For more than a decade the Cassini spacecraft has orbited the planet Saturn and visited its moons.

And on Friday, Sept. 15, it will plunge into Saturn's atmosphere and completely disintegrate.

Its demise will be the end of a space mission that has yielded an unprecedented amount of knowledge about a mysterious planet. And it will continue collecting and transmitting data until the very end of its life.

Launched in 1997, the mission was a collaboration between NASA, the European Space Agency and the Italian Space Agency (ASI).

After traveling roughly 1 billion miles, according to NASA, Cassini entered Saturn's orbit in 2004 and began sending information that frequently surprised scientists on Earth.

Among those surprises: Cassini revealed a huge six-sided jet stream on the planet's top that holds huge hurricane-like storms within it. There is a lot about this hexagon researchers don't know, such as why it is there and how it has managed to sustain itself for so long.

The craft flew to Enceladus, a tiny moon with ingredients that could make it suitable for life.

Cassini also dispatched the Huygens lander to Titan, Saturn's largest moon, where it discovered a vast underground ocean, and liquid methane on its surface that undergoes a cycle similar to that of water on Earth.

Combined, the Cassini-Huygens mission cost about $3.26 billion, according to NASA. That includes $1.4 billion for prelaunch development, $704 million for mission operations, $54 million for tracking and $422 million for the launch vehicle.

Cassini gathered data on Saturn's famous rings and found they are made up of odd-sized clumps of particles — some as small as grains of sand, others that are miles long.

The space between the rings and the planet also is home to another mystery: extremely small, almost smoke-like, particles of dust. Researchers think they may have gotten that way by being ground up, but are not sure what process might have made that happen, project scientist Linda Spilker said in an interview with CNBC.

"The question is, what happened to the larger particles, how were they ground up into dust?" Spilker said.

Since April, the craft has been making a series of dives between the planet and its rings in what NASA has dubbed The Grand Finale.

On Monday, the craft made a flyby of Titan that slowed it down enough to direct it toward Saturn rather than through the furthest reaches of its atmosphere, as it has been doing.

On Thursday, the cameras took their final images of Saturn and its system. Cassini will then point its antenna back toward Earth and begin transmitting data as it slowly sinks into Saturn's atmosphere, burning up on its descent.

In its final days, the ship was set to collect data that may help precisely determine Saturn's current size, understand its magnetic and gravity fields, and learn the mass of the rings and take a sample of their particles, both for the first time.

Asked where in space she would next like to send a spacecraft, Spilker said she would send another craft back to the Saturn system, replete with the considerably more sophisticated technology available today than scientists had when building Cassini and Huygens in the 1980s.

Her first stop would be Saturn's tiny moon Enceladus, where she would take samples of its ocean, which harbors many of the conditions needed to sustain life.

"I would want to know if the ocean of Enceladus is indeed inhabited rather than just habitable," she said.

NASA will be streaming video of Cassini's final moments with live commentary through several outlets, such as NASA TV, online at NASA's website and on the NASA JPL YouTube channel, beginning at 7 a.m. ET.

The last signal and data from Cassini are expected at about 8 a.m. ET.

Those who want a raw feed of cameras from mission control can tune into NASA JPL's raw feed on YouTube, on Ustream, or on any of the other locations found here.