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Science Independently confirmed2 publishers 2 min read Published Updated

Juice's precise Earth flyby leaves more propellant for Jupiter's icy moons, ESA says

ESA's Juice spacecraft needed one small nudge, from six correction slots set aside, to line up a 28 September Earth flyby that added 3.5 km/s. Its operators say the unburned propellant will go to observing Jupiter's icy moons; ESA has not said how much was saved.

The Scientist · Science desk

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What happened

  • The pass bent Juice's trajectory 20 degrees away from its pre-flyby path, a change made with Earth's gravity and very little fuel.
  • Juice came within 8,640 km of the Indian Ocean at 11:45 UTC and took a series of pictures with its onboard monitoring cameras.
  • The flyby was the third chance to test the science instruments on a real target, after a 2024 lunar-Earth gravity assist and 2025 observations of Comet 3I/ATLAS.
  • ESA expects to publish images and spectra from some instruments in the coming weeks, including high-resolution Moon and Earth images from the JANUS camera.
  • One more Earth flyby, in January 2029, will put Juice on its final track to Jupiter, where it arrives in 2031.

Why it matters

  • What's now possible capability Propellant saved on the approach carries over to Jupiter, where Juice's operators intend to spend it on observing the icy moons.
  • What it limits constraint With one Earth flyby left before arrival, instrument teams have few remaining chances to calibrate against well-understood conditions before the moon passes begin.
  • What's now possible capability Juice's days in the magnetotail, paired with Smile's measurements near Earth, give researchers a way to tie activity far down the tail to the northern lights over the poles.

The six in that count were opportunities: windows ESA set aside in the four weeks before the pass for adjusting Juice's approach [18]. The one that was used, a tiny nudge, put the spacecraft on the trajectory that made the most of Earth's gravity [18]. The other five went unused [20]. Operators have tracked Juice with extra care since 17 August and will keep doing so until 10 October [19].

"The flyby required ultra-precise navigation in real time. Thanks to our very careful planning, we used only a small amount of the propellant reserved for this flyby," said Angela Dietz, Juice's spacecraft operations manager [5]. "This gives us more to use at Jupiter to carry out observations of the planet's icy moons," she said [6].

That account comes from the operators themselves. ESA did not say how much propellant was left over, or how it converts into observing time at Jupiter. I think the single nudge is good evidence of careful navigation on the way in. As evidence about the science budget at Jupiter it is weaker, until ESA puts a figure on the reserve.

The instrument work took months to plan. Teams from ESA's spacecraft operations, science operations and technical centres worked with the external teams behind Juice's 10 science instruments to decide which to switch on and when [8]. "Juice's journey to Jupiter provides only a few opportunities to calibrate and validate the instruments under well-understood environmental conditions," said Claire Vallat, the Juice project scientist who led that effort [9].

Power forced some of the choices. Instrument activities "sometimes have to be prioritised, for example when Juice was in Earth's shadow this morning, and relying on battery power alone," Vallat said [10]. On this flyby, she said, calibration activities "were prioritised based on their relevance to preparing the instruments for their work at Jupiter, while also considering whether an opportunity is unique or can be scheduled later in the journey" [11].

ESA describes an Earth flyby as relatively straightforward next to the 35 flybys of Jupiter's giant moons, among them Ganymede and Europa, that Juice will make later [12]. Discussions on instrument operations for the Europa passes started 10 years ago and will continue until Juice flies past Europa in the early 2030s [13].

What to watch

  • Any ESA figure for the propellant left over after the flyby, and whether it is assigned to extra moon passes or longer observations.
  • Whether the instrument teams' evaluation of the flyby data turns up calibration problems that have to be fixed before Jupiter.
  • The number of correction burns Juice needs ahead of its January 2029 Earth flyby, the last before arrival.

Clarity's read

What the record supports and how the coverage leans. The claims behind it follow.

Reality

Evidence58
Adoption
Not scored
Hype gap+12
Incentives45
Confidence62
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Claim ledger

Ranked by verification strength, evidence, and original report placement.

  1. [1]

    Juice skimmed the very outer edge of Earth's atmosphere on 28 September, using Earth's gravity to alter its route to Jupiter using very little fuel.

    Reported SupportedView cited source
  2. [2]

    The flyby deflected Juice by an angle of 20 degrees compared to its pre-flyby path.

    Reported SupportedView cited source
  3. [3]

    The flyby increased Juice's velocity by 3.5 km/s.

    Reported SupportedView cited source
  4. [4]

    Juice's closest approach was at 13:45 CEST (11:45 UTC) on 28 September, 8640 km above the Indian Ocean, and it took a series of images with its onboard monitoring cameras.

    Reported SupportedView cited source
  5. [5]

    "The flyby required ultra-precise navigation in real time. Thanks to our very careful planning, we used only a small amount of the propellant reserved for this flyby," said Angela Dietz, Juice's Spacecraft Operations Manager.

    Reported Supported Source: Angela Dietz, Juice Spacecraft Operations Manager, quoted by ESAView cited source
  6. [6]

    "This gives us more to use at Jupiter to carry out observations of the planet's icy moons."

    Reported Supported Source: Angela Dietz, Juice Spacecraft Operations Manager, quoted by ESAView cited source
  7. [7]

    The flyby was the third opportunity to test Juice's science instruments on a real surface in space, after the 2024 lunar-Earth gravity assist and the 2025 observations of Comet 3I/ATLAS.

    Reported SupportedView cited source
  8. [8]

    Colleagues from ESA's spacecraft operations, science operations and technical centres spent months working with the external teams working on Juice's 10 science instruments to plan which instruments to switch on and when.

    Reported SupportedView cited source
  9. [9]

    "Juice's journey to Jupiter provides only a few opportunities to calibrate and validate the instruments under well-understood environmental conditions."

    Reported Supported Source: Claire Vallat, Juice project scientist, quoted by ESAView cited source
  10. [10]

    "Given the limited time available and operational constraints, instrument activities sometimes have to be prioritised, for example when Juice was in Earth's shadow this morning, and relying on battery power alone."

    Reported Supported Source: Claire Vallat, Juice project scientist, quoted by ESAView cited source
  11. [11]

    "During this flyby, calibration activities were prioritised based on their relevance to preparing the instruments for their work at Jupiter, while also considering whether an opportunity is unique or can be scheduled later in the journey."

    Reported Supported Source: Claire Vallat, Juice project scientist, quoted by ESAView cited source
  12. [12]

    ESA says an Earth flyby is relatively straightforward compared to Juice's upcoming 35 flybys of Jupiter's giant moons, which the release names as including Ganymede and Europa.

    Reported SupportedView cited source
  13. [13]

    For the Europa flybys, discussions on instrument operations started 10 years ago and will continue until Juice flies past Europa in the early 2030s.

    Reported SupportedView cited source
  14. [14]

    During the Earth flyby, Juice spent several days flying through the magnetotail, measuring magnetic fields and charged particles far from Earth.

    Reported SupportedView cited source
  15. [15]

    The European-Chinese Smile mission watched the northern lights and measured magnetic fields and particles close to Earth; ESA says Juice and Smile's observations together provide a unique opportunity to connect activity in the distant magnetotail with what is happening at Earth's poles.

    Reported SupportedView cited source
  16. [16]

    ESA expects to publish images and spectra from some of Juice's instruments in the coming weeks, after evaluation by instrument teams, including high-resolution images of the Moon and Earth from the JANUS camera.

    Reported SupportedView cited source
  17. [17]

    In January 2029 Juice will make a third flyby of Earth to put it onto the final track to meet Jupiter in 2031.

    Reported SupportedView cited source
  18. [18]

    In the four weeks before the flyby, spacecraft operators only had to give Juice one tiny nudge, out of six opportunities set aside, to put it on exactly the right approach trajectory to make the most of Earth's gravity.

    Reported SupportedView cited source
  19. [19]

    Operators have been tracking the spacecraft extra carefully since 17 August and will continue to do so until 10 October.

    Reported SupportedView cited source
  20. [20]

    Five of the six course-correction opportunities set aside before the flyby went unused.

    Derived Supported

Sources

2 independent publishers whose own reporting we read for this story.

  1. esa.int

    1 article · September 28, 2026

    Successful Earth flyby improves Juice’s course to Jupiter
  2. scientificamerican.com

    1 article · September 29, 2026

    See the cool photos this Jupiter-bound spacecraft took while swinging by Earth

Topics and entities

Topics

  • Magnetosphere and space weather
  • Planetary Science Missions

Entities