This is the longest mission Juno has ever undertaken, and it is extraordinarily long in mission standards.
Known as 'the burn,' the goal of the maneuver is to keep Juno's solar-powered spacecraft out of Jupiter's shadow, due on November 3. If Juno were to fall in the shadow's path, it would mean the end of the mission.
How did Juno undergo the maneuver?
Beginning at 7:46 pm EDT on September 30th, the spacecraft used its reaction-control thrusters to propel itself in the right direction. In doing so, Juno's orbital velocity changed to 126 mph (203 kph) and used up 160 pounds (72 kg) of fuel.
If Juno had not made this shift, it would have needed 12 hours to cross Jupiter's shadow, which would eventually use up all of the spacecraft's battery power. Without power, and with rapidly dropping temperatures, Juno would have most likely frozen up and would have been unable to re-start, upon leaving the shadow.
Scott Bolton, Juno principal investigator at the Southwest Research Institute, said: "With the success of this burn, we are on track to jump the shadow on Nov. 3."
Bolton further added: "Jumping over the shadow was an amazingly creative solution to what seemed like a fatal geometry. Eclipses are generally not friends of solar-powered spacecraft. Now instead of worrying about freezing to death, I am looking forward to the next science discovery that Jupiter has in store for Juno."
What is Juno doing up in Space?
Since 2011, Juno has been navigating in and observing deep space.
At the start of its mission, on July 4, 2016, Juno entered a 53-day orbit around Jupiter. The plan for this mission was to minimize the size of its orbit a few months after deployment. Furthermore, the plan was to decrease the number of scientific fly-bys of the gas giant, to every 14 days.
However, plans can change, and the project team recommended that NASA renounce this method for fear that the spacecraft's fuel delivery system would fail.
All that being said and done, Juno is still delivering and gathering information about Jupiter, as per its original plan — it just takes longer to do so.
It's because of its longer mission time, precisely, that Juno had to undergo this recent maneuver to avoid being in Jupiter's shadow.
Ed Hirst, Juno project manager at NASA's Jet Propulsion Laboratory, said: "Pre-launch mission planning did not anticipate a lengthy eclipse that would plunge our solar-powered spacecraft into darkness."
"That we could plan and execute the necessary maneuver while operating in Jupiter's orbit is a testament to the ingenuity and skill of our team, along with the extraordinary capability and versatility of our spacecraft," declared Hirst.
Luckily, thanks to the team's forward-thinking maneuver, Juno should be able to continue its tracking of Jupiter for a while yet.