Early this morning the Cassini spacecraft relayed information that it had successfully swapped to a backup set of propulsion thrusters late Wednesday.

The swap was performed because of degradation in the performance of the primary thrusters, which had been in use since Cassini's launch in 1997. This is only the second time in Cassini's 11 years of flight that the engineering teams have gone to a backup system.

The thrusters are used for making small corrections to the spacecraft's course, for some attitude control functions, and for making angular momentum adjustments in the reaction wheels, which also are used for attitude control.

The redundant set is an identical set of eight thrusters. Almost all Cassini engineering subsystems have redundant backup capability.

Cassini has successfully completed its original four-year planned tour of Saturn and is now in extended mission operations.