Abstract
Moonlight has a polarization state that varies with lunar phase angle, with a disk-averaged degree of linear polarization ranging from approximately 0 to 8%. The moon is frequently used as a calibration source for satelliteborne instruments based on detailed radiometric models of the moon, but this calibration method can only work well for polarization-insensitive instruments without information on the polarization state of the moon incorporated into the model. Additionally, understanding the polarization state of moonlight is necessary for passive polarimetric remote sensing methods utilizing moonlight illumination to operate at night. Previously, images of degree of linear polarization (DoLP) were recorded at a limited number of phase angles, and measurements of DoLP for some individual regions of the moon were made across a wide range of phase angles. However, there is no known database of the disk-averaged polarization state of moonlight as a function of phase angle. We present images of the DoLP and angle of polarization of the moon, and we used those images to calculate a disk-average DoLP for more than 30 phase angles. We believe that these are higher resolution DoLP images than any previously published, that no similar angle of polarization images have been published, and that this is the most complete set of disk-averaged DoLP values obtained across a wide range of phase angles.
Disk-averaged and Disk-resolved Polarization of Moonlight Across Lunar Phases
Moonlight has a polarization state that varies with lunar phase angle, with a disk-averaged degree of linear polarization ranging from approximately 0 to 8%. The moon is frequently used as a calibration source for satelliteborne instruments based on detailed radiometric models of the moon, but this calibration method can only work well for polarization-insensitive instruments without information on the polarization state of the moon incorporated into the model. Additionally, understanding the polarization state of moonlight is necessary for passive polarimetric remote sensing methods utilizing moonlight illumination to operate at night. Previously, images of degree of linear polarization (DoLP) were recorded at a limited number of phase angles, and measurements of DoLP for some individual regions of the moon were made across a wide range of phase angles. However, there is no known database of the disk-averaged polarization state of moonlight as a function of phase angle. We present images of the DoLP and angle of polarization of the moon, and we used those images to calculate a disk-average DoLP for more than 30 phase angles. We believe that these are higher resolution DoLP images than any previously published, that no similar angle of polarization images have been published, and that this is the most complete set of disk-averaged DoLP values obtained across a wide range of phase angles.