January 12, 2012 PASADENA, Calif. -- Engineers with NASA's
Cassini mission are conducting diagnostic testing on a part of
the spacecraft's radio system after its signal was not detected
on Earth during a tracking pass in late December. The spacecraft
has been communicating with Earth using a backup part. The issue
occurred with the ultra-stable oscillator, which is used for one
type of radio science experiment and also as a means of sending
data back to Earth. The spacecraft is currently using an
auxiliary oscillator, whose frequency stability is adequate for
transmitting data from the spacecraft to Earth. Tests later this
month will help mission managers decide whether it will be
possible to bring the ultra-stable oscillator back into service.
Some of the data collected for the radio science experiment
using the auxiliary oscillator will be of lesser quality than
that from the ultra-stable oscillator. Signals used for
occultation experiments - where scientists analyze how radio
signals are affected as they t