NASA Resurrects Cassini Spacecraft In Time for Saturn Moon Flyby


NASA reawakened the Cassini spacecraft today (Nov. 24) from a forced hibernation while in orbit around Saturn, after three weeks of stalled science work due to a computer glitch.

All of the probe's science instruments have been reactivated and the spacecraft is in good health, just in time to record observations of Saturn's icy moon Enceladus during a close flyby set for Tuesday, Nov. 30, NASA officials said. [Cassini's Greatest Hits: Photos of Saturn]

Cassini had been operating in a protective standby mode — called "safe mode" — since Nov. 2 because of an ill-timed flip of a data bit in Cassini's command and data system computer.

The unexpected bit flip prevented Cassini's main computer from registering a vital instruction, and the spacecraft went into standby mode as a result.

"Engineers have traced the steps taken by the computer during that time and have determined that all spacecraft responses were proper, but still do not know why the bit flipped," NASA officials said in an update released today.

The computer glitch marked the sixth time Cassini has gone into safe mode since its launch in 1997. During these periods, the probe beams engineering and spacecraft health data to its mission operations center at NASA's Jet Propulsion Laboratory in Pasadena, Calif., but cannot perform science observations.

The glitch prevented Cassini from studying Titan, Saturn's largest moon, during a Nov. 11 flyby of the cloud-covered satellite.

The upcoming Nov. 30 flyby will bring Cassini to within about 30 miles (48 kilometers) of the surface of Enceladus, Saturn's sixth-largest moon. The frigid world has icy geysers jetting from its south pole and — possibly — a bubbly, subsurface ocean of liquid water.