NASA: Mysterious space whisper could be Mars Polar Lander

January 28, 2000
Web posted at: 9:09 a.m. EST (1409 GMT)

From CNN Space Correspondent Miles O'Brien

PASADENA, California (CNN) -- Managers of the Mars Polar Lander Team say a series faint radio signals captured by a dish antenna at Stanford University are offering some "tantalizing" circumstantial evidence that the spacecraft may be phoning home.

A series of additional tests will likely give engineers more definitive word after the weekend.

"We are trying to keep an even keel," said Project Scientist Richard Zurek. "On Monday morning we may have some answers."

Since December 3rd, the date the $165 million spacecraft was supposed land, the Stanford antenna has sent commands to the spacecraft to activate its low power UHF antenna four times. In two of those instances, December 18th and January 14th, the antenna received transmissions on the correct frequency, from the right direction and at the anticipated times.

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"It is plausible that it is real," said Polar Lander Flight Director Sam Thurman. "But we're not there yet. We do not have a smoking gun."

The absence of signals on during the two other attempts (on December 10th and 14th) can be attributed to problems on the ground either sending or recording the transmissions - and thus are not being interpreted as evidence that would undermine a theory that MPL is transmitting. In fact, because the problems were on Earth, the dearth of signals on those occasions actually makes it less likely that the UHF signals are from another source.

In order to draw some conclusions, scientists Stanford are conducting a series of tests. In one, they will fine tune the antenna to better isolate the signal. In another, they will command the lander to turn itself on and off at precise times - then check for comparisons in the received signals. They will also deliberately point the antenna away from Mars - to further exclude the possibility they may be capturing stray signals from an earthbound source. UHF radio signals are used in wireless communications and TV broadcast transmissions.

"If we can duplicate the results," said Thurman. "then we may get to the point where these things look like a lander."

The UHF transmitter on Mars Polar Lander was not designed to transmit directly to Earth. It was supposed to use the Mars Climate Orbiter - and then after its loss - the Mars Global Surveyor (in Mars orbit) - as a relay. Isolating such a faint signal is a difficult challenge.

"There is a tremendous amount of (radio) clutter," says Zurek. "It takes a lot of processing to pull these signals out."

The Polar Lander team has asked their colleagues at Stanford to take their time processing the data. Both teams will be working through the weekend. While the Stanford team looks for this cosmic needle in the haystack, the team at the Jet Propulsion Lab will be planning what to do if the lander is still operating.

If the lander is alive, it reamins doubtful it will be able to return any scientific results. If its UHF transceiver is working, ground controllers will only be able to issue very rudimentary commands - "Questions with a 'yes' or 'no' answer," said Zurek.

But answers to those queries might give engineers valuable insight into what went wrong during the lander's descent.