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Cassini studies tiny, distant moon Kiviuq

Morgan Rehnberg, Correspondent
May 16, 2015, 0:31 UTC

Sen—In the nearly 11 years since the Cassini spacecraft began studying the Saturn system, rarely has it observed an object so distant as tiny Kiviuq. And, yet, Kiviuq—just 16 km across—is but the nearest of the elusive Inuit family of Saturnian moons.

Its highly elongated and inclined orbit takes it more than 14.76 million km from Saturn, nearly 40 times further than the distance from the Earth to the Moon.

Last week, Cassini spent more than ten hours taking images of Kiviuq in the hope of providing scientists with the data necessary to better understand its shape, orientation, and rotation. This is easier said than done, however; Kiviuq is so small that it fits within a single pixel on even the spacecraft’s most telescopic camera.

Even though the moon shows up as nothing but a speck in these so-called “unresolved” images, such observations can provide a wealth of information to scientists. By measuring how much Kiviuq appears to brighten or fade repeatedly over the course of the imaging session, researchers can construct what is known as a light curve.

Like most irregular satellites, Kiviuq is believed to be more potato-shaped than round. That means that from different angles, the moon will present a larger or smaller surface from which to reflect sunlight towards Cassini’s cameras. By correlating the amount of reflected light observed on the light curve with the angle of the spacecraft and the Sun, scientists can estimate the various dimensions of Kiviuq even though Cassini was nearly ten million kilometers away from its diminutive target.

The Cassini-Huygens mission is a collaborative effort between NASA, ESA, and the Italian Space Agency. Launched in 1997, it reached Saturn in 2004 and has since been studying the planet, its moons, and its rings. In 2005, the Huygens probe made the first landing on Titan, Saturn’s largest moon. After completing its second mission extension in 2017, Cassini will make a series of close passes to the planet and then end its time at Saturn by plunging into the planet’s atmosphere.