LOS ANGELES: A solar-powered spacecraft is spinning towards Jupiter for the closest encounter with the biggest planet in our solar system.

Nasa’s Juno spacecraft fires its main rocket engine late on Monday to slow itself down from a speed of 150,000 mph (250,000 kph) and slip into orbit around Jupiter. With Juno on autopilot, the delicately choreographed move comes without any help from ground controllers.

Juno is travelling through a hostile radiation environment, “but it should be able to withstand it,” said Kenny Starnes, programme manager for Lockheed Martin, which built the spacecraft. Juno’s camera and other instruments were switched off for the arrival so there won’t be any pictures at the moment the spacecraft reaches its destination.

Scientists have promised close-up views of Jupiter when Juno skims the cloud tops during the 20-month, $1.1 billion mission.

The fifth rock from the sun and the heftiest planet in the solar system, Jupiter is what’s known as a gas giant — a ball of hydrogen and helium — unlike rocky Earth and Mars.

With its billowy clouds and colourful stripes, Jupiter is an extreme world that likely formed first, shortly after the sun. Unlocking its history may hold clues to understanding how Earth and the rest of the solar system developed.

Named after Jupiter’s cloud-piercing wife, Juno is only the second mission designed to spend time at Jupiter. Galileo, launched in 1989, circled Jupiter for 14 years, beaming back splendid views of the planet and its numerous moons.

It uncovered signs of an ocean beneath the icy surface of Europa, considered a top target in the search for life outside Earth. Juno’s mission: To peer through Jupiter’s cloud-socked atmosphere and map the interior from a unique vantage point above the poles.

Published in Dawn, July 5th, 2016