Only clue I found was during the briefing video at the end of the tutorial, the film showed a screen in Russian with the Minister of Defense symbol on the left and the A.T.O.M organization symbol on the right. The words are in Russian:

Across the top:
MINISTER DEFENSE USSR

Across the bottom:
ARCHIVE ORGANIZATION A.T.O.M.

Stamp at the bottom:
ABSOLUTELY SECRET

The briefing video also ends with the phrase 'let there be A.T.O.M.', which doesn't make sense in English. Might essentially mean Rebirth?

Haha, six years later, and I have the same question.
But now, in the future, we have chat GPT, and that's what he told me:

"Yes! In ATOM RPG, the acronym A.T.O.M. stands for "Advanced Technologies of Outer Mind" in the game's lore. It's a secretive organization that survived the nuclear apocalypse and plays a key role in the game's story.

Their purpose is to preserve pre-war knowledge, technology, and civilization, similar to how the Brotherhood of Steel operates in Fallout."