It's design to disrupt your input / output carrier signal so we can pinpoint your location. (rottentomatoes.com)
During three flybys of Enceladus, between April 2010 and May 2012, the scientists collected extremely precise measurements of Cassini's trajectory by tracking the spacecraft's microwave carrier signal with NASA's Deep Space Network. (sciencedaily.com)
Stardust did not send images in real time, so all scientists and engineers could do was watch the radio carrier signal to see whether the spacecraft survived the bombardment. (scientificamerican.com)