The Jet Propulsion Laboratory (JPL) has developed an Imaging Spectrometer Program which consists of aircraft and space-borne instruments for remote mineralogical and vegetation mapping of the Earth's surface. The JPL program grew out of the Landsat Project and was developed in response to NASA's interest in follow-on sensors to the Thematic Mapper on Landsat. NASA encouraged development of advanced multispectral line array detectors directed at Landsat applications. The JPL program takes advantage of several recent breakthroughs in infrared detectors which make it possible to significantly improve the quality of information that can be derived from terrestrial remote sensing. Since the mid-1970s, geologists have recognized that important mineralogical information could be obtained through the use of high-resolution spectral reflectance data in the 0.4 to 2.5 micrometer region. Vibrational and electronic transitions in the crystal lattices play a role in the reflectance behavior of layered silicates, carbonates, and oxide minerals. These are the materials that are most often exposed and make up the weathering products of many rocks; hence they are the most important in geologic remote sensing. Imaging spectrometry can also be used to discriminate, identify, and map vegetation units, as well as determine their state of health and vigor. With the recent development of new techniques for measuring and quantifying the amount of plant cover on soil surfaces, imaging spectroscopy can contribute to soil erosion forecasts and geologic studies in arid lands. In the past, the application of spectral imaging to the identification of materials has been greatly hampered by insufficient spectral resolution. The imaging spectrometer program at JPL was designed to improve the spectral resolution by an order of magnitude from that of the Thematic Mapper on Landsat. The JPL program focuses on technology development and includes optical design studies, the development of area array shortwave infrared detectors, cooling systems, data compression, and onboard data processing. The first instrument, the Airborne Imaging Spectrometer (AIS), incorporates an existing optical system modified to use a 32 × 32 infrared area array detector. The instrument operates in the 1.2 to 2.4 micrometer region with 128 bands covering a swath width of 320 meters. It has a 10-meter instantaneous field of view (IFOV). Flights were initiated in 1984 and the results substantiate the expectations of significantly superior discriminability among vegetation units over that provided by the Thematic Mapper. Spectra were taken over land masses in the continental U.S., Europe, and Australia. The AIS results were so encouraging that the decision was made to proceed to the next generation of JPL imaging spectrometer, the Advanced Visible and Infrared Spectrometer (AVIRIS), an airborne imaging spectrometer that will provide equivalent data to that expected from an Earth-orbiting system. AVIRIS covers the spectral region 0.4 to 2.4 micrometers with 224 bands and a swath width of 11 km. Its IFOV is 20 meters. The AVIRIS development effort is now nearing completion and operational flights are scheduled on the National Aeronautics and Space Administration (NASA) U-2. The AVIRIS will provide the fundamental data to be used by the scientific community to develop the techniques of material identification. In addition, new methods of image data analysis will be developed to extract information efficiently from the high-dimensionality data that will be acquired. Since the ultimate goal is a free-flyer for remote sensing from Earth orbit, a proposal for a Shuttle Imaging Spectrometer Experiment (SISEX), which was to serve as a precursor to the free-flyer version, was submitted to NASA and received approval. The instrument was designed to acquire image data in 192 bands simultaneously in the wavelength range 0.4 to 2.5 micrometers with an IFOV of 30 meters. Because of the delay in Space Shuttle flights as a result of the Challenger accident, a decision has recently been reached to discontinue development of the SISEX instrument and concentrate on the next generation of imaging spectrometers, the High Resolution Infrared Imaging Spectrometer (HIRIS). The HIRIS is to be a free-flyer, operating with similar measurement characteristics as SISEX but with a 30 km swath. Unlike SISEX, HIRIS will produce a continuous data stream with a raw data rate of 393 Mbps. This will require a companion operational ground data system. The instruments will be discussed in detail and results will be presented from the flights of AIS and AVIRIS.