After SpaceX refused to investigate Starlink further as a military alternative to GPS in 2020, a group of researchers wondered how to do it without the help of Elon Musk (or his company that created the Internet constellation). I found
For the past two years, Professor Todd Humphreys has led a group of University of Texas researchers in his engineering of reversing signals from satellite Internet constellations in hopes of developing a new navigation system separate from the Global Positioning System. and the system operates in Europe. Russian and Chinese equivalents, MIT Technology Review reports.
In a non-peer-reviewed study, Humphreys created a comprehensive characterization of the signal without the group breaking his Starlink’s signal encryption or accessing satellite-fed user data. claimed to have done so. “The signals in Starlink his system are a closely guarded secret,” Humphreys told MIT Technology Review. “Even in our early discussions, when SpaceX was more cooperative, they didn’t reveal the signal structure to us. We had to start from scratch, building basically a little radio telescope to eavesdrop on their signals.”
Starting with a Starlink unit programmed to transmit high-definition YouTube videos of Spanish tennis player Rafael Nadal, the group began tracking the satellite’s synchronization sequences and detected their patterns of transmission — about four sequences every millisecond. These sequences — repeating patterns of signals beamed down to Earth by the satellite — help receivers coordinate with them, leaving clues to the satellite’s distance and velocity.
The earthbound receiver, using the timing of the signals received from the satellite and information publically available about its orbit, can then calculate the distance to the satellite and approximate a location within 30 meters, Humphreys told MIT Technology Review. With tweaking, the geolocating capabilities could become as accurate as GPS’, which tends to be accurate to about 16 feet in commercial use.
The discovery, while a potential breakthrough for geolocation services, also revealed a possible security concern about Starlink signals — which are currently key to keeping Ukrainian communication services running as Russia has invaded the country — if used as a navigation system. Mark Psiaki, an aerospace professor and GPS expert at Virginia Tech, told MIT Technology Review: Navigation systems that operate on open source sequences are arguably spoofable because everyone knows how to spot these signals and create fake signals. ”
Starlink has become a staple of wartime communications in Ukraine, so the recent failure by officials is said to be devastating. Musk tweeted earlier this week that Russia was actively working to destroy satellites, but Humphreys’ findings that the signals were predictable and repeatable underscore the possibility of Starlink’s intentional jamming.
author alexandre khalfallah
source Researchers Who Reverse-Engineered Starlink Signals Find Security Flaw (businessinsider.com)