Cassini launched in 1997, flying by Venus and Jupiter on its way to Saturn, where its captured close-up images of the planet and its rings.
The Cassini probe will soon run out of fuel and is now planned to be destroyed by diving it into the Saturn's atmosphere on September 15.
And in recent years, one of the greatest reminders of this is the volume of research and images sent back to Earth from NASA's Cassini spacecraft, which first entered Saturn's system in 2004.
On Wednesday, Cassini will skim the outer edge of Saturn's rings for the final time, en route to its fateful encounter with Titan.
NASA plans to crash the spacecraft into Saturn to avoid any chance Cassini could someday collide with Titan, the ocean-bearing moon Enceladus or any other moon that has the potential to support indigenous microbial life. Curt Niebur, Cassini program scientist at NASA headquarters in Washington, D.C., told NBC News MACH in an email. Cassini's fuel tank is practically empty, so with little left to lose, NASA has opted for a risky, but science-rich grand finale. There will be no turning back once it flies past Titan, and embark on a new path around Saturn.More news: Pence Stares Down North Korean Troops
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Another option would be to guide the probe further out into space, but Nasa believes sending it to its destruction will yield far more scientific discoveries.
It is sure to be a bitter-sweet experience for scientists as Cassini makes its final close-proximity pass of Titan.
The spacecraft will dive in between Saturn and its rings to study its composition before falling into planet's atmosphere. The spacecraft will examine the lakes and seas of liquid hydrocarbons in the northern polar region of Titan.
After almost 20 years in space, seven of them spent traveling to the ringed planet, Cassini feels like family.
One reason scientists want to make sure Cassini is incinerated at the end of its journey is to ensure that any of its earthborn microbes do not contaminate the biotic or prebiotic worlds out there. We're going to go shooting between Saturn and its rings, threading the needle, which means we'll be able to taste the ring particles, be able to understand more about what those are made of. "We discovered that Europa's plume candidate is sitting right on the thermal anomaly", says William Sparks of the Space Telescope Science Institute in Baltimore. "What we learn from these final orbits will help to improve our understanding of how giant planets - and planetary systems everywhere - form and evolve".