The Atlantis astronauts, basking in the flawless launch of the Magellan Venus probe, turned to more mundane pursuits Friday, studying lightning storms, growing space crystals and troubleshooting snags.

As Atlantis sailed over Hawaii late in the day, tracking cameras and other instruments at an Air Force ground station presumably locked onto the orbiter as maneuvering jets were fired in a military experiment to learn more about how to detect vehicles in flight.But commander David Walker, 44, co-pilot Ronald Grabe, 43, Mary Cleave, 42, Norman Thagard, 45, and Mark Lee, 36, had little to say other than to pass on periodic experiment updates.

Walker and company are scheduled to wrap up the fourth post-Challenger mission with a landing Monday at Edwards Air Force Base, Calif.

Cleave and Lee spent most of the day operating a compact device built to create ultra-pure crystals of indium in the weightlessness of space.

The device works by slowly moving a circular heating element along 7.5-inch samples of indium. As the heating element moves along, a "melt zone" is created and as the heater creeps past, the material behind it resolidifies. The result is a single crystal of exceptional purity.

When the shuttle's maneuvering jets were fired for the Air Force tracking test, however, Cleave said the resulting vibration appeared to disturb the experiment.

The astronauts also conducted extensive Earth photography, including observations of lightning storms over Africa, and mission control asked for photographs of an oil spill from a supertanker near the coast of Saudi Arabia.