NASA seeks to identify habitable exoplanets and explore signatures of life with the Habitable Worlds Observatory and through a series of missions to Europa. The former requires single photon sensing detectors that measure fluxes as low as one photon per hour, while the latter requires detectors that maintain performance after exposure to intense high-energy space radiation. Single-photon sensing and photon-number resolving CMOS image sensors are promising for these missions. One such sensor, the Quanta Image Sensor (QIS), has deep sub-electron read noise (DSERN) that remains unchanged even after exposure equivalent to that experienced over ten 11-year mission lifetimes. The dark current increases modestly after one mission lifetime and can be returned to beginning-of-life values with cooling of similar to 4 - 6 K. In this paper, we present pre-irradiation results obtained from another DSERN sensor, the BAE HWK4123 in the Hamamatsu ORCA-QUEST camera. We find the read noise, photon transfer, and full well depth agree with reported values for the camera, while the dark current is 2.8x higher than the reported value. We also present a radiation test program plan, including simulations of the environment at L2 and around Jupiter.
