A NASA Earth mission concept has been developed that focuses on a set of science objectives related to the measurement of plant physiology and functional type for terrestrial and aquatic ecosystems. The NRC Decadal Survey specifically calls for the HyspIRI mission to measure terrestrial and aquatic ecosystems. A review of the literature in conjunction with analysis of ongoing ecosystem research established imaging spectroscopy in the solar reflected portion of the spectrum as the appropriate approach to address these objectives. For these topics a detailed requirement analysis was performed that specified the measurement objectives, measurement requirements, instrument requirement and oilier requirements. These were distilled into a single set of spectral, radiometric, spatial, uniformity and temporal requirement. Key among these are: spectral coverage from 380 to 2500 nm at 10 nm sampling, radiometric resolution and precision giving high signal-to-noise ratios for dark aquatic targets, spatial sampling of 60 m, spectral and spectral IFOV uniformity > 95%, and temporal coverage with a 19 day repeat at the equator. From these requirements a baseline mission concept was formulated with an optically fast and uniform Offner spectrometer design form at the core. In addition, appropriate spacecraft, orbit, and launch vehicle characteristics were specified to achieve the mission requirements. The high data volumes on orbit and on the ground are addressed with currently available technology. Overall, this NASA Earth mission concept has high heritage and low risk from the perspectives of science, instrumentation and overall mission.