The U.S. space agency NASA is preparing for the next phase of its latest Mars mission now that the "Mars Odyssey" spacecraft has successfully entered the Red Planet's atmosphere. Flight controllers will spend the next few months bringing it to a lower orbit to begin inspection of the Martian surface.

The flight team at the Jet Propulsion Laboratory in California navigated the Odyssey to within one kilometer of its desired entry point at the Martian north pole after the 150 million kilometer, six-month journey from Earth.

Lead navigator Bob Mase says delivering the spacecraft was the toughest, most critical part of the mission. "The navigation team," he said, "was challenged to hit a bull's eye for this mission and I'm pleased to report that that's exactly what we were able to deliver."

Next, beginning Friday, comes a demanding, around-the-clock operation. It is called aerobraking. Mission navigators will take advantage of the friction of Mars' thin atmosphere to slow Odyssey, lower its orbit to a 400-kilometer altitude and reduce its current 18.5 hour elliptical orbit to a two-hour circular one.

Mission Manager David Spencer says the flight team must take great care not to drop the spacecraft too far, thereby causing too much friction in the thicker part of the Martian atmosphere that could burn up Odyssey's solar energy panels. "The solar array," he said, "provides most of the drag, and the solar array actually gets quite hot. The solar array can reach temperatures up to 350 degrees Fahrenheit [177 degrees Celsius]. In fact, this is the limiting factor on how deep we can go into the Mars atmosphere."

Once the Odyssey is at its lowest orbit by mid-January, it can begin its 2.5 year program to map the planet's surface mineral composition for the first time. It will search especially for signs of water in an effort to help determine if Mars ever supported life.

Project scientist Steven Saunders notes that the orbiter will also take pictures of possible landing sites for future Mars probes. Then, when its main mission is complete in 2004, Odyssey will become a communications relay for those landers. "He said, "Odyssey is really going to be a major step in building a science and communications infrastructure for Mars for the rest of the Mars program. I know this is going to be a blockbuster science mission, and the best is yet to come."

One mission official called the successful orbit of Mars Odyssey redemption after the last two U.S. Mars probes failed to reach their target in 1999. For outgoing NASA chief Daniel Goldin, who presided over an overhaul of the Mars exploration program, the mission is a triumph. Mr. Goldin said, "It's a magnificent demonstration of the American will to succeed in spite of problems."