NASA prepares for Juno spacecraft to enter Jupiter’s orbit following five-year flight

AFTER five years of hard work it all comes down to these 35 minutes for the Juno spacecraft. If anything goes wrong, there is nothing anyone can do.

This 2010 artist's rendering depicts NASA's Juno spacecraft with Jupiter in the background. Picture: NASA/JPL

AFTER 1795 days and 2.9 billion kilometres, NASA’s Juno probe is on the brink of giving humankind its most detailed look at Jupiter.

It’s currently hurtling towards the giant gas planet at 30km per second.

If all goes according to plan, Juno will map the gravitational and magnetic fields of Jupiter, characterise its internal structure and study the source of its raging 618km/h winds.

Juno will also hunt for water in Jupiter’s atmosphere, which may help explain how Earth got its water.

But before any of that can happen the solar powered probe must successfully pull off arguably the most critical phase of the mission since launching nearly five years ago.

The key event will take place about noon tomorrow AEST when the Juno probe will commence a 35-minute engine burn designed to allow the spacecraft to slow down enough for it to be captured by Jupiter’s powerful gravity.

In order to do so, Juno will have to survive a circuit-frying radiation storm generated by Jupiter’s powerful magnetic field. If anything goes wrong, there is nothing anyone can do.

The maelstrom of high energy particles travelling at nearly the speed of light is believed to be the harshest radiation environment in the Solar System.

To cope with the conditions, the spacecraft is protected by special radiation-hardened wiring and sensor shielding.

Its all-important “brain” — the flight computer — is housed in an armoured vault made of titanium and weighing almost 175kg.

If Juno successfully enters Jupiter’s orbit, NASA researchers will know via a very simple radio signal — a three second beep.

“I can tell you when that completes, you’re going to see a lot of celebration,” said Rick Nybakken, Juno’s project manager, “because that means we’ll be in orbit around Jupiter, and that’ll be really cool.”

NASA technicians stow solar array #2 against the body of NASA's Juno spacecraft in 2011. Picture: AP/NASA.

NASA Program Executive Diane Brown (L), Juno Mission Principal Investigator Scott Bolton (C) and Robert Kondrk (R), Apple vice president for Content and Media Apps, attend a press conference about the mission. Picture: Robyn Beck

A 1/5 scale model size of NASA's solar-powered Juno spacecraft is displayed at the Jet Propulsion Laboratory in Pasadena, California. Picture: Richard Vogel/AP

The gas giant is the largest planet in our solar system, containing more mass than all the other planets combined — and scientists are chomping at the bit to learn more.

It will be the first time NASA has had a spacecraft orbiting Jupiter in more than a decade. Previously, the space agency’s unmanned Galileo spacecraft spent eight years orbiting the gaseous planet after launching in 1989.

However the Juno probe will be extremely close, flying to within 4667km of Jupiter’s swirling cloud tops. By comparison, Galileo made wide orbits at distances of hundreds of thousands of kilometres in order to avoid serious danger from the radiation.

“Looking for the kind of data Juno is looking for, you have to go in the kind of neighbourhoods where you could find trouble pretty quick,” Juno’s principal investigator Dr Scott Bolton said.

“We are not looking for trouble, we are looking for data,” he added.

As a further safeguard, Juno is programmed to follow a long orbital path that avoids Jupiter’s radiation belts as much as possible.

Despite all the precautionary measures being taken by NASA, the probe is not expected to last much longer than its planned lifespan of 20 months.

Unusually for a robotic space mission, Juno is carrying passengers — three Lego figures depicting the 17th century Italian astronomer Galileo Galilei, the Roman god Jupiter, and the deity’s wife Juno. Lego made the figures out of aluminium rather than the usual plastic so they could withstand the extreme conditions of space flight.

Also on board is a plaque dedicated to Galileo and provided by the Italian Space Agency. It shows a portrait of Galileo and text written by the astronomer in January 1610 while observing Jupiter’s four largest moons — later to be known as the Galilean moons.

The mission is part of the US space agency Nasa’s New Frontiers program of robotic space missions which last year saw the New Horizons spacecraft obtain close up views of dwarf planet Pluto.

Tomorrow morning’s nailbiting leg will mark the culmination of the mission so far after launching in August 2011 — and it’s going to provide some very nervous moments for the men and women behind it.

This artist's rendering provided by NASA and JPL-Caltech shows the Juno spacecraft above the planet Jupiter. Picture: NASA/JPL-Caltech

WHAT WE STILL DON’T KNOW ABOUT JUPITER

Jupiter is a ball of mostly hydrogen and helium and was probably the first planet to form. It’s 11 times wider than Earth and is 300 times heavier.

The most prominent feature of the gaseous planet is the Great Red Spot, a fierce storm in the atmosphere larger than Earth that has lasted for centuries. However in recent years the spot has been mysteriously shrinking.

It was once an oval about 41,036km wide in the late 1880s but when observed in 2014 it had shrunk to its smallest known size of 16,495km across.

Juno will explore how deep into the atmosphere the Great Red Spot extends to give researchers a better understanding of its nature. It will also be able to give researchers an idea of the amount of water in the planet’s atmosphere.

Jupiter’s aurora lights are the brightest in the solar system, making Earth’s northern and southern lights look exceptionally dim. The spectacular phenomena can stretch for tens of thousands of kilometres around the poles of the planet.

Juno will use sensors to identify the electrons and types of positive ions that produce the magical light show in order to allow researchers to better understand it.

As mentioned, one of the big questions Juno is expected to answer is whether or not Jupiter has a solid core. If that does prove to be the case, it will have a slight and measurable impact on Juno orbit. A constant radio signal being sent to Juno and relayed back to Earth will give scientists a picture of the internal makeup of the planet.

What the weather looks like below the stormy belt of clouds that surrounds the planet is also something scientists believe Juno can help them answer.

By analysing microwaves the spacecraft will be able to measure the chemical composition of the atmosphere over 500km below the tumultuous cloud tops.

— With AAP