The Opportunity rover is on track to roll onto Mars (search) as early as Sunday, just days before its twin could resume its own work exploring the Red Planet, NASA said Wednesday.

Opportunity unfolded its front wheels and locked them into position, leaving just a few more tasks before being ready to travel the final 10 feet from its lander and onto the surface of Mars, mission members said during a news conference at the Jet Propulsion Laboratory. The National Aeronautics and Space Administration still wants to adjust the forward tilt of Opportunity's lander, pitching it down 5 degrees to smooth the six-wheeled robot's path. Engineers hoped to complete that work in time for a late Sunday roll-off, rover activity lead scientist Rick Welch said. Meanwhile, engineers worked to regain full control of Spirit, which has been sidelined for a week on the other side of the planet with crippling software problems. "We are working to get complete control of the vehicle but still aren't quite there yet," said Jennifer Trosper, a mission manager. Spirit began using its high-gain antenna again late Wednesday, which should speed the transmission of data needed to debug the rover's computer system. NASA sent Spirit and Opportunity on the $820 million mission to Mars to probe for geologic evidence of the past presence of water on what is now a largely dry, dusty planet.