ment. We'll use the term &quot;visibility event&quot; to
   designate such an appearance. The set of time intervals resulting
   from the search is returned as a SPICE window.

   The Search Process
   ==================

   The search for visibility events is treated as a search for state
   transitions: times are sought when the state of the ray
   changes from &quot;not visible&quot; to &quot;visible&quot; or vice versa.

   Step Size
   =========

   Each interval of the confinement window is searched a