Deep time: An artist's illustration of Planck, a 1.5-metre telescope with two ultra-sensitive detectors of cosmic microwave background radiation, or CMB.
Credit: ESA
CMB is the cooled remnant of the first blast that travelled freely across the heavens, a kind of 'fossil' radiation released shortly after the so-called Big Bang. In detecting this radiation – omnipresent but with no particular source – Planck will be seeing the universe as it was almost at its origin.
It will observe the microwaves by measuring minuscule differences in temperature across patches in space, thought to be the imprints left by CMB by the earliest seeds of today's huge concentrations of matter, such as galaxies.
The probe may also yield clues on the mysterious dark matter that scientists say accounts for around 25 per cent of all the stuff in the universe, but which has never been directly detected.
Feat of engineering
Likewise for dark energy, a theoretical phenomenon that could account for 70 per cent of the remainder. It could explain why the universe is expanding at an accelerating rate, rather than slowing down.
Herschel is a feat of engineering, combining the need for lightness with optical precision.
Its huge primary mirror – 3.5 metres across – features an unprecedented fusion of 12 silicon carbide petals into a single piece. The mirror has had to be polished to eliminate any imperfections bigger than a few thousandths of a millimetre high. Planck's two detectors hold a claim on being the most sensitive CMB sensors ever built.
Herschel is scheduled to work for three years. Its mission will end when the helium used to cool its instruments runs out. Planck is set to yield data for at least 15 months, perhaps longer depending on its own cooling capacity.
