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Magellan’s Radar Turned on; Venus Mapping to Resume Saturday

September 14, 1990

PASADENA, Calif. (AP) _ Engineers turned on Magellan’s radar Friday for the first time in a month, preparing the sometimes unruly spacecraft to start mapping the rugged landscape of cloud-covered Venus.

″I personally am excited and jumping around,″ said Ed Sherry, technical assistant to the Magellan project manager at NASA’s Jet Propulsion Laboratory.

The last and only other time engineers used Magellan’s radar was during a picture-making test on Aug. 16, only hours before they lost touch with the spacecraft for 14 hours. Radio contact was lost again for 17 1/2 hours starting Aug. 21.

″I am delighted to see the blue sky that we knew was at the end of this tunnel,″ Sherry said Friday after engineers received confirmation at 8:14 a.m. PDT that they successfully turned on the radar.

Magellan’s radar was to remain on standby until Saturday, when it will be ordered to send radar waves through Venus’ thick clouds and bounce them off the rugged surface. Magellan then will collect the reflected radar echoes and send the data to Earth, where it will be made into pictures and maps.

If all goes well, the National Aeronautics and Space Administration hopes to release new pictures of Venus early next week, Sherry said.

He cautioned that NASA may lose contact with Magellan again because engineers have yet to determine the cause of the earlier blackouts.

But they have equipped Magellan with new computer commands that should allow them to restore contact within four to 24 hours if it is lost again, then resume mapping within two weeks.

NASA’s official stance is that Magellan’s $744 million mapping mission won’t start until late this month. But if everything works well this weekend, officials may declare retroactively that mapping began Saturday, Sherry said.

″We’re not being foolhardy and rushing into a restart of operations,″ said David Okerson, a Magellan engineer.

Magellan’s first pictures of Venus - made during the Aug. 16 radar test - showed surprisingly violent forces shape the planet.

The pictures revealed vast flows of solidified lava, volcanic cinder cones, huge meteorite impact craters, extensive ″Venusquake″ faults, numerous valleys and mountain ridges and large calderas. The calderas are volcanic craters created when the summit of a volcano collapses as lava flows out from vents on the volcano’s flanks.

Sherry said that during the weekend, Magellan will fly over Ishtar Terra - a continent-like highland area about the size of Australia - and a plain on Ishtar that is named Lakshmi Planum.

Optical cameras can’t penetrate Venus’ thick clouds. Magellan’s radar penetrates the clouds to make pictures 10 times more detailed than those produced by Earth-based radar or radar on the Soviet Venera 15 and 16 spacecraft, which visited Venus in the mid-1980s.

Magellan went into orbit around Venus on Aug. 10 after a looping 948 million-mile voyage from Earth. It was launched from the space shuttle Atlantis on May 4, 1989.

Magellan’s primary mission will last 243 days - the time it takes for Venus to rotate once as Magellan circles the planet in a nearly polar orbit.

The spacecraft should be able to map 70 percent to 90 percent of the surface during the initial mapping mission. But NASA officials have said they expect to extend Magellan’s mission so the entire planet can be mapped.

Magellan made its Aug. 16 pictures during two orbits around Venus. But only 1 1/2 orbits worth of picture data were returned before contact was lost. Sherry said half the remaining picture information was radioed to Earth on Wednesday night. Engineers hoped to retrieve the remainder early Saturday.

Despite 900-degree Fahrenheit surface temperatures created by a runaway ″greenhouse effect,″ Venus is the planet most like Earth in terms of size, mass, density and distance from the sun.

Scientists hope to learn the extent to which Venus is shaped by forces similar to those that sculpted Earth’s terrain.

They are particularly interested in knowing if Venus has plate tectonics, which is the movement of giant plates of crustal rock that makes continents drift slowly across the face of the Earth.

Many scientists doubt Venus has drifting plates, and believe its crustal movements are caused by ″hot spots″ in which molten material bubbles upward - the process that created the Hawaiian Islands on Earth.

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