SIGNAL FROM MARS PROBE FIRST IN 9 DAYS.
The Mars Pathfinder team was feeling pretty good Tuesday after getting its first signal in weeks from the spacecraft's main transmitter.
``We had very good news this morning,'' said Brian Muirhead, the Pathfinder project manager at the National Aeronautics and Space Administration's Jet Propulsion Laboratory in Pasadena.
``We got the signal right when we expected it. It went off right when we expected it,'' he said.
That was the first signal from the main transmitter since Sept. 27 - Pathfinder's 83rd day on the surface of the Red Planet - when communications hit a snag.
``We were nine days in kind of limbo. We'd gotten signals from the auxiliary transmitter, but we weren't consistently getting them,'' Muirhead said.
Today, controllers expect to get some new engineering data from the spacecraft. On Thursday, they'll do a full run of engineering data to check all the on-board instruments. Gathering new scientific data and images remains a few days off.
Also today, mission scientists have scheduled a 10 a.m. briefing to reveal new scientific findings about the planet's interior composition and an analysis showing that at least one rock is a conglomeration of rock types.
Muirhead said that although recent communication has been through the lander's low-gain antenna, the latest seems to have come through the high-gain antenna. He suspects a broken switch locked the main transmitter onto the high-gain antenna. That would be just one of several engineering problems the Pathfinder team is trying to work around.
The principal difficulty stems from aging batteries, which had provided backup power when energy demands got high. Recently, a problem developed when the sun rose and several instruments turned on simultaneously before the solar panels were fully powered. The resulting drain caused a brownout and a computer shutdown. That, in turn, threw off the computer's clock.
``The challenge to us now is to develop (computer) sequences that work properly within the time we have enough energy from the solar array,'' Muirhead said. The goal is to have instruments working during the peak solar hours, from 10 a.m. to 2 p.m. on Mars.
``It's exactly the same problem as the rover guys faced when their battery died,'' he said.
Muirhead said he has ``reasonable evidence'' that commands to turn off the lander battery finally got through. That means it won't drain power from the solar panels.
For now, the Pathfinder's foot-high Sojourner rover is driving itself in a slow circle around the lander using a built-in program, Muirhead said.
Both rover and lander have outlived their primary missions - seven days for the rover and 30 for the lander.
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|Publication:||Daily News (Los Angeles, CA)|
|Date:||Oct 8, 1997|
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