Flyby
A flyby is a mission or manoeuvre in which a spacecraft passes close to a body without stopping or orbiting it.
In a flyby, a spacecraft travels past a planet, moon, asteroid or comet, studying it during a close approach that may last only hours. Flybys are cheaper than going into orbit, because the craft does not need to brake.
Many of the first close-up views of small bodies came from flybys. The Galileo spacecraft, on its way to Jupiter, flew past asteroid Gaspra in 1991 and asteroid Ida in 1993, discovering that Ida has a tiny moon, Dactyl. The Giotto probe flew through the cloud around Halley's Comet in 1986, and NASA's Lucy mission flew past the small asteroid Dinkinesh in 2023, finding that it has a contact-binary moon.
Flybys can also be used to change a spacecraft's path. By passing close to a planet, a probe can steal or give up a little of the planet's orbital energy, a trick called a gravity assist, which helps it reach distant targets.
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Level: Explorer Ages 10 and up