Science File / An exploration of issues and trends affecting science, medicine and the environment. : Satellite Ready to Release Probe Into Jupiter’s Atmosphere

When Galileo first turned his telescope toward Jupiter nearly 400 years ago, he discovered four moons--the first evidence that Earth was not the only center of things.

Late Wednesday night, his $1.6-billion namesake--a NASA satellite that has been traveling toward Jupiter since 1989--was due to spring loose a 747-pound probe and let it fall headlong into the scorching Jovian atmosphere.

Carrying its heat shield before it like an upside-down umbrella, and holding onto a parachute to slow its descent, the probe still has 50 million miles to travel before reaching its destination. Then it will have just 75 minutes to beam back information about Jupiter’s dense, lightning-charged atmosphere before burning up.

While the mission designers at the Jet Propulsion Laboratory in Pasadena call the probe’s release a critical point in the mission, it seems unlikely it will suffer the kind of disaster that silenced JPL’s last major planetary mission, the Mars Observer. Observer spun off into space after an apparent explosion during the rocket firing that was to put the satellite into orbit around Mars.

JPL ground personnel have kept in close touch with Galileo, and since June 28th have been sending a series of separation commands. As of Wednesday night, all systems were go.