URGENT NASA Restores Contact With Magellan
PASADENA, Calif. (AP) _ NASA engineers today received a brief radio signal from Magellan, raising hope they could restore full radio contact after losing touch with the Venus- orbiting spacecraft for the second time in five days.
A NASA tracking station detected a brief blip transmitted by Magellan just after it emerged from behind Venus at 12:30 p.m. PDT, said Alan Wood, a spokesman at the National Aeronautics and Space Administration’s Jet Propulsion Laboratory.
The signal indicated that Magellan was spinning as it sent signals into space so some would reach Earth. The next signal was expected later in the afternoon.
NASA engineers had said they expected to resume such intermittent contact with the wayward spacecraft as a step toward restoring a steady radio link.
The signal bolstered statements made earlier by officials who said they doubted Magellan had experienced a complete breakdown.
″We do not believe anything like a massive failure occurred,″ said Steve Wall, a Magellan project official.
Before the signal was acquired, several computer commands sent to Magellan’s presumed position near Venus failed to restore contact immediately, Engineer David Okerson had said.
″We’re maneuvering ourselves toward a situation where the spacecraft does come back,″ he explained at the time.
Wall said Magellan’s radio signal fluttered in and out of contact with Earth before fading away Tuesday night, indicating the spacecraft simply turned its antenna away from Earth and didn’t fail completely. Magellan and Venus were almost 149 million miles from Earth today, he added.
Officials are optimistic about restoring full contact by Thursday, said Ellen Stofan, assistant to Magellan’s chief scientist. Okerson said engineers would work as long as necessary to regain control of Magellan.
Earlier, project manager Tony Spear reported that Magellan’s automatic safety systems apparently didn’t start automatically Tuesday night. Last Friday those systems helped restore intermittent and then steady contact after Magellan’s radio link failed the first time.
When Magellan failed to respond to initial rescue efforts early this morning, laboratory spokesman Bob MacMillion said: ″Bad news. Nothing. Not a peep out of it. It’s kind of a mystery.″
The engineers lost contact at 7:03 p.m. PDT Tuesday while tracking Magellan with a NASA Deep Space Network antenna dish near Canberra, Australia, said laboratory spokesman Jim Doyle.
The latest blow to Magellan’s $744 million mission to map Venus came Tuesday night, less than eight hours after the space agency released Magellan’s first snapshots of Venus.
The pictures revealed a remarkably violent landscape shaped by impact craters, quake faults, vast lava flows, and ridges and valleys like those in the western United States.
The loss of Magellan would be another major trauma for NASA, which grounded the space shuttle fleet temporarily because of fuel leaks and found the Hubble Space Telescope was impaired by a flawed mirror.
Magellan’s computers are programmed to react to an emergency by making the spacecraft spin slowly while beaming radio signals across the sky so that some will reach Earth intermittently.
Those systems allowed the engineers to locate the spacecraft last Friday morning, more than 14 hours after they lost contact with it the first time. Eight hours later, they restored steady contact by sending Magellan a command to stop spinning and keep one of its antennas pointed at Earth.
Magellan’s mission is to map 70 percent to 90 percent of Venus’ surface using radar to peer through the planet’s thick clouds, which prevent the use of optical cameras. The spacecraft went into orbit around Venus on Aug. 10, after a roundabout 948-million-mile trip since it was launched from the shuttle Atlantis 15 months ago.
When Magellan’s first Venus pictures were released during a Tuesday morning news conference, Spear said that as far as engineers could tell, ″the spacecraft is healthy,″ despite last week’s malfunction.
He and other engineers said they still hadn’t figured out the cause of the problem. But Spear had been optimistic enough to say he still planned to have Magellan start its formal Venus mapping mission the first week of September.
Spacecraft system engineer John Slonski said one leading theory to explain last week’s loss of contact with Magellan was that a cosmic ray or a high- energy particle from the sun caused a blip in its computer memory.
″We’re not ruling out a software flaw or some hardware problem″ or perhaps some unknown electrical fields surrounding Venus, Spear said.
He also said cosmic ray ″hits″ on spacecraft electronics can be expected to interfere with Magellan about once each year.
Magellan made its first pictures of Venus during a test conducted just before last week’s malfunction.
As promised by NASA, Magellan’s first pictures are 10 times more detailed than the best radar images of Venus made by two Soviet probes and a giant radio telescope in Puerto Rico. They show details as small as 400 feet across.
The pictures show ″Venus is intensely fractured and faulted,″ with at least part of its terrain shaped by geological forces ″even more violent than I imagined before,″ Magellan project scientist Steve Saunders said Tuesday.
The pictures cover a small portion of the planet near Hawaii-like volcanic highlands.
The pictures show plains covered by six- to 10-mile-wide lava flows that solidified and then were cracked by faults. Saunders said the flows resemble those in Hawaii or along the Columbia and Snake rivers in the Pacific Northwest.
Also visible are a couple of volcanic cinder cones, a 20-mile-wide meteorite crater and long, parallel sets of two- to three-mile-wide valleys and ridges that look like the basins and ranges of Utah and Nevada, Saunders said.