A spacecraft flight that explores a planet or other astral body by passing it without being captured into its orbit and without having its flight path altered by the body's gravitational pull. The craft therefore has only a limited amount of time to gather data. Fly-by spacecraft, which follow either an escape trajectory or a continuous solar orbit, must be capable of surviving long interplanetary periods. Deep-space fly-bys have included encounters by the Voyager probes, Mariner spacecraft, and Pioneer probe series.