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By Roger Highfield on

Building the Interplanetary Internet

Science Director Roger Highfield discusses how the internet is going off world, with Queen Elizabeth Prizewinner, Vint Cerf.

A decade ago, Vint Cerf shared the inaugural Queen Elizabeth Prize for Engineering, receiving the award from the late monarch herself at an event in Buckingham Palace. Today, the new Engineers gallery in the Science Museum celebrates his achievement, and his vision to boldly take the internet where it has never gone before, across the solar system.

Human stories like those of Vint Cerf are at the heart of the Engineers gallery, where visitors have the opportunity to take a closer look at iconic objects such as the first digital camera, and a miniature atomic clock that the entire GPS system depended upon, as well as learn more about the remarkable people who invented them.

The 2013 Queen Elizabeth Prize for Engineering – often called engineering’s equivalent of the Nobel prizes – was awarded to Louis Pouzin, Robert Kahn, Vinton Cerf, Sir Tim Berners-Lee and Marc Andreessen for their work on the Internet and the World Wide Web; technologies that have revolutionised the way we communicate.

I spoke to Vint Cerf by video for the Braemar Summit earlier this month, when he talked about his vision to extend the internet across the solar system, to speed communication, whether of astronauts to mission control, enabling probes to download their data, or to ensure digital twins of spacecraft and rovers on Earth can help their space siblings overcome obstacles.

Widely known as one of the ‘Fathers of the Internet,’ Cerf is the co-designer (with Bob Kahn) of the architecture of the internet, notably the communication protocols used to deal with packet switching which, unlike ordinary telephone communications, dices a message into ‘packets’ that can travel independently over many different channels, to be reconstructed into the original message at the other end.

The result of his and Kahn’s efforts while working for the US Advanced Research Projects Agency was TCP/IP, (Transmission Control Protocol/Internet Protocol), where the first part checked for errors and the second dealt with domains and destinations.

Two decades later, Cerf was inspired by an extraordinarily successful Mars mission, which released the Sojourner rover on the Red Planet in July 1997, and wanted to extend the internet to space. He was ‘so excited by that success’ that, in the spring of 1998, gathered with experts at Jet Propulsion Laboratory in California to ask how to create the Interplanetary Internet: ‘We need a backbone network, like the internet…we need much richer connectivity.’

Extending the internet to space has had to overcome novel obstacles – the distances involved are astronomical, with Earth-Mars round trip communications lag ranging from seven minutes to 40 minutes, depending on their relative orbits, and planets constantly rotate and move around, potentially blocking signals between spacecraft and astronauts. As a result, they had to develop a new protocol to contend with often-disrupted communication paths.

Back in the 1970s Cerf and Kahn did not design the internet to store data, partly because memory was too expensive, so the protocols they developed meant, in effect, that if a link along a path breaks, a router discards the packet and subsequently resends it from the source. However, networks in space are more prone to disruptions, requiring a different approach.

In 2003, Cerf and a small team of researchers introduced bundle protocols which like the Earthly internet means that packets of data travel from source to destination by way of routers that switch the direction in which the data moves along the network though with the additional property of nodes that can store information. This store-and-forward feature allows bundles to navigate toward their destinations one hop at a time, despite large disruptions and delays. As spacecraft are deployed, they can be repurposed as nodes in the network.

The first successful in-space demonstration of the Interplanetary Internet was carried out on board Surrey Satellite Technology’s UK-DMC1 satellite launched in 2003, a model of which can be found in the Science Museum gallery.

The Interplanetary Internet is steadily growing. In 2004, the Spirit and Opportunity Mars rovers were supposed to transmit data back to Earth directly through the deep space network — three 70-meter antennas in Australia, Spain, and California. However, the channel’s available data rate was twenty-eight kilobits per second and, when they turned the radios on, they overheated.

One of the JPL engineers used prototype software to reprogram the rovers and orbiters from hundreds of millions of miles away to create a store-and-forward interplanetary internet with four times the speed and three nodes – the rovers on Mars, the orbiters and the deep space network on Earth – which has been running ever since.

The latest protocols are running between Earth and the International Space Station and have been tried out on the Deep Impact spacecraft, EPOXI, that was off to visit a comet. They will also be part of LunaNet, which is being developed to provide communications and navigation for the Artemis crewed moon mission, and he is working with European, Japanese and Korean space agencies.

The kind of store-and-forward, intermittent capability could be useful on Earth, Cerf adds, for instance for taking data from sensors that only transmit data intermittently, or to deal with poor mobile phone connectivity.

Find out more about the key milestones of the Queen Elizabeth Prize for Engineering (QEPrize) as they celebrate the 10-year anniversary of the prize this October.