Special signal tones the DSN will receive during entry, descent, and landing

During entry, descent, and landing (EDL), the spacecraft will encounter turbulent conditions. The spacecraft will experience intense heating from friction caused by speeding into the atmosphere; it will jostle when the parachute deploys; and the lander and rover will bounce along the surface in the airbags before they come to a rest on the Martian surface.

The quick and intense movements caused by entry and landing make it difficult to accurately track the spacecraft during this phase, so the communications leads have set up a series of basic, special individual radio tones that will ring during different phases of the entry, descent, and landing process. In order for the engineers to know if the parachute deployed, a tone of a certain pitch will sound. Yet a different tone will ring when the airbags deploy. Engineers on Earth will track the EDL process by listening for 128 distinct tones (out of 256), all of which have individual meanings throughout the EDL process.