Square Kilometre Array precursor looks to filter out satellite interference

Starlink isn't the biggest problem, but increasing numbers of orbiting transmitters isn't helpful

The Australian Square Kilometre Array Pathfinder (ASKAP) – a precursor project for the full Square Kilometre Array – has started work on techniques to help it cope with increased satellite traffic.

The 36-telescope array is already operating in a remote area of Australia that has been designated a radio quiet zone – no television broadcasts or mobile phone signals trouble the dishes. But as the 'scope's purpose is gazing at the heavens, it still must contend with orbiting sources of signal.

ASKAP head of data operations Dr Matthew Whiting told the Supercomputing Asia 2024 conference in Sydney today that increasing numbers of satellites are concerning.

Asked if Elon Musk's thousands-strong Starlink satellite broadband constellation is causing problems, he rated that service's birds "no more trouble than anybody else."

Satellites that do give ASKAP trouble transmit in the same bands the science org uses for its observations.

"We do notice satellite signals are getting worse," Whiting observed. "There is work in actively predicting and mitigating satellite interference," he added. "We can mitigate known bright satellites, and we are building things to track satellites."

Those "things" will matter more once the full SKA goes to work – sometime after the planned end of construction in 2029.

Whiting conceded he is unsure how much of the tech his team has created to process data from ASKAP will be used on the full SKA, as the latter uses a different image format. But he assured the conference his team is actively and positively engaged with SKA boffins.

ASKAP tech will therefore be a known quantity to the SKA team. Whiting explained his team's efforts see data gathered by "correlators" – large servers that collect data from individual dishes – before aggregating it for despatch to the Pawsey Supercomputing Centre in the Australian city of Perth.

Forty-one thousand lines of bash scripts and the Slurm Workload Manager automate various tasks that prepare data for use in various processing pipelines.

ASKAP has recently started using Pawsey's "Setonix" supercomputer, which was commissioned in 2022. Whiting told the conference Setonix's improved performance compared to Pawsey's old "Galaxy" machine actually created problems for ASKAP, because the project's filesystem struggled to handle the throughput of data the newer supercomputer created.

"We need Setonix to keep up with our data rate" – ASKAP produces four terabytes an hour at its peak – "but only at that scale do you see these problems," Whiting explained.

He also offered a piece of advice to other HPC users: be kind to staff at supercomputing facilities.

"The key thing is to work with Pawsey staff, to stop us annoying them," he offered. "I have made a career out of annoying supercomputing platform staff," he added – but not so much that they stop helping. ®

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