For the second time in a year, NASA has switched off the Cassini Plasma Spectrometer (CAPS), a magnetosphere monitoring instrument on the U.S. space agency’s multibillion-dollar Cassini Saturn orbiter.

The CAPS instrument was turned off between June 1 and June 2, NASA said in a June 6 press release. The agency shut down the instrument after an unexpected voltage shift tripped a circuit breaker. The same problem prompted the agency to power down CAPS in June 2011.

In both cases, NASA said, the likeliest cause for the tripped breaker was a short circuit within the instrument. Engineers determined that tin plating on electronics components had grown small “whiskers,” which eventually grew long enough to touch another conducting surface and cause a short.

CAPS had been active since March, when NASA engineers switched it back on after determining the cause of last year’s short.

The flagship Cassini mission, launched in 1997, arrived at the Saturn system in 2004. The spacecraft is now exploring the gas giant and its moons as part of an extended science mission slated to wrap up in 2017.

The Cassini mission also carried the European Space Agency’s piggyback Huygens probe, which in 2005 descended into the atmosphere of Titan, Saturn’s largest moon.

The Jet Propulsion Laboratory in Pasadena, Calif., manages the Cassini mission for NASA.



Long-dormant Cassini Instrument Back Online