1,2,2,3,4,3,2,2,6,7,3,10,12,13,- 1Universidad del País Vasco / Euskal Herriko Unibertsitatea, Escuela de Ingenieria de Bilbao, Física Aplicada I, Bilbao, Spain (ricardo.hueso@ehu.es)
- 2INAF-IAPS, Institute of Space Astrophysics and Planetology, Rome, Italy
- 3DLR, Institute of Planetary Research, Berlin, German
- 4CSIC-IAA Astrophysics Institute of Andalucía, Granada, Spain
- 5Italian Space Agency (ASI), Rome, Italy
- 6INAF-OAPD, Astronomical Observatory of Padova, Italy
- 7CISAS G. Colombo, Padova University, Italy
- 8LIRA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, Meudon, France
- 10School of Physical Sciences, Open University, Milton Keynes, UK
- 11Hokkaido University, Hokkaido, Japan
- 12NASA Goddard Space Flight Center, Code 690, Greenbelt, MD 20771, USA
- 13Reichman University, Herzliya, Israel
- *A full list of authors appears at the end of the abstract
JUICE (JUpiter ICy moons Explorer) is the first Large ESA mission in the Cosmic Vision Science program. JUICE was launched in 2023 and is aimed to study the Jupiter system in 2031-2035 where it will answer major science goals of the Jovian atmosphere and the Galilean satellites (Grasset et al., 2013). JANUS (Jovis, Amorum ac Natorum Undique Scrutator) is the high-resolution camera on JUICE and operates in the spectral range 340-1080 nm. The instrument is equipped with 13 filters and a detector of 1,504x2,000 pixels with a pixel FOV of 15 microrad and a total FOV of 1.29ºx1.72º (Palumbo et al. 2025).
JANUS imaged the Earth during and shortly after a Lunar and Earth Gravitational Assist maneuver (LEGA) on 19-20 August 2024. Earth observations offer a real testbed scenario to the science investigation of the Jovian atmosphere (Fletcher et al. 2023). Close approach observations were acquired at spatial resolutions of 126-256 m/pix and covered a narrow strip of the planet in which the spacecraft flew from the night-side over Madagascar, moved over the Indian Ocean, Cambodia and Vietnam and observed the terminator and dawn over Luzon Island. Later observations were acquired over morning to noon hours flying above tropical latitudes over the Western Pacific. Additional observations acquired on September 9, 2024 provided a low-resolution multi-filter portrait of the Earth and the Moon.
The high-resolution images contain atmospheric airglow, convective clouds illuminated by a full Moon, fires in rural areas, lights over the ocean from maritime traffic, city lights over Cambodia and Vietnam, and bright pixels compatible with meteoroids of 1-30 g entering Earth's atmosphere. Images over the terminator and dawn show crepuscular rays under extreme incidence angles with highly convective clouds projecting elongated shadows. Day-time observations show gravity waves on elevated cirrus clouds, sun glint on multi-filter images of the tropical Western Pacific, convective storms over tropical latitudes over the Northwest Pacific and internal waves in the ocean. We compared multi-filter images of the ocean and cloud systems over 12 filters through the JANUS spectral range with spectra obtained by the EnMAP and PRISMA instruments on Earth observing satellites showing good agreement.
These Earth images confirm the expected instrument performance and the ensemble of observations contains a large variety of atmospheric features that are good analogs to multiple systems in Jupiter's atmosphere (Hueso et al. 2026). Additional observations of the Earth will be acquired during the next two Earth flybys on September 2026 and January 2029 providing new data at a wider variety of spatial resolutions.
References
- Fletcher et al. Jupiter Science Enabled by ESA’s Jupiter Icy Moons Explorer, Space Science Reviews (2023).
- Grasset et al. JUpiter ICy moons Explorer (JUICE): An ESA mission to orbit Ganymede and to characterise the Jupiter system, Planet. and Space Sci. (2013).
- Hueso et al., JANUS observations of Earth in preparation for its investigation of Jupiter’s atmosphere, Annales Geophysicae, in preparation (2026).
- Palumbo et al. The JANUS (Jovis Amorum ac Natorum Undique Scrutator) VIS-NIR Multi-Band Imager for the JUICE Mission, Space Science Reviews (2025).
Ricardo Hueso, Pasquale Palumbo, Cecilia Tubiana, Ganna Portyankina, Luisa María Lara, Katrin Stephan, Angelo Zinzi, Alice Lucchetti, Livio Agostini, Luca Penasa, Alessio Aboudan, Arrate Antuñano, Athena Coustenis, Junichi Haruyama, Elke Kersten, Klaus-Dieter Matz, Manish Patel, Romolo Politi, Thomas Roatsch, Mitsuteru Sato, Amy Simon, Frank Trauthan, Takahashi Yukihiro, and Yoav Yair
How to cite: Hueso, R., Palumbo, P., Tubiana, C., Portyankina, G., Lara, L. M., Stephan, K., Zinzi, A., Luchetti, A., Agostini, L., Penasa, L., Coustenis, A., Haruyama, J., Kersten, E., Matz, K.-D., Politti, R., Patel, M., Sato, M., Simon, A., Takahashi, Y., and Yair, Y. and the JANUS Earth flyby team: JANUS observations of the Earth during and shortly after JUICE’s Lunar and Earth Gravity Assist (LEGA) on August 2024, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5763, https://doi.org/10.5194/egusphere-egu26-5763, 2026.
