JPL

Mars Mission Status

Radio telescopes in The Netherlands, England and at Stanford University in California have begun listening for a possible signal from Mars Polar Lander today.

The array of fourteen 25-meter (82-foot) antennas at Westerbork in The Netherlands as well as the 76-meter (about 250- foot) antenna at Jodrell Bank, near Manchester, England have three 30-minute listening opportunities today. The 45-meter (150- foot) antenna at Stanford University is also able to listen during these windows. An array located near Bologna, Italy is not being used today.

Mission managers for Polar Lander say it will take each of the stations some time to review their data. "We want to make sure we have checked and double-checked these data before we can confirm whether or not there is a signal," said Richard Cook, project manager for Mars Polar Lander at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "I don't think we'll know anything either way until sometime next week."

Stanford University

2/1/00

Scientists keep searching for a signal from Mars Polar Lander

Mars Polar Lander, phone home. That was the command researchers issued thrice last week from NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. But scientists at the Earth receiving station in Stanford, Calif., detected no response from the lander, which had fallen silent Dec. 3 just as it was about to enter the Martian atmosphere. This week scientists will continue to study the data collected at the "Dish" radio telescope in hopes that sophisticated computer analysis will locate a signal among all the background noise.

Mission officials stress that the recent try is a long shot, and the process of data analysis and confirmation will not yield immediate results. Scientists at Stanford and JPL will continue their sophisticated analysis of the data. In the meantime, commands issued from NASA's Deep Space Network on Feb. 1 and 2 will tell the lander to reset its clock and send a signal to Earth on Friday, Feb. 4. The international scientific community has offered to help confirm any signals. Scientists at radio telescopes in the Netherlands, England and Italy will be listening for a reply, as will scientists at Stanford if they can get time on the Dish, which is booked for another research project.

All this effort was spawned by a faint signal detected by the Dish on Jan. 4. "It was the radio-frequency equivalent of a whistle," says Ivan Linscott, a senior research associate at Stanford's Space, Telecommunications and Radioscience Laboratory. Akin to the single, narrow tone that accompanies television broadcast tests, the whistle was at the ultra-high frequency (UHF) of 401.5 megahertz -- the right place to indicate a possible communication from the lander.

Just as the pitch of a train whistle drops as the locomotive approaches, the characteristics of the space whistle changed. "The pitch actually had a little curvature to it, and it was that characteristic that got our attention," Linscott says. Some of the changes in the space whistle came from the Doppler Effect created through the rotation of Mars and the Earth. A much larger effect, however, was produced when temperature- sensitive crystals in the lander's transmitter warmed up, creating a frequency profile that fell, then rose, in a characteristic way, Linscott says.

Even though Linscott says scientists are "still hopeful," the search has been frustrating. "It's like having a loved one missing in action," says JPL research scientist John Callas. "You've given up hope, and then there's been a report of a siting and your hopes are raised. Emotionally it's a little bit tough. I think in reality the chances are small, but we want to make sure. We have a responsibility to be sure, and that's why we're here."

Detecting a signal, even if one is there, is no easy feat. Space is noisy. "UHF frequencies are a pretty busy place up here," says Linscott. "But we still manage to find quiet places, or at least moments in those quiet places, to listen."

The transmitter on the lander has a broadcast power of about 14 watts, says Callas. For comparison, the beacon on the Mars Global Surveyor, which is currently in orbit 380 kilometers (228 miles) above the surface of the Red Planet, is weaker -- only 1 watt. Boding poorly for the mission is the fact that this week the sensitive Dish detected the weaker signal from the surveyor, but not the stronger signal from the lander.

But the main problem is the weakness of the signal. And signals weaken as they traverse the roughly 300 million kilometers (about 180 million miles) from Mars to Earth. "We expect a signal hitting the Dish to be something of the order of one billionth of a billionth of a milliwatt [one-thousandth of a watt] of power," says Callas. "It's extremely tiny. This is equivalent to listening to a cell phone from Mars."

More possible woes

To help them face these considerable technical challenges, the researchers have a powerful tool on their side: the exquisitely sensitive 150-foot-diameter Dish, which SRI International operates and maintains and the U.S. government owns. From a grassy knoll on the Stanford campus, the parabolic reflector of this radio telescope concentrates electromagnetic waves (radio waves) into an aluminum collecting horn built by SRI's Mike Cousins that Linscott calls "the jewel in the crown."

From there, the signal is fed into a transducer, says Cousins, site manager of the Dish. A transducer changes one type of energy into another. Unlike the pressure waves of audio, electromagnetic waves from space need to be manipulated by transducers and fed into computers before scientists can "see" or "hear" the data.

Using sophisticated software, Linscott and colleagues search among the weak signals for narrow, single tones. "Because of the processing that's involved in trying to extract them out of the background noise, it's not like we put headphones on and hook in like the now-famous image of [Jodie] Foster's search in the movie [Contact]," Linscott says. "We don't have headphones. What we have are the computers that record the signals from the sky, and more computers to try and analyze those."

Even if scientists are able to eventually detect a signal from the lander, will that mean the spacecraft could still serve a useful purpose?

"If the lander is there and it's talking to us, that tells us a tremendous amount of information," Callas says. "It tells us it got to the surface of Mars safely or in a reasonably safe configuration and that it's generating power, that its computers are operating, that it can hear us, and that it can use at least part of its UHF system. That would go a long way to understanding what might have gone wrong to put us where we are today." A functional UHF system might even allow scientists a means of reconfiguring the lander and recovering the mission -- a possibility that Callas admits is "extremely optimistic."

It will take some time to find out the mission's fate. While strong signals can be displayed in real time as spectra when they arrive, weak signals require lengthier processing. Because of the weakness of the signal, it takes "a fair amount of sophistication in the processing of this data using computer software to try to extract the signal," Callas says. "The human eye is an additional aid to the processing because we can make some displays on the computer screen. By looking at them we can recognize patterns a lot more readily than a computer algorithm can."

Support for signal processing came in part from the Bosack Foundation, established by Stanford alumni Leonard Bosack and Sandy Lerner, founders of Cisco Systems. Mars mission support comes from JPL. Lockheed Martin Astronautics Inc. of Denver is the agency's industrial partner for development and operation of the spacecraft.

Stanford graduate students who helped develop the signal-processing techniques used include Mitch Oslick, who earned his doctorate and now works for Phillips Electronics, and Neza Maslakovic, who will finish her doctoral work this summer.

Phoos of the Dish

Space Science News for February 1, 2000

Listening for Mars Polar Lander: More telescopes have joined the search for Mars Polar Lander after Stanford scientists failed to confirm a radio signal from the missing spacecraft last week.

JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109.

Mars Polar Lander Mission Status

Mission managers for Mars Polar Lander report that radio scientists at Stanford University have not detected a signal from the spacecraft in data they collected last week. Stanford will continue to analyze the data and it is still possible that more detailed analysis might reveal a signal.

In the meantime, additional radio telescopes around the world have offered their assistance in helping to confirm if the signal picked up by Stanford is from Polar Lander. The project has accepted offers of help from an array of fourteen 25-meter (82-foot) antennas at Westerbork in The Netherlands as well as the 76-meter (about 250-foot) antenna at Jodrell Bank, near Manchester, England and an array located near Bologna, Italy.

"The international community has shown a real interest in being involved in our search. We appreciate their efforts and I think it shows that Mars is something that captivates everyone's imagination," said Richard Cook, project manager for Mars Polar Lander at NASA's Jet Propulsion Laboratory, Pasadena, CA.

New commands will be sent to the lander from NASA's Deep Space Network around the clock on Tuesday and Wednesday this week, Feb. 1 and 2. These commands will essentially tell the spacecraft, if it is functioning, to reset its clock and send a signal to Earth. On Friday, Feb. 4, windows will open for the antennas in The Netherlands, England and Italy to begin listening. The antenna at Stanford may also listen during these windows.

The one-way light time from Earth to Mars is currently about 16 minutes. Mars is presently about 300 million kilometers (181 million miles) from Earth.

Mars Polar Lander is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, D.C. Lockheed Martin Astronautics Inc., Denver, Colo., is the agency's industrial partner for development and operation of the spacecraft. JPL is a division of the California Institute of Technology, Pasadena, Calif.

January 27, 2000

Radio scientists at California's Stanford University are continuing to process data from communications attempts made yesterday and today to determine if they have picked up a signal coming from Mars Polar Lander using their 45-meter (150-foot) antenna.

There were three 30-minute communications windows yesterday and three more listening windows today. It takes about 18 hours to process the data from each window. So far, Stanford scientists have looked at one of the three data sets taken yesterday and say they have not detected anything unusual. It will take several days to complete the processing and the researchers do not expect to have confirmation of a signal until some time next week.

"The signal we are looking for is very, very weak, about 1 watt of power -- or like looking for a Christmas tree light on Mars," said Richard Cook, Polar Lander project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Because of the weakness of the signal, we want to be absolutely sure we have something so we will check and double check these data before we will be willing to confirm there is a signal."

January 25, 2000

Mission managers have decided to send another set of commands to Mars to investigate the possibility that a signal detected by a radio dish at California's Stanford University came from Mars Polar Lander.

The commands were sent at 10 a.m. PST today. They will instruct the lander, if it is operating, to send a signal directly to Earth to the antenna at Stanford on Wednesday, January 26, at approximately 1 p.m. PST. The Stanford receiving station will listen again during the window on Wednesday to see if it picks up a signal that could originate from Mars. The results of this test will not be immediate and it will take the team several days to process the data.

Mission managers sent commands several times in December and January instructing Polar Lander to send a radio signal to the 45-meter (150-foot) antenna at Stanford. Although no signal was detected in real-time, the team in charge of the Stanford antenna says that after additional processing of the data they may have detected a signal that could have come from Mars during tests on December 18 and January 4. Because the signal was so weak, it took several weeks for the Stanford team to process their data and reach this conclusion.

"This week's test is a real long-shot, and I wouldn't want to get anyone too excited about it," said Richard Cook, Polar Lander project manager at NASA's Jet Propulsion Laboratory, Pasadena, CA. "The signal that the Stanford team detected is definitely artificial, but there are any one of a number of places it could have originated on or near Earth. Still, we need to conduct this test to rule out the possibility that the signal could be coming from Polar Lander."

If in fact the signal were from Polar Lander, two failures would have had to occur. First, the lander's X-band radio that it would use to transmit directly to Earth would have to be broken. Second, there would have to be a problem somewhere in the relay with Mars Global Surveyor that prevented the signal from being picked up and relayed by the orbiter. It is unlikely that a broken transmitter on the lander could be fixed, and unclear whether a problem with the relay could be resolved.

Although the Stanford data from the previous tests took several weeks to process, the team expects to have results within several days now that they know what they are looking for.

Even if the signal were coming from the lander, there is little hope that any science could be returned. However, it would give the team a few more clues in trying to eliminate possible failure modes.

Mars Polar Lander is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, DC. Lockheed Martin Astronautics Inc., Denver, CO, is the agency's industrial partner for development and operation of the spacecraft. JPL is a division of the California Institute of Technology, Pasadena, CA.

JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109

January 17, 2000

NASA CONCLUDES ALL ATTEMPTS TO COMMUNICATE WITH LANDER

"The final set of planned commands were sent on Jan. 6 to place the spacecraft in UHF safe mode. Since then, we've had a series of relay communications sessions using Mars Global Surveyor to listen for the lander around the clock," said Richard Cook, the project manager for Mars Polar Lander at NASA's Jet Propulsion Laboratory. "These attempts have ended today concluding our attempts to recover the spacecraft."

Mars Global Surveyor continues to perform special targeted observations of the Mars Polar Lander landing site in hopes of imaging the lander or its parachute. No evidence of the spacecraft has been sighted so far and these attempts will continue through early February. The team has started in depth analysis of terrain hazards within the landing footprint in support of the JPL Mars Polar Lander/Deep Space 2 Failure Review Board.

Mars Polar Lander and Deep Space 2 are managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, DC. Lockheed Martin Astronautics Inc., Denver, CO, is the agency's industrial partner for development and operation of the spacecraft. JPL designed and built the Deep Space 2 microprobes. JPL is a division of the California Institute of Technology, Pasadena, CA.