During his three-orbit flight on February 20, 1962, John Glenn used this photometer/rangefinder to measure the airglow layer around the Earth. Sometimes called a Voasmeter photometer - after Robert Voas, who trained early astronauts for NASA - the device allowed Glenn to look through the filter and make measurements with the small dial. Information could be gathered from these observations on the intensity of both sunlight and starlight.

Glenn was the first astronaut to use hand-held cameras in space and performed some simple scientific experiments and Earth observations during his short flight. For photography, he carried a modified Leica camera for standard black and white images and an Ansco Autoset camera - modified with ultraviolet film- aboard the spacecraft. Other devices such as a rangefinder and this photometer were used in making astronomical observations which were continued with better equipment on successive Mercury missions.

NASA transferred this rangefinder to the Museum along with all other Friendship 7 equipment in 1967.