The Applied Physics Laboratory announced today that MESSENGER's first "Deep Space Maneuver" was successful, putting the Mercury orbiter on track for an October 24, 2006 flyby of Venus. MESSENGER still has a very long way to go to get to Mercury (here's a timeline), but this successful engine burn is a big deal because it's the first time its large thruster has been fired since the launch.
The maneuver used up 18 percent of MESSENGER's fuel in a 524-second burn -- second only to the Mercury orbit insertion burn in magnitude. It changed MESSENGER's speed by 316 meters per second. The MESSENGER website has a nifty backgrounder explaining how each of the flybys and deep space maneuvers contributes to making the changes to the geometry of MESSENGER's Sun-centered orbit that are necessary to position it for Mercury orbit insertion.