Before the Terran ascent, the general population of Earth did not believe in the existence of extra terrestrial life, even though alien visitors and alien activity had been recorded and witnessed throughout all of human history. During the 20th and the early 21st century flying objects believed not to be of Earth origin were called UFO’s, Flying saucers and Flying discs.
This of course is in no small part due to the fact that the Freons, the Ferons and the mysterious Vrill all used space ships and planetary Landers in disc shape. (These cultures were among the most active pre Astro earth visitors)
While almost everything there is to know about the Freons and Ferons is known and their technology compared to modern standards is considered crude and primitive, very little is known about the Vrill.
To this day no real evidence has been found that they really had a secret Earth base and interacted with a small group of Germans exclusively.
The only evidence that supposedly existed was stored in a warehouse in England that had been completely destroyed in a fire, long before the Ascent.