A series of images crosses the African continent, from eastern Madagascar to the Gulf of Guinea. It was not taken by a satellite specialising in Earth observation, but by JUICE, a European spacecraft travelling to Jupiter. During its close flyby of Earth on 28 September 2026, JUICE used Earth's gravity to change its trajectory. The JANUS science camera took advantage of this manoeuvre to observe landscapes it was not designed to monitor permanently. ESA released the African mosaic on 16 October.
The scene deserves better than a caption simply saying "Africa from space". It tells the story of a navigation operation, an instrumental test, and the limitations of a processed image. The regions visible have not all been photographed with the same pixel size or in the same cloud conditions. The mosaic is not an instantaneous, homogeneous map of the entire continent: it is an assembly of successive views acquired over a few minutes by a moving craft.
First, a manoeuvre to reach Jupiter
JUICE, for *Jupiter Icy Moons Explorer*, is to study Jupiter and several of its icy moons. Reaching this destination would require a lot of fuel if the spacecraft had to accelerate directly from Earth. The engineers therefore use gravitational assists: by passing close to a planet with a pre-calculated trajectory, the vehicle changes its speed and direction relative to the Sun. This is neither a magic engine nor free propulsion; the exchange of momentum is made possible by the geometry of the encounter with a planet that is itself moving around the Sun.
According to ESA, JUICE passed about 8,640 kilometres above the Indian Ocean during its closest approach on 28 September, around 11:45 UTC. The agency says the flyby altered its trajectory by about 20 degrees and increased its speed by about 3.5 kilometres per second in the frame of reference used for the mission. These figures describe highly precise navigation. In the weeks leading up to the flyby, the teams monitored the spacecraft and only needed a small correction among several planned windows. A missed flyby would have compromised the subsequent stages of the journey; it was therefore not a photo opportunity organised for public relations.
However, the proximity of Earth provided a valuable scientific opportunity. It is difficult to test a camera designed for Jupiter's moons on such a complex object before arriving on site. Our planet provides a variety of surfaces, clouds, atmosphere, and lighting geometries. Teams can measure the instrument's behavior, compare filters, and verify the chain that transforms raw data into usable images.
What JANUS recorded over Africa
JANUS is a multi-colour camera developed to examine the surfaces and environment of the Jovian system. During the flyby, it acquired 740 images of Earth and the Moon over several days, using its 13 filters and different resolutions. The mosaic released by ESA covers a much shorter period: approximately four minutes of acquisition, from 13:46 to 13:50 CEST. The images follow a band from Madagascar through Mozambique, Malawi, Zambia, the Democratic Republic of the Congo and Angola, and then towards the Gulf of Guinea.
This list of countries does not claim to show every city or border. The band depicted is approximately 250 to 300 kilometres wide; the resolution varies along the path. ESA indicates that a pixel represents approximately 150 metres on the ground near Madagascar, and then approximately 375 metres towards the Atlantic as the spacecraft moves away. At this scale, one can recognise geographical features or vegetation contrasts, but not identify a person, a car or the detail of a small dwelling. Clouds also obscure some areas, particularly over parts of Angola.
To create the continuous view, the specialists combined about 40 red, green and blue images on a geographical grid based on the position and orientation of the probe. Overlapping images were merged together. The map background comes from Natural Earth. The colours were adjusted consistently to remain close to what a human eye would see, but it remains a processed product, not a single panoramic shot taken in a single instant. Saying this does not detract from its interest; it makes the photography more understandable.
A video, but not the same camera
ESA also released an 48-second film of the flyby. It first shows the Earth in crescent shape, then a wider view of the globe with Africa and a small dot corresponding to the Moon. This sequence comes from the JMC surveillance cameras, installed mainly to check the antennas and structures of JUICE. Their role is different from that of JANUS. The film illustrates the encounter with Earth, while the JANUS mosaic highlights a scientific imaging test. In our edition, the two media must carry separate credits and captions so that the viewer does not take the JMC images for detailed views of the scientific camera.
These animated views are from JUICE's JMC surveillance cameras, not the JANUS science camera used for the main mosaic. Credit: ESA/JUICE/JMC; 48-second film, 2026 — CC BY-SA 3.0 IGO.
This contrast can be a great educational tool. Two instruments on the same spacecraft, at the same time, do not produce the same information. The value of an image depends on its objective, field of view, resolution, filters, and how it is processed. A control camera answers the question "are the vehicle and its components in good condition?" A science camera seeks to measure properties of the observed world. The most spectacular of the two images is not necessarily the most useful for a detailed study.
What does this have to do with Central Africa?
The transition from the mosaic to the Gulf of Guinea gives this flyby an immediate regional interest, but it does not create a new service for observing Africa. JUICE will not regularly fly over Douala to track the coast, forests, or weather. Its mission remains the exploration of Jupiter. If one wishes to document the evolution of a Cameroonian coastline or a Congolese watershed, programs such as Copernicus, Landsat, or local measurements will be much better suited.
The deeper interest is methodological. A research team in Central Africa can use this publication to teach observational geometry, ground resolution, and the difference between raw images and mosaics. Students can be asked why pixel size increases, what a cloud prevents from being seen, and how the position of a vehicle is used to place images on a map. The JANUS band can also be compared to a Sentinel scene taken at a recent date: what details appear in one image but not the other? Simply keep the dates, sensors, and resolutions in the comparison.
The continuation of the mission, without anticipating its discoveries
The flyby on 28 September helped JUICE continue its journey. ESA is planning further gravitational assists before its arrival in the Jupiter system, scheduled for 2031. The images of Africa indicate that the JANUS instrument was able to be used during a test close to Earth; they do not indicate the quality of any future observations of the icy moons, which will be made in a different luminous and radiative environment.
The good news is twofold. Yes, an interplanetary spacecraft captured authentic images of several regions in Africa during a historic navigation operation. No, this publication should not be told as the launch of permanent ground-based monitoring or as a discovery on Jupiter. In between lies the true richness of the subject: to see how a team transforms a trajectory opportunity into scientific control, and then into an image that anyone can examine with specific questions.