The general parts of a remote sensing information system in agriculture are described, with special emphasis on the optical spectrum. Scene radiance spectra of cultivated and uncultivated vegetation, soils, and water are presented from 0.4 to 2.8 and 4 to 16 µm wavelengths. These spectra from natural scenes illustrate various radiometric aspects of field spectroscopy as distinguished from laboratory spectroscopy on natural samples. Temporal information in the agricultural scene is combined with spectral information in a radiometric space model. This model is the basis of a system design to acquire data containing spatial, spectral, and temporal information of a flight swath from an aircraft or spacecraft platform in a format for efficient extraction of ultimate user information. The gap between current airborne data acquisition systems and the desired system specifications is discussed. Airborne instrumentation requirements such as bandwidth and noise-equivalent reflectance, emissivity and temperature changes are described in the light of ultimate user mission requirements.