In 1963 Kardashev he examined quasar CTA-102, the first Soviet effort in the search for extra-terrestrial 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 creeated the Kardashev classification scheme to rank such civilizations. Serious Russian efforts in SETI predate similar programs in the US by some years. Other notable experts in the USSR were Vasevelod Troitskii and Losef Samuilovich Shklovskii (Kardashev's former professor).
Kardashev became a Corresponding Member of the Division of General Physics and Astronomy on December 12, 1976, and has been Academician of the Division of General Physics and Astronomy since March 21, 1994.