The U.S had the U2 spy plane and the Hexagon spy satellite, did the USSR have similar capabilities? Are there any known incidents of Soviet planes or satellites that managed to take pictures over US airspace?
Yes eventually they also had their own satellite intelligence gathering program. Unfortunately I am on mobile and can't recall all details but the book "Trust But Verify: Imagery Analysis in the Cold War" by David T. Lindgren is highly recommended to understand the whole ELINT and IMINT history.