Spacecraft Juno on final approach to planet Jupiter

Voyage extending to five years almost at an end in quest to unlock secrets of giant world

A computer generated images of the spacecraft on its approach to Jupiter.

A five-year multimillion kilometre journey is almost at an end as the Juno spacecraft prepares for a July rendezvous with the giant planet Jupiter.

The craft was launched in 2011 by the US National Aeronautics and Space Administration and overseen by the Jet Propulsion Laboratory in Pasadena. Its mission is to observe the largest planet in the solar system from as close as possible.

Juno will fly over the poles, skimming to within as little as 5,000km above the thick cloud tops that prevent us from knowing what lies beneath.

The spacecraft’s cameras will give us close-ups of these clouds and the s storms that drive them at speeds up to hundreds of kilometres per hour.


But Juno also carries a battery of experiments that can look below the surface at the planet’s solid core, measure water and ammonia levels under the cloud tops and study its magnetic field.

Gravitational pull

Juno reached a milestone of sorts this weekend, crossing an invisible yet important threshold where Jupiter's powerful gravitational pull finally becomes stronger than the counterbalancing pull of the sun.

From now on the spacecraft will be using its rocket engine to resist the enormous gravitational tug of this gas giant.

Juno will fire this engine on July 4th to slow it and allow it to drop into a smooth orbit around the planet.

The spacecraft will circle the planet 37 times, collecting data all the while for transmission back to Earth and analysis by an army of scientists.

One sight that all will want to see is a close-up view of the famed Jovian auroras. Like the planet itself these "northern lights" are on a grand scale, flashing across the poles to give an enormous fireworks display.

Just as dramatic will be Juno’s end, a one-way descent down through the clouds and certain destruction.

Scientists are hopeful Juno will be able to send back data right to the end as it plummets through the heavy atmosphere to certain destruction.

Dick Ahlstrom

Dick Ahlstrom

Dick Ahlstrom, a contributor to The Irish Times, is the newspaper's former Science Editor.