First recorded by Klaatu (US #62/CAN #45 1976).
Other hit version by The Carpenters (US #32/MOR #18/UK #9/CAN #9/IRE #1 1977).
From the wiki: “‘Calling Occupants of Interplanetary Craft’, written by Terry Draper, John Woloschuk, was first recorded by Canadian band Klaatu in 1976 for release on their debut album 3:47 EST. John Woloschuk, a member of Klaatu and one of the song’s composers, recalled:
‘The idea for this track was suggested by an actual event that is described in The Flying Saucer Reader, a book by Jay David published in 1967. In March 1953 an organization known as the ‘International Flying Saucer Bureau’ sent a bulletin to all its members urging them to participate in an experiment termed ‘World Contact Day’ whereby, at a predetermined date and time, they would attempt to collectively send out a telepathic message to visitors from outer space. The message began with the words … ‘Calling occupants of interplanetary craft!”
“After its release, the Klaatu recording would open night transmissions of the pirate radio station Radio Caroline. Even more bizarre, the song got caught up in rumors that it presaged a Beatles reunion – that ‘Klaatu’ was just a pseudonym for the Fab Four’s return to the recording studio (and possible reunion concert).