During its transit to Jupiter, the European Space Agency’s (ESA) Juice spacecraft momentarily redirected its sensors toward a seldom-seen celestial interloper, designated 3I/ATLAS. In doing so, it successfully acquired critical telemetry from an entity originating from beyond the confines of our Solar System.
The Navigation Camera (NavCam) aboard the Juice mission documented 3I/ATLAS in November of 2025. Credit: ESA / Juice / NavCam.
The initial detection of 3I/ATLAS occurred on July 1, 2025, facilitated by the NASA-supported ATLAS survey telescope situated in Rio Hurtado, Chile.
This celestial body, also identified as C/2025 N1 (ATLAS) and A11pl3Z, is believed to have traversed into our Solar System originating from the direction of the Sagittarius constellation.
The object’s trajectory follows an orbital path exhibiting the most extreme dynamic characteristics ever precisely quantified within the Solar System, thereby substantiating its extraterrestrial provenance and remarkable velocity.
On October 30, 2025, 3I/ATLAS achieved its perihelion, marking its closest proximity to the Sun. This passage brought it within 1.4 astronomical units (AU) of our star, positioning it just inside the orbital path of Mars.
“From a very early stage after its identification, we recognized that the orbital configuration would permit observations from the Juice spacecraft. This would afford us a vantage point for observing the comet from a perspective entirely dissimilar to what is achievable from Earth,” stated Dr. Marco Fenucci, a mathematician and specialist in the dynamics of near-Earth objects at ESA’s Near-Earth Object Coordination Centre.
Predictive modeling indicated that Juice would be the spacecraft achieving the nearest approach to 3I/ATLAS shortly subsequent to the object’s perihelic passage, specifically in November 2025.
“Typically, the lead time for preparing crucial operations, such as instrument pointing campaigns or flyby maneuvers, extends to approximately nine months,” commented Angela Dietz, the Juice spacecraft operations manager.
“Upon the emergence of ATLAS, it became apparent that our window of opportunity was considerably constrained.”
The Juice mission commenced its dedicated observations of 3I/ATLAS on November 2, 2025, continuing this data acquisition through November 25. The closest point of engagement occurred on November 4, at an approximate distance of 0.4 AU.
For the purpose of gathering measurements from this interstellar visitor, the spacecraft employed five of its sophisticated instruments: JANUS, MAJIS, UVS, SWI, and PEP.
Due to operational thermal limitations, these observational windows were restricted to six segments of 45 minutes each, supplemented by a final, extended session of 4 hours.
Cumulatively, these efforts yielded 126 scientific data files, aggregating to a total volume of 11.18 gigabits.
However, the research team faced an extended waiting period for the analysis of these findings.
It was not until the spacecraft entered its cold-cruise phase in mid-January 2026 that the high-bandwidth data transmission became feasible.
The highly anticipated data downlink was successfully executed across two distinct 11-hour transmission sessions on February 17 and 20, 2026, utilizing the ESTRACK deep space antennas located in New Norcia and Malargüe, respectively.
“A particularly gratifying aspect of our professional responsibilities is the inherent collaborative nature of these endeavors, involving numerous contributing entities,” remarked Dietz.
“I believe that our capacity to rapidly optimize this campaign and maximize its scientific return within such a compressed timeline is a significant achievement to be celebrated!”
“Upon reaching Jupiter, we are scheduled to conduct a series of flybys of its icy moons with remarkable frequency, at times with intervals of only a few weeks.”
“The 3I/ATLAS campaign has significantly bolstered my confidence in Juice’s ability to promptly fulfill scientific objectives with minimal advance notice, and has demonstrated that complex operational plans can be devised and implemented within exceptionally stringent time constraints,” stated Federico Giannetto, a spacecraft operations engineer for the Juice mission.
