Arizona Daily Wildcat
Two decades of waiting for the Galileo spacecraft to reach Jupiter came to an end today for UA scientists who helped plan the mission.
Ann Sprague and Donald Hunten will be at the NASA Ames Research Center this afternoon watching as the probe enters Jupiter's atmosphere. The craft's 746-pound probe must enter the atmosphere at precisely the right angle before it begins sending data back.
Scientists then will analyze the data Galileo gathers.
Hunten has been involved in the project's design since the early 70s and advised NASA to use an orbiter and probe, he said.
They will be anxiously waiting for data, Sprague said.
Radio messages signaling success or failure will take 52 minutes to travel from Jupiter to Earth.
The $1.5 billion Galileo mission began Oct. 18, 1989. The craft, a probe and an orbiter, is equipped with instruments to study the atmospheric conditions of the giant gaseous planet.
Any error in the delicate launching could dash hopes pinned on Galileo's six-year, 2.3 billion-mile journey.
First, the 2 1/2-ton Galileo orbiter must withstand heavy radiation on its way toward the planet.
Then, the atmospheric probe that it released in July must make a precise entry into Jupiter's dense atmosphere so it can parachute through ammonia clouds to the layers beneath.
It's supposed to start sending data to the orbiter at about 3 p.m. today.
And the probe has only a maximum of 75 minutes to relay information before the orbiter must break off contact and begin two years of orbits around Jupiter and eight of its 16 moons.
"It has been a long time coming," said UA scientist and mission co-investigator Martin Tomasko. Tomasko will use the data to measure the net heating and cooling rate and amount of sunlight absorbed into Jupiter's atmosphere.
The mission provides scientists with a "good way to test ideas of dynamics," he said.
The project has had a series of setbacks. Galileo's launch was delayed because of the explosion of the Challenger shuttle in 1986.
Then its high-capacity main antenna failed to open properly, leaving scientists to find another way to send data home using a slower small-capacity antenna. That reduced the its ability to capture and send home pictures; scientists had hoped for thousands of images. "There is no way to make up for the fact that the big antenna did not open," Sprague said.
But UA researchers remain optimistic.
Bill Sandel, researcher at UA's Lunar and Planetary Laboratory, will also be working with data from the probe. Scientists, he said, are "just getting to the most interesting part of the mission."
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