he field of view
               (FOV) of which is to be used for an target intersection
               search: the direction from the observer to a target
               is represented by a ray, and times when the specified
               ray intersects the region of space bounded by the FOV
               are sought.

               [1,c1] = size(inst); char = class(inst)

               The position of the instrument designated by 'inst' is
               considered to coincide with that of the ephemeris
