The Spirit Mars rover has successfully completed a 115-degree "turn in place" atop its lander and now stands poised to roll off onto the martian surface early Thursday. The long-awaited 10-foot move is expected to be completed just before dawn East Coast time. If all goes well, a rear-facing navigation camera will take a parting snapshot of the lander as Spirit's surface exploration finally gets underway.

An artist's concept of Spirit driving off its lander. Credit: NASA/JPL

"We are very excited to be where we are today." said Kevin Burke, lead egress engineer at the Jet Propulsion Laboratory in Pasadena, Calif. "We are headed in the generally north-northwest direction, that is our exit path, and we're sitting exactly where we want to be. We're very excited about this and we're really looking forward to tomorrow and getting on with things."

Mission manager Jennifer Trosper said Spirit's subsystems are performing flawlessly and that the rover had completed all of the scientific observations - visible light and infrared panoramas - that were required before roll off.

"And so, really there's nothing left to do on the lander," she said. "Tomorrow, we're going to egress onto the surface of Mars."

Engineers initially hoped to drive Spirit directly off its lander. But bunched-up airbag material posed a threat to the straight-ahead due-south exit and engineers had to come up with another route. After studying photographs from the rover, they decided to turn it 115 degrees to the right so it faced the north-northwest. The move was carried out in three stages over the past two days and Burke said no problems were encountered.

A view from Spirit looking at its driveway to the surface. Credit: NASA/JPL

The deck of Spirit's lander platform is believed to be about 16 inches above the martian surface. The lip of the flexible egress aid the rover will roll down as it exits is about five inches off the surface. In ground tests, the rover could handle drop offs as high as 22 inches and Burke said tomorrow's egress should be no problem.

NASA commentary from the Jet Propulsion Laboratory is scheduled to begin at 3:45 a.m. EST. If all goes well, Spirit will roll onto the surface between 4 a.m. and 5 a.m. A news conference is planned once the move is complete.

"We will be driving 3 meters (9.8 feet) forward on the surface of Mars and leaving our lander for good," Burke said. "Not without a parting shot, though. We do plan on taking a couple of images of our lovely delivery system and give the engineers their due and (let them) see their hardware for the last time. I believe we should be on the surface with knowledge sometime about one o'clock a.m. PST (4 a.m. EST), we should have our first image, a rearward looking image of our lander in the background. We're really looking forward to seeing that."

Video coverage for subscribers only:
   VIDEO: WEDNESDAY'S PREVIEW BRIEFING ON SPIRIT'S FIRST DRIVE QT
   SUBSCRIBE NOW