An artist's impression of Juno once it has reached its target Jupiter. Credit: NASA/JPL

An artist's impression of Juno once it has reached its target Jupiter. Credit: NASA/JPL

Sen—NASA's latest mission to Jupiter will perform its first deep space manoeuvre this week with an engine burn that will send it heading back towards the Earth.

That may sound odd. But the $700 million Juno probe, which was launched just over a year ago on August 5, 2011, atop an Atlas V rocket, is using the pull of the planets to speed it on its way.

It is a kind of interplanetary snooker. Even so, it will not reach Jupiter until 2016 when it will go into a polar orbit to find out what the Solar System's largest planet is made of by mapping every part of it.

NASA report that Juno, which is now 489 million km (304 million miles) away from Earth, is in excellent health. It had travelled 760 million km (472 million miles) since launch.

The cover protecting its main engine was ordered to be removed on August 23 by mission control and the probe's battery is now 100 per cent charged for the upcoming burn, on August 30, lasting around half an hour. There will be a second next week on September 4.

Juno's principal scientist Scott Bolton, of the Southwest Research Institute at San Antonio, Texas, told Sen yesterday: "Everything is going great!

"We'll be firing the main engine for the first time. It is one of two burns. They are designed to basically set up the trajectory so that the flyby of the Earth, which will happen in October, gives us the proper gravity-assist.

"This burn was planned right from the beginning in the trajectory and it is split into two parts because it is a long burn that is needed and the engines don't normally burn for more than 40 minutes at a time.

Juno's position in space on August 22 according to NASA's Eyes on the Solar System

"The burn basically just lines things up so that the spacecraft's trajectory goes past the Earth at the right distance and in the right direction so that its gravity can twist us around and speed us up so that we can reach out to Jupiter."

Last week, Juno's mission operations team prepared the spacecraft for the upcoming manoeuvres, pre-heating helium tanks that pressurise the propulsion system, pressurising the fuel tanks, and uplinking a sequence of commands to be run by the onboard computer.

Juno, which is travelling at a speed of 55,800 km per hour (34,700 mph), has four of its instruments already switched on and collecting data. They are the Magnetometer experiment, the Jovian Energetic-particle Detector Instrument (JEDI), the Microwave Radiometer (MWR) and the Radio and Plasma Wave Sensor (WAVES).