The Curiosity rover took its first steps Friday inside a clean room at the Jet Propulsion Laboratory, kicking off a test campaign to prove the $2.3 billion robot can operate on the surface of Mars.

Credit: NASA/JPL-Caltech/Spaceflight Now

Surrounded by an attentive team of engineers and scientists, the six-wheeled rover drove forward and backward several times on a cushioning blue mat Friday afternoon. The test occurred at the Jet Propulsion Laboratory in Pasadena, Calif.

"This is fantastic," said Ashwin Vasavada, the mission's deputy project scientist. "It works...I'm sure there's a huge collective sigh of relief all around JPL right now."

"It's the first full integrated test of the rover, where we have all the wheels assembled, the mobility system as well as the electronics that drive the rover," said Rene Fradet, the mission's flight system manager.

Curiosity is the centerpiece of the Mars Science Laboratory mission launching toward the Red Planet on Nov. 25, 2011. The spacecraft will touch down on Mars in August 2012.

The rover was hooked up to an electrical umbilical for the test, which used basic command sequences and not the advanced software to be employed on Mars.

"What we're doing today is testing very low-level commanding of the motors and steering actuators," Vasavada said. "Right now, we're just using very low-level commands like 'rover, turn on' and 'rover, go forward.'"

Engineers jacked up the rover on a riser and spun the wheels earlier this month, but Friday's test was the first test on solid ground.

This was the first wheels-on-the-floor test," Veronica McGregor, a JPL spokesperson, told Spaceflight Now.

The Curiosity rover turns its wheels in a steering test Friday. Credit: NASA/JPL-Caltech/Spaceflight Now

"This is the first time it's actually been put on the ground and driven," Fradet said.

The rover also turned its wheels to test the steering system. Each wheel is powered by an actuator, and the steering system includes four of the motors.

Fradet said Curiosity is about 80 to 90 percent assembled and is mainly lacking its robotic arm and some electronics. About 500 employees work on the project at JPL, not including the MSL science team spread across the United States, Fradet said.

Teams attached the wheels to the rover in late June and bolted on its remote sensing mast earlier this week.

NASA will attempt more ambitious drive tests, including turns and inclines, when all the electronics are inside the rover. Curiosity will operate with limited autonomy while at Mars, so software tests will also be crucial to ensure it can think for itself.

"Not only is it the first time we're seeing this rover drive, but when you look at this clean room, the entire set of spacecraft parts are all in this clean room right now together," Vasavada said. "That's just really cool to see."

The rover's wheels were spin-tested in early July. Credit: NASA/JPL-Caltech

Engineers are also preparing and testing the mission's cruise stage, descent and landing system, and heat-shielding aeroshell.

In an interview last week, NASA's top Mars program official said MSL is on track for launch next fall. The mission has schedule and budget margin, said Doug McCuistion, the head of the agency's Mars exploration program.

"Technical issues and problems are the kinds of problems you see on any spacecraft mission at this point in its life cycle," McCuistion said. "We don't have any technical show-stoppers that we see right now. We're pushing our way to integrating the rover."

Engineers are still reviewing titanium on the spacecraft to ensure it can withstand the mission. The titanium is from a metals supplier that allegedly provided falsely-certified materials to government customers.

McCuistion said teams identified about 120 areas with suspect titanium. Engineers have replaced some parts and proven others are within specifications through testing.

"Right now, I would say we're on the order of 80 to 90 percent through the problems with titanium, and I don't see any big issues left," McCuistion said.

MSL's launch was delayed from 2009 until 2011 by multiple technical problems, including late deliveries of its actuators.