A new detector evaluation method (DEM) is proposed to determine the response of graphene detectors to low fluxes of photons, neutral atoms/molecules, and ions in the space environment of high to ultra-high vacuum. The method, aimed mainly at evaluation for space applications of new graphene detectors, is also applicable to other detectors operating in non-space environments. DEM will test graphene response to very low fluxes of atoms and molecules, ions, and photons; if sensitive to extremely low fluxes of a few 100/s, the timing of pulses produced by bunched events may open up an entirely new avenue to time-of-flight mass spectrometry. Closely coordinating with the NASA GSFC Detector Systems Branch, DEM will characterize the detector response to enable low-cost demonstrations of ionosphere-thermosphere investigations in low-Earth-orbit in CubeSats and sounding rockets. Space-borne measurements require knowledge of the response to the three kinds of particles: photons, ions, and neutrals, to properly design experiments. DEM controls vacuum pressure at the detector and can validate the application of these new detectors to a new series of mass spectrometers that can operate over a broad range of vacuum pressures (0.1 milliTorr and lower) because of their small size DEM will add value to cost effective NASA balloon, sounding rocket, and satellite investigations.