First gravity-assist manoeuvre using Earth

On 02/07/1990, the European Space Agency’s Giotto spacecraft executed the first-ever Earth gravity-assist maneuver by a deep-space probe, using the planet’s gravitational field to alter its trajectory and continue its mission. This event occurred exactly five years after Giotto’s launch on 02/07/1985, marking a carefully timed return to Earth’s vicinity after its initial mission phase. Giotto was originally launched to study Halley’s Comet, successfully performing a close flyby on 14/03/1986 and capturing some of the first detailed images of a comet’s nucleus. After completing this primary objective, mission planners extended its use by designing a trajectory that would bring the spacecraft back toward Earth. During the 1990 flyby, Giotto passed at an altitude of approximately 22,700 kilometers above Earth’s surface. The planet’s gravity was used to change the spacecraft’s speed and direction without expending additional fuel, effectively redirecting it toward a new target. This maneuver was notable because, although gravity assists had previously been used with planets such as Venus and Jupiter by missions like NASA’s Mariner 10 and Voyager probes, Giotto was the first spacecraft to use Earth itself in this way after traveling through deep space. The success of this Earth swing-by enabled Giotto to proceed toward Comet Grigg–Skjellerup, which it later encountered on 10/07/1992, providing further scientific observations of cometary material. The 1990 Earth gravity assist demonstrated a new level of mission flexibility and efficiency in space navigation. It showed that spacecraft could revisit Earth after interplanetary travel to gain additional momentum, a concept that has since been applied in multiple missions to extend operational lifetimes and expand scientific reach.