Spacelab mission set for launch; monkeys join shuttle's crew

Barely a week after Discovery returned to Cape Canaveral, launch crews are ready to send another shuttle into orbit. The space ship Challenger will carry the European-made Spacelab on a seven-day mission of scientific and industrial research.

Liftoff was scheduled, at this writing, for a one-hour launch window that opens at noon Eastern daylight time on April 29. Challenger is due to land at Edwards Air Force Base in California.

Spacelab -- designed and built by the 11-member European Space Agency (ESA) -- provides a shirt-sleeve environment for scientist-astronauts and a working laboratory for experiments that make use of the virtually gravity-free space environment.

Other equipment mounted in the payload bay -- such as an Indian cosmic-ray detector and a United States instrument for analyzing Earth's atmosphere -- can be controlled and monitored from within the lab.

Although Spacelab has flown before, this is the first time that four scientists will orbit with experiments they themselves have designed. In fact, the Mission commander, Col. Robert F. Overmyer of the Marines, and shuttle pilot Col. Frederick D. Gregory of the Air Force will essentially be running Challenger for the benefit of a five-member scientific research team. It includes NASA scientist-astronauts William E. Thornton, Norman E. Thagard, and Don L. Lind, plus Lodewijk van den Berg of EG&G Energy Measurements and Taylor Wang of NASA's Jet Propulsion Laboratory.

There will be animal ``astronauts,'' too. NASA wants to try out orbital animal facilities developed at its Ames Research Center. So two or three squirrel monkeys and two dozen rats will accompany the human shuttle team. Their adaptation to weightlessness will be studied along with that of their human companions.

Several key experiments require fine-tuned stability of the spacecraft. Basically, the laboratory will be a gravity-free environment. But small movements of Challenger can introduce disturbing gravity forces since.

Thus, for these experiments, Astronauts Overmyer and Gregory will orient Challenger with its tail toward Earth and one wing pointed in the direction of the craft's orbital motion. This will minimize the thruster firing needed to hold Challenger's attitude and thus minimize tiny but unwanted gravity forces on the gravity-sensitive experiments. These will be clustered within three feet of Challenger's center of gravity.

An atmospheric modeling project is one of these key experiments, and it represents a major advance for this type of study. Such experiments on Earth simulate an atmosphere in rotating ``dishpan'' containers. They have given insight into circulation patterns and how they develop and evolve. But flat dishpans cannot adequately represent a spherical star or planet and its atmosphere. Now, with Earth's gravity virtually eliminated in Spacelab, a University of Colorado/Marshall Space Flight Center experiment will explore the dynamics of the atmospheres of Jupiter and the Sun in the round.

Called a geophysical fluid flow cell, the equipment simulates an atmosphere using silicone oil sandwiched between an inner stainless-steel hemisphere and an outer sapphire hemispherical shell. It is roughly the size of a baseball. The inner dome can be heated to simulate the solar and internal heating of Jupiter's atmosphere, and the Sun's atmosphere. Electric forces simulate the effect of planetary or solar gravity.

Because of the heavy schedule, the crew has been divided into two shifts, so the lab will be active around the clock.

Two small satellites will also be launched. Webber State College's Northern Utah Satellite will be used to calibrate aircraft radars. And the Defense Advanced Research Projects Agency Glomr will be orbited for studies involving control of ground-based sensors.