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"Magellan' mapping project suspended

Two months after the balky spacecraft Magellan began sending back the most detailed images ever of the planet Venus, violent radiation from the sun forced scientists Friday to suspend their historic mapping project. The hiatus had long been expected because the planet's normal path in the solar system has put the sun in a direct line between Venus and Earth.

As a result, the radar images the Magellan has taken during nearly 700 orbits around Venus are now being degraded by interference from solar radiation, and the spacecraft's radio antenna cannot communicate clearly with Earth because of electrical noise from the sun's flaring surface.

Mapping operations are to resume within two weeks, said deputy mission director Douglas Griffith.

Before the solar static began, however, the Magellan's unparalleled radar images of the Venusian surface had shown delighted scientists an intriguing view of a planet pocked with gigantic meteor craters, mile-high volcanic domes and vast plains cleaved by sinuous lava flows, along with seismic faults and shattered valleys and ridges.

As the images temporarily ceased returning to Earth Friday, mission engineers at the Jet Propulsion Laboratory in Pasadena said the Magellan's solar panels, which generate the electrical energy to operate its radio and its radar imaging equipment, are beginning to veer out of control because of the planet's position in what astronomers term "superior conjunction" with the sun.

The panels are receiving conflicting commands from their own solar sensors and the on-board computer that is programmed to keep the panels facing the sun directly, said Griffith.

The scientists already are using magnifying glasses to analyze enlarged photographic mosaics, made from 165 strips of crisp, high-resolution radar images each covering an area of the planet's surface averaging 16 miles wide and 10,000 miles long. The images have a resolution fine enough to reveal objects the size of a football field.

Photographing Venus from orbit is impossible because the planet's 900-degree surface _ more than hot enough to melt lead _ is eternally shrouded in dense clouds of sulfur dioxide. But radar can pierce the clouds easily. Radar signals reflected from the surface back to the spacecraft can create clear images of surface features and their heights and depths.

Venus researchers are now discovering more and more evidence that Earth's nearest planetary neighbor holds a surface that is ravaged, shattered, deformed and highly unusual.

"It's impossible for your mind to keep up with this flood of data," said Ellen R. Stofan, a geologist who is the Magellan's deputy project scientist. "Unlike the Earth, we can't find any place on the planet where there isn't evidence of volcanic activity, perhaps even recent activity that has created rivers of lava. And the impact craters we find are astonishing because they seem so completely fresh."

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