The Juno spacecraft is using Earth for a gravity assist this Wednesday, October 9th! In case you aren’t familiar with Juno, it is a NASA spacecraft built to study Jupiter. I feel a special connection with Juno, because I watched it launch from Cape Canaveral aboard an Atlas V rocket on August 5, 2011.*(For more on that see the end of the article).
Juno is scheduled to reach Jupiter in 2016. Fun fact: Juno is the first spacecraft sent to the outer Solar System that uses solar power as its primary energy source. Juno has three huge solar panels, each nearly the size of a tractor trailer. They folded up neatly while inside the Atlas V for launch, then opened outward once in space. These panels will face the Sun, collecting energy for the duration of the voyage. Juno weighs about 8,000 pounds and is named for the Roman goddess Juno, wife of Jupiter (known as Zeus in Greek Mythology).
To get to Jupiter, Juno will perform a gravity assist using Earth. Essentially, it will use Earth’s gravity to slingshot itself out into space. The gravity assist will give Juno an extra boost of speed then it will coast the rest of the way to Jupiter. Juno is a very large spacecraft, and it will most likely be possible to view it as it makes its flyby. Unfortunately for viewers in the United States, Juno will not be visible. Observers in parts of Africa and Asia will be on the lookout. Don’t worry, you can tune in on Slooh.com for a live news feed of Juno‘s flyby. Click here for an observational chart of how to spot Juno around the world.
So what is Juno going to do once it gets to Jupiter? Juno will orbit Jupiter thirty-three times between July of 2016 and October of 2017. It will travel in highly elongated orbits that will be slightly shifted so that after all thirty-three passes, Juno will have passed over the entire surface of Jupiter. The purpose of this elongated orbit is that it allows the craft to skim very close to Jupiter, but then takes it away again, therefore minimizing its exposure to the strong radiation coming from Jupiter. Juno will map Jupiter’s gravitational and magnetic fields, helping us better understand the structure of the planet. It will study Jupiter’s aurorae at its poles. Juno will also measure its chemical composition more closely, including its water content. All of this information about our Solar System’s oldest planet will help scientists gain a better understanding of how Jupiter formed, which will in turn better our understanding of the formation of our entire Solar System.
Will Juno stay out there forever? Juno has a very specifically timed mission, and once it completes its work, Juno will crash into Jupiter’s atmosphere. At the end of its mission, Jupiter’s radiation will have destroyed most of the spacecraft’s instruments despite its thick shielding. The main reason for the crash down is to prevent Juno from landing accidentally on one of Jupiter’s moons. An accidental landing of an Earth spacecraft could contaminate these environments, which would complicate future study.
*Below is the full dome footage that I captured of the Juno launch. We were as close as civilians could get (we were bussed in). The actual blastoff happens around two minutes in. If you watch the whole thing you can hear mission control doing preflight checks and the countdown. Also, there was a dad with his two kids who was VERY excited about the whole affair, and provides some humorous commentary throughout the video. We were far enough away that we experienced the launch in stages. First we saw the light of ignition, then a few seconds later we heard the rumble of the engines, then a few seconds later we felt the heat blast. Yes, in 95 degree Florida heat from over a mile away we still felt the heat blast from the rocket. It was truly an awesome experience.