David Perlman, Chronicle Science Editor

A new spacecraft more powerful and sophisticated than any other is flying flawlessly toward Mars, and its date to begin orbiting the planet on March 10, NASA officials reported Thursday.

Navigation perils still await the craft called the Mars Reconnaissance Orbiter, or MRO, but if it succeeds, it will circle less than 200 miles from pole to pole above the Martian surface, joining the most intensive exploration of the planet ever undertaken — with still more missions headed there in coming years.

Three other spacecraft are currently orbiting the planet, and two robot rovers are probing the Martian rocks in search of signs of ancient water.

The new spacecraft, which was launched from Cape Canaveral on Aug. 12, is now 15 million miles from Mars, and will be 134 million miles from Earth when it arrives, James Graf, the orbiter’s project manager, said at a Washington press briefing Webcast around the country.

So accurate has been the ship’s trajectory so far, Graf said, that two planned maneuvers controlled by Earth-bound engineers to correct its in-flight course have been canceled. The ship is set to begin its first orbit around the planet with a brief burn of its main propulsion engine at precisely 1:24 p.m. PST on the appointed date.

That first orbit will carry the craft on a long, looping course over 35 days as far as 27,340 miles above the Martian surface and as close as 249 miles above it. Then it will begin a six-month series of extremely delicate and dangerous maneuvers called aerobraking in which the orbiting spacecraft will briefly slow down and descend slightly as it skims into and out of the planet’s atmosphere, much like a flat stone skimming the surface of a lake.

After hundreds of orbits slowed by aerobraking, the MRO will reach its final near-circular polar orbit less than 200 miles above the surface — closer than any other Martian orbiter has attained, Graf said. Then the six instruments aboard the craft will begin at least five years of detailed surface observations.

A telescope more powerful than any ever sent to a planet will study rocks the size of office desks; a mineral-mapping infrared spectrometer will identify any water-formed deposits that might exist; and a radar designed and built by the Italian Space Agency will probe as deeply as a half-mile beneath the surface to look for signs of underground ice or even water.

“This mission will greatly expand our scientific understanding of Mars, pave the way for our next robotic missions and help us prepare for sending humans to Mars,” said Douglas McQuistion, director of NASA’s Mars exploration program.

“MRO’s instrument capabilities are unprecedented,” added Michael Meyer, the lead scientist for NASA’s Mars missions.

The arrival of the new orbiter will focus a major force investigating the planet’s atmosphere and its surface.

Two Mars rovers, Spirit and Opportunity, have already far exceed their life expectancy of only three months and are still probing Martian rocks more than two years after they landed. Meanwhile, three orbiters — two from America and one from the European Space Agency — are acting as radio relay stations for the priceless data gathered by the hardy rovers.

One of the MRO’s major tasks will be to scout out safe sites for two Mars landing missions due in coming years, said McQuistion.

Next year, he said, a relatively small spacecraft called Phoenix will be launched for a landing near Mars’ north polar region, where it will use a unique camera system to study the planet’s ice cap and dig 3 feet into the subsurface to collect ice and soil samples for analysis on board.

The following year, a huge new robotic rover called the Mars Science Laboratory, weighing more than 1,000 pounds, will take off for the Red Planet with even more powerful instruments and the ability to roam more than a dozen miles of Mars’ surface for at least a year.

Its tools will be able to crush Martian rocks for its instruments to analyze, gathering still more information to help scientists determine whether Mars was once a warm and wet planet, and if so, how long that period — so hospitable to life — might have existed.