Communications With Earth: Special Signal Tones

During the entry, descent and landing phase of the Mars Exploration Rover mission, engineers listened anxiously for 128 distinct tones that indicated when steps in the process were activated; one sound indicated the parachute deployed, while another signaled that the airbags had inflated. These sounds were a series of basic, special individual radio tones.

Since the landing site for the Mars Science Laboratory has not yet been chosen, it is unclear if the same tones will aid engineers in keeping track of their spacecraft's status during entry, descent and landing. The mission will always have coverage through the Mars Reconnaissance Orbiter and, perhaps (depending on where it lands), real-time direct-to-Earth coverage with tones.