Bound for planet Jupiter in 2015, the unmanned space probe Juno swings past Earth to catch a gravity assist boost from its home planet. Launched in 2011, Juno slips past Earth at a distance of only 350 miles, boosting its speed to 93,000 miles per hour relative to the sun, fast enough to cross the distance between Earth and its moon in three hours (by comparison, the Apollo manned missions of the 1960s took three days to make that trip). But as it comes out of Earth’s shadow, Juno goes into a failsafe mode to protect the spacecraft against an unanticipated fault. Juno is brought back online within two days as it continues on the final leg of its flight to Jupiter.
