ESA’s ExoMars TGO Refines Interstellar Trajectory by 10x.
The European Space Agency (ESA) has achieved a landmark success in deep-space tracking, utilizing a spacecraft orbiting Mars to dramatically improve the predicted path of the rare interstellar comet 3I/ATLAS. By innovatively leveraging data from the ExoMars Trace Gas Orbiter (TGO), ESA’s planetary defence team boosted the accuracy of the comet’s location by a factor of 10, a crucial demonstration for global space safety efforts.
The Challenge of Tracking a Visitor from Beyond.
Since its discovery in July 2025, tracking the fast-moving comet 3I/ATLAS—only the third known object to visit our Solar System from interstellar space—presented a unique challenge. Traveling at speeds up to 250,000 km/h, its trajectory was initially calculated using observations solely from Earth-based telescopes. While functional, Earth’s fixed vantage point limited the precision required for such a fleeting, high-speed visitor.
New Perspective from the Red Planet.
The breakthrough came when ESA’s teams coordinated the ExoMars TGO to turn its eyes away from Mars’s surface and towards the distant comet. During its closest approach to Mars (about 29 million km in October), the TGO provided a revolutionary new viewing angle.
- Closer View: TGO was approximately ten times closer to 3I/ATLAS than any Earth-based observatory.
- Triangulation: By combining this Mars-based data with traditional Earth observations, scientists could precisely triangulate the comet’s position.
This combined effort successfully refined the comet’s path, reducing the uncertainty of its location ten-fold and allowing astronomers worldwide to aim their instruments with greater confidence for final scientific observations before the comet vanishes into interstellar space.
A Vital Rehearsal for Planetary Defence.
Although 3I/ATLAS posed no threat to Earth, this exercise represents a vital test case for Planetary Defence. The success proves that assets currently operating throughout the Solar System, even those not originally designed for asteroid detection—like TGO’s CaSSIS instrument—can be quickly repurposed to track potential threats.
Historic Data Submission.
The project also made history, with the resulting data on comet 3I/ATLAS becoming the first astrometric measurements from a spacecraft orbiting another planet to be officially accepted into the Minor Planet Center (MPC) database.
This successful “rehearsal” hones the essential skills needed to quickly determine the trajectory of any future unexpected asteroid or comet that might pose an impact risk. It underscores the value of leveraging a widespread network of space assets to ensure the safety and defence of Earth.