Deep Space Observations of Terrestrial Glitter

Abstract:

DSCOVR spacecraft drifts about the Lagrangian point between 1.4 and 1.6 million km from Earth, where the Earth Polychromatic Imaging Camera (EPIC) delivers observations of the entire sunlit face of the Earth every one (in winter) or two (in summer) hours. At any instance, there is a preferred (specular) spot on the globe, where a glint may be observed by EPIC. While monitoring reflectance at these spots (terrestrial glitter), we observe occasional intense glints originating from neither ocean surface nor cloud ice. Based on circumstantial evidence, we argue that mountain lakes in the Andes are among the causes. We also examine the time averaged reflectance at the spots and find it exceeding that of the neighbors, with the excess monotonically increasing with the separation distance. This specular excess is found in all channels and is more pronounced in the latest and best calibrated version of the EPIC data, thus opening the possibility of monitoring geometric calibration by using a potential distant glint as a beacon.