He had worked for several years in an Israel Defense Force unit developing the modern tank and had apparently passed information about it to Russia, Israel Radio reported.
He was arrested in 1988.
That same year, a Tel Aviv court sentenced him to 13 years in prison for espionage and contact with a foreign agent.
The High Court, which in the past rejected an appeal by Londin, allowed publication of the story for the first time this week. Londin, who was 60 at the time of his arrest, had cited his failing health in asking that the sentence be commuted.
Another convicted spy for the former Soviet Union, Marcus Klingberg, is serving an 18-year prison term in Israel.
Klingberg's name made the headlines last week as Israeli media reported a proposed spy swap involving Klingberg and Jonathan Pollard, now serving a life sentence in a U.S. prison for spying for Israel.