Polarization images of the Moon as a function of the lunar phase

Abstract

Moonlight has a partial polarization state that varies with the lunar phase angle. This needs to be characterized for the Moon to be used as a calibration source for polarization-sensitive instruments or as the illumination source in nighttime passive remote sensing. To contribute to this characterization, a pixelated polarization imager was calibrated with a telescope and with a telephoto lens and used to record images of the Moon at 40 phase angles from -138° to 125°. High-resolution images of relative intensity, degree of linear polarization (DoLP), and angle of polarization (AoP) were recorded in a spectral band from 400-1000 nm and were used to calculate disk-averaged DoLP values. These images are made available to readers. Results showed higher DoLP in regions of lower reflectivity (the Umov effect), higher DoLP for waning phases (maximum DoLP of 8.3%) than for waxing (maximum DoLP of 6.8%), and consistent DoLP to disk-averaged values published previously for wavelengths contained within our broader band.