## Baseline and antennas

In equation 1, the instrumental gain is implicitely described as a product of two antenna gains:

| (16)

This is usually satisfied, unless averaging in time or frequency introduce a decorrelation. For a point source at the phase center, the true visibilities are constant in the uv plane with value (,0), where is the source flux density, so we have a set of equations:

| (17)

or equivalently:

|  |  | (18)
|  |  | (19)