The FLD-ll is a computing photometer that determines and displays real-time values of the luminescence and reflectance coefficients of scenes within its field of view. It senses luminescence by limiting the spectral bandwidth of the received energy to the spectral half-bandwidth of a Fraunhofer line-an absorption feature in the solar spectrum-by means of a. solidetalon Fabry-Perot filter. The Fraunhofer lines of interest are generally very narrow (less than 0.1 nm) and are appreciably reduced in intensity from the continuum. The FLD-II can operate from either helicopter or fixed-wing air-craft. The sensitivity of the instrument permits detection of the luminescence of <0.3 ppb of rhodamine WT dye at the 589.0-nm Fraunhofer line. The FLD-II can perform the fol-lowing functions: (1) remote tracking of fluorescent dyes for the study of current flow and rate of dispersion in large bodies of water; (2) detection of oil spills and leaks; (3) de-tection of the luminescence of in vivo chlorophyll of stressed vegetation in order to identify geochemical anomalies in the soil and the onset of crop disease; and (4) detection and mon itoring of pollutants that exhibit an inherent luminescence, such as effluents from phosphate processing plants, laundry detergents containing luminescent brighteners, lignin sulfo nate (a pulp mill effluent waste product), and others. This paper presents both details of the airborne FLD (optical system) and it's extension to an orbiting imaging system with applications to earth resources studies.