In a beige-coloured cubicle, on the ground floor of a nondescript suburban office block in Pasadena, California, history is being made.

In fact, history is made here every day.

This is the Jet Propulsion Laboratory’s (JPL) mission control for Nasa’s Voyager spacecraft. You can tell that from the homemade cardboard sign beneath the computer monitors that reads: “Voyager Mission Critical Hardware PLEASE DO NOT TOUCH!”

This is the unlikely control centre for one of the most ambitious and audacious missions in human history.

Over the past 40 years, the two Voyager spacecraft have explored Jupiter, Saturn, Uranus and Neptune. They have sent back detailed views of these strange worlds, revealing moons encased in ice, covered in volcanoes and bathed in gasoline smog. The missions have changed our perspective on the Earth and, with golden gramophone records attached to their sides, are now taking human culture to the stars.

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Voyager: A long, long trip into the unknown

Remarkably, both Voyager spacecraft are still working. Whenever Voyager 1 sends back a signal, it is from the furthest distance any human-made object has travelled from Earth.

Voyager 1 left the solar system in 2013 and is (at the time of writing) 20 billion kilometres (12 billion miles) away. Voyager 2, on a different trajectory, is 17 billion kilometres (10.5 billion miles) away. Maybe it’s easier to imagine it like this: it takes a radio signal, travelling at the speed of light, 38 hours to travel from the Earth to Voyager 1 and back. And it’s some 30 hours for Voyager 2. (For their latest position, visit the Voyager home page.)

The signals are received by Nasa’s deep space network – giant satellite dishes scattered around the world, designed to pick up data from distant spacecraft. As I watch, duty mission controller Enrique Medina calls-up a ground station near Canberra, Australia to establish contact with Voyager 2. The spacecraft is so far away, engineers need to line-up two receivers to capture the signal from the edge of the Solar System.

Little more than a computer terminal in a small room, the Voyager mission control is a humble affair (Credit: Richard Hollingham)

“The power of the transmitter on the spacecraft is around 12 watts,” says Medina. “When it’s on high power, it’s 20 watts – around the same as a lightbulb on a fridge.”

Think about that. I live in the countryside 40km (25 miles) from London and struggle to receive a mobile phone signal. Nasa can pick up messages from 20 billion kilometres away, sent using a 40-year-old, 12-watt transmitter.

“It never ceases to amaze me,” says Medina. “This is 1970s technology we’re talking about.”