Balky Cassini Instrument Unlikely To Be Reactivated

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WASHINGTON — In a development that weakens the case for extending NASA’s flagship Cassini mission beyond 2017, an agency official said Jan. 10 that an instrument on the multibillion-dollar Saturn probe that was shut down in June likely will not be reactivated.

The Cassini Plasma Spectrometer (Caps), which measures the energy content and charge of subatomic particles, was switched off for the second time in a year last summer after it tripped a circuit breaker. Ground operators speculated then that tin plating on the instrument’s electronic components had sprouted small metallic whiskers that touched another conducting surface and caused a short. The same problem forced a Caps shutdown in 2011.

Curt Niebur, lead program scientist for NASA’s New Frontiers series of medium-sized planetary missions, told scientists assembled in Atlanta for a Jan. 10 meeting of NASA’s Outer Planets Assessment Group it was “doubtful” Caps would be turned back on.

“Cassini’s healthy, it’s generating great science, but it’s in a competitive environment.” Niebur said, referring to NASA’s tight planetary science budget. “And Cassini operations are not cheap; $59 million a year is still a lot of money.”

NASA’s Planetary Science Division has a budget of about $1.19 billion for 2013,  about 21 percent less than 2012.

Cassini is managed for NASA by the Jet Propulsion Laboratory in Pasadena, Calif. The mission launched in 1997, reached the Saturn system in 2004 and wrapped up its primary science mission in 2008. The probe is continuing to explore the gas giant and its moons as part of an extended mission slated to run through 2017.

Before the current mission extension ends, senior NASA reviewers will have to decide whether an additional extension is worth the cost. If Cassini does not continue operating, one possible end-of-mission scenario involves plunging the spacecraft into Saturn’s atmosphere, similar to how the Galileo probe was steered into Jupiter in 2003.

Cassini’s Caps instrument includes sensors provided by the Los Alamos National Laboratory in Los Alamos, N.M.; the Centre de Recherches en Physique de L’Environnement Terrestre et Planetaire in Paris; the VTT Technical Research Centre in Finland; and a European team led by the Mullard Space Science Laboratory at Britain’s University College London.

Cassini cost NASA about $2 billion to build and launch, according to a Jet Propulsion Laboratory website dedicated to the mission.