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Scientists Make Last Effort To Contact the Mars Lander

By Kathy Sawyer

NASA’s Mars team was poised to try one last-ditch effort between midnight and dawn Tuesday to contact its missing lander on the Red Planet.

Hopes had all but faded that they will recover the Mars Polar Lander or the two microprobes it was carrying when the craft entered the Martian atmosphere Friday, handlers admitted early Monday.

“Tuesday night will be pretty much the last high-probability chance that we’ll have,” flight operations manager Richard Cook told reporters at a Monday briefing here at the Jet Propulsion Laboratory, which manages the Mars missions for NASA.

If that effort failed, it will certainly leave the team in the previously unthinkable position of having lost three landers and one orbiter -- the entire $360 million panoply of robots aimed at Mars this year -- in what was to have been a vital second wave of research in a sequenced exploration of Mars.

The team, working carefully through a series of hypotheses about the missing Lander’s condition, has eliminated almost all the most likely single-problem scenarios.

After that, the assumptions take the engineers deeper into complexity and rapidly lower in probability of success, according to flight operations manager Sam Thurman, though efforts will continue on for two weeks before the mission is formally pronounced deceased.

Monday night’s exercise would again employ the spacecraft’s omni-directional UHF antenna, which does not require accurate pointing. It was to transmit to NASA’s orbiting Mars Global Surveyor as it passed 250 miles overhead, carrying an instrument that would act as a relay. The same gambit failed Sunday, but in the meantime, controllers have sent the lander new commands that would switch it into a different “mode” that could produce better results.

Handlers decided to postpone until Tuesday night a major full-sky search originally planned for Monday night. It would use a totally separate communications path: the spacecraft’s main antenna, a medium-speed dish that has to be accurately pointed. Setting up the scan was taking longer than expected, Cook said, adding that there is not much hope for success with this approach in any case.

Managers of the two experimental penetrating microprobes also heard nothing but silence through another long night. The probes, which hitchhiked aboard the Polar Lander on its 416-million-mile journey, were supposed to have separated as the three craft entered the Martian atmosphere about 3 p.m. Friday. They were to slam into the surface at 400 mph, send back a signal and prospect for subsurface water ice.

As NASA braced for the fallout, planetary experts were raising questions about whether the push to make missions cheaper has gone too far and whether the degree of risk accepted on this mission was too high. Some were focusing on the specifics of how to prevent such problems on the next missions in the pipeline to Mars.

If the lander is at that spot, engineers would then know that the parachute, retro-rockets and other crucial components during the complex descent had worked properly and could be checked off the list, said project scientist Richard Zurek. But controllers said that process could take a couple of weeks.