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

During entry, descent, and landing (EDL), the spacecraft encounters turbulent conditions. The spacecraft experiences intense heating from friction caused by speeding into the atmosphere; it jostles when the parachute deploys; and the lander and rover 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 set up a series of basic, special individual radio tones that 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 sounds. Yet a different tone rings when the airbags deploy. Engineers on Earth track the EDL process by listening for 128 distinct tones (out of 256), all of which have individual meanings throughout the EDL process.

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