A last-ditch effort to find signs of the Mars Polar Lander is underway, but it will take more than a week of analysis before members of the mission team can determine whether or not the spacecraft has tried to contact Earth, the mission's flight operations manager said Wednesday.
"Trying to detect a radio signal in this case is something akin to trying to see if somebody's standing on Mars with a penlight," said Sam Thurman, of NASA's Jet Propulsion Laboratory (JPL).
A final attempt to find the missing spacecraft began Tuesday when controllers at JPL sent commands to the lander telling it to broadcast a series of six UHF signals toward Earth during the next two days. A giant radio-receiving dish at Stanford University began listening for signs of the lander midday Wednesday -- the time when the first atrophied signal would have reached Earth.
During desperate efforts to communicate with the lander, mission controllers had sent a series of commands to Mars, instructing the spacecraft to broadcast a signal when the 150-foot (45-meter) radio antenna at Stanford University would be listening.
At the time, the dish's operators hadn't noted any sign from the lander, but after combing through data for several weeks; they recognized a very faint feature that could have originated from the craft.
Having given up all hope that the Polar Lander would ever be found, Thurman said he was "blown away," when he got a phone call from members of the Stanford team. He said he felt like he had just returned from the funeral of a dear friend. "Imagine coming back from the funeral and getting a phone call from someone saying, ' I think I may have a message from the deceased that he's really not dead after all.'"
The extremely faint radio signals were about the correct frequency to have come from the lander's UHF antenna, Thurman said. That antenna was the transmitter that the craft would have used to communicate with the Mars-orbiting satellites that were to have been relay stations for sending data back to Earth, but it did have a test mode that could broadcast signals out into space.
Still, the signal could have come from any number of other sources, Thurman warned. They could be interference from terrestrial UHF TV signals, or certain satellite communications.
But the team at Stanford wanted another chance to listen, so Thurman and his crew organized one last set of communication attempts, which went out Tuesday.
"The experiments we are doing today and tomorrow are designed to more-definitively establish whether the earlier contacts were a bona fide signal or if they weren't," Thurman said. Now engineers and scientists are waiting to examine any radio signals that might come back, but they don't expect it to be an easy task.
Even if it turns out that the signals are, in fact, from the lander, there still would be no hope that the craft could accomplish any of the science goals it was sent to Mars to achieve, Thurman said. There is simply no way to receive anything more than a few bits of data from the faint, messy signal.
Still, just knowing that the craft made it to the surface would be much more satisfying than having no clue, Thurman said. The most the team could hope to discover from transmissions might be to glean information about which direction the machine is facing, and whether it landed on a flat or sloped surface.
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