To prevent the spacecraft from accidentally crash landing on one of Saturn's moons, potentially contaminating it with microbes from Earth hitching a ride aboard the spacecraft, NASA made a decision to end the mission by having it burn up while entering the planet's atmosphere.
While ground-based observers will be watching the spacecraft's demise, the researchers said, it will occur on the planet's dayside during local noon, so it's unlikely to cause any visible disturbance.
"We've had an incredible 13-year journey around Saturn, returning data like a giant firehose, just flooding us with data", project scientist Linda Spilker said this week from the Jet Propulsion Laboratory in Pasadena, California. "It's going to do this as long as it can".
The last signal and data from Cassini are expected at about 8 a.m. ET.
"It's essentially now a real-time instrument", Maize said.
By 3:30 a.m., Cassini will be gone. Even though scientists and engineers scrub each spacecraft before it leaves Earth, there's always a chance that some microbes are still stuck on its surface.
It has been making discoveries at the ringed planet for the past 13 years, but the Cassini space probe's epic journey is almost at an end.
With low fuel, there is no way to abort the final maneuver. Enceladus has oceans beneath its ice and the presence of some of the necessary elements for life.
Scientists now know Titan has lakes and seas filled with liquid methane and ethane.
What other discoveries were made by Cassini? Such contamination could harm or create potential life.
Just before 2am today the Cassini spacecraft sent a routine message, as it has done dozens of times before during its 4.9 billion-mile mission.
In response to a call from NASA, people around the world shared more than 1,400 images of themselves waving at Saturn on July 19, 2013, the same day that Cassini turned its camera back toward the direction of the Saturn-eclipsed sun and took an image of Earth in the process.
NASA's Deep Space Network complex in Canberra, Australia will receive the last transmissions, barring a torrential rainfall in the region.
During multiple close flybys, Cassini used its full science payload to detect and analyze water-rich plumes erupting from the moon's south pole far into space, a spectacular discovery that McEwen considers one of the highlights of the entire mission.
It's also a loss for many of us humans who don't depend on it for scientific data. The team is sad, but proud of accomplishing their goals, he said. "[The Cassini mission and its team] have left the world informed but still wondering", said Maize at a September 13 press conference, with a beaming smile and trying to hold back tears. Little moon Enceladus is believed to have a global underground ocean that could be sloshing with life more as we know it.
Cassini was first launched in 1997 and it reached the Saturn system around 2004 where it has stayed since, taking pictures and carefully studying the gas giant.
In the near term, though, numerous same researchers will be working on America's Clipper mission to Europa, a moon of Jupiter that in many ways is just a big version of Enceladus. Among the classes of missions eligible for this competition were those to study the "ocean worlds" of Enceladus or Titan, or Saturn itself.