The Cassini spacecraft made its final approach to the moon Hyperion orbiting around the gas giant Saturn on May 31. The vehicle is nearing the end of its mission life, and astronomers are beginning to take more risks with the spacecraft.

Hyperion is a relatively small moon of Saturn, measuring just 111-by-82-by-64 miles, with an average radius of only 82 miles from side-to-side.

Astronomers believe this satellite of Saturn possesses a porous interior, which provides a sponge-like texture to its exterior, unlike those seen on other planetary bodies in the solar system.

The moon tumbles erratically as it orbits around Saturn. Every time a spacecraft has passed the satellite, the same face of the moon has been observed by astronomers. It is nearly impossible to predict, with any degree of accuracy, which side of Hyperion will face a robotic observatory during any given approach.

The closest approach ever between the Cassini spacecraft and Hyperion took place on Sept. 26, 2005, when the orbiting observatory flew just 323 miles away from the surface of the satellite. Roughly six minutes before this approach, while the vehicle was still 1,200 miles away, it was struck by an electrical current from the moon, measuring 200 volts.

The Cassini science team released a short video showing the moon as Cassini approached. Some of the features on the satellite appear to show a smiley face on Hyperion.

"@CassiniSaturn RT if you see a happy face pic," one commenter wrote on the Casini Twitter page.

Hyperion was named after the Titan god of watchfulness from mythology, following its discovery by a trio of astronomers in 1848.

Dione, another moon of Saturn, will be visited by Cassini on June 16. At the time of closest approach during that flyby, the vehicle will be just 321 miles away from the satellite. In October, Enceladus will be the destination point for two visits by the spacecraft, one of which will be at the remarkably close distance of just 30 miles.

Near the end of 2015, the Cassini spacecraft will leave the equatorial plane of Saturn, where most moons orbit, preparing for a dazzling end to its journey. During the last stage of its mission, the vehicle will make a series of dives between Saturn and its innermost ring, to view the second-largest planet in the solar system and its magnificent ring system from an angle never seen before.

Although the encounter took place on May 31, photographs and data were not immediately available for release to the public.

"Mission controllers expect images from the encounter to arrive on Earth within 24 to 48 hours [after the flyby]" mission controllers wrote.