WASHINGTON — Four years ago, Spirit, the first of two NASA Mars Exploration Rovers, took its first steps – or more accurately rolls – onto Mars’ surface to begin what was meant to be a 90-day mission. Today, the rovers still are trekking across the martian surface.

Launched June 10, 2003, on a Delta 2 rocket from Cape Canaveral Air Force Station, Fla., Spirit landed in the red planet’s Gusev Crater Jan. 3, 2004. After 12 days on its lander platform, the rover rolled onto the red planet’s surface.

“It kind of takes your breath away,” Mark Maimone, rover mobility software engineer at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., said about seeing Spirit place its six wheels onto the planet’s surface. Maimone has led the development of the rovers’ mobility software system since the project began in summer 2000.

Spirit’s rollout “was a time, as you might imagine, of great jubilation and at the same time of fatigue,” said Alfonso “Al” Herrera, a mission manager for the Mars rovers. Herrera started working with the rovers in September 2001 with the test and integration group and served in other positions in the program before becoming one of the mission managers.

The rover team has gone from a high of a few hundred personnel down to a few dozen on staff, Maimone said in a Dec. 31 phone interview. Part of that decline is due to automating some of the day-to-day processes, he said. “It’s gotten a lot easier.

“In addition, many personnel have been shifted to the Mars Science Lab team, NASA’s next rover, Herrera said

Following launch, the team continued to test Spirit and work out some of the bugs.

In the fall of 2003, researchers conducted some last minute navigational and drive tests on rover models because the cameras, essential for checking the vehicle’s location and mapping the planet’s terrain, risked overheating in the summer, Maimone said. Software code was tested, completed and even uploaded to Spirit while the rover was on its journey to Mars, Herrera said in a Jan. 4 phone interview.

One of Spirit’s first scientific tasks was to examine a nearby rock dubbed Adirondack. Before it could complete that
task, a software glitch caused

Spirit to begin a constant cycle of rebooting its onboard computer. This cycle prevented Spirit from communicating properly and performing its designated tasks.

At that point, the euphoria the rover team had experienced with Spirit’s successful landing and journey onto the surface turned to trepidation, Herrera said. “Initially there’s that knot in your stomach.”

Eventually the team was able to capture diagnostic information from Spirit for severalminutes-long intervals before it inevitably rebooted, Herrera said. By piecing together information from those breaks, the rover team discovered a memory-management problem with the software for Spirit’s flash memory, which is capable of storing information even when the rover’s power is off, according to NASA’s Web site. Problematic files stored during Spirit’s flight to Mars subsequently were erased. As a preventative measure, similar files were wiped from Spirit’s twin
rover, Opportunity, which launched July 7, 2003, and landed on Mars Jan. 25, 2004, Herrera said.

With the reboot problem solved, Spirit resumed examining Adirondack. The rover used a device on its robotic arm to bore a shallow hole into the rock. Spirit then used a microscopic imager attached to the arm to view the rock’s interior. The results confirmed Adirondack was volcanic in origin, just as scientists had hypothesized.

That flash memory problem was the first of many obstacles encountered and overcome by the twin rovers. Both Spirit and Opportunity have lasted for four years on Mars; quite a feat considering that since 1960 almost two-thirds of the missions to the red planet have failed, including a Soviet orbiter that lasted only a few days, according to an August 2007 Mars Phoenix press kit.

Clinton Parks is the web producer for SpaceNews.com and copy editor for SpaceNews. He is responsible for copy editing and curation for the SpaceNews.com website, and page design, copy editing in the weekly newspaper. He also contributes to specialty...