The Mercury-bound spacecraft MESSENGER completed the first part of a two-part deep-space maneuver today, providing the expected 90% of the velocity change needed to place the spacecraft on course to fly by Mercury for the third time in September 2009.

A 4.5-minute firing of its bi-propellant engine increased the probe's speed relative to the Sun by 219 meters per second (489 miles per hour) to a speed of about 30.994 kilometers per second (69,333 miles per hour).

MESSENGER was 237.9 million kilometers (147.8 million miles) from Earth when today's maneuver began at 3:30 p.m. EST. Mission controllers at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., verified the start of the maneuver about 13 minutes, 14 seconds later, when the first signals indicating spacecraft thruster activity reached NASA's Deep Space Network tracking station outside Goldstone, Calif.

"It was a perfect maneuver," said APL's Eric Finnegan, MESSENGER Mission Systems Engineer. "Initial data analysis indicates an extremely accurate maneuver execution. After sifting through all the post-burn data I expect we will find ourselves right on target."

The remaining 10% of this deep-space-maneuver's velocity change will be imparted to the spacecraft during the second part, which will occur on December 8, 2008. The total planned velocity change is 247 meters per second.

One final deep-space maneuver on November 29, 2009, will target the probe for Mercury orbit insertion in March 2011, making it the first spacecraft to orbit the planet closest to the Sun.