NASA/JPL
An artist's concept of Cassini at Saturn, where it is studying its rings and moons.
By Managing editor
updated 6/16/2011 6:17:04 PM ET 2011-06-16T22:17:04

NASA engineers shut down part of the Cassini spacecraft at Saturn after an apparent short circuit in one of the 14-year-old probe's science instruments.

Cassini mission managers decided to stop using the Saturn probe's plasma spectrometer on Tuesday following a series of unexpected voltage readings, NASA officials said Wednesday.

The problem began on May 1, when an unexpected voltage shift was detected, officials at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. That suggested a short circuit was at work, but when another event occurred on June 11 it suggested a second short circuit had occurred, they added.

At all times Cassini's instruments and engineering systems continued working normally.

"Analysis of telemetry data from the spacecraft by the engineering team pointed to the Cassini plasma spectrometer instrument as the cause of the voltage shifts," JPL officials said, adding that the instrument has an extra set of capacitors in its power lines to reduce signal noise. "The concern was that one or more of these capacitors may have short-circuited, which would cause the voltage to shift and explain the observed changes. Although the instrument was operating properly, engineers decided to turn it off as a precaution until the events could be better understood."

The plasma spectrometer is one of 12 instruments the Cassini uses to study Saturn. The instrument is used to measure the energy and electrical charge of particles around Saturn.

While Cassini's plasma spectrometer is offline, its 11 other instruments are expected to continue working normally.

"The plan is to resume normal plasma spectrometer operations after further analysis is completed to understand the cause of the issue better," JPL officials said.

NASA launched the Cassini spacecraft toward Saturn in 1997 and it arrived at the ringed planet in 2004. The orbiter has been circling the planet to study its rings and moons ever since. Cassini also carried the European Huygens lander to Saturn. The lander touched down on Titan, Saturn's largest moon, in 2005. 

Cassini's mission was originally slated to end in 2008, but NASA has extended the Saturn flight twice, most recently until 2017. The Cassini mission is a cooperative effort by NASA, the European Space Agency and the Italian space agency.

You can follow Space.com Managing Editor Tariq Malik on Twitter @tariqjmalik. Follow Space.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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