An infrared interferometer spectrometer and radiometer (IRIS) is a scientific instrument of the Voyager space probes which enables the measurement of three distinct properties.
The thermometer allows for the observance and measurement of heat energy emitting from an object, and the spectrometer enables the identification of various elements, molecules, and compounds which may be present in an atmosphere and/or on the surface of a body.
The separate radiometer allows for the measurement of reflected infrared, visible, and ultraviolet light off of a body.
[2] In 1971, an early prototype was used on Mariner 9 to examine Mars.
During the Voyager trip past Saturn, the IRIS discovered complex organic molecules in Titan's atmosphere.