Answer:
The reason for phonograph installation is to provide information about humans to interstellar aliens.
Explanation:
Phonographs are archaic forms of gramophone which are able to record and reproduce sound.Phonographs were used in early days in voyagers to help transmit information about humans to nearby alien species in space.
I think that would be the moon
"too small to clear objects that are in its orbital path" , which means that it probably not a planet.
hope this helps