Scientists have unveiled a new method of repurposing satellite data to monitor Earth’s changes, marking a breakthrough in information resources and unlocking a wealth of new climate and gravitational field data.
Thousands of satellites orbit the planet, continuously transmitting signals between space and Earth. Now, researchers from the FFG project Estimation at the Institute of Geodesy at Graz University of Technology (TU Graz) have developed a method for detecting minute changes in the signals they transmit, enabling a new way to monitor Earth’s dynamic processes.
From Groundwater to Orbit
Shifts in sea levels and groundwater reserves alter Earth’s gravitational field, subtly influencing the trajectories of orbiting satellites. By analyzing changes in orbital positioning, scientists can work backward to identify shifts in the gravitational field and their underlying terrestrial causes.
“The increasing availability of satellite internet in particular means that we have a huge amount of communication signals at our disposal, which significantly exceed those of navigation satellites in terms of number and signal strength,” says Philipp Berglez from the Institute of Geodesy.
“If we can now use these signals for our measurements, we not only have better signal availability, but also much better temporal resolution thanks to the large number of satellites,” Berglez added. “This also allows us to observe short-term changes. This means that, in addition to determining the position and changes in the Earth’s gravitational field that are relevant for climate research, weather phenomena such as heavy rain or changes in sea level can also be tracked in real-time.”
Difficult to Access Data
Private companies like Starlink, OneWeb, and Amazon guard information on their ever-changing signal structures. Additionally, these companies do not make orbit data and distance measurements publicly available, obfuscating the precise locations of their satellites.
These efforts to guard corporate advantages and proprietary technologies make it extremely difficult for scientists to use the torrent of gravitational data that could be extracted from satellite networks. The high potential for error when only relying on estimates makes this difficult.
After conducting a detailed analysis of Starlink signals, the TU Graz researchers finally devised a way to capture meaningful data. Their analysis identified constantly audible but tonally shifting sounds within the signals. Leveraging the Doppler effect, in which the frequency of a wave changes relative to an observer’s relative position, the researchers could accurately identify Starlink satellite positions within about 50 meters. Using the Doppler effect in this manner already enables many radar systems used by police and meteorologists to determine speed, distance, and location.
Revising Data Collection
Researchers need to conduct additional work to revise the method for precise data collection, improving the accuracy to just a few meters. While successful as a proof of concept, the tests only used an off-the-shelf antenna. Further improvements to equipment and methods will increase accuracy.
One such improvement researchers aim to make is to use an antenna that can follow satellites or collect signals incoming from multiple directions. Instead of relying on a single antenna, they also plan to employ several networked antennae to triangulate their readings and reduce error rates.
The more measurements the team can collect, the more accurately they can plot the satellite’s orbit, giving them a more substantial basis to calculate Earth’s gravitational field changes. Finally, the researchers are working on new processing methods to filter through signals.
Researchers Hopeful for Continued Progress
“By being able to utilise the communication signals for geodesy, we have revealed enormous potential for the even more detailed investigation and measurement of our Earth,” says Berglez.
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“Now it’s all about improving precision. Once we have succeeded in doing this, we will be able to understand even more precisely what changes our world is undergoing,” Berglez added.
Finally, the researchers wish to alleviate any potential privacy concerns related to their work. While monitoring signals, they are not decoding what the messages say.
“Just to be on the safe side, I would like to make the following clear: we are analysing communication signals here, but we cannot and do not want to know their content.
“We only use them for positioning and observing orbits,” Berglez added, “in order to determine the Earth’s gravitational field.”
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted atryan@thedebrief.org, and follow him on Twitter@mdntwvlf.