The Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) is a revolutionary new sounding instrument which combines a number of advanced technologies to observe atmospheric weather and chemistry variables in four dimensions. Large area format Focal Plane detector Arrays (LFPAs) provide near instantaneous large area coverage with high horizontal resolution. A Fourier Transform Spectrometer (FTS) in front of the LFPAs enables atmospheric radiance spectra to be observed simultaneously for all elements of the LFPAs thereby providing high vertical resolution sounding information. The fourth dimension, time, is provided by the geosynchronous satellite platform, which enable near continuous imaging of the atmosphere's three-dimensional structure. As a consequence, the GIFTS will improve the observation of all three basic atmospheric state variables (temperature, moisture, and wind velocity) allowing much higher spatial, vertical, and temporal resolutions than is now achievable with currently operational geostationary weather satellites. The displacement of the measured water vapor and cloud features will be used as tracers of the transport of atmospheric water as well as tropospheric constituents (e.g., CO and O3) which impact air quality. The key advance that GIFTS achieves beyond current geostationary wind measurement capabilities is that the water-vapor winds will be altitude-resolved throughout the troposphere. Thus, GIFTS observations will lead to a significantly better understanding of weather and climate processes, including the atmosphere's water cycle and the transport of greenhouse and pollutant gases. The continuous assimilation of GIFTS atmospheric state observations in advanced Numerical Weather Prediction (NWP) models is expected to greatly improve forecasts of storm development and motion as well as extend the useful range of global synoptic scale weather predictions. GIFTS, planned to be launched in 2005, as NASA's third New Millennium Program (NMP) Earth Observing (EO-3) satellite mission, will serve as the prototype of Advanced Baseline Sounder (ABS) systems to fly on future operational geosynchronous satellites. At this conference, the GIFTS will be described and expected capabilities demonstrated through results from airborne FTS measurements with similar spatial and spectral resolution.