GM-APD imaging arrays for direct imaging of exoplanets

Exoplanet detection and characterization is one of NASA´s main science goals. Current missions, such as Kepler, are identifying exoplanet candidates for further study at an unprecedented pace. The upcoming Wide Field InfraRed Survey Telescope (WFIRST) mission is the top-ranked large space mission in the New World New Horizons decadal survey, and will “settle essential questions” in exoplanet research. This paper evaluates photon-counting Geiger-mode avalanche photodiode (GM-APD) imaging arrays for use in the WFIRST Astrophysics Focused Telescope Assets (AFTA) mission design, specifically in the area of direct imaging of exoplanets. A review of both current and state-of-the-art performance for GM-APD devices is presented, including the effects of radiation damage on device performance. Projected performance for next-generation devices is presented based on preliminary testing and state-of-the-art benchmarks for the technology. Simulated data for typical exoplanet signals is used to compare GM-APD performance with a state-of-the-art electron-multiplying charge coupled device (EMCCD), a current candidate for the WFIRST-AFTA mission.