Now that science is beginning, a lot of people are asking questions about how this mission will be different from Galileo. To be sure, Juno and Galileo share a lot of similar instruments -- plasma waves, magnetometer, energetic particles, radio science. All of these instruments are designed to investigate Jupiter's magnetic field, energetic particle environment, and internal structure. What makes them different?

It's mostly about location. "Fields and particles" instruments do in-situ investigations, meaning that they measure properties of Jupiter at the location of the spacecraft. This is in contrast to remote sensing investigations, which measure properties of Jupiter from a distance.

If you are an in-situ investigation examining a 3-dimensional structure like Jupiter's magnetosphere, you need to take your spacecraft to as many different locations within the 3-D structure as you can. Because it focused on Jupiter's moons, Galileo was constrained to an orbit close to the plane of the moons' orbits, confining it to only a 2-D slice of the magnetosphere around the equator. Galileo also avoided Jupiter's donut-shaped radiation belts, mostly staying relatively far away from Jupiter outside Europa's orbit, so hardly probed the magnetosphere close to the planet.

In contrast to Galileo, Juno has a polar orbit that will fly to a wide variety of different latitudes and distances from Jupiter. And its orbit takes it through the donut hole of the radiation belts, very close to the planet.

Here are two views comparing the Galileo and Juno orbital trajectories at Jupiter, created using a really terrific visualization tool built by Science News. You can see that while Galileo samples a lot of longitudes, all its orbits are in one plane and mostly pretty far from Jupiter.