Pre-flight and on-orbit calibration of the spectral imagery acquired with the Advanced Responsive Tactically Effective Military Imaging Spectrometer (ARTEMIS) will make use of solar radiation-based methods. Preflight spectral calibration relies on views of a specially-coated to provide a set of known absorption features. Radiometric calibration is determined from views of a spectrally-flat panel illuminated by the sun. At-aperture radiance from the panel is determined through combined measurements by multispectral, well-calibrated transfer radiometers and a hyperspectral, field-portable spectrometer. ARTEMIS will rely on vicarious methods for the long-term evaluation of the sensor's calibration. The on-orbit radiometric calibration uses the reflectance-based method to provide at-sensor, hyperspectral radiance for the entire spectral range of ARTEMIS. Vicarious calibration of the spectral response will make use atmospheric absorption features and solar Fraunhofer lines across the solar reflective spectrum. The absolute uncertainty of the solar-based radiometric calibrations is less than 3% in spectral regions not affected by strong absorption.