  We present the progress of characterization of a low-noise, photon counting
Electron Multiplying Charged Coupled Device (EMCCD) operating in optical
wavelengths and demonstrate possible solutions to the problems of Clock-Induced
Charge (CIC) and other trapped charge through sub-bandgap illumination. Such a
detector will be vital to the feasibility of future space-based direct imaging
and spectroscopy missions for exoplanet characterization, and is scheduled to
fly on-board the AFTA-WFIRST mission. The 512$\times$512 EMCCD is an e2v
detector housed and clocked by a N\"uv\"u Cameras controller. Through a
multiplication gain register, this detector produces as many as 5000 electrons
for a single, incident-photon-induced photoelectron produced in the detector,
enabling single photon counting operation with read noise and dark current
orders of magnitude below that of standard CCDs. With the extremely high
contrasts (Earth-to-Sun flux ratio is $\sim$ 10$^{-10}$) and extremely faint
targets (an Earth analog would measure 28$^{th}$ - 30$^{th}$ magnitude or
fainter), a photon-counting EMCCD is absolutely necessary to measure the
signatures of habitability on an Earth-like exoplanet within the timescale of a
mission's lifetime, and we discuss the concept of operations for an EMCCD
making such measurements.
