The signals had been traced to space, but the US researchers were unable to determine which satellite was transmitting them. The breakthrough came when SINTEF researchers got in touch and offered data from SINTEF’s own monitoring stations in Trondheim and Amsterdam.
When we heard that the team at the University of Texas was searching for a space-based source, we contacted them and asked whether they would like some of our data,” says Aiden Morrison, Senior Research Scientist at SINTEF.
Professor Todd Humphreys at the University of Texas later described SINTEF’s message as a “dream email”. The data gave the researchers the information they needed to take the next step in their search for the source of the signals.
Measurements accurate to within a few metres
SINTEF’s measurement infrastructure made it possible to record the same signals at two locations simultaneously. By comparing the extremely small differences in the times at which the signals reached the monitoring stations in Trondheim and Amsterdam, the researchers were able to calculate where they originated.
Analysing these time differences allowed the researchers to determine the transmitter’s position to within a few metres. The analysis showed that the signals came from Kosmos 2546, a Russian satellite launched in 2020.
“Identifying the source of a signal requires both advanced measurement systems and the ability to analyse extremely small differences in when signals reach different receivers. It is precisely this combination of accurate measurements and advanced signal analysis that makes it possible to identify and understand signals of this kind. This expertise is important for satellite communications, navigation and emergency preparedness,” says Morrison.
Why were the signals transmitted?
The researchers still do not know for certain why the signals were transmitted. One possible explanation is that they were connected with tests of technology capable of affecting or disrupting GPS signals. Another is that they form part of a communications or alert system.
Important for society and emergency preparedness
Satellite signals are a fundamental part of modern society. They are used in navigation, transport, communications, financial markets, power systems and emergency preparedness. When these signals are disrupted, the consequences can be serious for both civilian and military users.
The ability to detect and trace such signals is important because an increasing number of critical societal functions depend on satellite-based navigation and precise timing.
Collaboration for safer navigation
The growing threat from jamming and spoofing is an important reason why the Norwegian authorities organise Jammertest at Andøya every year. Jamming blocks or disrupts satellite signals, while spoofing transmits false signals that can cause navigation systems to calculate an incorrect position.
The test site enables public authorities, industry and research organisations to investigate how such interference affects everything from individual devices to critical societal systems that depend on precise positioning, navigation and time synchronisation.
SINTEF has participated in the tests for several years and has collaborated with the organisations behind the initiative, including the Norwegian Communications Authority (Nkom), the Norwegian Metrology Service, the Norwegian Public Roads Administration, the Norwegian Mapping Authority, the Norwegian Space Agency and the Norwegian Defence Research Establishment (FFI).
The aim is to develop knowledge about how equipment, critical infrastructure and essential public services can be made more resilient to interference with satellite-based navigation.
Read NRK's story about the discovery: Mysterious Russian Satellites Discovered
The mystery became a documentary
The story attracted international attention through a documentary by Veritasium on YouTube. The documentary follows the researchers’ efforts to uncover the source of the mysterious signals and shows how GPS interference can affect ships, aircraft and other critical infrastructure.
The documentary follows the effort to identify the satellite and highlights how observations from SINTEF gave researchers in Texas a rare opportunity to study a real-world case of possible signal manipulation, ultimately helping them solve a mystery that had occupied them for months.
The measurements from Trondheim therefore became an important piece of the puzzle in identifying the satellite and demonstrate how Norwegian expertise in signal analysis and satellite communications can help solve complex challenges of international significance.
