The Cassini spacecraft that has orbited Saturn for the past 13 years would weigh 4,685 pounds on Earth and, at 22 feet high, is somewhat longer and wider than a small moving van. Bristling with cameras, antennas and other sensors, it is one of the most complex and sophisticated instruments ever set loose in interplanetary space.
On Friday morning, the world will hear it die.
At the Jet Propulsion Laboratory in California, the scientists of the Cassini mission will figuratively ride their creation into oblivion in the clouds of Saturn. They will collect data on the makeup of the planet's butterscotch clouds until the last bitter moment, when the spacecraft succumbs to the heat and pressure of atmospheric entry and becomes a meteor.
So will end a decadeslong journey of discovery and wonder.
Launched in 1997, Cassini and its traveling companion, the Huygens lander — named for 17th-century astronomers — would go on provide the first hard look at Saturn, its rings and moons. Cassini, the only spacecraft to orbit the giant, has spent five months exploring the territory between the gaseous planet and its dazzling rings. It's darted 22 times between that gap, sending back ever more wondrous photos.
On Monday, Cassini flew past the moon Titan one last time for a gravity assist — a final kiss goodbye, as NASA calls it — nudging the spacecraft into a deliberate, no-way-out path.
The European Space Agency's Huygens still rests on Titan. It parachuted down in 2005, about six months after Cassini arrived at Saturn, and relayed data for more than an hour from the moon's frigid surface. Still believed intact, Huygens remains the only spacecraft to land in one of our outer planetary systems.
Little was known about Saturn's biggest and haze-covered moon before Cassini and Huygens showed up. They revealed seas and lakes of methane and ethane at Titan — the result of rainfall — and provided evidence of an underground ocean, quite possibly a brew of water and ammonia.
Over at the little moon Enceladus, Cassini unveiled plumes of water vapor spewing from cracks at the south pole. These geysers are so tall and forceful that they actually blast icy particles into one of Saturn's rings. Thanks to Cassini, scientists believe water lies beneath the icy surface of Enceladus, making it a prime spot to look for traces of potential life.
During its final plunge early Friday, Cassini will descend at a scorching 76,000 mph before it vaporizes. It should be over in a minute. The point of this final exercise is to prevent the spacecraft and its plutonium from crashing into Enceladus or Titan. NASA wants future robotic explorers to find worlds where life might possibly exist, free of Earthly contamination.
"The mission has been insanely, wildly, beautifully successful, and it's coming to an end," NASA program scientist Curt Niebur said. "I find great comfort in the fact that Cassini will continue teaching us up to the very last second."
Contributing: New York Times, AP