| Description: light_source_incidence_angle is an angle measured from the local surface normal vector to the direction of a photon arriving from the light source. For rings, the normal vector is that on the same side of the rings as the light source, so values always range between 0 and 90 in units of degrees. The value is always equal to 90 - | observed_ring_elevation | This will enable users to perform database searches based on the effective ring opening angle when they are not concerned about the distinction between north-side and southside viewpoints. We have included the 'light source' prefix to the term so that this quantity is not confused with 'incidence angle', a term that is generally associated with sunlight rather than stars or radio transmitters. Required in the label if the value is constant for the observation. If the angle varies for the observation, the min and max attributes are required in the label. Optional as a field in the data table. |