This proposal develops a compact cryo-vacuum compatible spectral binning focal plane array (FPA) infrared spectrometer. Target specifications for the spectrometer under this Phase I proposal are 128x128 pixel elements, long wave infrared operation, 0.1 mm wavelength resolution, and 10 spectra/sec sweep rate. The system incorporates innovative cryo-compatible sensor technology to achieve high calibrated sensitivity in cryo-temperature cycled environments. Integrated spectrally selective layers provide the design flexibility needed to achieve high resolution narrowband spectral response across the infrared range. The spectral binning FPA developed under this proposal requires no moving parts and replaces more bulky and less reliable spectrometer solutions based on gratings, swept etalons, and prisms. The spectrometer will find immediate use in spectrally resolving and calibrating infrared light sources and detectors in the AEDC Space Systems Test Facility at Arnold Air Force Base. Additionally, the technology will serve a broader application base by virtue of its low size, weight, power, and cost (SWaP-C) and capacity for fast, high resolution and sensitivity infrared sweeps under both room temperature and cryo-vacuum conditions.