So I recall this being briefly discussed, under the "Classic Wizard" code name, in the 1986 book by William Burroughs, _Deep Black_ (his history of US space intel). Obviously didn't have details like how the computer systems processing the data worked, but it's been known for a while. The Soviet's paid far more attention to tracking NATO ships, launching 33 nuclear reactor powered radars (program named US-A, RORSAT to NATO) between 1967 and 1988 and a series of similar ferrets as well. One of the Soviet RORSAT's broke apart and scattered uranium across the Great Slave Lake region of Canada(1).<p>Fact that will probably be of interest to the crowd here: the huge radio antenna on the Stanford campus was used by the CIA in the 1960's to spy on Soviet radar! (2) In the mid-1960's, the US realized that bored Soviet operators would have their powerful new ballistic missile tracking radar (Dnestr, NATO name Hen House) track the moon. And the US tried to always have antenna pointed at the moon listening for signal reflections when the geometry of Earth and Moon were right- the one at Stanford and a Navy antenna on the East Coast were the primary stations for this, but other antennas were used as well.<p>1: <a href="https://en.wikipedia.org/wiki/Kosmos_954" rel="nofollow">https://en.wikipedia.org/wiki/Kosmos_954</a><p>2: <a href="https://www.cia.gov/resources/csi/static/Moon-Bounce-Elint.pdf" rel="nofollow">https://www.cia.gov/resources/csi/static/Moon-Bounce-Elint.p...</a>