This image was originally found in on page 86 of the book
Man and Space (Life Science Library, 1964)

Caption:
SIMULATING A SPACE FLIGHT
Dressed for space, a dog follows a Soviet scientist into a pressure chamber for a simulated flight. As early as 1951, the Russians began sending animals on ballistics shots, gradually increasing the altitudes. By spring 1957 a dog had ascended 132.5 miles and returned safely.