Johns Hopkins Gazette: July 25, 1994

By Emil Venere

Hopkins astronomers Paul Feldman and Doyle Hall are taking
advantage of Comet Shoemaker-Levy 9 to study Jupiter as they
never have before.
     Dr. Feldman, a professor of physics and astronomy, and Dr.
Hall, an associate research scientist, have observed the Jovian
system for years, using satellites to record ultraviolet light
from the planet and its moons.
     But Shoemaker-Levy has suddenly made Jupiter a scientific
priority, meaning that astronomers who use satellites to
observe the giant gaseous planet are receiving more precious
observing time than they usually do. And for good reason. The
cometary collisions are providing some of the most exciting
astronomical research opportunities in the history of science. 
     Shoemaker-Levy is getting plenty of media attention. That
would have been evident to anyone who tried to make a turn onto
San Martin Drive on July 16, the day the collisions began. The
road was closed to accommodate all the vehicles from television
crews and journalists congregating at the Space Telescope
Science Institute.
     "This event was not a fizzle, as had been predicted by
many astronomers," Dr. Feldman said.
     Professor Feldman and Dr. Hall are working with a team of
astronomers studying Jupiter with a satellite called the
International Ultraviolet Explorer (IUE), and Dr. Feldman is
involved with the Hubble Space Telescope's comet observation
team. Dr. Hall also heads a team of Hopkins scientists who are
observing Jupiter with another orbiting instrument, a satellite
called the Extreme Ultraviolet Explorer (EUVE), operated by the
University of California at Berkeley.
     But the IUE has a distinct advantage over the other two
satellites. It orbits the Earth from a much farther distance --
a geosynchronous orbit about 22,000 miles above the planet.
That means the satellite has a clear view of Jupiter all the
time. Other space instruments, like EUVE and Hubble, are in a
low-Earth orbit, only a few hundred miles high, and will have
their view of Jupiter blocked by Earth at times.
     Scientists viewing Jupiter with IUE normally have to
compete for viewing time with hundreds of scientists from the
United States and Europe. Ordinarily, they get observing time
two or three times a year, perhaps a total of 24 hours each
time. But the researchers are now given carte blanche to
observe the Jovian system. They began shortly before the
collisions started and plan to continue until mid-August, when
Jupiter's line of sight will get too close to the sun to make
observations practical.
     "We are simply taking advantage of this opportunity to
enhance our knowledge of Jupiter, using the techniques and
tools that we've been using all along," Dr. Feldman said.
     IUE is operated by NASA, the European Space Agency and the
Science and Engineering Research Council of the United Kingdom.
     Hopkins scientists have been using IUE to study Jupiter
since 1979, making a detailed record of the Jovian system's
ultraviolet spectrum. Therefore, any changes that result from
the comet's impact will be obvious. The scientists will be able
to identify any material introduced to the system from the
comet, which will help them to determine what the intruder is
made of.
     The astronomers also will use ultraviolet data to analyze
how the impacts affect Jupiter's atmosphere and its southern
aurora, a colorful display of charged particles from the sun
interacting with Jupiter's magnetic field.
     That research will tell scientists something about how
large the impacts were and how much energy they deposited.
Coupled with research being done at observatories around the
world, scientists wll reap a bumper crop of information about
the complex Jovian system.
     "There is already a lot of new Jupiter science coming out
of this and many new discoveries have already been reported in
the press, but it will take months to distill the data and
reach firm conclusions," Dr. Feldman said.

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