Although Mercury lies just a hop, skip, and a jump from Earth, it will take MESSENGER five years to get there. The extended travel results because, to go into orbit around Mercury, the spacecraft must match the planet’s high orbital speed by taking advantage of several gravity assists along the way.
The current schedule calls for liftoff in 2004. Three months after launch, the spacecraft makes the first of two Venus flybys. Three more orbits around the sun bring MESSENGER back to Venus on March 16, 2006. The spacecraft, now moving much more rapidly, heads closer to the sun for two flybys of Mercury. The first occurs on July 21, 2007, and the second on April 11, 2008. The four planet flybys, in conjunction with two firings of the spacecraft’s onboard rocket, set MESSENGER up for its final approach to Mercury. It gets there on April 6, 2009, when it fires its engine once more to put it in orbit.
The animations below illustrate MESSENGER’s path from Earth to Mercury and its two Mercury flybys before the spacecraft goes into orbit around the planet.