Juno | Welcome to Jupiter

UPDATE: The Juno spacecraft was successfully captured into a long eccentric orbit. The main engine burned about 35 minutes to slow down as planned when Juno was at its closest to Jupiter depicted in the animation below. The spacecraft performed as expected. All scientists breathed a sigh of relief.

Original Post: The Juno spacecraft launched in August 2011. It coasted away from Earth and returned for a gravity assist flyby in October 2013. That flyby boosted the speed of Juno enabling it to coast away from the Sun and toward Jupiter. It arrives at Jupiter on the 4th of July at 9:30 CDT.

The trajectory brings Juno toward Jupiter over the north pole going 160,000 mph (257,000 km/h) . Its rocket will fire for about 35 min to slow it down in order to be captured in a highly eccentric polar orbit. Previous spacecraft have never visited Jupiter in this kind of orbit or this close. What will Juno encounter?

Juno is Huge

A human figure is shown next to the spacecraft. Three sets of solar panels extend out to capture the weaker light from the Sun. The diameter of the spacecraft is 66 ft (20 m). It is 15 ft (4.5 m) tall. It would take up as much space as a professional basketball court. Click to embiggen.



How Did Juno Get There?

This video illustrated the complex path taken by Juno. Our launch rockets are not powerful enough to give a spacecraft the speed needed to coast as far as Jupiter. The Sun pull them back before they reach that far. Juno was launched so it would return to Earth and transfer some of Earth’s momentum to the spacecraft. That gravitational assist gave it the necessary speed and direction. Watch as Earth orbits the Sun twice while waiting for the return flyby of Juno. No audio.


Details of Arrival Maneuvers

Juno must complete a series of choreographed maneuvers in a short time upon arrival. The transit time for radio communication is about 45 min one way. It must do these actions on its own. Video has no audio.

  • Engine cover opens
  • Thrusters orient Juno away from the Sun so the main engine can slow it down
  • Thrusters spin Juno to a faster rotation rate
  • Main engine fires about 35 min to slow the spacecraft for capture in orbit
  • Thrusters spin Juno to a slower rotation rate
  • Thrusters orient Juno back toward the Sun so the solar panels can function


Science Orbits of Juno

The highly eccentric science orbits will be traveled at least 33 times according to the primary mission plan. Each orbit takes about 14 days and is perturbed somewhat from the previous orbit.




At closest approach, Juno is about 3000 miles from the cloud tops of Jupiter. This close approach brings Juno through intense radiation zones twice each orbit, here pictured in reds, yellows, and oranges.




Science Goals

Four and a half billion years ago our solar system formed from a collapsing cloud of dust and gas called a nebula. The Sun was first followed by Jupiter. It follows that Jupiter is composed of the same hydrogen and helium gases as the Sun. But, we don’t know much about the internal structure of the planet since it is shrouded in clouds. We can see the cloud tops as they rotate around the planet. Juno will pass close to those clouds. The instruments will penetrate deeply looking for structure and composition, giving us our best detailed analysis of them.




What is at the core of Jupiter? Is there a rocky core? Is it something more exotic such as metallic hydrogen? Juno should help give some insights into answers.




Radiation is a danger to the spacecraft. Jupiter’s magnetic field traps and energizes electrons to very high intensity. These can be harmful to electronics. So, they must be protected inside a special vault made of thick titanium. The dosage levels received by Juno will be equivalent to a human getting 100,000,000 dental x-rays in a year.



The public is invited to participate in this mission via JunoCam. Amateurs can upload their own ground based images of Jupiter. Plus, Juno has an imaging system. The public will have input and a vote on what targets to capture on Jupiter. You can see details and sign up at the link above.


9 thoughts on “Juno | Welcome to Jupiter

  1. This really was wonderful. I didn’t watch in real time, but hooray for videos, and all those scientists on Twitter, expressing their excitement.

    Have you ever read Loren Eiseley’s piece, “The Fifth Planet”? It’s in his book titled The Star Thrower. It’s only about ten pages, but it’s — interesting. There’s no way to describe it, but if you can find it, it’s worth it.

    Liked by 1 person

    • The sun sends protons and electrons outward as a sort of wind. The magnetosphere captures the electrons easily as they are not massive like protons. Earth does that too.
      Many electrons are directed toward the poles along the magnetic field lines and cause aurorae.
      Jupiter traps many many more electrons. They get accelerated back and forth in the magnetosphere to high speeds. Those rapid accelerations of the electrons causes them to radiate their excess energy as electromagnetic radiation.
      Maybe too much information? 🙂


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