Here subscripts p and q represent the two polarisation channels measured by each antenna. The Stokes visibility vector depends on the brightness distribution and on the length and orientation of baseline ij . Examples are receiver noise, and correlator offsets.
Examples are decorrelations, which usually give diagonal matrices with identical elements.
Fortunately, the elements of and tend to be small or close to unity in practice, and will be ignored here. Thus it is assumed that, in the case of a central point source, all instrumental effects can be factorised into antenna-based contributions. The 4 x 4 interferometer response matrix then consists of a direct matrix product of two 2 x 2 antenna-based response matrices. This antenna response matrix can be decomposed into a product of matrices, each of which models a specific instrumental effect in the signal path. In a VLA antenna, the circularly polarised IF-signals are a combination of the signals of the two linear dipoles.