LOS ANGELES - After a nearly five-year journey, a solar-powered spacecraft is passing Jupiter's inner moons as it readies for the closest encounter with the biggest planet in the solar system.

NASA's Juno spacecraft will fire its main rocket engine late Monday to slow itself down from a speed of 150,000 mph (250,000 kph) and slip into orbit around Jupiter.

Juno chief scientist Scott Bolton said at a morning briefing that the spacecraft is expected to survive rings of debris and a hostile radiation environment because it's "built like an armored tank."

NASA released a series of images taken last week during the approach, showing the destination planet glowing yellow in the distance, circled by its four inner moons.

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

Image: NASA.gov