VIEW PRIMARY [PLANE|FIELD Kn] View some sub-cube of the (up to 4-D) primary Beams. The 2nd argument indicates whether VIEW shows all Fields for a given fre- quency plane (PLANE keyword), or all Frequency-dependent beams for a given Field. The 2nd and 3rd arguments are optional if the beam is only 2-D or 3-D, which occurs for a single field or a frequency-independent beam in Mosaics (narrow band approximation).