The Messenger spacecraft continued to fine-tune its orbit around Mercury yesterday afternoon when mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., successfully executed the second orbit-correction maneuver of the mission.

The 3-minute, 8-second engine burn stretched the spacecraft's orbit around the innermost planet from 11 hours 48 minutes to a precise 12 hours.

This second of an expected five maneuvers planned for the mission's primary orbital phase began at 5:20 P.M. EDT, and used approximately 1.9 kilograms of fuel.

"Messenger's first orbit-correction maneuver, which took place in June, reset the periapsis altitude of the orbit to 200 kilometers, but also shortened the orbital period.

This second maneuver has reset the period to its nominal value of 12 hours," says APL's Peter Bedini, Messenger project manager.

Messenger Mission Systems Engineer Eric Finnegan, of APL, said the engine burn was "on target and a sweet success. We're precisely where we need to be to continue to capture amazing data from Mercury's surface."

The next orbit-correction maneuver is scheduled for September 7 and will lower the periapsis altitude from about 470 kilometers back to 200 kilometers.