America's space shuttle Columbia has opened a new kind of research opportunity for space scientists. Because the shuttle itself is reusable, so, potentially, are any instruments or scientific experiments it carries. No longer must equipment be built to the rigorous, and expensive, standards required when it has to function unattended for long periods in orbit. This cost-cutting advantage, plus the fact that astronauts can help operate instruments, means that more investigators now can do a wider range of science than ever before in space.
If instruments lose accuracy in orbit, they can be recalibrated when returned to Earth. Scientists then can often compensate for the inaccuracies. If an experiment fails, it can be reflown on a subsequent shuttle mission. Also, long-term studies can be made over a number of years with instruments being sent up from time to time as needed.
All of these advantages were demonstrated with the scientific payload carried by Columbia on its second test flight in November. Having made preliminary studies of their results, the investigators now say they generally are delighted with the research possibilities of the shuttle.
The thunderstorm study is typical. For this, astronauts Richard Truly and Joe Engle used a standard movie camera and photocells to photograph thunderheads and record lightning flashes. Because failure of one of their fuel cell electric generators forced them to cut their time in orbit from five days to 54 hours, the astronauts got only a little film footage and recorded only one lightning flash. However, principal investigator Bernard Vonnegut of the State University of New York at Albany says the potential for this kind of thunderstorm study has been proved. With quite inexpensive equipment and making little demand on astronaut time or capability, he now has the prospect of making detailed observations of thunderstorms from the perspective of space.
Dr. Vonnegut says a thunderstorm is still rather a mystery. He describes it as being something like a fountain of warm air rising up to penetrate the stratosphere and reaching speeds of 100 to 200 miles an hour. No one yet knows how that vigorous cloud generates electricity, what the electricity does within it, or what role electrification may play in rainfall.
The puzzle has been compounded, Vonnegut adds, by two relatively recent discoveries. Satellite observations show there is 10 times as much lightning over land as over water. Again no one knows why this should be so. Also, meteorologists had thought that clouds and water were necessary to produce lightning. But planetary scientists now know that other planets do it without water.
Vonnegut says there is some indication that the strength of thunderstorm convection and the area of the storm are related to lightning. By photographing thunderstorms and recording their lightning from space, he expects to gain new insights that should help clear up some of the mysteries. The photographs will include stereo pairs so the storms can be seen in three dimensions. By carrying on this study as shuttle opportunities permit, Vonnegut hopes to build up a library of thunderstorm images and lightning data that will become a unique resource for weather scientists.
For Allan H. Brown and David K. Chapman of the University of Pennsylvania also, the opportunity to do their experiment over again is of paramount importance. Their study of plant growth under weightless conditions needed the full five days to show meaningful results. Thus, when the time in orbit was reduced to 54 hours, their experiment with the dwarf sunflower Helianthus annuus became one of the few aspects of the mission that can be called a near total failure, Dr. Brown says.
Nevertheless, they did gain valuable experience in working with their experimental package, which is carried in a locker on board the spacecraft. Among other things, they found the temperature running unexpectedly high at 81 degrees F. instead of 5 to ten degrees lower. This could significantly affect both their own and future biological experiments on the shuttle. The cause must be understood and taken account of, Brown says. His experiment is a pilot project for a larger study to be made with Spacelab - a laboratory carried in the shuttle payload bay in which several people can work and which is being supplied by the European Space Agency.
These biological studies are of more than academic interest. Brown and Chapman are trying to find out the relation between seedling growth and soil moisture content. Brown explains that, on Earth, gravity tends to make moisture migrate downward. In space, without this gravitational effect, moisture and soil may interact differently. What are good growing conditions on Earth might drown seedlings under weightless conditions. If future manned space stations are to provide some of their own food from on-board gardens, a new set of gardening skills needs to be developed based on such experiments.
As a platform for doing science, the shuttle not only allows experimenters to work with relatively cheap equipment, it also is a test bed for developing equipment for other uses. For example, resource scientists would like to have a ''smart'' satellite that took only the images they wanted. Resource-surveying satellites, such as Landsat, now inundate their users with data, much of which is irrelevant. Roger T. Schappell of Martin Marietta Aerospace in Denver and his co-workers are developing a system that would enable such satellites to discriminate between different kinds of surface features and only take data for those in which users are interested.
The FILE (Feature Identification and Location Experiment) package Columbia carried is a step toward such a system. Dr. Schappell says it is equipped to distinguish between water, bare land, vegetation, and clouds and snow. What he calls a ''very preliminary'' look at the data suggests that the system can indeed do this. Even though he didn't get all the data hoped for, Schappell says he has enough to work with.
Other experiments to map ocean surface color, measure carbon monoxide concentrations in the atmosphere, and match infrared ''signatures'' of land features as seen from space with their true geological nature also returned enough data for their respective research teams to carry on with their development. The ocean color test, in particular, allowed Hongsuk H. Kim of the NASA Goddard Space Center and his colleagues to use what he calls off-the-shelf aircraft equipment - not something specifically designed for space - to develop a system for locating concentrations of chlorophyll from orbit. Such concentrations should indicate areas where there is much plant and other food to sustain fish populations.
One of the most successful of the equipment tests was that of the imaging radar. This obtained virtually all the data wanted and confirmed that such radar can indeed obtain high-quality images of land formations from orbit. It is similar to radar used to map the sea surface from the Seasat satellite and that has been successfully used from aircraft.
Its images, which have a photograph-like quality, can be taken day or night, through clouds and vegetation. It was such a radar, carried by aircraft, that uncovered a previously unknown network of ancient Mayan irrigation canals in Central America. Indeed, this is the kind of radar planetary scientists hope to send to Venus to make detailed maps of its surface, if this often postponed project is eventually funded. Meanwhile, the shuttle offers a new opportunity to use that radar for geological mapping here on Earth.