After almost 20 years of nail-biting, a half-dozen pale Jet Propulsion Laboratory scientists finally realized their dream Thursday: Their intrepid Galileo spacecraft successfully delivered its long-awaited one-two punch to Jupiter, jabbing the giant planet's midsection with a precisely parachuted probe and then powering its mother ship into Jovian orbit.
At precisely 3:10 p.m. the pint-sized probe signaled that it had slipped safely beneath the clouds of Jupiter, the first Earthly object to penetrate the foreboding atmosphere of the giant gaseous planet. And about two hours later, the Galileo itself fired its engines and settled into orbit around the solar system's largest planet.
"It's been a perfect day," said Project Manager William O'Neil. "Not only are we in orbit, we're in a very good orbit. We're ecstatic."
After a journey of six years, two loops around Earth and one around Venus, the orbit burn was off by a mere one-tenth of one percent.
In addition, the sturdy craft managed to sail smoothly through the worst part of Jupiter's wild magnetic environment--"the thing we lost the most sleep over the last few years," said O'Neil.
After more than four months of silence, the probe survived its scorching plunge into the Jovian atmosphere and phoned home. Amid whoops and cheers at JPL in Pasadena, project scientist Torrence Johnson laughed out loud with relief, and called it a "fantastic accomplishment. . . . You never really believe that these things are going to work." Johnson was one of the scientists who first proposed the project to Congress more than two decades ago.
Then, at 5:19 p.m., word came that the burn had begun--putting Galileo on the right path for its two-year tour of the Jupiter system. The 49-minute burn had to go perfectly, or the next two years of perfectly timed loop-de-loops around Jupiter and its four largest moons would have been thrown hopelessly off course.
Finally, at 6:10 p.m. came confirmation that the engine burn was complete and Galileo was indeed orbiting Jupiter.
NASA Administrator Dan Goldin told an assembled throng of scientists, engineers and their families, "I'm going to sleep very well tonight."
Cornell astronomer Carl Sagan, on hand for the festivities, pointed out that last year, when comet Shoemaker-Levy crashed into Jupiter, the planet got a new shooting star. "Now," he said, "it has a new artificial satellite."
Goldin said it was about time that JPL engineers had a chance to sit back and relax. "Maybe this portion of the mission isn't snake-bitten [like the rest of it]," he said.
Goldin, who had said minutes earlier that the anticipation was making him "a little crazy," called the events "a whole day of celebration for JPL."
The problem-plagued 2.3 billion-mile mission--which Goldin likened to "The Perils of Pauline"--had passed its first critical tests Thursday. It came as a particular relief because mission scientists had not heard from the 745-pound probe since July, when it separated from the mother ship.
Moreover, as probe mission specialist Marcie Smith pointed out, "We have no control over it." Because the one-way travel time for light from Earth to Jupiter is 52 minutes, no instructions could be radioed to the craft in time to make adjustments if anything went wrong. Flying on parallel paths, probe and mother ship headed toward a rendezvous point at speeds exceeding 100,000 miles per hour.
At the moment the probe plunged into Jupiter's atmosphere, the mother ship was cruising directly overhead, receiving data beamed to it from the probe about the structure of Jupiter's atmosphere. Scientists expected it to encounter continent-sized hurricanes, 250 mph winds and fierce lightning.
The mission controllers won't get any real information from the probe until Sunday and Monday, when they expect to get between 20 and 40 minutes of data from Thursday's 75-minute plunge.
While Galileo was mainly silent prior to that, it did send back indications early Thursday morning that a tape recorder that had earlier failed to rewind appeared to be working properly, recording data from Jupiter's volcanic moon Io as it flew within 800 feet of its sulfurous yellow surface.
Speaking to the press about an hour before the rendezvous, Goldin praised NASA engineers for pulling the troubled mission out of one rough spot after another over the past 20 years. He also made it clear that Galileo was the last of its kind planned for NASA, and used the conference as a podium to present his vision for NASA's future: a continuous series of small, robust spacecraft that could be launched to various planets as often as once a month.
In the past 20 years, he pointed out, NASA has launched only three major planetary missions: Mars Observer ("which disappeared," said Goldin), Galileo, and Cassini--already built and getting ready for its trip to Saturn's rings. The old way, Goldin said, "didn't get us very far." Galileo, he said, was NASA's "pilot pigeon" to Jupiter, setting the stage for what comes beyond.