Publication:STRNCSTRNT1951
Sources
This is the first book edition of Astronauci. An older record has been updated using information from bibliography_of_polish_editions from http://lem.pl , compiled by Lech Keller.
According to the bibliography, Astronauci (The Astronauts) were written in the city Kraków between November 1950 and May 1951 and first published as a serial novel in the Sztandar Młodych (The Standard of the Young) daily newspaper in 1951.
However, in essay in a magazine on literature http://dekadaliteracka.pl/?id=233 Henryk Markiewicz insists that the novel was not published in Sztandar Młodych, and Lem in an interview (Rozmowy ze Stanisławem Lemem, 1987) states that it was commissioned by the president of Czytelnik, i.e. the publisher of the book version. So this is something to check in other sources.