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In Brief:

August 17, 1999
Web posted at: 8:53 a.m. EDT (1253 GMT)

NASA satellite clocks latest hurricane at 90 mph

(CNN) -- The SeaWinds instrument onboard NASA's QuikScat ocean-viewing satellite collected pictures and other data on Hurricane Dora as it whipped through the eastern tropical Pacific Ocean at speeds of nearly 90 mph.

The image shows surface wind speed and direction in the vicinity of the hurricane, which was centered near 14.5 degrees north latitude and 117.8 degrees west longitude on August 10.

With its broad, 1,800-kilometer-wide (1,116-mile-wide) swath and nearly all-weather capabilities, the SeaWinds scatterometer is bounces microwaves off the seas to get frequent surface wind speed and direction measurements over the global oceans.

Coupled with other satellite measurements of cloud patterns, water vapor and rain, the data help scientists predict the intensity, location and movements of hurricanes and other severe marine weather patterns.

The orbiting SeaWinds radar instrument is managed for NASA by the Jet Propulsion Laboratory, which also built the it and is providing ground science processing systems.

Related Sites:
   • Planetary Photojournal: NASA's Image Access Home Page
   • Winds: NASA's QuikSCAT Mission News

Galileo passes by Callisto

(CNN) -- NASA's Jupiter orbiter speeded past the heavily cratered jovian moon Callisto on Saturday, giving scientists more data on its atmosphere.

The planned pass helped rein in the Galileo spacecraft for October and November fly-bys of Jupiter's highly volcanic moon Io.

The Callisto fly-by started around 4:30 p.m. EDT, with the craft passing as close as 2,296 km (1,427 miles).

During the event, Galileo passed behind the moon as seen from Earth, so scientists collected weak radio signals that will give them insight in Callisto's atmosphere. Callisto, nearly the size of the planet Mercury, is one of Jupiter's four largest moons.

Galileo also took ultraviolet spectrometer readings of the nearby jovian moon Ganymede in hopes of catching auroral activity there.

This week, the spacecraft is playing back data acquired in the past several days.

Flight team members are analyzing some unexpected results from the fly-by, probably the result of Jupiter's intense radiation environment wearing away at Galileo's instruments.

In one incident, the spacecraft's tape recorder stopped, resulting in the loss of two observations of Callisto by an infrared spectrometer and other data.

The playback also will provide data on a magnetic field around Io and images of Io, another moon Amalthea and Jupiter.

Balloon captures antimatter

WASHINGTON (CNN) -- An instrument on a balloon 60-stories high has captured antimatter in the upper reaches of Earth's atmosphere, scientists said Tuesday.

The experiment, led by Shuji Orito of the University of Tokyo, was designed to search for evidence that galaxies made entirely of antimatter exist in the universe.

"We have collected excellent data, which should contain several hundred antiprotons among a hundred million cosmic-ray particles that passed through our detector," Orito said.

There is no evidence of antimatter galaxies yet. It will take several months to see if the data include evidence of anti-helium, a sophisticated form of antimatter that would prove their existence, said Jonathon Ormes, head of the Laboratory of High Energy Astrophysics at NASA's Goddard Space Flight Center, in Greenbelt, Maryland.

A balloon with a similar instrument has been released and refined annually since 1993 in a continuing search for anti-helium particles.

"The discovery of anti-helium would be stunning," Orito said. "That is why we search for such exotic objects, although there exist no compelling reasons to believe that anti-galaxies do exist."

Such a discovery would rewrite science books worldwide, Ormes said. In similar balloon flights from 1993 to 1998, no anti-helium had been detected.

Galileo orbiter survives radiation blast

(CNN) -- NASA's Galileo orbiter survived an unexpected blast of radiation just before completing the third in a series of fly-bys of Jupiter's moon Callisto.

The radiation blast was the strongest by far that Galileo ever has endured since its approach to Jupiter in 1995.

The bombardment occurred as Galileo headed toward Jupiter's moon Callisto, when the spacecraft flew within 452,000 kilometers (281,000 miles) of Jupiter's cloud tops around 7 a.m. EDT Thursday.

"We anticipated the spacecraft's star scanner would detect about 300 to 400 pulse counts of radiation, so imagine our surprise when the instruments showed Galileo had flown through 1,400 pulse counts," said Galileo project manager Jim Erickson.

"Then again, that's why we're exploring Jupiter and its moons -- to discover these unusual phenomena."

The cause of the outburst is unknown, but it could be due to Galileo's proximity at the time to Jupiter and a "plasma sheet" area brimming with charged particles trapped in a disc rotating with the planet's magnetic field.

Also, the radiation dose occurred just a week after the largest heat output since 1986 from Jupiter's volcanic moon Io.

The radiation level endured by Galileo during this fly-by was many times higher than the levels engineers expect the spacecraft will encounter during its swings by Io in October and November. So engineers have renewed optimism that the spacecraft, now operating beyond its planned lifetime, will survive this risky encounter.

"This was a great dress rehearsal for the Io encounters," said Erickson. "We've been wondering how the spacecraft might hold up when it gets close to Io. This latest brush with radiation makes us think that the odds of survival may be fairly good."

The radiation did trigger four spacecraft faults, but all of them were handled correctly by onboard software.

After the radiation blast, the spacecraft went on to fly by Callisto at an altitude of 2,299 kilometers (1,429 miles) on Saturday. The flyby included experiments involving changes in the spacecraft's signal as it passed behind Callisto to study the structure of its tenuous atmosphere.

Currently, Galileo is sending pictures and other data from the flyby to Earth.

Galileo, managed by NASA's Jet Propulsion Laboratory, has been orbiting Jupiter and its moons since December 1995.

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