NASA's 2001 Mars Odyssey spacecraft finished an aerobraking process Friday used to tighten its orbit around the Red Planet in preparation for mapping surface minerals and chemicals.

The technique involved Odyssey dipping into the planet's atmosphere to get a drag effect on the spacecraft. By using Mars' atmosphere, scientists saved the expense of launching additional heavy fuel for rocket firings.

Odyssey's thrusters will finish putting the spacecraft into its final, circular mapping orbit at an altitude of 249 miles later this month. Science observations will begin two or three weeks later.

"The spacecraft has performed remarkably well," said Roger Gibbs, the mission's deputy project manager at NASA's Jet Propulsion Laboratory.

Odyssey was launched on its $297 million mission April 7. It carries three science instruments. One of them, a radiation environment experiment, malfunctioned and was shut down in August. Troubleshooting to determine if it can be fixed will resume next month.