All You Need to Know About NASA's Juno Spacecraft & What Will We Learn from its Mission to Jupiter?

On August 12 2013, NASA's Juno Spacecraft reached the halfway point on it's journey to Jupiter.
Since launching back in 2011, it has traveled a little over 9.46 Astronomical Units(The distance from the Earth to the Sun is 1 AU), and has performed a series of planetary flybys and deep space maneuvers. In October of this year, Juno will come within 350 miles of Earth's surface. This is known as a gravity assist, or a gravitational slingshot. After Juno says its farewells to planet Earth for the final time, it will race towards the Jovian system before its slated arrival time of 3:29 a.m. UTC, give or take a few minutes!

But before we start asking about what we are expecting to learn from Juno's voyage, let's ask ourselves a few simpler questions about Juno itself..


Why the name Juno?
In Greek and Roman mythology, Jupiter was the king of the gods, as well as god of the sky and thunder. Jupiter drew a veil of clouds around himself to hide his mischief, and his wife, the goddess Juno, was able to peer through the clouds and reveal Jupiter's true nature.


Why does Juno need a gravity assist from Earth?
Well, to put it simply, there just wasn't enough rocket power available to launch a payload of Juno's size directly to Jupiter- over 400 million miles away. Instead, Juno was launched out past the orbit of Mars, before it performed crucial Deep Space Maneuvers to set itself up for October's flyby of Earth. Juno Mission Project Manager Rick Nybakken explains further;

"On Oct. 9, Juno will come within 347 miles (559 kilometers) of Earth. The Earth flyby will give Juno a kick in the pants, boosting its velocity by 16,330 mph (about 7.3 kilometers per second). From there, it's next stop Jupiter... Almost like a second launch for free"!

Confused? Well, think of it this way. If a golfer hits a putt towards the edge of the hole, and the ball does not fall into the cup, instead, hitting the very edge of the hole and "Lipping out", the ball will shoot off in another direction at a faster speed than before. You got the hang of this? Right, let's move on.


When Juno arrives at Jupiter in 2016, it will orbit the gaseous planet for around a year, completing 33 orbits around the planet's poles, using onboard scientific equipment to probe beneath the planet's obscuring yet beautiful clouds.

The main goals of the Juno mission are:

-To find out how much water is in Jupiter's atmosphere, which helps determine which planet formation theory is correct (or if new theories are needed).
-To look deep into Jupiter's atmosphere to measure composition, temperature, cloud motions and other properties.
-To map Jupiter's magnetic and gravity fields, revealing the planet's deep structure
-To explore and study Jupiter's magnetosphere near the planet's poles, especially the auroras – Jupiter's northern and southern lights – providing new insights about how the planet's enormous magnetic force field affects its atmosphere.

Juno's patch to Jupiter
credit: NASA

One of the main mission objectives is to discover how a giant planet like Jupiter came into being, and how it evolved. This cloudy world is a primary example of a giant planet, and can also give us clues as to how other giant gas planets(called "Hot-Jupiters") which we have discovered orbiting other stars, may have formed.

Juno will accomplish this by studying the planet's cloudy atmosphere and its overall composition. By the end of the mission it is hoped that we will be able to see how Jupiter was born, and how important of a role it played in the formation of other planets in the solar system.

Using the suite of scientific instruments aboard Juno, teams back on Earth will study the magnetosphere of Jupiter, which will tell us if Jupiter has a solid core, and how big or small it might be.

End Mission

After completing primary mission objectives and 33 orbits around Jupiter in 2017, Juno will perform a series of de-orbit burns to take the spacecraft out of Jovian orbit and into a destructive re-entry in Jupiter's upper atmosphere.

But first, on October 9th 2013, Juno will return to within 350 miles of Earth to say one last goodbye to planet Earth, before heading to Jupiter to try and unlock some of the secrets of our solar system's biggest planet.