NASA Uses Its Last "Silver Bullets" To Make Contact With Mars Polar Lander

       Mission controllers for NASA's Mars Polar Lander have revised their strategy as they continue trying to make contact with the spacecraft.

       "We're nearing the point where we've used up our final silver bullets," said the mission's project manager, Richard Cook of JPL, after Sunday night's unsuccessful attempt to communicate with the spacecraft.

       Engineers will try to contact the lander again on Tuesday, Dec. 7 at 12:20 a.m. Pacific Standard Time, by directing Mars Polar Lander to use its UHF radio to communicate through a relay system onboard NASA's currently-orbiting Mars Global Surveyor. Most of the attempts to receive a signal from the lander over the past few days have used its medium gain antenna.

       "Our probability of success will diminish significantly after this next attempt," Cook said, "but the team is still exploring all possibilities for establishing comunications with the lander."

       Controllers are preparing a set of computer commands to have the lander conduct a full sky search for Earth within the next couple of days.

       Mars Polar Lander is part of a series of missions in a long- term program of Mars exploration managed by JPL for NASA's Office of Space Science, Washington, D.C. JPL's industrial partner is Lockheed Martin Astronautics, Denver. JPL is a division of the California Institute of Technology in Pasadena.

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Mars Polar Lander Mission Status -- December 5, 1999

       Another telecommunications strategy to hear from NASA's Mars Polar Lander produced no results today, but the mission flight team is proceeding through its contingency checklist in continuing attempts to communicate with the spacecraft.

       From about 11 to 11:30 a.m. PST today, the team listened for but detected no signals from the lander's UHF transmitter, which would have been relayed through the already-orbiting Mars Global Surveyor spacecraft. This was the first attempt at using the Global Surveyor; until then, engineers had tried to use the lander's medium gain antenna to transmit directly to Earth.

       "We continue to work through our plan, which gives us confidence that we haven't exhausted all the possibilities," said Mars Polar Lander Project Manager Richard Cook. "But clearly, the team is getting more frustrated" as attempts to reach the lander yield no results.

       No contact has yet been made in continuing efforts to communicate with the two Deep Space 2 Mars microprobes that also impacted Mars about 60 kilometers (abut 35 miles) north of the lander on Dec. 3, said Deep Space 2 Project Manager Sarah Gavit. Mission engineers believe the probes have entered a phase where they broadcast their data automatically for one minute out of every five.

       Gavit said that data from last night's try at hearing signals from the probes that could have been recorded on NASA's Mars Global Surveyor orbiter would be reviewed later today. The team will also look for microprobe signals that could be relayed by Global Surveyor during another transmission today, she said. "If we haven't heard from them in the next 24 hours (by about noon Monday PST), we will have exhausted our opportunities to hear from them."

       Tonight, Sunday, Dec. 5 from 10:10 to 11:10 p.m., an attempt will be made to listen for signals from the lander that would be sent through its medium gain antenna if the lander is in safe, or standby mode, and its antenna is not pointed correctly.

       On Tuesday, Dec. 7, at 12:20 a.m. PST, attempts to hear signals from the lander's UHF transmitter will be made again using Mars Global Surveyor. This attempt would detect signals if Polar Lander is in safe mode. After Tuesday's post-midnight attempt, Cook said, "I think we will be at the point of diminishing returns in terms of getting in contact with the lander."

       Mars Polar Lander is part of a series of missions in a long- term program of Mars exploration managed by JPL for NASA's Office of Space Science, Washington, D.C. JPL's industrial partner is Lockheed Martin Astronautics, Denver. JPL is a division of the California Institute of Technology in Pasadena.