With a straight face, Matt Heverly will tell you he frequently gets text messages from Mars in the middle of the night.

With a straight face, Matt Heverly will tell you he frequently gets text messages from Mars in the middle of the night.

"My wife hates it when the cell phone rings at 2 in the morning," he said. "But I sleep a lot better after I get those messages."

Heverly, 32, does not need his medication adjusted nor does he wear a hat fashioned out of tin foil to ward off rays from space invaders.

He is the driver of Opportunity, one of the two six-wheeled robots sent to Mars in 2003 as part of NASA's Mars Exploration Rover Mission. Opportunity and her sister robot, Spirit, landed in 2004 and began exploring the Martian surface. The mission is led by NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"When it arrives safely at its location, we get a text message that says, 'I'm safe,' " he said. "And that comes at whatever time Mars' evening is. It could be 2 o'clock in the morning our time."

Heverly, a Medford native, was the guest speaker at the Medford Rogue Rotary Club on Friday. His father, Mike, is a longtime member.

In an interview before his presentation, Matt Heverly said the rovers were initially expected to operate only about 90 days. But unexpected high winds from what amounts to dust devils keep cleaning the robots' solar panels of dust, allowing them to recharge, he explained.

"I was still in graduate school when they landed," said Heverly who has a master's degree in robotics from Boston University. "When I got at JPL, there were several people who had only planned to work on this project for 90 days.

"By then it was roughly nine months into the project and they had other things they needed to do," he added. "They asked if anyone could drive this rover. I quickly raised my hand."

He has been driving the rover for a little more than three years, checking out sites that scientists deem interesting.

Each morning, Matt Heverly has a teleconference with scientists around the world to discuss the daily objective.

"During our eight-hour planning day we put together a sequence of commands that we will send to the rover," he said. "When the rover is done, that's when it sends us back a message that says whether it made it safely or not."

Thus far, Opportunity has traveled about 101/2 kilometers since landing in Eagle Crater. It has explored Endurance Crater and traveled farther south to Victoria Crater.

"We are now currently down in Victoria Crater," he said. "We went about halfway around the crater and decided the best place to go in the crater was only a few meters from where we initially happened to drive up the first time. So we had to drive all the way back."

The crater is a geologic timeline for the geologists, he said.

"He sends me pictures that make me drool all over my laptop," interjected his father, a geologist by training.

Although Matt Heverly jokes he keeps checking out returning photographs for dinosaur bones, he hasn't seen anything that would excite sci-fi buffs.

"But we have found water for sure," he said. "The scientists keep uncovering evidence that Mars was once a wet place."

Both rovers are a bit worn. One of the wheels on Spirit has locked up. And the shoulder joint on the robotic arm of Opportunity is starting to fail.

When the robots landed, Mars and Earth were about 124 million miles apart. A radio signal traveling at the speed of light at 186,000 miles per second, it took the signal about 11 minutes to reach the robots.

"The delay time doesn't have much meaning to us," he said. "We do planning cycles per day. When we drive, we send commands up overnight. The rovers wake up in the morning, see this laundry list of things they are to do that day, say, 'Drive a meter, turn right, drive another meter.' "

When Matt talks to a group of young students, he says driving the rover is like playing a boring video game. He gives the robot commands via a keyboard.

"Our job is to decide how to safely use the software and hardware on board to get it (to do) what the scientists' want it to do," he said. "The scientists come in and look at the latest images and say, 'We want you to go explore this rock over here.' Our job is to safely get the rover to that rock.

"When they first started, they worked on Mars time," he said. "But the Martian day is 40 minutes longer than the first day."

That additional time soon put the earthlings on an unearthly schedule. Now they try to plan for two days of planning during one shift back on Earth.

In addition to operating the robot, Heverly is also designing new rover concepts for planetary missions.

He is currently working with a robot named Athlete which has wheels on the end of each of its six legs.

"It can drive on benign terrain and walk on rough terrain," he said. "That's designed for our return to the moon."

Reach reporter Paul Fattig at 776-4496 or e-mail him at pfattig@mailtribune.com.