I was producing ice charts for the Arctic from 1965 to early 1973. Initially, we used ship and aircraft reports. Even without satellites, we had enough information for me to know that the ice extent then was far greater at that time than it is now and also greater than the so-called "normal" extent used in most comparisons.
Although 1979 is said to be the start of the satellite era for ice-mapping, I started using satellite photographs from about 1966 and by the end of the 1960s I had complete coverage available to me for both the Arctic and Antarctic.