The European Space Agency (ESA) is to be congratulated for a job well done with its Planck telescope, whose four-and-a-half-year mission to study remnant microwave radiation from the Big Bang finally came to an end Oct. 23.

Along with its sister telescope, Herschel, whose mission ended in April, Planck helped plant ESA at the forefront of astronomy research. Planck provided the most precise maps yet of the early universe — just 380,000 years after the Big Bang. Not only did Planck redefine the structural makeup of the universe — between matter, dark matter and dark energy — it also showed that the universe is 100 million years older than previously thought.

Planck’s original mission was to create two full-sky surveys of the early universe over a 15-month period; it had taken five by the time its high-frequency sensor, one of two main instruments, ran out of coolant in January 2012. ESA went on to conduct three more surveys with the low-frequency sensor before managers began winding things down this past August. 

In a textbook example of how to close out a mission, ESA managers put Planck in a safe orbit around the sun — it had operated at the gravitationally stable sun-Earth Lagrange L2 point — and passivated the craft by exhausting its fuel tanks. The final command to shut down the spacecraft was successfully sent Oct. 23.

Turning out the lights on a successful mission is always bittersweet. But those who participated in Planck certainly can take heart and pride in the fact that their mission broke new ground in the astronomy field and, with scientists still poring over the data, will yield additional discoveries in the months ahead.