In 1963 Kardashev examined quasarCTA-102, the first Soviet effort in the search for extraterrestrial intelligence (SETI). In this work he came up with the idea that some galactic civilizations would be perhaps millions or billions of years ahead of us, and created the Kardashev classification scheme to rank such civilizations. Kardashev defined three levels of civilizations, based on energy consumption: Type I with "technological level close to the level presently attained on earth, with energy consumption at ≈4×1019erg/sec (4 × 1012 watts)". Type II, "a civilization capable of harnessing the energy radiated by its own star", and Type III, "a civilization in possession of energy on the scale of its own galaxy". Serious Russian efforts in SETI predate similar programs in the US by some years. Other notable experts in the USSR were Vsevolod Troitskii and Iosif Samuilovich Shklovskii (Kardashev's former professor).
Kardashev, Nikolai (1985). "On the Inevitability and the Possible Structures of Supercivilizations" in "The search for extraterrestrial life: Recent developments; Proceedings of the Symposium, Boston, MA,June 18–21, 1984". pp. 497–504. Bibcode:1985IAUS..112..497K.