Donald Keyhoe, The Flying Saucers are Real
“ Our explorers would have no idea of what awaits them. The planet might be uninhabited. It might be peopled by a fiercely barbarous race. Or it might have a civilization far in advance of the Earth.The explorers would first try to get a general idea of the whole planet. Then they would attempt to examine the most densely populated areas, types of armament, any aircraft likely to attack them. Combing the radio spectrum, they would pick up and record sounds and signals in order to decipher the language. As on the Earth, they might hear a hodgepodge of tongues. ”

