Himalia is the most massive and second largest non-Galilean moon of Jupiter. Yet, due to its distant orbit, we still don't have sharp images of it. Does Juno have enough fuel to alter its orbit with the help of Jupiter's gravity in order to reach the outermost moons?

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    $\begingroup$ “with the help of Jupiter's gravity” forgive me if I’m not understanding, but isn’t that literally just called orbiting. $\endgroup$
    – Topcode
    Commented Oct 18, 2022 at 18:14
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    $\begingroup$ The question is much more answerable if you remove "with the help of Jupiter's gravity" and replace it with "with gravitational assists from the other moons" $\endgroup$
    – uhoh
    Commented Oct 18, 2022 at 21:38
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    $\begingroup$ @uhoh Well, Mark Foskey answered why this doesn't work when the probe is orbiting the body in question already. I'll ask a separate question on gravitational assists from the moons. $\endgroup$
    – Nullnummer
    Commented Oct 19, 2022 at 5:46
  • $\begingroup$ About fuel of Juno - it should have significant amount of fuel left. It was planned to reduce orbital period from 56 days to 14 days, but its main egine malfunctioned. The required delta v was about 350m/s. spaceflight101.com/juno/juno-mission-trajectory-design Plus some reserve fuel after that - so probably Juno could technically reach outer satellites of Jupiter. But, as other comments said - it's not the purpose of Juno. $\endgroup$
    – Heopps
    Commented Oct 19, 2022 at 5:59
  • $\begingroup$ @Heopps Thank you. No other comment said that it's not the purpose of Juno and it would be good if NASA decided to study bodies that we don't know that much about as yet. $\endgroup$
    – Nullnummer
    Commented Oct 19, 2022 at 7:43

1 Answer 1


When you are in orbit about a planet, it cannot provide you a gravitational assist to get in into a higher orbit about that planet (except very gradually via tidal forces). When a probe uses Jupiter for a gravitational assist, it is relying on Jupiter's gravity along with its motion relative to the sun to pick up speed relative to the sun.

It is possible to use the Galilean moons to get into a higher orbit, but I don't know if it would be possible for Juno to use that method to get closer to the outer moons. Considering that the camera is intended mainly for public outreach, I don't think planners have even considered it. That's just not what Juno is for.

Still, I recognize you asked if Juno had the fuel to do it, and I don't have that answer. But I did think this would provide useful background.


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