The Mars Science Laboratory fired up its rocket engines Jan. 11 in a critical maneuver to refine its path toward an August landing on the red planet, NASA officials said.

The deep-space maneuver began at 6 p.m. EST and lasted nearly three hours to put the 1-ton Curiosity rover and mothership on track for a planned touchdown in a huge martian crater in early August. It is the biggest — and most important — course change the rover will make on its 567-million-kilometer trip to Mars.

“I just left a group of happy flight team controllers in our mission control,” said rover cruise mission manager Arthur Amador of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “We took a big step towards our encounter with Gale Crater on Mars.”

NASA launched the $2.5 billion Curiosity rover Nov. 26. The car-size rover is designed to study Mars’ vast Gale Crater to determine if the region is, or once was, capable of supporting microbial life. The six-wheeled robot carries a nuclear power source and 10 science instruments — including a rock-zapping laser — to perform the mission.

The Jan. 11 course correction was required because NASA intentionally launched Curiosity away from Mars at the mission’s start in order to avoid any chance that parts of the spacecraft’s Atlas 5 rocket could hit the red planet and contaminate the martian surface. “We do that on all of our missions to Mars to protect the planetary environment there,” Amador said.

To put the rover back on track, mission managers commanded Curiosity to fire its eight rocket thrusters to change the spacecraft’s velocity by about 19.8 kilometers per hour. The change places Curiosity on a path that will approach about 40,000 kilometers closer to Mars than before, and about 14 hours earlier than the previous course.

“The timing of the encounter is important for arriving at Mars just when the planet’s rotation puts Gale Crater in the right place,” JPL’s Tomas Martin-Mur, chief navigator for the mission, said in a statement.

Several more engine burns, up to five in all, are scheduled to further tweak the Curiosity rover’s path toward Gale Crater. The next one is slated for March 29.

Amador said a team of 12 mission controllers watched over the Jan. 11 course correction. While the mission managers were confident of success, there was still some tension.

“These are important things, in terms of we have a very valuable spacecraft on its way to Mars with a superb science payload,” Amador said. “We’re very protective of it, so there’s a certain amount of tension when you come upon a moment like this … and that is relieved.”

By 12 p.m. EST on Jan. 12, the Curiosity rover had completed about 130.6 million kilometers of its trip to Mars. It will be streaking through space at a speed of about 16,600 kilometers per hour relative to Earth, mission managers said.

During the cruise to Mars, rover mission managers plan at JPL to perform a series of health checks and equipment tests to make sure Curiosity is in tip-top shape for its landing Aug. 4, California time. They also are working to understand why the spacecraft’s celestial-navigation software reset itself Nov. 29. The glitch has not posed a serious concern, but engineers want to understand its cause.

The Curiosity rover is NASA’s latest mission to the red planet. It follows the Phoenix Mars Lander, which launched in 2007 and ended its mission to the martian arctic in 2008, as well as the powerful Mars Reconnaissance Orbiter launched in 2005 and the smaller twin rovers Spirit and Opportunity launched in 2003.

The Mars Reconnaissance Orbiter and Opportunity rover are still going strong, though the Spirit rover was decommissioned last year. A European orbiter called Mars Express is also currently circling the red planet.

“It feels good to be back on the road to Mars here,” Amador said. “I always tell people that it feels kind of familiar, this path that we’ve traveled between the Earth and Mars now.”