Launched from Earth nearly 20 years ago, NASA's Cassini spacecraft will make its final close proximity flyby of Saturn's moon Hyperion on Sunday -- coming within 19,000 nautical miles of the ringed planet's irregularly-shaped satellite.

The galactic encounter will occur at about 9:30 a.m. EDT Sunday and images will be transmitted back to Earth between 24 and 48 hours later, NASA said.

Engineers hope the Cassini craft will be able to photograph Hyperion's surface with greater detail than ever before. The oval-shaped moon's chaotic rotation is unpredictable, however, which makes it difficult for scientists to anticipate which parts of the moon will present itself to Cassini's camera.

Hyperion, first discovered in 1848, is one of Saturn's estimated 150 natural satellites -- but one of the planet's most peculiar, due largely to its irregular shape and sponge-like appearance. Cassini has made several passes near Hyperion in the last decade, including a very close encounter of just 314 miles on its first flyby in 2005.

Cassini, launched in October 1997 with the European Space Agency's Huygens spacecraft, will make several more important mission maneuvers in the next three years.

On June 16, the spacecraft will perform its closest pass -- just 321 miles -- over the icy moon Dione. In October, it will make two flybys of the moon Enceladus, which is unique for its jets of icy spray, coming within 30 miles on the final pass.

Late this year, Cassini will depart Saturn's equatorial plane and take a yearlong preparation for the mission's ambitious final year, NASA said. The spacecraft will end the mission in 2017 by repeatedly diving through the space between Saturn and its rings.

The Cassini spacecraft, named after Italian astronomer Giovanni Cassini, will subsequently be destroyed by entering Saturn's atmosphere in the planet's northern summer in 2017, mission specialists said.

Since it began exploring Saturn in 2004, the Cassini orbiter has taken some spectacular photographs of the ringed planet -- including a panoramic shot, titled "The Day the Earth Smiled," in which our planet can be seen as a small blue dot.

The Huygens spacecraft landed on Saturn's largest moon, Titan, in January 2005 and sent back numerous images of the satellite's surface -- the first ever taken of the rocky lunar surface.

The spacecraft was named after Dutch astronomer Christiaan Huygens.

The joint NASA-ESA Cassini-Huygens missions are the first explorations of Saturn and its moons since the Pioneer 11, Voyager 1 and Voyager 2 spacecraft passed by the planet between 1979 and 1981. The Voyager probes, in fact, are still transmitting scientific data back to Earth and will continue to do so until they run out of power in about 2025, NASA said.

Voyager 1 entered interstellar space in 2012, the first spacecraft ever to do so, and Voyager 2 is expected to do the same within a few years.