A rare encounter: How Juice came to observe 3I/ATLAS
ESA’s Jupiter Icy Moons Explorer spacecraft observed the interstellar comet 3I/ATLAS during a November 2025 campaign that took advantage of an unusual orbital geometry that placed the spacecraft in a favourable position relative to the comet’s path. The interstellar object, first detected on July 1, 2025, passed through the inner solar system on a trajectory that brought it closest to the Sun in late October, and calculations by flight dynamics and near‑Earth object teams indicated that Juice would be the nearest deep‑space asset capable of imaging it. Operations teams at ESA’s European Space Operations Centre accelerated planning and instruction uploads with just four months to prepare before observations commenced on November 2, 2025, under tight thermal and pointing constraints as the spacecraft continued toward its Jupiter system mission.
Juice approached 3I/ATLAS to within about 0.4 astronomical units, or roughly 60 million kilometres, during the observation window that extended through November 25, 2025. The campaign required coordination among engineering and scientific instrument teams to streamline pointing and data collection, bypassing some standard calibration steps to meet the compressed timeline. The spacecraft operated in a hot‑cruise thermal condition with its high‑gain antenna oriented toward the Sun for thermal protection while delivering commands to its science payloads, enabling the Navigation Camera, spectrometers, and other sensors to capture imagery and measurements across multiple days.
The campaign demonstrated deep‑space operational flexibility at ESA under compressed planning conditions, showing that missions en route to outer solar system targets such as Jupiter can provide valuable data on transient, fast‑moving objects from beyond the solar neighbourhood. The observations of 3I/ATLAS add to a small set of spacecraft encounters with interstellar objects and offer comparative perspectives to ground‑based efforts, reinforcing the role of existing interplanetary assets in opportunistic science campaigns beyond their primary exploration goals.
