  Herein is discussed the performance of spaceborne nulling interferometers
searching for extra-solar planets, in terms of their extinction maps projected
on-sky. In particular, it is shown that the designs of Spatial Filtering (SF)
and Achromatic Phase Shifter (APS) subsystems, both required to achieve planet
detection and characterization, can sensibly affect the nulling maps produced
by a simple Bracewell interferometer. Analytical relationships involving cross
correlation products are provided and numerical simulations are performed,
demonstrating marked differences in the aspect of extinction maps and the
values of attained fringes contrasts. It is concluded that depending on their
basic principles and designs, FS and APS will result in variable capacities for
serendipitous discoveries of planets orbiting around their parent star. The
mathematical relationships presented in this paper are assumed to be general,
i.e. they should apply to other types of multi-apertures nulling
interferometers.
