Nasa seeks contact with Mars probe

Nasa is working through possible solutions

The US space agency (Nasa) will try to establish normal communication again with its Mars rover Spirit on Friday.

Engineers know the vehicle is alive but they have received no useful data from the probe for more than 24 hours.

Efforts to contact Spirit will begin in earnest when the buggy "wakes up" with the Martian dawn at about 11 GMT.

Engineers are puzzled why their rover, which had unpacked itself perfectly after landing and taken stunning pictures, should suddenly break down.

Model help

The only contact from Spirit has been a simple signal to indicate it has received Earth transmissions - but there has been no data return.

All Nasa can hear is "pseudo-noise", a random series of zeroes and ones in binary code and not anything the scientists can decipher.

It is terribly easy to knee-jerk a reaction and make matters worse Prof Colin Pillinger

"What it means is the radio was on but the computer wasn't sending information over to it," said deputy project manager, Richard Cook.

Engineers are working on two theories to explain Spirit's problems.

One is a corruption of the flight software. The second is corruption of computer memory. Either could leave Spirit's power supply healthy but still allow adequate time for recovering control of the rover.

Nasa is using a full-scale engineering model at the Jet Propulsion Laboratory (JPL) in California to work through scenarios and possible solutions.

No rush

"In all exploration you are always going to have anxious moments," JPL director Charles Elachi said. "The key thing that is important is that we stay calm and thoughtful... you can do harm by reacting too fast."

Spirit and Opportunity are identical

The point was echoed by British scientist Professor Colin Pillinger whose European Beagle 2 lander is still missing on the planet.

"They will need to mull over all the things that could have gone wrong. It is terribly easy to knee-jerk a reaction and make matters worse," he told the BBC.

"I feel for them. We've already been in touch with them to say 'we're totally behind you guys, we hope you get this back'."

Incoming lander

Spirit landed on Mars on 3 January, for a planned three-month mission to explore the geological history of the planet. Its aim was to tour Gusev Crater, studying its rocks and soil for signs of water, past or present.

When its troubles began on Wednesday, the six-wheeled robotic geologist was parked in front of a football-sized rock, its tool-laden arm extended and prepared to grind the rock's surface.

Commands were being fed via a radio telescope in Canberra, Australia, but bad weather over the facility interrupted the transmission.

Scientists were asked whether the Australian-fed commands being cut short could have caused the rover's current problems. They consider this unlikely, however.

"We believe the architecture does not allow this to happen," said Pete Theisinger, the Spirit project manager.

Meanwhile, the rover Opportunity is still on course to land on Mars on Sunday, at 0505 GMT.

The vehicle is aimed at a plain known as Meridiani Planum, which is near the Martian equator. It will be halfway around the planet from Gusev Crater.

Independent audit

The US landers are identical. Nasa will be keen, therefore, to trace the source of Spirit's problems because it could have implications for the way Opportunity is deployed.

After the failure in 1999 of Nasa's Mars Polar Lander and Mars Climate Orbiter, the agency opened the rover project to independent scrutiny.

Outside auditors have studied every detail in the plans, looking for any flaws which might scupper a successful mission for the rovers.

Nasa says everything was done that was humanly possible to send the vehicles to Mars in good working order.