The OH Interferometer Observations (OHIO) concept is an option for the generalized far infrared Fabry-Perot instrument, optimized for satellite-based measurement of the OH radical in the earth's stratosphere with the simplest possible instrument configuration. This paper gives refined design parameters for OHIO. The design presented uses entirely existing, demonstrated technology, does not require stored cryogens, and concentrates on thermal emission measurements of OH, the one stratospheric species which can be measured uniquely and well in the far infrared from a satellite. Measurements are of the F1, 7/2+ yields F1, 5/2- transition at 118.455 cm-1 (84.42 micrometers ), which has been demonstrated to be the best spectral feature for atmospheric measurements of OH. The current design parameters, including realistic values for Fabry-Perot transmission, detector performance, and filtering required to suppress radiation passed in the higher orders of the grating monochromator, are demonstrated to be within a factor of four of what is required for global measurements of OH. Thus, with a modest further improvements in detector performance and spectrometer design, we may soon be able to demonstrated a working concept for a potential satellite instrument.