The Explorers' Club, № MXXXIII

Operation AXIOM: The Space Race—The 50th Anniversary of Salyut 3, Part I
25 June 1974: Salyut 3 lifted off from the Kazakh S.S.R.'s Baikonur Cosmodrome atop a Proton-K rocket; "Salyut 3" was a cover name for a military Almaz ("Diamond") spy station, O.P.S.-2, which was equiped with a Rikhter R-23 autocannon; the gun was fixed in place, so that the whole station moved to aim it; Salyut 3's low orbit, military crews, & communications activity betraying its secret purpose.

Commentary: An earlier, civilian-model space station that would have been designated "Salyut 3," but it failed to achieve its proper orbit & so was given the generic satellite designation "Kosmos 557." Kosmos 557's brief orbital career overlapped with Skylab being in orbit by eight days (14-22 May 1973), but was not acknowledged by the Soviets until much later. Thus, this military-model Salyut 3 & Skylab marked the first time two acknowledged space stations were in low Earth orbit simultaneously.

Bonus! Space Race Song o' the Day: Salyut 3
Robert Duncan, "Gunfight Epiphany (Theme from Terriers)" from the Gunfight Epiphany single (Space Cadet Mike Papa Whiskey)

Semper exploro.