VIR is a Visual and Infrared Imaging Spectrometer in a single optical head. A Shafer telescope is combined with an Offner spectrometer. Spectral images are formed on two matrix detectors to cover the 0.25-1 µm and 1-5 µm ranges. The design uses a dual arm optical and focal design with mapping ability to 5 µm.
The spectrometer consists of three modules: the optical system, 5.0 kg mass; the proximity electronics, 3.0 kg and 5 W; and the cryocooler including driving electronics, 1.3 kg and 12.6 W. A mechanical and thermal mounting of 5.0 kg mass accommodates the spectrometer subsystems.
The Visible and Infrared (VIR) Mapping Spectrometer "sees" from 0.3-5 microns covering the near ultraviolet (UV), visible and infrared regions of the spectrum. The instrument produces an image of the spectrum and has on board its own calibration lamp, which it imaged as part of the tests performed in the weeks after launch.