The foreoptics, fiber optic system and calibration source of the Airborne Visible/ Infrared Imaging Spectrometer (AVIRIS) are described. The foreoptics, based on a modified Kennedy scanner, is coupled by optical fibers to the four spectrometers. The optical fibers allowed convenient positioning of the spectrometers in the limited space and enabled simple compensation of the scanners thermal defocus (at the -23°C operating temperature) by active control of the fiber focal plane position. A challenging requirement for the fiber optic system was the transmission of the spectral range 1.85 to 2.45 microns at .45 numerical aperture. This was solved with custom fluoride glass fibers from Verre Fluore. The on-board calibration source is also coupled to the spectrometers by the fibers and provides two radiometric levels and a reference spectrum to check the spectrometers alignment. Results on performance of the assembled subsystems are presented.