JUNO’S PATH TO JUPITER
After the Atlas V rocket launched Juno into space, it placed the spacecraft in a parking orbit, in which it coasted around Earth. At a particular point in this orbit, the rocket fired again to put Juno on course toward Jupiter. Before separating from Juno, a set of thrusters fired to spin up the spacecraft along with its upper stage. Once Juno separated from the rocket, its three large solar arrays unfurled to begin charging its batteries.
While on its way to orbit, Juno communicated with ground controllers using the antennas on the Atlas rocket. But once the spacecraft detached from the last rocket stage, it began communicating with Earth directly. NASA’s Deep Space Network, with giant antennas in California, Spain and Australia, locked onto its signal.
Juno spent two years cruising the inner solar system before arriving at Jupiter.
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TEST AS YOU FLY
Extensive testing is done to ensure Juno makes it to Jupiter
Test as you fly
THE FLIGHT PLAN
Juno’s trajectory takes it on a five-year voyage, circling the inner solar system before arriving at Jupiter.
The Flight PlanJuno launched in August 2011 and took about five years to travel to Jupiter, first looping around the inner solar system and swinging past Earth to get a boost in its speed that propelled it onward to its destination. But why not send it directly to Jupiter?
Though the journey may seem long, Juno’s flight plan allowed the mission to use Earth’s own gravity to speed the craft on its way. To get the necessary speed from a rocket would require a much more powerful launch vehicle and a lot more fuel. Many space missions have used this technique, called a gravity assist (also sometimes called a “gravitational slingshot”), to get to their destinations.
In July 2016, Juno fired its main engine for the last time and slipped into polar orbit around Jupiter where it remains today, working diligently to unravel the planet’s many exciting mysteries.
AMOUNT OF FUEL
Since there are no filling stations in space, Juno has to carry enough fuel for its entire trip.
Amount of fuelJuno carries six spherical propellant tanks – four containing fuel (called hydrazine) and two holding oxidizer (called nitrogen tetroxide). Juno has a main engine, and 12 smaller thrusters. When the main engine is used, the two propellants combine and they burn to give Juno thrust.
The main engine was used for large adjustments to the trajectory, like orbit insertion. Together, the propellants have a mass of just over 4,400 pounds (2,000 kilograms) at launch, accounting for 55 to 60 percent of the spacecraft’s mass.
Aboard Juno, there are also 12 thrusters that fire bursts of hydrazine for smaller adjustments or maintenance of its trajectory, to adjust its rotation and to adjust its orientation in space. Juno also has two tanks of liquid helium used to pressurize the tank, allowing the propellants to flow.