Sunlight Glinting from Water: not a hazard for WFC3 IR

We analyze the potential hazard of an HST instrument inadvertently observing a glint of sunlight reflected from water. During nominal operation, the detectors are protected from such illumination. However, because of an anomaly on HST in which the instruments were not commanded to their safe conditions, we wondered what could happen in worst-case scenarios. This report examines one such scenario: what is the likelihood and potential effect on WFC3’s IR detector if HST were to observe sunlight glinting from water? As the irradiance on the detector from a (flat) sea-surface glint potentially could be more than a thousand times greater than that of the reflection from clouds, which we also derive and compare to NICMOS observations, and because the likelihood of HST aiming at such a glint is not entirely negligible, we proposed a groundbased test on a flight-like detector. GSFC persons performed a test similar to the one proposed herein, with no apparent damage to the tested IR detector, which was similar to the WFC3 IR flight array.