The University of Texas at Austin researchers hacked SpaceX’s Starlink Satellite’s Signal to use it as a GPS alternative without help or support from Elon Musk’s company.

For your information, GPS (global positioning system) is a group of 31 satellites monitored by the US government. These satellites transmit radio signals from an altitude of 12,500 miles. The signals are picked up by GPS receivers installed in phones, vehicles, etc.

How it all Started?

In 2020, The US Army-funded researcher at the University of Texas, Todd Humphreys, offered SpaceX an innovative method to help its continually evolving Starlink constellation to offer exact navigation, position, and timing. This can be achieved with a few software tweaks.  

Initially, SpaceX was thrilled at the idea. However, later, Musk decided not to pursue this proposal. According to Humphreys, Musk said that “every other LEO communications network has gone into bankruptcy. And so we have to focus completely on staying out of bankruptcy. We cannot afford any distractions.”

Hence, Humphreys was on his own in this task. Throughout the past two years, the Humphreys team at the university’s Radionavigation Lab worked at reverse engineering signals sent by Starlink internet satellites in LOE (low earth orbit) to ground-based receivers.

Research Details

After a breakthrough in this research, Humphreys published a non-peer-reviewed paper in which he explained that regular beacon signals from the constellation that help receivers establish a connection with the satellites could serve as a potent navigation system. All this was done without any involvement from SpaceX.


In the paper (PDF), Humphreys provided a complete characterization of Starlink’s signals thus far and claims to have taken the first step towards creating a brand-new global navigation technology that encourages the independent operation of GPS or its Russian, European, and Chinese counterparts.

The Starlink signal capture process (the University of Texas at Austin)

He further stated that the Starlink system signals structure had remained closely guarded and wasn’t even revealed when SpaceX cooperated on this idea in 2020. So, the team started the research from scratch and developed a radio telescope for monitoring their signals.

The university acquired a Starlink terminal and streamed high-definition tennis videos from YouTube to create a consistent source of signals from Starlink that could be eavesdropped from a nearby antenna. They gradually learned that Starlink used orthogonal frequency division multiplexing technology to encode digital transactions.

They didn’t break Starlink’s encryption or access user data on the satellites. They relied on synchronization sequences to encourage receiver coordination. Each sequence contained clues to the velocity and distance of the satellite.

Starlink satellites transmit four sequences every millisecond, which proved fantastic for dual usage of their system. By repeating the process for different satellites, a receiver can locate itself within thirty meters of range.

“We were pleasantly surprised to find that they more synchronization sequences than is strictly required.”

Todd Humphreys – University of Texas

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Posted by Charlie