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Cold Keeps Pathfinder out of Touch

October 23, 1997

LOS ANGELES (AP) _ The Mars Pathfinder’s radio transmitter is not communicating with Earth because it has been off so long that its internal temperatures have fallen to an estimated 58 degrees below zero, scientists believe.

Communications were lost Oct. 7, and scientists can’t tell if the rover is still roaming around the red planet.

``It’s possible it’s driving around and keeps calling home and there’s no answer,″ said Brian Muirhead, project manager at NASA’s Jet Propulsion Laboratory in Pasadena.

Controllers on the ground this week were still struggling to get back in touch with the spacecraft that landed on July 4. They haven’t given up hope of keeping the 109-day-old mission going.

Their current hypothesis is that temperatures are too cold for Pathfinder’s radio transmitter to operate properly. Usually, when the transmitter is on, spacecraft hardware warms up to about minus 22 degrees by late afternoon on Mars. But with the lack of use, internal temperatures have dropped by about 40 degrees. The lander’s transmitter contains crystals that vibrate at a precise frequency that changes with temperature.

``We’re way outside the range that these crystals were designed to operate in,″ Muirhead said.

For the past three weeks, controllers have been sending a range of frequencies to the lander from Earth’s transmitter, ``like turning the dial on your radio,″ Muirhead said.

They hope the lander will ``lock up to the frequency, wherever it is,″ he added. They’ve sent the lander repeated commands to turn on its transmitter and send a signal, to no avail.

Muirhead said the mission has more than met its primary goals _ a week of operations for the rover and a month for the lander. Continued operations at this stage would be a bonus.

``We were just trying to put another layer of frosting on the cake,″ he said.

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