Starlink hacked, used as GPS alternative


When Elon Musk's SpaceX refused to cooperate to create a reliable and accurate backup to the world's Global Positioning System, researchers just hacked Starlink's signals to create the backup anyway. What does this mean for planetary navigation?

Gizmodo reported on Friday that a team of researchers out of the University of Texas at Austin leveraged Starlink as a GPS alternative by using the over 3,000 satelites that make up its network to replace some two dozen GPS satellites. Here's some background on both systems. Each of Starlink's thousands of satellites maintain a non-geostationary position in low-Earth orbit, and GPS satellites follow one of six different orbits that circle the planet twice every day. Yet they both share a common characteristic: they beam signals down to the surface of Earth. Starlink delivers internet, while signals from the multiple GPS satellites are used by navigation devices to triangulate their exact position on the planet.

The University of Texas at Austin's Radionavigation Laboratory recognized that Starlink could also serve as an accurate and reliable backup to the Global Positioning System, but SpaceX declined to participate and stopped cooperating with researchers. So then, Todd Humphreys led the team of researchers to go forward anyway without any need for an intimate knowledge of what exactly the Starlink satellites were broadcasting; they just needed the signals, and SpaceX has no way to hide those.

Without SpaceX's cooperation, it took Humphreys' team almost two years to reach their goal. They took a laborious multi-stage approach:

  1. Purchase Starlink Service.
    Researchers began by buying a Starlink terminal and its corresponding Internet service.

  2. Stream HD YouTube Videos.
    Then, they began to stream videos of tennis legend Rafael Nadal 24 hours a day.

  3. Use an Antenna to map the satellites.
    Researchers paired the setup with an antenna nearby that was used to detect the regularly repeating synchronization sequence signals that Starlink's service uses to help the ground-based receivers stay connected.

UT Austin's researchers were able to conduct these steps without ever having to attempt to crack or break the encryption that Starlink uses to keep its internet service exclusive to paying subscribers. 

The repeating synchronization signals are sent at precisely timed intervals: four sequences every millisecond, which is the same approach that the GPS system also uses. Pairing this information about the movement of Starlink's satellites - information that SpaceX readily shares online to mitigate the risk of costly collisions with hardware from other companies - and cross-referencing it with the source of the signal and how far away that individual satellite is, can all be used to calculate the location of a receiver with an accuracy of about 98 feet. 

While this remains a far cry from the potential millimeter accuracy that GPS system can achieve with advanced receiver equipment (the likes of which the United States military utilizes in its operations), Humphreys, who shared the team's work on decoding the Starlink signal structure in a non-peer-reviewed paper, argued that if the SpaceX team chose to cooperate, simple software updates and additional data encoded in the synchronization signals could improve the positional accuracy to less than a meter, which is comparable to GPS accuracy in consumer hardware used for planetary navigation, including car and walking directions, map applications on mobile phones, and more. 

Services like GPS and GLONASS were built with military applications in mind, and they prioritize security, which is something that SpaceX skimps on and isn't suitable for advanced propulsion and trajectory applications, such as rocketry, missiles, and interceptors. So there's always a risk that a bad actor can try and spoof and fake them for nefarious purposes, now that UT Austin has published the exact specifications for how Starlink's satellites work. It is likely that, given the widespread exposure, SpaceX is now likely to voluntarily cooperate and to enter the U.S. security shield program by disclosing more of its data in an encrypted fashion.