DLR: Multispectral camera JANUS photographs interstellar comet 3I/ATLAS
At the end of 2025, comet 3I/ATLAS approached the sun. To observe this, ESA activated its JUICE probe.
Hubble image of 3I/ATLAS
(Image: NASA, ESA, STScI, D. Jewitt (UCLA), M.-T. Hui (Shanghai Astronomical Observatory). Image Processing: J. DePasquale (STScI))
The European spacecraft Jupiter Icy Moons Explorer (JUICE) had a unique encounter: it passed the interstellar comet 3I/ATLAS. The European Space Agency (ESA) activated several instruments on the probe ahead of schedule to capture the encounter.
(Image:Â ESA/JUICE/JANUS)
Among the activated instruments was the JANUS multispectral camera, which was primarily developed by the German Aerospace Center (DLR). It observed the comet between November 5 and 25, 2025, shortly after it passed its closest point to the sun. The shortest distance between JUICE and the comet was 63 million kilometers.
During this time, the camera took over 120 images. Seven filters in the spectral range of 380 to 1,015 nanometers – from blue to near-infrared – were used. According to the DLR, these are the first images showing the comet's intense activity shortly after perihelion. The behavior of 3I/ATLAS near the sun was therefore typical for a comet. Its interstellar origin made no difference.
JUICE captures details of the comet
3I/ATLAS showed an extended coma that obscured the comet's nucleus, the DLR reported. The coma is a cloud of dust and gas surrounding the nucleus and tail of the comet. In addition, the images showed the tail and morphological structures such as jets, jet-like structures, streams, filaments, and detachments.
(Image:Â ESA/JUICE/JANUS)
"JANUS performed excellently much earlier than planned, revealing very faint structures in the comet's tail and precise radiometry of the brighter coma near the nucleus," said Ganna Portyankina from the DLR Institute of Space Research. Due to JUICE's position relative to the receiving antennas on Earth, the probe could only transmit the photos in mid-February 2026.
The goal of JUICE is the Jupiter system. The European probe, launched in 2023, is scheduled to arrive there in mid-2031. The mission aims to explore the Jupiter system, particularly the moons Ganymede, Europa, and Callisto. The mission is scheduled to end in late 2031 with the probe impacting Ganymede.
No science on the way to Jupiter
Initially, no scientific tasks were planned for the journey to Jupiter. From Earth, comet 3I/ATLAS would no longer be visible on its path around the sun from autumn 2025. However, this was the comet's most active and therefore scientifically most interesting phase. ESA activated the JUICE probe because, from its position on the other side of the sun, it had a view of 3I/ATLAS.
3I/ATLAS is an interstellar comet. It was discovered in early July 2025. It is only the third known celestial body to have come into our solar system from interstellar space. This is what "3I" stands for; "ATLAS" (Asteroid Terrestrial-impact Last Alert System) is an automated early warning system for asteroids. It includes several observatories that discovered the celestial body. It was even mistaken for an extraterrestrial spacecraft.
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3I/ATLAS came closest to Earth at the end of last year. The encounter was harmless: it passed our planet at a distance of over 270 million kilometers. After traversing the solar system, it will never return.
(wpl)
