Pathfinder Rover Overcomes Glitch, Obeys Commands

After a frightening night of wondering why the little Mars rover Sojourner wouldn’t communicate with its mother ship, the Pathfinder, engineers at the Jet Propulsion Laboratory were ecstatic Saturday afternoon when the rover’s modem finally responded to commands.

The modem repair set the stage for the most intriguing part of the mission: the deployment of Sojourner down Pathfinder’s ramp to begin it’s six-wheeled exploration of the Martian surface. It is expected to proceed full-bore with that journey today.

“It feels like we’ve been reinvited to the party,” said rover coordinator Matt Wallace.

“We’re verging on near miracles, my wonderful team,” project manager Tony Spear said. Spear announced that the Pathfinder had been renamed the Sagan Memorial Station in honor of the late astronomer. “I wonder if Carl Sagan is smiling on us,” he said.

Amid an otherwise flawless arrival on Mars, the rover developed a problem familiar to all online computer uses: Its modem wasn’t working. As the Earth set on Mars last night, before the problem was fixed, the rover was speaking to Pathfinder only in short grunts, like a grumpy teenager. “We’re just getting one syllable, not full sentences,” deputy project manager Brian Muirhead said.

“The rover’s talking!” flight engineers called to each other. “We’re alive! All right!” It appeared that the Pathfinder had simply rebooted--or recycled, as the engineers called it--itself over Friday night. “We’re a little perplexed as to what happened,” said Wallace, who added, “The spacecraft is fine.”

Engineers remained somewhat concerned that they didn’t know exactly what had caused the problem. “Until we understand [how it got fixed] we won’t know for sure what the cause was,” said Wallace. “But if it was correctable once, we feel there’s a high probability we could correct it again.”

All other systems on the rover and lander appeared to be working perfectly, and the rover was expected to roll out onto the salmon-colored Martian sands sometime late Saturday.

The repair of the communications gap between the rover and lander was a great relief to the 100 waiting scientists eagerto get their instruments on the rich rock treasures scattered over the Martian landscape.

“I hate to pat myself on the back, but this is the best place we could have possibly landed,” said project scientist Matthew Golombek, who was responsible for choosing the site. “When we saw those first images, 70 scientists were jumping up and down, cheering. I am the happiest person I could be.”

Among the geological treasures waiting to be explored were rocks of all sizes and textures and colors, from a few inches to more than 10 feet high, layered, spotted, knobby, flat, round, white, blue, red, sandy and clumpy.

Curiously, said Golombek, the Viking landing of July 1976--NASA’s last visit to the Red Planet--was scheduled to set down in this very terrain. “They got scared away,” he said, because images taken from the Viking orbiter showed the landscape to be too lumpy for a safe landing. So mission controllers diverted the craft to a smoother site.

Good thing too, said Golombek, because the Viking lander drifted down to the surface to stand on thin legs like an insect. “With those three spindly legs, it could have been curtains for Viking.”

Pathfinder was able to absorb hard knocks from sharp rocks because it fell encased in air bags constructed of four layers of bullet-proof material. “What a way to [land],” said Golombek.

The great variety of rock forms and soil types at the site were exactly what the scientists ordered, said Golombek. One flat black form on the horizon looked exactly like an analyst’s couch. In the distance 20 miles or so away, twin peaks rose through the dusty pink haze. The foreground was strewn with huge boulders.

One grouping of large rocks leans almost in unison toward the northwest, like a family of Martian pigeons. The fact that they are all slanting in the same direction suggests they were pushed over by flowing water, said Golombek. Water, hypothesized to have existed on ancient Mars, is a crucial ingredient to life.

Geologists believe that the Ares Vallis, where the Pathfinder landed, is the outflow of an ancient flood plain created when more water than held in all the Great Lakes somehow pushed through the Martian crust in a two-week period--”the solar system’s largest flood,” Golombek said. The gushing water carved out the valley in the process and collected a rich grab bag of different kinds of Martian rocks--perfect hunting ground for the rover.

Equally interesting is that the soil appeared to come in at least three different colors, suggesting that some was probably native to the region while other patches had been carried there by water and winds.

One rock has an almost flat shape, like a table top, while others rose in jagged peaks. The Pathfinder camera could also see the rim of a large crater several miles away and an enormous boulder. “We came very close to that rock,” said Smith, who said the pathfinder could have been in “real trouble” if it had landed closer. In general, it is a far more varied landscape than Viking encountered, said Golombek. Some of the mountains in the distance appeared to be more than a thousand feet tall, and layers or strata appeared to be etched in some of the outcroppings.

It will be a while before the six-wheel rover gets around to exploring these intriguing surroundings. First, its ramps need to be unsprung from their stowed position, curled up like rolls of tinfoil. Then it needs to stretch up from its crouched position to its full one-foot height. Both events were expected to occur some time Saturday night.

After the ramps are out and the rover is standing, it needs to be released from its base, and given the command to proceed down its runway at a stately pace of one-half-inch per hour. Once on Martian soil, it will make a few practice turns to get accustomed to the territory.

“The first couple of days, we’ll just have a learner’s permit,” said Wallace. If all goes well, Sojourner will then begin a weeklong analysis of the Martian soil and rocks, beaming them back to Earth via relay with its mother ship.

Should the communications problem recur, the rover does have the capability to explore Mars on its own. It can find rocks, avoid obstacles and obtain scientific data. But without a link to a lander, it would probably not be able to communicate those findings back to Earth.

But thanks to Saturday’s successful repair, that now appears unlikely.