Mimicking the sequence of events followed by its twin rover Spirit in June, Opportunity fired its thrusters to reduce its spin rate from 12 times per minute to the much slower two times per minute.

With that complete, flight controllers switched on the spacecraft's celestial navigation system, which identifies stars and determines their positions in the sky so the spacecraft can remain properly oriented during the journey to Mars.

Coincidentally, the Red Planet was one of the first bright points of light "seen" by Opportunity's star scanners, although it's not actually used to help the probe navigate.

Those events were the first notable exercises for Opportunity since it was successfully launched from Earth by a Delta 2 Heavy rocket late Monday, and officials couldn't be more pleased with how things are going.

"Opportunity is behaving in an excellent fashion," Pete Theisinger, NASA's Mars Exploration Rover project manager, told SPACE.com. "It's working as trouble free as Spirit and we are thrilled with its performance."

The next major event on the agenda is set for July 18 when the spacecraft's thrusters will be fired to make what's called a trajectory correction maneuver.

When Opportunity was launched atop the Delta 2 Heavy and got its final push out of Earth orbit, the spacecraft and upper stage were not on a direct course for Mars. This was planned so the rocket's third stage would miss Mars and go into solar orbit, avoiding any potential of contaminating the Red Planet with space junk.

To set up Opportunity for its landing, the spacecraft must slightly alter its path so it is on a collision course with Mars. The July 18 maneuver will do that and additional thruster firings during the coming weeks will fine-tune the trajectory.

As of 9 a.m. EDT (1300 GMT) Thursday, Opportunity has traveled 4.1 million miles (6.6 million kilometers) since launch. The twin probe Spirit, which was launched June 10, has traveled 51.3 million miles (82.6 million kilometers).

"We have two well behaving spacecraft on the way and more serious hurdles yet to come," Theisinger said.

The Mars teams now will turn their attention toward the entry, descent and landing phases of the mission, he said, with a focus the rest of this summer on planning and training.

The two probes are to land on opposite sides of the planet and hunt for clues about when water might have once flowed on Mars. Spirit is to touch down first on Jan. 4. Opportunity is to follow on Jan. 25.