| Description: ring_longitude specifies the inertial longitude of a ring feature relative to the prime meridian. In planetary ring systems, the prime meridian is the ascending node of the planet's invariable plane on the Earth's mean equator of J2000. Longitudes are measured in the direction of orbital motion along the planet's invariable plane to the ring's ascending node, and thence along the ring plane. Values range from 0 to 360 in units of degrees. Note: The invariable plane of a planet is equivalent to its equatorial plane for every ringed planet except Neptune. Required to be the second field in ring occultation profiles. In labels, the min and max attributes are required. |