On its way to Jupiter, ESA’s Juice spacecraft briefly turned its gaze toward a rare interstellar visitor, 3I/ATLAS, capturing valuable data from an object born beyond our Solar System.
This image of 3I/ATLAS was captured by the Navigation Camera (NavCam) onboard Juice in November 2025. Image credit: ESA / Juice / NavCam.
3I/ATLAS was first spotted on July 1, 2025, by the NASA-funded ATLAS survey telescope in Rio Hurtado, Chile.
Also known as C/2025 N1 (ATLAS) and A11pl3Z, the interstellar comet appears to have entered the Solar System from the direction of the constellation of Sagittarius.
The object follows the most dynamically extreme orbit ever measured in the Solar System, underscoring its interstellar origins and the extraordinary speed.
On October 30, 2025, 3I/ATLAS reached perihelion, its closest point to the Sun. It came within 1.4 AU (astronomical units) of our home star — just inside the orbit of Mars.
“Almost since the time of discovery, we realised that the geometry of the orbit would allow observations from the Juice spacecraft, which would observe the comet from a completely different angle than what we can do from Earth,” said Dr. Marco Fenucci, a mathematician and near-Earth objects dynamicist at ESA’s Near-Earth Object Coordination Centre.
Calculations predicted that Juice would be the closest spacecraft to 3I/ATLAS right after the object reached perihelion, in November 2025.
“Preparations for things like payload pointing campaigns or flybys are usually in the order of nine months,” said Juice spacecraft operations manager Angela Dietz.
“When ATLAS came, we knew there was not a lot of time.”
Juice officially began its 3I/ATLAS observations on November 2, 2025, continuing through to 25 November. The closest approach was on 4 November at about 0.4 AU.
The spacecraft used five of its instruments — JANUS, MAJIS, UVS, SWI, and PEP — to take measurements of the insterstellar visitor.
Thermal constraints limited these observations to six 45-minute slots and one final 4-hour slot.
Together, these generated 126 science files with a total of 11.18 Gbits of data.
But the scientists would have to wait to see the results.
Only after the spacecraft entered cold-cruise phase in mid-January 2026 would the high bit rate downlink be possible.
The long-awaited data downlink took place in two 11-hour passes on February 17 and 20, 2026 via ESTRACK’s New Norcia and Malargüe deep space antennas, respectively.
“That’s the nice thing in our job – it is always a team effort of many parties involved,” Dietz said.
“I think, the fact that we could optimise this campaign in little time and maximise the output is something to be proud of!”
“At Jupiter, we will perform flybys of the icy moons at a high cadence, sometimes only a couple of weeks apart.”
“The 3I/ATLAS campaign has made me even more confident that Juice can quickly achieve scientific objectives with short warning times, and that complex operations can be planned and executed within very limited timeframes,” said Juice spacecraft operations engineer Federico Giannetto.
