The GEO-CAPE ROIC In-Flight Performance Experiment (GRIFEX) is a 3U CubeSat that will perform engineering assessment of a JPL-developed all digital in-pixel high frame rate Read-Out Integrated Circuit (ROIC). Its high throughput capacity will enable the proposed Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission concept to make hourly high spatial and spectral resolution measurements of rapidly changing atmospheric chemistry and pollution transport with the Panchromatic Fourier Transform Spectrometer (PanFTS) instrument in development.