Originally created 07/06/97

Mars mission has ups and downs during second day on red planet



PASADENA, Calif. - NASA scientists brainstormed Saturday to fix potentially crippling problems that left Mars Pathfinder's robot rover stuck aboard the lander with tantalizing rocks just out of reach.

In a ballet of engineering, optimism and movements of two planets 120 million miles apart, controllers worked to fix a radio link to the Sojourner rover and make sure a ramp deployed so it could safely leave Pathfinder.

The remote-controlled pride and joy of Pathfinder's mission was to be the first mobile vehicle to operate on another planet - if it got going. Mission controllers said that would not happen before 7:40 p.m. Saturday.

Pathfinder's camera, meanwhile, was to continue making photographs to ensure it had a full panorama stored in its memory. Then, about 6:30 p.m., the camera was to pop up to full height, about 51/2 feet.

The most serious problem was a computer glitch that kept Sojourner from transmitting data to the lander.

"We need to get this communication problem basically fixed," said Brian Muirhead, deputy program manager at NASA's Jet Propulsion Laboratory.

After two days of radio silence, the rover will automatically start a program stored in its memory that will direct it to drive off the lander and explore a small area nearby. But none of the information it collects would be radioed back to Earth unless the computer problem can be fixed, said rover manager Jacob Matijevic.

Matijevic said an apparent software problem prevented the rover's modem from sending data to the lander, Sojourner's only link to Earth. Some small packets of data got through, but larger ones were being dropped.

"We're just kind of getting one syllable across the net, but not full sentences," said Muirhead.

The spacecraft was out of communication with Earth until late Saturday morning, when Earth peeked over Mars' horizon as seen from Pathfinder. The rotation of Mars prevents Pathfinder from sending signals to Earth for several hours each day.

During that period, the rover's modem automatically reset itself hourly, an operation intended to fix the communications problem all by itself.

"In all likelihood some of the things that have already taken place over the last several hours may already have solved the problem," Matijevic said.

If not, controllers were to implement a series of fix-it commands developed in a brainstorming session from Friday night to Saturday morning.

Mission managers expected to have the problem with the rover's ramp solved by afternoon.

Material from air bags that cushioned the spacecraft's Friday landing got draped around one of Pathfinder's "petals," preventing deployment of front and rear ramps that would lead from the rover's 15-inch-high perch to the ground.

Controllers sent commands to the spacecraft to raise the petals and pull the air bags farther underneath. Photographs Friday showed the path was clear to deploy a ramp at the front of the rover, but were not clear enough to show the other ramp.

Controllers sent a signal to unfurl the front ramp, but had not received confirmation that the command had been received and executed. They were to resend the instruction Saturday afternoon.

Pathfinder was designed according to NASA's new "faster, better, cheaper" philosophy, so neither the lander nor rover has a backup modem. Matijevic insisted the modem was excellent throughout its testing.

So far, the camera has revealed a boulder-studded plain and impressive hills looming on the horizon. Although it appears flat, project scientist Matthew Golombek said the landscape around Pathfinder is hillier than that encountered by either of the 1976 Viking landers.

"There's rocks of all types and shapes and forms, and they're all there to look at," Golombek said. "That's exactly what we wanted."