“The University of Texas Hacked Starlink’s Signal So It Can Be Used as a GPS Alternative” How? What do they mean by this?
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In other words, the timing/synchronization signals sent from the satellites is reliable and precise enough that it can be used by a passive listening device to determine the location of itself relative to the locations of the satellites (basically how GPS works). Since the paths of the starlink satellites are known, this can be used to compute a location on Earth
A GPS satellite is a radio beacon which sends out a simple signal at fixed intervals. The receiver knows the position of each satellite and when it is supposed to send out these beacon signals. So by measuring the difference in time from when the satellite sent out the signal to it was received by the receiver it is possible to calculate how far away from the satellite it is using the speed of light. By getting signals from multiple satellites you can calculate your exact position.
But the Starlink satellites also transmits signals at regular intervals. By finding out the position of the Starlink satellites and when exactly it starts transmitting it is possible to use these signals the same way in order to find your position.
GPS satellites emit their orbital data, a time signal, and strings of characters in a known pattern. GPS receivers listen for these signals and note which letters in the string arrive at a particular moment.
Say four GPS satellites emit just the alphabet, in order. At your current position, at a particular instant, your receiver receives the letters “M, M, M, M.”
The GPS knows how how far away from each satellite it must be to receive “M, M, M, M”, and from these distances, calculates your position.
Now walk a few paces in a particular direction. This time the receiver receives “M,N,L,M.” The change in distance from each satellite caused one string to arrive a little later, and another string to arrive a little sooner than the others. Thus the GPS updates its position.
Starlink satellites emit precisely timed beacon signals, which are known strings of characters. The satellites’ precise orbital data is also known. These pieces of information can be combined to calculate position in a way that is similar to GPS.
An important bit of context here: “hacked” often just means “used in an unusual or unintended way.” They didn’t gain unauthorized access to Starlink, just used its existing features to do something new. We currently use specific satellites to run the GPS, but any satellites that do at least as much can be used in the same way.
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