A telescope built with expertise from Cardiff University will be switched off today.
Planck has been scanning the sky to map the relic radiation from the Big Bang, the Cosmic Microwave Background or CMB.
Researchers in Cardiff built one of the telescope's instruments.
During its mission, the telescope has helped scientists to gain a better understanding of the universe and its origins, revealing the universe is older than previously thought at 13.8 billion years.
Mission controllers have fired Planck's thrusters to empty its fuel tanks. Now its on its way to a "parking" orbit around the sun.
Today its transmitters will be switched off and Planck will fall silent.
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