A shuttle full of experiments
America's space shuttle has been billed as a superb platform for scientific research. The second mission of the Columbia should begin to show off some of that capability.
Seven experiments are mounted in Columbia's equipment bay, to survey the Earth as the shuttle orbits upside down, or stowed in the cabin with the astronauts. All are sponsored by the Office of Space and Terrestrial Applications (OSTA) of the National Aeronautics and Space Administration (NASA).
The experiments are as diverse as a study of weightless plant growth and a survey of carbon monoxide air pollution. Most of them can run unattended, controlled by their own timers and computers while also being receptive to astronaut or ground station command. But one - a study of lightning - requires astronaut help to film lightning flashes from the vantage point of orbital flight.
In spite of many decades of research, lightning still is something of a mystery to meteorologists. Its causes are poorly understood. Its role in general weather and its relation to the storms that generate it are ill-defined.
Even the forms it takes are not completely known. Besides the familiar strokes that flash from cloud to cloud or between cloud and ground there is ball lightning. Sometimes, as high-flying pilots have discovered, a cloud will send an intense, narrowly beamed stroke upward like the sudden thrust of a gigantic ''Star Wars'' light sword.
A NASA briefing document quotes such an observation made in 1973 by U-2 pilot Ronald Williams while flying at a height of 20 kilometers near a vigorous thunderhead. ''I was surprised to see . . . a bright lightning discharge, whitish-yellow in color that came directly out of the center of the cloud at its apex and extended vertically upward far above my altitude,'' Mr. Williams said. ''The discharge was very nearly straight like a beam of light, showing no tortuosity or branching. Its duration was greater than an ordinary lightning flash, perhaps as much as five seconds.''
With something like 1,800 thunderstorms raging around the planet at any one time, astronauts Joe Engle and Richard Truly should have plenty of opportunity to photograph lightning and the clouds that accompany it. Their photos, together with matching spectrograms of the flashes and photoelectric data taken automatically, should give meteorologists new perspective on one of the most awesome phenomena in nature.
Other OSTA experiments, while less dramatic, should be equally valuable scientifically.
The radar mapper is similar to that used on the former Seasat satellite to map ocean waves. The power of such radar to penetrate even beneath foliage was shown when such an instrument in an aircraft disclosed the remains of a complex and ancient Mayan irrigation system long-hidden beneath the Central American jungle.
The radar on Columbia is expected to produce maps of land forms that resolve detail as small as 40 meters across. These will be compared with other geological data to assess the potential of radar mapping as a tool for mineral exploration.
Still other instruments will scan ground and atmosphere at various infrared wavelengths. One set will gather data on the spread of carbon monoxide pollution in the atmosphere at heights of about 7 to 8 kilometers and 10 to 12 kilometers. Another instrument set will survey the ground at various infrared wavelengths. Its data will then be compared with measurements taken on the ground to try to find the best wavelengths for identifying rock types as seen from space.
Yet another experiment will take pictures of the surface using visible red and near-infrared light. This will test a system that can automatically tell the difference between land and water, cloud or snow-cover and bare ground, farm land and forest. It is part of a long-term effort to give future earth surveying satellites an ability to be discriminating in the observations they make - picking out only wheat fields or desert lands, for example, when this is desired.
Along with the land surveying, there is instrumentation to study the color of sea water. This may lead to a system to detect chlorophyll and locate concentrations of the tiny marine plants that are at the base of ocean food chains. Their presence may reveal areas where fish congregate.
The final experiment is one that will rest quietly in a locker throughout the flight requiring no attention at all. Although it has a formidable name - Heflex Bioengineering Test - it is only a group of humble dwarf sunflowers placed onboard to see how they grow under weightless conditions with varying degrees of moisture in the soil. Heflex, which stands for Helianthus annuus flight test, is the only aspect of the OSTA program, beyond supervision and photography by the astronauts, that requires the presence of a living being.