Signal Gives Mars Lander Team New Hope
Leaders of the Mars Polar Lander mission said Wednesday they are “cautiously optimistic” that their errant craft--declared officially lost only last week--is still alive and trying to contact Earth.
On Friday, project managers received a phone call from a persevering Stanford University radio astronomer who detected faint signals coming from Mars on a deep space antenna.
“The data had an appealing arc to it,” said Ivan Linscott, a senior researcher at Stanford’s Space Telecommunications and Radio Science Laboratory who found the signals last week.
“I was blown away,” said Sam W. Thurman, the flight operations manager for the mission. “Imagine coming back from the funeral of a dear friend and getting a phone call saying . . . he’s not dead after all.”
Thurman’s team began sending new commands to Mars on Wednesday, asking the lander to send a pattern of three long signals back to Earth. If the craft is responding, some of the signals already have reached the Stanford antenna.
But Thurman and Linscott said it would be several days before they could analyze the antenna data and determine if the signals from the missing lander are present within the data.
A definitive answer is expected next week.
The $165-million spacecraft was expected to reach Mars on Dec. 3 and had not been heard from since that day--despite extensive rescue attempts by engineers at Pasadena’s Jet Propulsion Laboratory, which manages the project for NASA.
Thurman says that the signals may be from the lander because they clearly are not from any natural source and because they reached Earth at the right time: in response to test calls made to the lander Dec. 18 and Jan. 4.
But the UHF signals also could have come from television stations or Earth-orbiting satellites. “The Earth is a planet awash in electromagnetic radiation of many kinds,” Thurman said.
Though they reached Earth weeks ago, the extremely faint signals were recognized only after a small team of scientists repeatedly reanalyzed the data. They saw hints that the signal had come from the direction of Mars and displayed an arc-like pattern, as would be expected as the craft warmed up.
Linscott said the mood at the 150-foot-diameter antenna in the Stanford hills was “extremely upbeat” but cautioned that it was far from certain that the signals were from the lander.
Such weak signals would not come from the craft’s main antenna used for communicating with Earth, but from a smaller antenna built to send signals to the Mars Global Surveyor, which is orbiting the Red Planet. If the system was working, the larger, orbiting craft would have relayed an easily detectable signal to Earth. But it is believed that the weak signal did not go through a larger craft and was sent directly into space by the lander.
If it is indeed a signal coming from Mars, detecting it is something of a miracle in itself. Thurman equated it with “trying to see someone on Mars with a penlight.”
There is only a short window of time left for mission leaders to establish contact with the lander. The life of the craft is just 90 days and 52 of those have elapsed.
“Whatever we do, we have to do it quickly,” said David Paige, a professor of planetary science at UCLA and lead investigator for the lander’s scientific experiments.
Even if the craft was recovered, there is little chance that it could accomplish its scientific mission, because it could send only a trickle of information back to Earth and probably could not transmit any images.
But contact could provide valuable information about what happened to the craft. That would improve the odds of success in the next mission to Mars, which now is planned for 2001 but probably will be postponed until 2003.
Theories range from the craft having tumbled or fallen so that its main antennas are disabled to it having landed in the shade of a hill so its solar power generation is compromised to it having been destroyed during landing.
This week, officials at Malin Space Science Systems Inc. in San Diego said they would continue to take pictures of the lost craft’s landing site with a camera on board the orbiting Mars Global Surveyor.
They hope to capture a picture of the lander’s large white parachute, but it would be very difficult to distinguish that from a patch of frost. Malin scientists say that their task is like “trying to find a specific needle in . . . a haystack-sized pile of needles.”
Paige, one of the mission scientists whose mood remained buoyant throughout the loss of the lander, said he was continuing to test a lander prototype and instruments ranging from robotic arms to gas analyzers and weather sensors--in preparation for the next mission.
Yet he hadn’t stopped thinking about the lost lander. Finding it, he said, would be “miraculous.”
“It’s sort of like one of these soap operas where a main character dies and then a few episodes later comes back again because it was all a dream,” Paige said. “What a plot twist.”
