Destined for Jupiter's icy moon Europa, the Europa Clipper spacecraft—the largest NASA has ever flown on an interplanetary mission—is being readied to launch in October 2024. Between now and then, thousands of hours of work will go into assembling and testing the spacecraft to ensure it's hardy enough to survive a six-year 1.6-billion-mile (2.6 billion kilometer) journey and sophisticated enough to perform a detailed science investigation of this mysterious moon.