Planck will be the third spacecraft to investigate the CMB, after Nasa's COBE and WMAP satellites.

BBC: Telescopes ready for rocket ride

The first was COBE, launched in 1989, followed by WMAP, launched in 2001.

CNN: Better 'baby picture' of universe emerges

COBE's temperature sensitivity was adequate, its angular resolution was poor, so it could not distinguish the features necessary to gauge the universe's age.

ECONOMIST: The universe

But by mapping the tiniest of temperature fluctuations in the CMB, first done by the Cobe satellite in 1991, astronomers can "see" the distribution of matter in the early Universe.

BBC: Pictures of the early Universe

COBE, and 35 times its sensitivity to temperature.

ECONOMIST: The universe

COBE, was a relatively crude instrument.

ECONOMIST: Telescopes are getting bigger, better and less tangible