I get the sense that this topic is popular because "aliens y'all". It's much more likely to be radiation. It's possible that atomic tests kick luminous particles into the upper atmosphere. But it's not aliens.
From Wikipedia: "During World War II, Menzel was commissioned as a lieutenant commander in the United States Navy and asked to head a division of intelligence, where he used his many-sided talents, including deciphering enemy codes. Even until 1955, he worked with the Navy improving radio-wave propagation by tracking the Sun's emissions and studying the effect of the aurora on radio propagation for the Department of Defense.[3][4] Returning to Harvard after the war, he was appointed acting director of the Harvard Observatory in 1952, and was the full director from 1954 to 1966. His colleague Dr. Dorrit Hoffleit recalls one of his first actions in the position was asking his secretary to destroy a third of the plates sight unseen, resulting in their permanent loss from the record."
On the papers, it doesn't mean that it must be aliens, but weird phenomena.
Assume for a moment their core hypothesis is correct, there were transient objects captured on film pre-Sputnik in LEO objects.
What might we say about their nature?
The authors' undisguised implication is "it's aliens" to be blunt; that's their motivation for this work.
Consequently they put effort (which may not be noted in the final published papers...) into the question of whether they could make any meaningful inference about the geometry and spectral properties of their "transients," their interest (of course) was that if they could make a meaningful argument for regular geometry, they had the story of the century in effect.
These efforts failed totally.
A natural inference might be, among the reasons this might be, is that the objects (remember we are assuming they exist) do not have such characteristics. The primary reason that would be true is if they were naturally occurring objects.
I looked this up and was surprised to learn that there are currently estimated to be on the order of a million small objects in the inner solar system.
So: the entire hypothesis hinges on "significant correlation with nuclear testing." Because otherwise, once can reasonably assume that transient traces of objects—when they are actually traces of objects—would in a quotidian way presumably be caused by some of these million objects.
Or so say I.
There is no end of peculiar and provacative history and data in UFOlogy, and even more murk; one needs to tread very carefully to not go down (or, be led down) to false conclusions, disinformation, and the like.
The authors of this paper seem singularly disinterested in that caution.
A cost-effective search for extraterrestrial probes in the Solar system
https://academic.oup.com/mnras/article/546/2/staf1158/822188...
*Not an actual quote