The MESSENGER Mission to Mercury completed a critical deep-space maneuver yesterday—155 million miles (240 million kilometers) from Earth—successfully firing its large bi-propellant engine to change the probe’s trajectory and target it for its first flyby of Mercury on January 14, 2008.

The maneuver was executed in two parts from the MESSENGER Mission Operations Center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. At 6 p.m. EDT, the probe fired its large main engine for just over five minutes, using about 70 kilograms (154 pounds) of propellant to change its velocity by 226 meters per second, or just over 505 miles per hour.

According to DTM Director and Principal Investigator of the mission Sean Solomon, “We are now en route to the closest glimpse of Mercury that anyone has ever seen. Over the next three months the suspense about what we will find will steadily build.”