Voyager 1 and Voyager 2 carried near-identical Ultraviolet Spectrometers (UVS) to study the composition, structure, and excitation of the upper atmospheres of the planets and their satellites. The spectrometers cover a spectral range of approximately 50 to 170 nm, in the extreme and far ultraviolet bands of the electromagnetic spectrum. The Voyager UVS instruments combine the capabilities for two very different kinds of observation in a single instrument. By emission spectroscopy, they measured airglow and auroral emissions from the atmospheres of the giant planets, several of their satellites, and the Io plasma torus. By occultation spectroscopy, they measured the absorption of sunlight and starlight by atmospheres to infer their composition and temperature profiles.
In addition to their planetary goals, the UVS instruments have been useful for probing the interplanetary medium and for astronomical observations.