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Shuttle team reaps a scientific harvest, despite malfunctions

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Despite continuing problems with some equipment, Challenger astronauts in space and the science team on the ground are reaping a substantial harvest of data from this troubled mission. ``We have been able to assure ourselves that the science return . . . will be very high,'' says mission scientist Eugene W. Urban.

The mission team, at this writing, was still trying to recover full use of the instrument pointing system (IPS), which enables sun-observing instruments to track their targets with high precision.

Experimenters also had not been able to fix a malfunctioning instrument called SOUP. SOUP is a combination of telescope and video cameras used for studying activity of the solar magnetic field and the polarization of the sun's visible light.

Otherwise, Mission 51-F was carrying out a fast-paced research plan.

Peter Meyer of the University of Chicago says the cosmic-ray sensor has already sent back enough data to keep him and his colleague, Dietrich Muller, busy for the next two years. They are studying the composition and energy characteristics of some of the high-energy cosmic-ray particles arriving at Earth from outer space.

Several of the instruments involve studies of what physicists call plasma, a gas made up of electrically charged particles. But since there are equal numbers of positively and negatively charged particles, the gas, as a whole, is electrically neutral. Much of the matter in the universe, such as stars, is in the form of a plasma. So, too, is the thin residual atmosphere through which the shuttle travels.

One experiment, in which an electron beam is shot into this plasma environment, has already produced brilliant light displays and much useful data.

Another experiment involves the effect of water, discharged by the shuttle's orbital maneuvering system thrusters, on the high atmosphere. The electrically charged plasma particles in this part of the atmosphere -- called the ionosphere -- reflect shortwave radio signals and bounce them around Earth.

Influenced by the water, some of the positively charged particles recombine with negatively charged electrons. This process opens ``holes'' in the ionosphere, which allow the radio waves to pass through without reflection. Experimenters, who are testing the physical properties of the ionosphere, have seen several instances of this from their ground stations. They report that the holes appear to be more circular and take longer to fill in than was expected.


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