Linking through public comms boosts radio telescope reach

Australian researchers use fibre-optic networks link telescopes 300 kilometres apart. Lauren Fuge reports.

Fibre optics are surprisingly robust in linking radio telescopes.
Fibre optics are surprisingly robust in linking radio telescopes.

Researchers at the Australian National University (ANU) have shown that radio telescopes can be linked through the telecommunications network, opening up exciting possibilities for ambitious astronomy projects such as the Square Kilometre Array.

In radio astronomy, the bigger your telescope dish, the better you can observe astronomical objects. Building dishes hundreds of metres in diameter is impractical, so instead astronomers build arrays of dozens of smaller radio antennas spread out over large distances, which separately measure signals from astronomical objects and send them via optical fibres to a supercomputer to be combined.

Together, they simulate a single giant dish. Crucially, each antenna is fitted with an atomic clock to record the precise timing of the signals so they are correctly synchronised.

Now for the first time, research published in the journal Optica demonstrates that two radio telescopes can be linked by transmitting a stable frequency reference more than 300 kilometres over a “real world” fibre optic network. In periodic phenomena such as radio signals, time and frequency have a known relationship, so this technique could be revolutionary for large radio telescope arrays.

“This highly stable method for transmitting the frequency reference promises to replace the need for expensive atomic clocks, which cost around $200,000 each,” says Ken Baldwin from the ANU Research School of Physics and Engineering, co-lead author of the study.

Importantly, the new technique can be easily implemented because it doesn’t require an overhaul of the rest of the fibre optic network.

“By running the experiment on optical fibres also carrying normal traffic, we showed that transmitting the stable frequency standard doesn’t affect the data or telephone calls on the other channels,” Baldwin adds.

“This is necessary to gain the cooperation of the telecommunications companies that own these fibre networks.”

This cost-effective and relatively simple technology could be applied to the Square Kilometre Array (SKA), a global effort to build the world’s biggest radio telescope by combining data from arrays in Australia and South Africa. This massive project will produce more daily data than the world’s current internet traffic.

Lauren Fuge is an Adelaide-based author and science communicator.
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