraft Operations Manager at ESA's European Space Operations Centre, but he also said it was a time for celebration after such “an extraordinarily successful mission."
Enabling Planck to look so far back in time was no easy task. The logistics of such a mission in the freezing cold of deep space meant that Planck’s own instrumentation had to be cooled to close to deep-space temperatures lest heat from on-board instruments blotted out the very faint CMB. This meant devising a cooling system that could maintain Planck’s instruments at just one-tenth of a degree above absolute zero, -273.15°C, the coldest temperature achievable in the Universe.
Liquid helium coolant for Planck’s High Frequency Instrument (HFI) ran out, on schedule, in January 2012, but Planck’s other principal measuring apparatus, its Low Frequency Instrument (LFI), continued to return data right up to Oct. 3, last.
The Planck mission goals were comfortably exceeded. The original intention was for Planck to conduct two complete surveys of the sky during its four-and-a-half year mission. In events, both the HFI and the LFI, in unison, conducted five full-sky sweeps. By the time the longer-life LFI was switched off at the beginning of October, it had completed its eighth survey of the entire sky.
Planck has returned a mountain of returned data for scientists to pore over for years to come, but even the first image from Planck, released early 2013, was revealing. Using the extremely faint signal from the CMB, after eliminating both radiation emissions from our own Milky Way galaxy and all other known galaxies, what remained resulted in an entirely new catalogue of objects, including many never-before-seen galaxy clusters in the most distant corners of our Universe.
The 2013 data meant calculations of the ‘stuff’ that makes up the Universe had to be revised. That "stuff" comprises obvious visible elements like stars, planets and galaxies, but also more tenuous dark matter, a material known to exist but only by dint of it being detected indirectly through the effect it has on gravitational forces. Then there is the theoretical 'makeweight' Universal ingredient — dark energy — a mysterious force thought to be responsible for accelerating the expansion of the Universe.
Planck’s legacy may be to make dark energy a little less dark and sinister — and we may not need to wait 13.77 billion years. As Dr. Jan Tauber, ESA's Planck project scientist, said in summing up the Planck mission, "Planck has given us a fresh look at the matter that makes up our Universe and how it evolved, but we are still working hard to further constrain our understanding of how the Universe expanded from the infinitely small to the extraordinarily large, details which we hope to share next year."