A new approach is unlocking hidden data from satellite mega-constellations to track Earth’s changes in real time.
By using the Doppler effect, scientists have found a way to analyze signals from Starlink and similar networks, revealing insights into climate, sea levels, and weather patterns. Precision is still a challenge, but the potential for global observation is enormous.
Unlocking New Data for Earth Observation
Reliable data is one of the most valuable tools in scientific research. The more data sources scientists can access, the more accurate their findings become. Until recently, researchers in navigation and satellite geodesy saw a major missed opportunity — while thousands of satellites in mega-constellations orbited Earth for communication purposes, their signals couldn’t be used for positioning or Earth observation.
Now, through the FFG project Estimation, scientists at the Institute of Geodesy at Graz University of Technology (TU Graz) have found a way to harness these previously untapped signals. By integrating them with data from navigation and research satellites, they aim to improve how we track environmental changes on Earth with greater precision.
Success with the Doppler Effect
Satellite-based Earth observation relies on detecting changes in sea level, groundwater levels, and other environmental factors that alter Earth’s gravitational field — subtly shifting satellite trajectories. By analyzing these orbital changes, scientists can extract valuable data about our planet.
“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. 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.”
Overcoming Challenges in Signal Analysis
One of the challenges in realizing the project was that the satellite operators, including Starlink, OneWeb, and the Amazon project Kuiper, do not disclose any information about the structure of their signals, and these signals are constantly changing. In addition, there are no precise orbit data or distance measurements to the satellites, which represents potential sources of error for calculations.
By analyzing the Starlink signal, the researchers nevertheless found a way to enable the desired applications. They detected sounds within the signal that were constantly audible. They then utilized the Doppler effect and investigated the frequency shift of these constant tones as satellites moved toward and away from the receiver. This allowed the position to be determined with an accuracy of 54 meters. Although this is not yet satisfactory for geodetic applications, for the investigations that have been carried out so far, only a fixed, commercially available satellite antenna was used to test and verify the basic principle of the measurement method.
More Insight into How Our World is Changing
The aim now is to improve the accuracy to just a few meters. This will be made possible by antennas that can either follow the satellites or receive signals from different directions. In addition, measurements are to be taken at several locations in order to increase accuracy and reduce the influence of errors. And with more measurement data, the researchers can calculate more precise orbit data, which in turn makes determining positions and calculating the Earth’s gravitational field more accurate. The navigation working group also wants to develop new signal processing methods that filter out more precise measurement data from signals that have so far been rather unusual for geodetic applications.
“By being able to utilize the communication signals for geodesy, we have revealed enormous potential for the even more detailed investigation and measurement of our Earth,” says Philipp Berglez. “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. Just to be on the safe side, I would like to make the following clear: we are analyzing communication signals here, but we cannot and do not want to know their content. We only use them for positioning and observing orbits in order to determine the Earth’s gravitational field.”
Meeting: AHORN 2024
Funding: Austrian Research Promotion Agency
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2 Comments
Is this why Elon is shutting down the National Weather Service? Now all weather information will be the sole provenance of Starlink at exhorbitant costs to the taxpayer.
Good question.