SpaceX’s Starlink Internet satellite could be reconfigured to function as a global positioning system (GPS), according to a new paper published by researchers at the University of Texas. For this, scientists had to intercept signals from satellites.

A study published in the MIT Technology Review examines the possibility of using Starlink satellite signals to determine position, navigation and time (PNT) coordinates. Initially, the researchers found that the antenna had internal shielding, and it is worth considering that time is crucial for GPS, but the clock on the Starlink dish turned out to be unreliable. Therefore, for the experiment it was decided to make its own signal receiver, for which a controllable parabolic antenna was used with publicly available data on the coordinates of Starlink satellites from SpaceX. To ensure the continuous availability of listening signals, the Starlink terminal has continuously downloaded high-definition videos from YouTube.

Tests showed that the Starlink signal was split into eight channels, each with a bandwidth of 240 MHz. Of these, SpaceX uses only six channels, and the bottom two channels are empty – the authors think this is because they are close to the frequencies used by astronomers.

The use of the positioning signal includes analysis of synchronization sequences. When transmitting from satellite to antenna, the signal uses OFDM frequency division orthogonal multiplexing. This allows you to split the main signal into several smaller signals, and the dish is responsible for combining or “synchronizing” them when received.

According to the researchers, a discrete receiver as they used could be used to predict timing sequences that could be used to reproduce a signal that matches the variables required for GPS positioning. Additionally, they found that the reproduced signal had a strong correlation with the actual Starlink signal.

This study also shows that it is very easy to tamper with Starlink scope, as attackers only need to generate synchronized signals similar to Starlink signals to confuse user terminals.