Interesting 1950s Evidence of UFOs Discovered by Swedish Scientists

I watched a video on UFOs. Apparently there is some mildly credible record of their appearance above Earth in the early 1950s that was discovered by Swedish astrophysicists examining old photographic plates made from telescopes of that era. Then there is the interesting Menzel gap named for a Harvard scientist who had photographic plates made at the Harvard Observatory of that era destroyed. He also was an artist beside being a scientist, and painted pictures of aliens with three dimensional transparent holes through them.

https://www.youtube.com/watch?v=5Gt-w38GeNc

https://en.wikipedia.org/wiki/Donald_Howard_Menzel

Plainly the observed artifacts may have been one-off items lofted by a clandestine agency as an experimental precursor of the satellite era begun by the Soviets in 1957.