This NASA handout illustration obtained April 6, 2017 shows NASA's Cassini spacecraft about to make one of its dives between Saturn and its innermost rings as part of the mission's grand finale. (HANDOUT / NASA/JPL-CALTECH / AFP)
LOS ANGELES - The US National Aeronautics and Space Administration (NASA)'s Cassini spacecraft made a final, distant flyby of Saturn's giant moon Titan, referred to informally as "the goodbye kiss" flyby by mission engineers.
With that, it headed toward a mission-ending plunge into the atmosphere of Saturn on Friday.
"Cassini has been in a long-term relationship with Titan, with a new rendezvous nearly every month for more than a decade," Earl Maize, Cassini project manager at NASA's Jet Propulsion Laboratory (JPL) in California, said in a statement. "This final encounter is something of a bittersweet goodbye, but as it has done throughout the mission, Titan's gravity is once again sending Cassini where we need it to go."
Cassini made its closest approach to Titan Monday at 12:04 pm PDT (1904 GMT) at an altitude of 119,049 km above the moon's surface. This distant encounter provided a gravitational nudge that sent the spacecraft toward its dramatic ending in Saturn's upper atmosphere. According to NASA, the spacecraft is scheduled to make contact with Earth on Tuesday. Images and other scientific data taken during the encounter are expected to begin streaming to Earth soon after. Navigators will analyze the spacecraft's trajectory following this downlink to confirm that Cassini is precisely on course to dive into Saturn at the planned time, location and altitude.
This NASA image released June 15, 2017 was taken with the Cassini spacecraft narrow-angle camera on June 9, 2017, as Cassini obtained the view at a distance of about 507,000 kilometers from Saturn's moon Titan. (HANDOUT / NASA / AFP)
Cassini is ending its 13-year tour of the Saturn system with an intentional mission-ending plunge into the atmosphere of Saturn on Friday to ensure Saturn's moons, in particular Enceladus, with its subsurface ocean and signs of hydrothermal activity, remain pristine for future exploration.
The long-lived spacecraft's fateful dive is a foregone conclusion - an April 22 gravitational kick from Saturn's moon Titan placed the two-and-a-half ton vehicle on its path to impending destruction.
After beginning its descent into Saturn's upper atmosphere, the spacecraft is expected to lose radio contact with Earth within about one to two minutes.
This NASA portrait received Oct 18, 2013 shows a view looking down on Saturn and its rings, created from images obtained by NASA's Cassini spacecraft on Oct 10, 2013. (GORDAN UGARKOVIC / NASA / AFP)
But on the way down, before contact is lost, eight of Cassini's 12 scientific instruments will be operating. In particular, the spacecraft's ion and neutral mass spectrometer (INMS), which will be directly sampling the atmosphere's composition, will potentially offer insights into the giant planet's formation and evolution, according to NASA.
On Thursday, other Cassini instruments will make detailed, high-resolution observations of Saturn's auroras, temperature, and the vortices at the planet's poles.
Cassini's imaging camera will take a last look at the Saturn system on the day before the plunge and will be off during this final descent.
Launched in 1997, Cassini has been touring the Saturn system since arriving there in 2004. During its journey, Cassini has made numerous dramatic discoveries. But the mission's end is drawing near because the spacecraft is running low on fuel.