The International Space Station (ISS) is orbiting the Earth 250 miles above our heads, but thanks the wonder of technology, it’s possible to talk live to its astronauts as if they were in the next room. That's exactly what happened at New Scientist Live in London.

BT’s broadcast technology helped deliver a live link-up with the ISS, where BT Sport’s Craig Doyle and Libby Jackson, of the UK Space Agency, talked to astronaut Paolo Nespoli. BT.com was at London’s Excel during the live broadcast to find out more.

[Read more: Who is Paulo Nespoli? Learn more about the Italian astronaut]

From space to London via the BT Tower

So how does video footage of Paolo get from the ISS to London?  The journey starts with three satellites that orbit the Earth, which transmit the footage to the Johnson Space Centre TV facility in Houston. It is then sent via fibre-optic cables to London.

After being converted to a UK-compatible TV signal, it goes to the BT Tower, where it is compressed and sent across the city to the Outside Broadcast (OB) truck stationed around the back of the Excel exhibition centre.

[Exclusive video: Go behind the scenes at the BT Tower]

Packed with state-of-the-art technology, this rather innocuous vehicle receives the signal from the BT Tower, decodes it to HD and transmits it to the screens in the auditorium at New Scientist Live.

The team in the OB truck is responsible for ensuring the link-up happens on time – Nasa allocated BT a strict timeslot for the broadcast. Once live, they monitor the link to ensure high-quality picture and sound.

Countdown to live

The job of hosting the live link fell to BT Sport’s Craig Doyle and the UK Space Agency’s Libby Jackson, who worked with Tim Peake during his time in space and who would provide the audience with an insight into life in space, ahead of the countdown to the link-up.

We spoke to them minutes before they took to the stage in front of the excited audience. Check out the video below to find out how they were feeling about the out-of-this-world experience.

Going live

Anticipation rose among the 1,700 people in the hall in Excel ahead of the link-up with the space station, which was travelling at 17,500mph in Earth orbit.

Mission Control broadcast at New Scientist Live

Live footage of Mission Control, which coordinates communication with Paolo Nespoli on the ISS, was broadcast to the audience:

"Station this is Houston – are you ready for the event?"

“European Space Agency this is Mission Control Houston, please call station voice check?”

As footage of Paolo spinning a globe appeared on the screens, we were live. Check out the video below to watch the broadcast and see the Italian astronaut talk about space.

[Read more: Emergency response - how BT's technology helps those in need]