NASA's Cassini spacecraft has had its last flyby of the moon Titan and is now on the course for its last set of 22 orbits around Saturn before it will make a deadly plummet into the ringed planet's atmosphere.

Last Close Encounter With Titan

The spacecraft made its 127th close brush with Titan on April 21 just a little past 11:00 p.m. PDT when it passed at 608 miles above the lunar surface and sent back to Earth images and other data of its last encounter with the moon.

Scientists involved with Cassini's radar investigation will look at their last set of radar images of the hydrocarbon seas and lakes across the north polar region of Titan this week.

The planned imaging coverage involves a region that was already captured by the spacecraft's imaging cameras but not by radar.

The team also wants to use these new data to analyze the compositions and depths of some of the small lakes on the moon and to investigate the bright feature called the "magic island" that changes over time.

"[Cassini scientists] conclude that the brightening is due to either waves, solids at or beneath the surface or bubbles, with waves thought to be the most likely explanation. They think tides, sea level and seafloor changes are unlikely to be responsible for the brightening," NASA said.

Prelude To The Grand Finale

The flyby placed the spacecraft on the course for the final phase of its mission called the Grand Finale, wherein the probe will eventually dive into Saturn's atmosphere and transmit data about the ringed planet's chemical composition until it loses its signal.

The close flyby of Titan is set to alter the orbit of the spacecraft so it will pass through the gap between Saturn and its rings.

As Cassini passed over the moon, the lunar gravity bent its path and slightly changed the probe's orbit. As a result, Cassini will start a series of 22 dives between the planet and its rings on April 26 instead of passing just outside of the planet's main rings.

Cassini project manager Earl Maize, from JPL, said that the probe is now on a ballistic path, which means that even if there would be no small course adjustments using the probe's thrusters in the future, Cassini would still get into the planet's atmosphere on Sept. 15.

The close encounter with Titan increased Cassini's velocity to about 1,925 miles per hour. After the flyby, Cassini reached the farthest point in its orbital path around the planet at 8:46 p.m. PDT on April 22.

The point known as apoapse is where each new lap by the probe around Saturn starts. The probe will have its final dive on April 26 during which it will be out of contact. The spacecraft will make the next radio contact with Earth on April 27 during which it will send another batch of images and other data.

"Cassini's up-close exploration of Titan is now behind us, but the rich volume of data the spacecraft has collected will fuel scientific study for decades to come," said mission project scientist Linda Spilker, from NASA's Jet Propulsion Laboratory.

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