THOR stands for THickness from Offbeam Returns. This Lidar system is designed to estimate the thickness of clouds by measuring the size of the reflected halo resulting from a laser entering a cloud. A refractive telescope with approximately 7.5-inch (19.05-centimeter) aperture is used to gather the returned light and collect it into a custom designed fiber optic bundle. The fiber optic bundle routes specific sections of the light focused by the telescope into ten Hamamatsu detectors.